Wideband Antenna

Abstract

To provide a broad band antenna capable of increasing a radiant gain.SOLUTION: A broad band antenna 10A comprises: an imbalanced feeding material 11 having a power supply part 20 and a non-power supply part 21; a resonance conductor 12 resonated with the power supply part 20 of the imbalanced feeding material 11; a ground conductor 13 resonated with the non-power supply part 21 of the imbalanced feeding material 11; and a fixing conductor 14 positioned between the resonance conductor 12 and the ground conductor 13 to be connected to the imbalanced feeding material 11. The resonance conductor 12 is formed by: a first resonance conductive part 22a extended in an axial front direction from the fixing conductor 14 in parallel to the power supply part 20; and a second resonance conductive part 22b extended in the axial front direction from the fixing conductor 14 in parallel to the power supply part 20. The ground conductor 13 is formed by: a first ground conductive part 25a extended in an axial rear direction from the fixing conductor 14 in parallel to the non-power supply part 21; and a second ground conductive part 25b extended in the axial rear direction from the fixing conductor 14 in parallel to the non-power supply part 21.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wideband antenna including an unbalanced feed material, a resonance conductor, and a ground conductor. [Background technology]

[0002] An antenna is disclosed that includes an unbalanced power supply material having a power supply part of a predetermined length and a non-power supply part of a predetermined length connected to the power supply part, a dielectric substrate having a predetermined dielectric constant, a resonant conductor molded into a plate having a predetermined area and resonating with the power supply part of the unbalanced power supply material, and a ground conductor molded into a plate having a predetermined area, integrated with the resonant conductor, and resonating with the non-power supply part of the unbalanced power supply material (see Patent Document 1).

[0003] The resonant conductor of this antenna is composed of a first resonant conductor portion spaced radially outward from the unbalanced power feed material and extending axially forward from the unbalanced power feed material in parallel with the power feed section, and a second resonant conductor portion located on the opposite side of the first resonant conductor portion across the unbalanced power feed material, spaced radially outward from the unbalanced power feed material, and extending axially forward in parallel with the power feed section. The ground conductor of the antenna is composed of a fixed portion electrically connected to the unbalanced power feed material via a fixing means, a first ground conductor portion connected to the fixed portion and spaced radially outward from the unbalanced power feed material and extending axially rearward from the unbalanced power feed material in parallel with the non-feed section, and a second ground conductor portion located on the opposite side of the first ground conductor across the unbalanced power feed material, connected to the fixed portion and spaced radially outward from the unbalanced power feed material, and extending axially rearward in parallel with the non-feed section. In the antenna, the first and second resonant conductor portions of the resonant conductor are joined to one side of a dielectric substrate, and the fixed portion of the ground conductor and the first and second ground conductor portions are joined to the same side of the dielectric substrate as the one side to which the first and second resonant conductor portions are joined. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2012-238944 Summary of the Invention [Problem to be solved by the invention]

[0005] In the antenna disclosed in Patent Document 1, the dielectric substrate having a predetermined dielectric constant functions as a capacitive element, so that the first and second resonant conductors and the power supply section joined to the dielectric substrate easily resonate, while the first and second ground conductors and the non-power supply section joined to the dielectric substrate easily resonate, thereby making it possible to obtain multiple resonant frequencies.The obtained multiple resonant frequencies are adjacent to each other in one direction and have some overlapping with each other, making it possible to significantly widen the relative bandwidth of the antenna.

[0006] In recent years, the importance of antennas has increased due to improvements in communication technology, and antennas are required to have not only a wide fractional bandwidth but also a high radiation gain. The antenna disclosed in Patent Document 1 has a wide fractional bandwidth, but the radiation gain cannot be increased, and it is difficult to transmit radio waves far away (to increase the radiation gain) while maintaining a predetermined electric field strength. Furthermore, if an obstacle made of a conductor such as metal is close to or present near the antenna when transmitting or receiving radio waves, the antenna's resonance point may fluctuate due to the obstacle, causing the frequency band of the antenna to change, making it impossible to transmit or receive radio waves of a specific frequency band, and reducing the conversion efficiency of converting high-frequency current into radio waves, which may make it impossible to transmit or receive radio waves of a frequency band as designed.

[0007] The object of the present invention is to provide a wideband antenna that has a wide relative bandwidth, can transmit and receive radio waves in a wide band, has a high radiation gain, and can transmit radio waves far away while maintaining a predetermined electric field strength (increasing the radiation gain). Another object of the present invention is to provide a wideband antenna that does not fluctuate the resonance point of the antenna, does not change the frequency band of the antenna, can maintain the conversion efficiency of converting high-frequency current into radio waves, and can transmit and receive radio waves in the frequency band as designed, even if an obstacle made of a conductor such as metal is close or exists nearby. [Means for solving the problem]

[0008] In order to solve the above problems, the wideband antenna of the present invention includes an unbalanced power feeder having a power feed section of a predetermined length and a parasitic section of a predetermined length connected to the power feed section and extending axially rearward from the power feed section, a resonant conductor that resonates with the power feed section of the unbalanced power feeder, a ground conductor that resonates with the parasitic section of the unbalanced power feeder, and a fixing conductor that is located between the resonant conductor and the ground conductor and is electrically connected to the unbalanced power feeder via a fixing means, wherein the resonant conductor is spaced radially outward from the unbalanced power feeder and has a first resonant conductor section that extends axially forward from the fixing conductor in parallel with the power feed section, and the ground conductor is formed from a first ground conductor portion that is spaced radially outward from the unbalanced power supply material and extends axially rearward from the fixing conductor in parallel to the non-power-supply section, and a second ground conductor portion that is located on the opposite side of the first ground conductor across the unbalanced power supply material, spaced radially outward from the unbalanced power supply material, and extends axially rearward from the fixing conductor in parallel to the non-power-supply section.

[0009] As one example of the present invention, a wideband antenna has a first parasitic element located between a first ground conductor and a second ground conductor, and the first parasitic element is composed of a first parasitic fixed part electrically connected to an unbalanced feed material via a fixing means, a first parasitic conductor part located between the unbalanced feed material and the first ground conductor, and extending axially forward from the first parasitic fixed part parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the first ground conductor, and a second parasitic conductor part located between the unbalanced feed material and the second ground conductor, and extending axially forward from the first parasitic fixed part parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the second ground conductor.

[0010] In another example of the present invention, the first resonant conductor portion and the second resonant conductor portion of the resonant conductor are in a line-symmetrical relationship with respect to the central axis of the unbalanced power supply material, the first ground conductor portion and the second ground conductor portion of the ground conductor are in a line-symmetrical relationship with respect to the central axis of the unbalanced power supply material, and the first parasitic conductor portion and the second parasitic conductor portion of the first parasitic element are in a line-symmetrical relationship with respect to the central axis of the unbalanced power supply material.

[0011] As another example of the present invention, in a wideband antenna, the axial length of the first parasitic conductor portion and the second parasitic conductor portion of the first parasitic element is λ / 8 to λ / 16.

[0012] In another example of the present invention, a wideband antenna has a second parasitic element located between a first ground conductor and a second ground conductor, axially forward of the first parasitic element and facing the first parasitic element, and the second parasitic element is formed from a second parasitic fixed part electrically connected to the unbalanced feed material via a fixing means, a third parasitic conductor located between the unbalanced feed material and the first ground conductor, and extending axially rearward from the second parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the first ground conductor, and a fourth parasitic conductor located between the unbalanced feed material and the second ground conductor, and extending axially rearward from the second parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the second ground conductor.

[0013] In another example of the present invention, the third parasitic conductor section and the fourth parasitic conductor section of the second parasitic element are in an axis-symmetric relationship with respect to the central axis of the unbalanced feed material, and in the wideband antenna, the axial length of the first parasitic conductor section and the second parasitic conductor section of the first parasitic element is λ / 8 to λ / 16, and the axial length of the third parasitic conductor section and the fourth parasitic conductor section of the second parasitic element is λ / 8 to λ / 16.

[0014]

[0015] In another example of the present invention, the first parasitic conductor section of the first parasitic element and the third parasitic conductor section of the second parasitic element are arranged opposite each other and spaced apart in the thickness direction of the wideband antenna, with one of the conductor sections being on top and the other being on the bottom, and the second parasitic conductor section of the first parasitic element and the fourth parasitic conductor section of the second parasitic element are arranged opposite each other and spaced apart in the thickness direction of the wideband antenna, with one of the conductor sections being on top and the other being on the bottom.

[0016] In another example of the present invention, a front end of the first parasitic conductor section of the first parasitic element faces and is slightly spaced axially rearward from the rear end of the third parasitic conductor section of the second parasitic element, and a front end of the second parasitic conductor section of the first parasitic element faces and is slightly spaced axially rearward from the rear end of the fourth parasitic conductor section of the second parasitic element.

[0017] In another example of the present invention, a wideband antenna has a power supply element shaped like a plate having a predetermined area and positioned axially forward of a resonant conductor, and the power supply element has a power supply fixing part electrically connected to the power supply part, a first power supply conductor part of a predetermined area extending radially outward from the power supply fixing part and positioned axially forward of a first resonant conductor part of the resonant conductor, and a second power supply conductor part of a predetermined area extending radially outward from the power supply fixing part and positioned axially forward of a second resonant conductor part of the resonant conductor.

[0018] As another example of the present invention, the first power supply conductor portion is formed with a plurality of first step portions arranged in a stepped pattern from the rear end to the front end of the first power supply conductor portion, and the second power supply conductor portion is formed with a plurality of second step portions arranged in a stepped pattern from the rear end to the front end of the second power supply conductor portion.

[0019] In another example of the present invention, the first and second feed conductor portions of the feed element are in an axisymmetric relationship with respect to the central axis of the unbalanced feed material.

[0020] In another example of the present invention, an unbalanced power supply material is formed from a first conductor extending in the axial direction, an insulator covering the outer peripheral surface of the first conductor, and a second conductor covering the outer peripheral surface of the insulator and extending in the axial direction, the power supply part of the unbalanced power supply material is formed from the first conductor, the non-power supply part of the unbalanced power supply material is formed from the first and second conductors and the insulator, the fixing conductor is electrically connected to the second conductor, and the power supply element is electrically connected to the first conductor. Effect of the Invention

[0021] According to the wideband antenna of the present invention, a high frequency current is induced in the first and second resonant conductors and the power feed section, causing the high frequency current to flow in the axial direction between the first and second resonant conductors and the power feed section, a high frequency current is induced in the first and second ground conductors and the parasitic section, causing the high frequency current to flow in the axial direction between the first and second ground conductors and the parasitic section, and the first and second resonant conductors and the power feed section resonate with the high frequency current in the axial direction induced in the conductors and the power feed section, while the first and second ground conductors and the parasitic section resonate with the high frequency current in the axial direction induced in the conductors and the parasitic section, thereby obtaining a plurality of resonant frequencies. The obtained resonant frequencies are adjacent to each other in succession in one direction and partially overlap with each other, so that not only can the fractional bandwidth (about 100 MHz to about 10.0 GHz) of the antenna be significantly widened, but also the first and second ground conductors and the parasitic section can be easily resonated with each other. A high-frequency current is induced in the land conductor section, causing the high-frequency current to flow in one axial direction of the first and second ground conductors, and a high-frequency current is induced in the first and second parasitic conductor sections extending in the axial direction of the first parasitic element, causing the high-frequency current to flow in the other axial direction of the first and second parasitic conductors. The high-frequency current flowing in one axial direction of the first ground conductor and the high-frequency current flowing in the other axial direction of the first parasitic conductor cancel each other out, and the high-frequency current flowing in one axial direction of the second ground conductor and the high-frequency current flowing in the other axial direction of the second parasitic conductor cancel each other out, thereby canceling out unwanted currents and improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization is generated, with the electric field vibration direction parallel to the axial direction of the antenna, and an antenna with high radiation gain can be obtained, and wideband radio waves can be transmitted over a wide range and far away while maintaining a specified electric field strength (increasing radiation gain). A wideband antenna can be made to have a high radiation gain with a VSWR (voltage standing wave ratio) of 2 or more and 3 or less, and can transmit and receive radio waves in all bands of the specific band (usable frequency band) in which it can be used. It is possible to make an antenna that can be used in broadband and can transmit and receive wideband radio waves with just one antenna.

[0022] In a wideband antenna in which the first and second resonant conductor parts of the resonant conductor are in a line-symmetrical relationship with respect to the central axis of the unbalanced power feed material, the first and second ground conductor parts of the ground conductor are in a line-symmetrical relationship with respect to the central axis of the unbalanced power feed material, and the first and second parasitic conductor parts of the first parasitic element are in a line-symmetrical relationship with respect to the central axis of the unbalanced power feed material, the first and second resonant conductor parts that are in a line-symmetrical relationship with the central axis of the unbalanced power feed material easily resonate with the power feed part at a plurality of resonant frequencies with the same electric field strength, and the first and second ground conductor parts that are in a line-symmetrical relationship with the central axis of the unbalanced power feed material easily resonate with the parasitic part at a plurality of resonant frequencies with the same electric field strength, and multiple resonant frequencies can be obtained, and the multiple obtained resonant frequencies are adjacent to each other in a row in one direction and partially overlap with each other, so that not only can the fractional bandwidth (about 100 MHz to about 10.0 GHz) of the antenna be significantly widened, but also instead, a high-frequency current is induced in the first and second ground conductors, which are arranged in an axis-symmetric relationship with respect to the central axis of the unbalanced power supply material, so that the high-frequency current flows in one axial direction of the first and second ground conductors, and a high-frequency current is induced in the first and second parasitic conductors, which are arranged in an axis-symmetric relationship with respect to the central axis of the unbalanced power supply material, so that the high-frequency current flows in the other axial direction of the first and second parasitic conductors, and the high-frequency current flowing in one axial direction of the first ground conductor and the high-frequency current flowing in the other axial direction of the first parasitic conductor cancel each other out, and the high-frequency current flowing in one axial direction of the second ground conductor and the high-frequency current flowing in the other axial direction of the second parasitic conductor cancel each other out, thereby canceling out unwanted currents and greatly improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization is generated, with the vibration direction of the electric field parallel to the axial direction of the antenna, and an antenna with high radiation gain can be provided, and wideband radio waves can be transmitted over a wide range and over a long distance while maintaining a specified electric field strength (increasing radiation gain).A wideband antenna can be made to have a high radiation gain with a VSWR (voltage standing wave ratio) of 2 or more and 3 or less, and can transmit and receive radio waves in all bands of the specific band (usable frequency band) in which it can be used. It is possible to make an antenna that can be used in broadband and can transmit and receive wideband radio waves with just one antenna.

[0023] In a wideband antenna in which the axial lengths of the first and second parasitic conductor sections of the first parasitic element are between λ / 8 and λ / 16, by setting the axial lengths of the first and second parasitic conductor sections of the first parasitic element to the above length, the combined length of the first and second parasitic conductor sections becomes λ / 4, and a high frequency current is induced in the first and second ground conductor sections with a length of λ / 4 so that the high frequency current flows in one axial direction of the first and second ground conductor sections, and a high frequency current is induced in the first and second parasitic conductor sections with a length of λ / 4 so that the high frequency current flows in the other axial direction of the first and second parasitic conductor sections, The high-frequency current flowing in one axial direction of the first parasitic conductor cancels out the high-frequency current flowing in the other axial direction of the first parasitic conductor, and the high-frequency current flowing in one axial direction of the second ground conductor cancels out the high-frequency current flowing in the other axial direction of the second parasitic conductor, thereby reliably canceling out unwanted currents and greatly improving the radiation gain of the antenna.As a result, a strong electromagnetic field of linear polarization is generated, with the vibration direction of the electric field parallel to the axial direction of the antenna, resulting in an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and over long distances while maintaining a specified electric field strength (increasing radiation gain).

[0024] A wideband antenna includes a second parasitic element located axially forward of the first parasitic element between the first ground conductor section and the second ground conductor section and facing the first parasitic element, the second parasitic element being formed from the second parasitic fixed section, a third parasitic conductor section extending axially rearward from the second parasitic fixed section, and a fourth parasitic conductor section extending axially rearward from the second parasitic fixed section, wherein a high-frequency current is induced in the first and second ground conductor sections so that the high-frequency current flows in one axial direction of the first and second ground conductor sections, a high-frequency current is induced in the first and second parasitic conductor sections extending in the axial direction of the first parasitic element so that the high-frequency current flows in the other axial direction of the first and second parasitic conductor sections, and A high-frequency current is induced in the body section, causing it to flow in the other axial direction of the third and fourth parasitic conductor sections, the high-frequency current flowing in one axial direction of the first ground conductor section and the high-frequency current flowing in the other axial direction of the first and third parasitic conductor sections cancel each other out, and the high-frequency current flowing in one axial direction of the second ground conductor section and the high-frequency current flowing in the other axial direction of the second and fourth parasitic conductor sections cancel each other out, thereby canceling out unwanted currents and improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization is generated, with the electric field vibration direction parallel to the axial direction of the antenna, resulting in an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and long distances while maintaining a specified electric field strength (increasing radiation gain).

[0025] In a wideband antenna in which the third and fourth parasitic conductor parts of the second parasitic element are in a line-symmetrical relationship with respect to the central axis of the unbalanced feed material, a high-frequency current is induced in the third and fourth parasitic conductor parts, which are in a line-symmetrical relationship with respect to the central axis of the unbalanced feed material, causing the high-frequency current to flow in the other axial direction of the third and fourth parasitic conductor parts, and the high-frequency current flowing in one axial direction of the first ground conductor and the high-frequency current flowing in the other axial direction of the third parasitic conductor cancel each other out, and the high-frequency current flowing in one axial direction of the second ground conductor and the high-frequency current flowing in the other axial direction of the fourth parasitic conductor cancel each other out, thereby reliably canceling out unnecessary currents and greatly improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization is generated, with the electric field vibration direction parallel to the axial direction of the antenna, making it possible to provide an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and over long distances while maintaining a specified electric field strength (increasing radiation gain).

[0026] In a wideband antenna in which the axial lengths of the first and second parasitic conductor parts of the first parasitic element are λ / 8 to λ / 16 and the axial lengths of the third and fourth parasitic conductor parts of the second parasitic element are λ / 8 to λ / 16, by setting the axial lengths of the first and second parasitic conductor parts of the first parasitic element to the above lengths and setting the axial lengths of the third and fourth parasitic conductor parts of the second parasitic element to the above lengths, the combined axial lengths of the first and second parasitic conductor parts become λ / 4 and the combined axial lengths of the third and fourth parasitic conductor parts become λ / 4, and a high frequency current is induced in the first and second ground conductors having a length of λ / 4 to obtain a A high-frequency current flows in one axial direction of the first and second ground conductors, and a high-frequency current is induced in the first to fourth parasitic conductors, which have a length of λ / 4, causing the high-frequency current to flow in the other axial direction of the first to fourth parasitic conductors. The high-frequency current flowing in one axial direction of the first and second ground conductors and the high-frequency current flowing in the other axial direction of the first to fourth parasitic conductors cancel each other out, reliably canceling out unwanted currents and greatly improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization is generated, with the electric field vibration direction parallel to the axial direction of the antenna, resulting in an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and over long distances while maintaining a specified electric field strength (increasing radiation gain).

[0027] A wideband antenna in which the first parasitic conductor part of the first parasitic element and the third parasitic conductor part of the second parasitic element are arranged facing each other with a space in the thickness direction of the wideband antenna, with one of those conductor parts being on top and the other being on the bottom, and the second parasitic conductor part of the first parasitic element and the fourth parasitic conductor part of the second parasitic element are arranged facing each other with a space in the thickness direction of the wideband antenna, with one of those conductor parts being on top and the other being on the bottom, is When the rear end of the third parasitic conductor part of the parasitic element and the front end of the second parasitic conductor part of the first parasitic element and the rear end of the fourth parasitic conductor part of the second parasitic element are overlapping in abutting contact with each other, and when the front end of the second parasitic conductor part of the first parasitic element and the rear end of the fourth parasitic conductor part of the second parasitic element are overlapping in abutting contact with each other, high frequency currents are not induced in the first to fourth parasitic conductor parts and the high frequency currents flowing in the first and second ground conductor parts cannot be cancelled out. However, when the first parasitic conductor part of the first parasitic element and the third parasitic conductor part of the second parasitic element are arranged facing each other at a distance in the thickness direction of the wideband antenna, The first parasitic element and the fourth parasitic conductor section of the second parasitic element are arranged opposite to each other in the thickness direction of the wideband antenna, so that a high-frequency current is induced in the first and second parasitic conductor sections extending in the axial direction of the first parasitic element, causing the high-frequency current to flow in the other axial direction of the first and second parasitic conductor sections, a high-frequency current is induced in the third and fourth parasitic conductor sections extending in the axial direction of the second parasitic element, causing the high-frequency current to flow in the other axial direction of the third and fourth parasitic conductor sections, and a high-frequency current flowing in one axial direction of the first ground conductor and a high-frequency current flowing in the other axial direction of the first and third parasitic conductor sections. Since the high-frequency currents flowing in one axial direction of the second ground conductor and the high-frequency currents flowing in the other axial direction of the second and fourth parasitic conductors cancel each other out, unnecessary currents are canceled out and the radiation gain of the antenna is improved. Therefore, a strong electromagnetic field of linear polarization is generated in which the vibration direction of the electric field is parallel to the axial direction of the antenna, resulting in an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and over long distances while maintaining a specified electric field strength (increasing radiation gain).

[0028] A wideband antenna in which the front end of the first parasitic conductor part of the first parasitic element faces the rear end of the third parasitic conductor part of the second parasitic element at a slight distance in the axial direction rearward, and the front end of the second parasitic conductor part of the first parasitic element faces the rear end of the fourth parasitic conductor part of the second parasitic element at a slight distance in the axial direction rearward, is configured such that the front end of the first parasitic conductor part of the first parasitic element abuts against the rear end of the third parasitic conductor part of the second parasitic element, and the front end of the second parasitic conductor part of the first parasitic element faces the rear end of the fourth parasitic conductor part of the second parasitic element at a slight distance in the axial direction rearward. When the front end of the first parasitic conductor of the first parasitic element and the rear end of the third parasitic conductor of the second parasitic element abut against each other, no high frequency current is induced in the first to fourth parasitic conductors, and the high frequency current flowing through the first and second ground conductors cannot be cancelled out. However, when the front end of the first parasitic conductor of the first parasitic element and the rear end of the third parasitic conductor of the second parasitic element face each other with a slight gap in the axial direction, and the front end of the second parasitic conductor of the first parasitic element and the rear end of the fourth parasitic conductor of the second parasitic element face each other with a slight gap in the axial direction, A high frequency current is induced in the first and second parasitic conductor sections extending in the axial direction of the power element, causing the high frequency current to flow in the other axial direction of the first and second parasitic conductor sections, and a high frequency current is induced in the third and fourth parasitic conductor sections extending in the axial direction of the second parasitic element, causing the high frequency current to flow in the other axial direction of the third and fourth parasitic conductor sections. The high frequency current flowing in one axial direction of the first ground conductor and the high frequency current flowing in the other axial direction of the first and third parasitic conductor sections cancel each other out, and the high frequency current flowing in one axial direction of the second ground conductor and the high frequency current flowing in the other axial direction of the second and fourth parasitic conductors cancel each other out, thereby canceling out unwanted currents and improving the radiation gain of the antenna. Therefore, a strong electromagnetic field of linear polarization whose electric field vibration direction is parallel to the axial direction of the antenna is generated, making it possible to provide an antenna with high radiation gain, and it is possible to transmit wideband radio waves over a wide range and far away while maintaining a specified electric field strength (increasing radiation gain).

[0029] A wideband antenna has a feeding element formed in a plate shape having a predetermined area and located axially forward of a resonant conductor, the feeding element having a feeding fixed part electrically connected to the feeding part, a first feeding conductor part of a predetermined area extending radially outward from the feeding fixed part and located axially forward from the first resonant conductor part of the resonant conductor, and a second feeding conductor part of a predetermined area extending radially outward from the feeding fixed part and located axially forward from the second resonant conductor part of the resonant conductor, wherein a high frequency current flows in the axial direction of the first feeding conductor part of the feeding element and a high frequency current flows in the axial direction of the second feeding conductor part of the feeding element, the first feeding conductor part of the feeding element and the first resonant conductor part of the resonant conductor resonate due to the high frequency current induced in those conductor parts in the axial direction, and the second feeding conductor part of the feeding element and the second resonant conductor part of the resonant conductor resonate in the axial direction. The axial high-frequency current induced in these conductors resonates, and the resonance of these conductors can provide multiple resonant frequencies with strong electric field strengths in different bands. This not only makes it possible to transmit wideband radio waves over a wide range and long distances while maintaining a predetermined electric field strength (increasing radiation gain), but also stabilizes the frequency band to be resonated by resonating between the first and second power supply conductors of the power supply element and the first and resonant conductors of the resonant conductor. Even if an obstacle made of a conductor such as metal is close to or present near the antenna, the resonance point of the antenna will not fluctuate, and changes in the frequency band of the antenna can be prevented. The conversion efficiency of converting high-frequency current into radio waves can be maintained, and radio waves in the frequency band as designed can be transmitted and received. In a wideband antenna, by increasing the size (area) of the first and second power supply conductor parts of the power supply element, the shift of the resonance point between the power supply part of the unbalanced power supply material and the first and second resonant conductor parts of the resonant conductor to a higher position can be increased, and by reducing the size (area) of the first and second power supply conductor parts of the power supply element, the shift of the resonance point between the power supply part of the unbalanced power supply material and the first and second resonant conductor parts of the resonant conductor to a higher position can be reduced.By changing the size (area) of the first and second power supply conductor parts of the power supply element, the shift of the fractional bandwidth (used frequency band) of the antenna to a higher position can be fine-tuned.

[0030] A high frequency current is induced in a first power supply conductor section in which a plurality of step-like first step portions are formed, causing a high frequency current to flow in the axial direction from the rear end to the front end of the first power supply conductor section, and a high frequency current is induced in a second power supply conductor section in which a plurality of step-like second step portions are formed, causing a high frequency current to flow in the axial direction from the rear end to the front end of the second power supply conductor section, causing the plurality of first step portions of the first power supply conductor section and the first resonant conductor section of the resonant conductor to resonate in multiple ways due to the high frequency current in the axial direction induced in those conductor sections, and causing the plurality of first step portions of the second power supply conductor section and the second resonant conductor section of the resonant conductor to resonate in multiple ways due to the high frequency current in the axial direction induced in those conductor sections, and strong electric field intensities with different bands are generated by the resonance of those conductor sections. Since it is possible to obtain multiple resonant frequencies of various frequencies, not only can wideband radio waves be transmitted over a wide range and long distances while maintaining a predetermined electric field strength (increasing radiation gain), but the first and second power supply conductor portions of the power supply element, in which multiple first and second step portions are formed, resonate with the first and resonant conductor portions of the resonant conductor, thereby stabilizing the frequency band to be resonated. Even if an obstacle made of a conductor such as metal is close to or present near the antenna, the resonance point of the antenna will not fluctuate, and changes in the frequency band of the antenna can be prevented. The conversion efficiency of converting high-frequency current into radio waves can be maintained, and radio waves in the frequency band as designed can be transmitted and received.

[0031] In a wideband antenna in which the first and second power supply conductors of the power supply element are in a line-symmetrical relationship with respect to the central axis of the unbalanced power supply material, a high-frequency current flows in the axial direction of the first and second power supply conductors, which are in a line-symmetrical relationship with respect to the central axis of the unbalanced power supply material, and the first and second power supply conductors of the power supply element and the first and second resonant conductors of the resonant conductor resonate at the same electric field strength due to the axial high-frequency current induced in these conductors, and multiple resonant frequencies with strong electric field strengths in different bands can be obtained by the resonance of these conductors.As a result, not only can wideband radio waves be transmitted over a wide range and far away while maintaining a predetermined electric field strength (increasing the radiation gain), but even if an obstacle made of a conductor such as metal is close to or present near the antenna, the resonance point of the antenna does not fluctuate, and changes in the frequency band of the antenna can be prevented, the conversion efficiency for converting high-frequency current into radio waves can be maintained, and radio waves in the frequency band as designed can be transmitted and received.

[0032] A wideband antenna in which the unbalanced power supply material is formed of a first conductor extending in the axial direction, an insulator surrounding the outer circumferential surface of the first conductor, and a second conductor surrounding the outer circumferential surface of the insulator and extending in the axial direction, the power supply section of the unbalanced power supply material is formed of the first conductor, the non-power supply section of the unbalanced power supply material is formed of the first and second conductors and the insulator, the fixing conductor is electrically connected to the second conductor, and the power supply element is electrically connected to the first conductor, the power supply section formed of the first and second resonant conductor sections and the first conductor easily resonates with high efficiency, and the first and second ground conductor sections and the non-power supply section formed of the first and second conductors and the insulator easily resonates with high efficiency, and a plurality of resonant frequencies can be obtained, and the obtained plurality of resonant frequencies are adjacent to each other continuously in one direction and some of these resonant frequencies overlap. As a result, not only can the relative bandwidth (about 100 MHz to about 10.0 GHz) of the antenna be significantly broadened, but also the high frequency current flowing in one axial direction of the first ground conductor and the high frequency current flowing in the other axial direction of the first parasitic conductor (and the third parasitic conductor) cancel each other out, and the high frequency current flowing in one axial direction of the second ground conductor and the high frequency current flowing in the other axial direction of the second parasitic conductor (and the fourth parasitic conductor) cancel each other out, thereby canceling unnecessary currents and improving the radiation gain of the antenna, so that a strong electromagnetic field of linear polarization in which the vibration direction of the electric field is parallel to the axial direction of the antenna is generated, resulting in an antenna with high radiation gain, which can transmit wideband radio waves over a wide range and far away while maintaining a predetermined electric field intensity (increasing radiation gain). The wideband antenna can maintain stable impedance by interposing an insulator between the first conductor and the second conductor, and can prevent a short circuit between the first conductor and the second conductor of the unbalanced feed material, thereby preventing damage to the high frequency circuit of the transmitter / receiver due to a short circuit between these conductors. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view of a wideband antenna shown as an example. [Diagram 2] End view of line AA in Figure 1. [Diagram 3] FIG. 2 is an end view of line BB in FIG. 1. [Figure 4] FIG. 13 is a perspective view of a wideband antenna shown as another example. [Diagram 5] FIG. 13 is a perspective view of a wideband antenna shown as another example. [Figure 6] FIG. 6 is an end view of line CC in FIG. 5 . [Figure 7] DD line end view of FIG. 5. [Figure 8] FIG. 13 is a perspective view of a wideband antenna shown as another example. [Figure 9] FIG. 9 is an end view of line E-E in FIG. [Figure 10] FIG. 13 is a perspective view of a wideband antenna shown as another example. [Figure 11] 11 is an end view of line FF in FIG. 10 . [Figure 12] End view of line GG in Figure 10. [Figure 13] FIG. 13 is a perspective view of a wideband antenna shown as another example. [Figure 14] A diagram showing the correlation between VSWR (Voltage Standing Wave Ratio) and the band used in a wideband antenna. [Figure 15] Smith chart showing impedance of broadband antennas. [Figure 16] 1 is a diagram showing the electric field strength measured in the circumferential direction of three planes (XY planes) of a wideband antenna. [Figure 17] 1 is a diagram showing the electric field intensity measured in the circumferential direction of three planes (YZ plane or ZX plane) of a wideband antenna. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The wideband antenna according to the present invention will be described in detail below with reference to the accompanying drawings, such as Fig. 1, which is a perspective view of a wideband antenna 10A shown as an example. Fig. 2 is an end view taken along line AA in Fig. 1, and Fig. 3 is an end view taken along line BB in Fig. 1. In Fig. 1, the axial direction is indicated by arrow X, the radial direction is indicated by arrow Y, the axial front direction is indicated by arrow X1, and the axial rear direction is indicated by arrow X2. In Figs. 2 and 3, the thickness direction is indicated by arrow Z. In Fig. 1, the central axis S1 is indicated by a dotted line.

[0035] The wideband antenna 10A is formed of an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonance conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, and a feed element 16. The unbalanced feed material 11 has a predetermined length and extends in the axial direction. The unbalanced feed material 11 is formed of a rod-shaped elongated first conductor 17 (center metal conductor) extending in the axial direction, a first insulator 18 with a circular cross section that envelops the outer circumferential surface of the first conductor 17 and extends in the axial direction, and a second conductor 19 (outer metal conductor) with a cylindrical cross section that envelops the outer circumferential surface of the first insulator 18 and extends in the axial direction. In the unbalanced feed material 11, the outer circumferential surface of the first conductor 17 and the inner circumferential surface of the first insulator 18 are fixed to each other, and the outer circumferential surface of the first insulator 18 and the inner circumferential surface of the second conductor 19 are fixed to each other.

[0036] The unbalanced power supply member 11 has a power supply section 20 set to a length (predetermined length) of approximately λ / 4, and a parasitic section 21 (the length of the parasitic section 21 can be increased by approximately 30 mm to λ / 4) connected to the power supply section 20 and set to a length (predetermined length) of approximately λ / 4. The power supply section 20 is formed of the first conductor 17 or the first conductor 17 and the first insulator 18, and extends approximately linearly in the axial direction. The parasitic section 21 is formed of the first conductor 17, the first insulator 18, and the second conductor 19, and extends approximately linearly from the power supply section 20 axially backward.

[0037] In addition to the first conductor 17, the first insulator 18, and the second conductor 19, the unbalanced power supply material 11 may include a second insulator (not shown) that covers the outer circumferential surface of the second conductor 19. In this case, the outer circumferential surface of the second conductor 19 and the inner circumferential surface of the second insulator are fixed to each other, and the power supply section 20 is formed from the first conductor 17 or the first conductor 17 and the first insulator 18, while the non-power supply section 121 is formed from the first conductor 17, the first insulator 18, the second conductor 10, and the second insulator. The first conductor 17 and the second conductor 19 can be made of conductive metals such as aluminum, copper, and alloys, and the first insulator 18 and the second insulator can be made of thermoplastic synthetic resin that is a material for fixing the impedance of the unbalanced power supply material 11, and it is preferable to use polytetrafluoroethylene having a plastic-type dielectric constant.

[0038] The resonant conductor 12 is a thin and elongated wire having a circular cross section in the axial direction, is made of a conductive metal (aluminum, copper, an alloy, etc.), and resonates with the power supply section 20 of the unbalanced power supply material 11. The resonant conductor 12 is formed of a first resonant conductor section 22a and a second resonant conductor section 22b arranged radially outwardly from the power supply section 20 with the power supply section 20 in between. The first resonant conductor section 22a and the second resonant conductor section 22b are made by forming the conductive metal into a linear or rod shape.

[0039] The first resonant conductor 22a has a base end electrically connected (fixed) to the fixing conductor 14. The first resonant conductor 22a is spaced radially outward from the unbalanced power supply 11 (power supply section 20) and extends axially forward from the fixing conductor 14 in parallel with the power supply section 20. The first resonant conductor 22a resonates with the power supply section 20 (first conductor 17 (center metal conductor)) of the unbalanced power supply 11. The second resonant conductor 22b has a base end electrically connected (fixed) to the fixing conductor 14. The second resonant conductor 22b is located on the opposite side of the first resonant conductor 22a across the unbalanced power supply 11 (power supply section 20), is spaced radially outward from the unbalanced power supply 11, and extends axially forward from the fixing conductor 14 in parallel with the power supply section 20. The second resonant conductor portion 22a resonates with the power supply portion 20 (the first conductor 17 (the central metal conductor)) of the unbalanced power supply material 11.

[0040] The first resonant conductor 22a forms an arc so as to gradually separate from the unbalanced power supply 11 (power supply section 20) from the fixing conductor 14 toward the axial front. The second resonant conductor 22b forms an arc so as to gradually separate from the unbalanced power supply 11 (power supply section 20) from the fixing conductor 14 toward the axial front. The first resonant conductor 22a may extend linearly from the fixing conductor 14 toward the axial front so as to gradually separate from the unbalanced power supply 11 (power supply section 20), and the second resonant conductor 22b may extend linearly from the fixing conductor 14 toward the axial front so as to gradually separate from the unbalanced power supply 11 (power supply section 20). In this case, the first and second resonant conductors 22a and 22b are inclined toward the axial front at a predetermined angle with respect to the unbalanced power supply 11 (power supply section 20).

[0041] The first resonant conductor 22a and the second resonant conductor 22b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11, and have the same cross-sectional shape and the same axial length L1. Furthermore, the radial distance L2 of the first resonant conductor 22a (inner edge) and the radial distance L2 of the second resonant conductor 22b (inner edge) with respect to the central axis S1 (center of the power supply part 20) of the unbalanced power supply material 11 are the same. The power supply part 20 of the unbalanced power supply material 11 has a parallel portion 23 extending in parallel with the first and second resonant conductors 22a and 22b, and an extension portion 24 connected to the parallel portion 23 and extending axially forward from the first and second resonant conductors 22a and 22b.

[0042] The ground conductor 13 is a thin and elongated wire having a circular cross section in the axial direction, is made of a conductive metal (aluminum, copper, an alloy, etc.), and resonates with the parasitic section 21 of the unbalanced power supply material 11. The ground conductor 14 is formed of a first ground conductor section 25a and a second ground conductor section 25b arranged radially outwardly from the parasitic section 21 with the parasitic section 21 in between. The first ground conductor section 25a and the second ground conductor section 25b are made by forming the conductive metal into a linear or rod shape.

[0043] The first ground conductor 25a has a base end electrically connected (fixed) to the fixing conductor 14. The first ground conductor 25a is spaced radially outward from the unbalanced power supply 11 (non-power-fed portion 21) and extends axially rearward from the fixing conductor 14. The first ground conductor 25a (ground conductor 13) is integrated with the first resonant conductor 22a (resonant conductor 12) and connected to the first resonant conductor 22a. The first ground conductor 25a has an inclined portion 26a that extends axially rearward from the fixing conductor 14 at a predetermined angle so as to gradually move away from the unbalanced power supply 11 (non-power-fed portion 21), and a straight portion 27a that extends axially rearward from the inclined portion 26a in parallel with the unbalanced power supply 11 (non-power-fed portion 21). The first ground conductor portion 25a (the inclined portion 26a and the straight portion 27a) resonates with the parasitic portion 21 (the second conductor 19 (the outer metal conductor)) of the unbalanced power supply material 11.

[0044] The second ground conductor 25b has a base end electrically connected (fixed) to the fixing conductor 14. The second ground conductor 25b is located on the opposite side of the first ground conductor 25a across the unbalanced power supply 11 (power supply section 21), and is spaced radially outward from the unbalanced power supply 11 and extends axially rearward from the fixing conductor 14. The second ground conductor 25b (ground conductor 13) is integrated with the second resonant conductor 22b (resonant conductor 12) and connected to the second resonant conductor 22b. The second ground conductor 25b has an inclined portion 26b that extends axially rearward from the fixing conductor 14 at a predetermined angle so as to gradually move away from the unbalanced power supply 11 (power supply section 21), and a straight portion 27b that extends axially rearward from the inclined portion 26b in parallel with the unbalanced power supply 11 (non-power supply section 21). The second ground conductor portion 25b (the inclined portion 26b and the straight portion 27b) resonates with the parasitic portion 21 (the second conductor 19 (the outer metal conductor)) of the unbalanced power supply material 11.

[0045] The first ground conductor 25a and the second ground conductor 25b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11, and have the same cross-sectional shape and the same axial length L3. Furthermore, the radial distance L4 of the first ground conductor 25a (inner edge) and the radial distance L4 of the second ground conductor 25b (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic part 21) are the same. The parasitic part 21 of the unbalanced power supply material 11 has a parallel part 28 extending in parallel with the first and second ground conductor parts 25a and 25b, and an extending part 29 connected to the parallel part 28 and extending axially rearward from the first and second ground conductor parts 25a and 25b. A connector 30 is attached to the rear end of the extending part 29 of the parasitic part 21 (the rear end of the unbalanced power supply material 11).

[0046] The fixing conductor 14 is made of a conductive metal (aluminum, copper, an alloy, etc.) and is formed into a ring shape. The fixing conductor 14 is located between the resonance conductor 12 (the first and second resonance conductor parts 22a, 22b) and the ground conductor 13 (the first and second ground conductor parts 25a, 25b), and is fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the unpowered part 21 located near the boundary between the power supply part 20 and the unpowered part 21) by welding (soldering, etc.) (fixing means), and is electrically connected to the unbalanced power supply material 11.

[0047] The first parasitic element 15 is made of a conductive metal (aluminum, copper, an alloy, etc.) and is located between the first ground conductor 25a and the second ground conductor 25b. The first parasitic element 15 is formed of a first parasitic fixed part 31, a first parasitic conductor part 32, and a second parasitic conductor part 33. In the first parasitic element 15, the first parasitic fixed part 31, the first parasitic conductor part 32, and the second parasitic conductor part 33 are integrally formed. The first parasitic fixed part 31 is formed in the shape of a rectangular thin plate having a predetermined area and is elongated in the radial direction, and is located between the rear end of the first ground conductor part 25a and the rear end of the second ground conductor part 25b. The first parasitic fixed part 31 is fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21) by being crimped to the unbalanced power supply material 11, and is electrically connected to the unbalanced power supply material 11. Note that the first parasitic fixed part 31 may be fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21) by welding (soldering, etc.) (fixing means).

[0048] The first parasitic conductor section 32 is formed in a rectangular thin plate shape having a predetermined area and is long in the axial direction, and is located between the unbalanced power supply member 11 (parasitic section 21) and the first ground conductor section 25a, and is spaced radially outward from the unbalanced power supply member 11 (parasitic section 21) and radially inward from the first ground conductor section 25a. The first parasitic conductor section 32 has a base end connected to the first parasitic fixed section 31 and extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The first parasitic conductor section 32 has an axial length L5 of λ / 8 to λ / 16. The first parasitic conductor section 32 is parallel to the straight section 27a of the first ground conductor section 25a. A high-frequency current flows through the first parasitic conductor portion 32 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the first ground conductor portion 25a.

[0049] The second parasitic conductor section 33 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located on the opposite side of the first parasitic conductor section 32 with the unbalanced power supply member 11 (parasitic section 21) sandwiched therebetween, and is located between the unbalanced power supply member 11 (parasitic section 21) and the second ground conductor section 25b, and is spaced radially outward from the unbalanced power supply member 11 and radially inward from the second ground conductor section 25b. The second parasitic conductor section 33 has a base end connected to the first parasitic fixed section 31 and extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The second parasitic conductor section 33 has an axial length L5 of λ / 8 to λ / 16. The second parasitic conductor section 33 is parallel to the straight section 27b of the second ground conductor section 25b. A high-frequency current flows in the second parasitic conductor 33 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing in the second ground conductor 25b. The first parasitic fixed portion 31 may be shaped like a ring like the fixing conductor 14, and the first parasitic conductor 32 and the second parasitic conductor 33 may be shaped like a line (wire or rod) like the first and second resonant conductors 22a, 22b and the first and second ground conductors 25a, 25b.

[0050] The first parasitic conductor section 32 and the second parasitic conductor section 33 are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 (center of the parasitic section 21) of the unbalanced power supply material 11 (parasitic section 21), and have the same cross-sectional shape and the same axial length L5. Furthermore, the radial separation dimension L6 of the first parasitic conductor section 32 (inner edge) and the radial separation dimension L6 of the second parasitic conductor section 33 (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 are the same. In the first parasitic element 15, the axial length L5 of the first parasitic conductor section 32 plus the axial length L5 of the second parasitic conductor section 33 is λ / 4.

[0051] The power supply element 16 is made of a conductive metal (aluminum, copper, alloy, etc.) and is formed into a thin plate having a predetermined area. The power supply element 16 is located (separated) axially forward of the resonance conductor 12 (the first resonance conductor portion 22a and the second resonance conductor portion 22b) and is installed at a front end portion 34 of the unbalanced power supply material 11 (power supply portion 21). The power supply element 16 is formed of a power supply fixing portion 35, a first power supply conductor portion 36, and a second power supply conductor portion 37. The power supply fixing portion 35 is fixed (coupled) to the front end portion 34 of the unbalanced power supply material 11 by being crimped to the unbalanced power supply material 11 (the first conductor 17 (the central metal conductor)), and is electrically connected to the unbalanced power supply material 11 (the first conductor 17 (the central metal conductor)). The power supply fixing portion 35 may be fixed (connected) to the unbalanced power supply material 11 (first conductor 17 (central metal conductor)) by welding (soldering or the like) (fixing means).

[0052] The first power supply conductor 36 is formed in a thin plate shape having a predetermined area and is long in the radial direction, and is located (separated) axially forward of the resonance conductor 12 (the first resonance conductor 25a and the second resonance conductor 25b), and extends radially outward from the power supply fixing part 35 (the front end 34 of the unbalanced power supply material 11). A plurality of first step portions 39 of the same shape and size are formed on the outer periphery of the rear end 38 of the first power supply conductor 36, which are arranged in a stepped manner (recessed in a stepped manner) from the rear end of the rear end 38, which forms a circular arc, to the front end extending straight in the radial direction. The first power supply conductor 36 resonates with the first resonance conductor 22a of the resonance conductor 12.

[0053] The second power supply conductor 37 is formed in a thin plate shape having a predetermined area and elongated in the radial direction, and is located (separated) axially forward of the resonance conductor 12 (the first resonance conductor 25a and the second resonance conductor 25b), and extends radially outward from the power supply fixing part 35 (the front end part 34 of the unbalanced power supply material 11). A plurality of second step parts 40 of the same shape and size are arranged in a step-like manner (recessed in a step-like manner) from the rear end of the rear end part 38, which forms an arc, to the front end extending straight in the radial direction. The second power supply conductor 37 resonates with the second resonance conductor part 25b of the resonance conductor 12. The first power supply conductor part 36 and the second power supply conductor part 37 are in a line-symmetrical relationship with respect to the central axis S1 of the unbalanced power supply material (the center of the power supply part 20), and have the same planar shape (the same shape and the same size) and the same area.

[0054] Fig. 4 is a perspective view of a wideband antenna 10B as another example. In Fig. 4, the axial direction is indicated by an arrow X, the radial direction is indicated by an arrow Y, the axial front direction is indicated by an arrow X1, and the axial rear direction is indicated by an arrow X2. The wideband antenna 10B in Fig. 4 differs from that in Fig. 1 in that it has a second parasitic element 41, and other configurations are the same as those of the wideband antenna 10A in Fig. 1. Therefore, the same reference numerals as in Fig. 1 are used, and the description of the wideband antenna 10A in Fig. 1 is used to omit the description of other configurations of this wideband antenna 10B.

[0055] The wideband antenna 10B is formed from an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonance conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, a second parasitic element 41, and a feed element 16. The unbalanced feed material 11, the resonance conductor 12, the ground conductor 13, the fixing conductor 14, the first parasitic element 15, and the feed element 16 are the same as those of the wideband antenna 10A in FIG.

[0056] The second parasitic element 41 is made of a conductive metal (aluminum, copper, an alloy, etc.), and is located between the first ground conductor 25a and the second ground conductor 25b, axially forward of the first parasitic element 15, and faces the first parasitic element 15. The second parasitic element 41 is formed of a second parasitic fixed part 42, a third parasitic conductor part 43, and a fourth parasitic conductor part 44. In the second parasitic element 41, the second parasitic fixed part 42, the third parasitic conductor part 43, and the fourth parasitic conductor part 44 are integrally formed. The second parasitic fixed part 42 is formed in a rectangular thin plate shape having a predetermined area and is elongated in the radial direction, and is located between the inclined part 26a of the first ground conductor part 25a and the inclined part 26b of the second ground conductor part 25b. The second parasitic fixed part 41 is fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21) by crimping, and is electrically connected to the unbalanced power supply material 11. The second parasitic fixed part 42 may be fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21) by welding (soldering, etc.) (fixing means).

[0057] The third parasitic conductor 43 is formed in a rectangular thin plate shape having a predetermined area and is long in the axial direction, and is located between the unbalanced power supply material 11 (parasitic section 21) and the first ground conductor 25a, and is located axially forward of the first parasitic conductor 32. The third parasitic conductor 43 is spaced radially outward from the unbalanced power supply material 11 (parasitic section 21) and radially inward from the first ground conductor 25a. The third parasitic conductor 43 has a base end connected to the second parasitic fixed section 42 and extends axially backward from the second parasitic fixed section 42 in parallel with the parasitic section 21 of the unbalanced power supply material 11. The third parasitic conductor 43 is parallel to the parallel section 27a of the first ground conductor 25a. A high-frequency current flows through the third parasitic conductor portion 43 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the first ground conductor portion 25a.

[0058] The fourth parasitic conductor section 44 is formed in a rectangular thin plate shape having a predetermined area and is long in the axial direction. The fourth parasitic conductor section 44 is located on the opposite side of the third parasitic conductor section 43 across the unbalanced power supply member 11 (parasitic section 21), and is located between the unbalanced power supply member 11 (parasitic section 21) and the second ground conductor section 25b, and is located axially forward of the second parasitic conductor section 33. The fourth parasitic conductor section 44 is spaced radially outward from the unbalanced power supply member 11 (parasitic section 21) and radially inward from the second ground conductor section 25b. The base end of the fourth parasitic conductor section 44 is connected to the second parasitic fixed section 42, and extends axially backward from the second parasitic fixed section 42 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The fourth parasitic conductor section 44 is parallel to the parallel section 27b of the second ground conductor section 25b. A high-frequency current flows in the fourth parasitic conductor 44 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing in the second ground conductor 25b. The first parasitic fixed part 31 and the second parasitic fixed part 42 may be formed into a ring shape like the fixing conductor 14, and the first parasitic conductor 32, the second parasitic conductor 33, the third parasitic conductor 43, and the fourth parasitic conductor 44 may be formed into a linear (line-like or rod-like) shape like the first and second resonant conductors 22a, 22b and the first and second ground conductors 25a, 25b.

[0059] The third parasitic conductor section 43 and the fourth parasitic conductor section 44 are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic section 21), have the same cross-sectional shape, and have the same axial length L7. Furthermore, the radial separation dimension L8 of the third parasitic conductor section 43 (inner edge) and the fourth parasitic conductor section 44 (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 are the same.

[0060] In the wideband antenna 10B, the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8 to λ / 16, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8 to λ / 16. When the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8, the length (2×L5) obtained by adding the length L5 of the first parasitic conductor portion 32 to the length L5 of the second parasitic conductor portion 33 is λ / 4, and the length (2×L7) obtained by adding the length L7 of the third parasitic conductor portion 43 to the length L7 of the fourth parasitic conductor portion 44 is λ / 4. Furthermore, if the axial length L5 of the first parasitic conductor section 32 and the axial length L5 of the second parasitic conductor section 33 are λ / 16, and the axial length L7 of the third parasitic conductor section 43 and the axial length L7 of the fourth parasitic conductor section 44 are λ / 16, then the length L5 of the first parasitic conductor section 32 plus the length L5 of the second parasitic conductor section 33 (2×L5) is λ / 8, the length L7 of the third parasitic conductor section 43 plus the length L7 of the fourth parasitic conductor section 44 (2×L7) is λ / 8, and the axial length of the first and second parasitic conductor sections 32, 33 (2×L5) plus the axial length of the third and fourth parasitic conductor sections 43, 44 (2×L7) is λ / 4.

[0061] In the wideband antenna 10B, a front end 45 of the first parasitic conductor portion 32 of the first parasitic element 15 is slightly spaced (in a range of 1 to 5 mm) axially rearward from a rear end 46 of the third parasitic conductor portion 43 of the second parasitic element 41, and a clearance (slight gap) is formed between the front end 45 of the first parasitic conductor portion 32 and the rear end 46 of the third parasitic conductor portion 43. A front end 45 of the second parasitic conductor portion 33 of the first parasitic element 15 is slightly spaced (in a range of 1 to 5 mm) axially rearward from a rear end 46 of the fourth parasitic conductor portion 44 of the second parasitic element 41, and a clearance (slight gap) is formed between the front end 45 of the second parasitic conductor portion 33 and the rear end 46 of the fourth parasitic conductor portion 44.

[0062] As with the wideband antenna 10D of FIG. 8, with the first parasitic conductor section on top and the third parasitic conductor section on the bottom, the first and third parasitic conductor sections may be arranged opposite each other and spaced apart in the thickness direction of the wideband antenna, or with the second parasitic conductor section on top and the fourth parasitic conductor section on the bottom, the second and fourth parasitic conductor sections may be arranged opposite each other and spaced apart in the thickness direction of the wideband antenna.

[0063] FIG. 5 is a perspective view of the wideband antenna 10C as another example, FIG. 6 is an end view taken along the line CC in FIG. 5, and FIG. 7 is an end view taken along the line DD in FIG. 5. In FIG. 5, the axial direction is indicated by an arrow X, the radial direction is indicated by an arrow Y, the axial front direction is indicated by an arrow X1, and the axial rear direction is indicated by an arrow X2. In FIGS. 6 and 7, the thickness direction is indicated by an arrow Z. In FIG. 5, the central axis line S1 is indicated by a dotted line. The wideband antenna 10C in FIG. 5 is different from that in FIG. 1 in that the resonance conductor 12, the ground conductor 13, and the fixing conductor 14 are formed into a rectangular thin plate shape, and other configurations are the same as those of the wideband antenna 10A in FIG. 1. Therefore, by using the description of the wideband antenna 10A in FIG. 1, the description of other configurations of the wideband antenna 10C will be omitted.

[0064] The wideband antenna 10C is formed of an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonant conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, and a feed element 16. The unbalanced feed material 11, the first parasitic element 15, and the feed element 16 are the same as those of the wideband antenna 10A in FIG. 1. The resonant conductor 12 is made of a conductive metal (aluminum, copper, alloy, etc.) and is formed into a thin plate having a predetermined thickness and a predetermined area. The resonant conductor 12 resonates with the feed section 20 of the unbalanced feed material 11. The resonant conductor 12 is formed of a first resonant conductor portion 22a and a second resonant conductor portion 22b arranged radially apart from each other with the feed section 20 in between.

[0065] The first resonant conductor 22a is made by forming a conductive metal into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the axial direction. The base end of the first resonant conductor 22a is electrically connected (fixed) to the fixing conductor 14. The first resonant conductor 22a is spaced radially outward from the unbalanced power supply material 11 (power supply unit 20) and extends linearly axially forward from the fixing conductor 14 in parallel with the power supply unit 20. The first resonant conductor 22a resonates with the power supply unit 20 (first conductor 17 (center metal conductor)) of the unbalanced power supply material 11.

[0066] The second resonant conductor 22b is made by forming a conductive metal into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the axial direction. The base end of the second resonant conductor 22b is electrically fixed (connected) to the fixing conductor 14. The second resonant conductor 22b is located on the opposite side of the first resonant conductor 22a across the unbalanced power supply material 11 (power supply unit 20), is spaced radially outward from the unbalanced power supply material 11, and extends axially forward from the fixing conductor 14 in parallel with the power supply unit 20. The second resonant conductor 22a resonates with the power supply unit 20 (first conductor 17 (center metal conductor)) of the unbalanced power supply material 11.

[0067] The first resonant conductor 22a and the second resonant conductor 22b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the power supply part 20), have the same planar shape, and have the same axial length L1. Furthermore, the radial separation dimension L2 of the first resonant conductor 22a (inner edge) and the second resonant conductor 22b (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 are the same.

[0068] The ground conductor 13 is made of a conductive metal (aluminum, copper, an alloy, etc.) and is formed into a thin plate with a predetermined thickness and a predetermined area. The ground conductor 13 resonates with the parasitic portion 21 of the unbalanced power supply material 11. The ground conductor 14 is formed of a first ground conductor portion 25a and a second ground conductor portion 25b that are arranged radially apart from each other with the parasitic portion 21 in between.

[0069] The first ground conductor 25a is made by forming a conductive metal into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the axial direction. The first ground conductor 25a is integrated with the first resonant conductor 22a (resonant conductor 12), and its base end is electrically connected (fixed) to the fixing conductor 14. The first ground conductor 25a is spaced radially outward from the unbalanced power supply material 11 (power supply unit 20), and extends axially backward from the fixing conductor 14 in parallel with the power supply unit 20. The first ground conductor 25a resonates with the non-power supply unit 21 (second conductor 19 (outer metal conductor)) of the unbalanced power supply material 11.

[0070] The second ground conductor 25b is made by forming a conductive metal into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the axial direction. The second ground conductor 25b is integrated with the second resonance conductor 22b (resonance conductor 12), and its base end is electrically connected (fixed) to the fixing conductor 14. The second ground conductor 25b is spaced radially outward from the unbalanced power supply material 11 (power supply unit 21), and extends axially backward from the fixing conductor 14 in parallel with the power supply unit 21. The second ground conductor 25b resonates with the non-power supply unit 21 (second conductor 19 (outer metal conductor)) of the unbalanced power supply material 11.

[0071] The first ground conductor portion 25a and the second ground conductor portion 25b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic portion 21), have the same planar shape, and have the same axial length L3. Furthermore, the radial separation dimension L4 of the first ground conductor portion 25a (inner edge) and the second ground conductor portion 25b (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 are the same.

[0072] The fixing conductor 14 is made by forming a conductive metal (aluminum, copper, alloy, etc.) into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the radial direction. The fixing conductor 14 is located between the resonance conductor 12 (first and second resonance conductor parts 22a, 22b) and the ground conductor 13 (first and second ground conductor parts 25a, 25b), and is fixed (connected) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the non-power-supply part 21 located near the boundary between the power supply part 20 and the non-power-supply part 21) by crimping, and is electrically connected to the unbalanced power supply material 11. The fixing conductor 14 may be fixed (connected) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the non-power-supply part 21 located near the boundary between the power supply part 20 and the non-power-supply part 21) by welding (soldering, etc.) (fixing means). In addition, the first parasitic fixed portion 31 may be shaped like a ring similar to the fixing conductor 14 in Figure 1, and the first parasitic conductor portion 32 and the second parasitic conductor portion 33 may be shaped like a line (wire-like or rod-like) similar to the first and second resonant conductor portions 22a, 22b and the first and second ground conductor portions 25a, 25b in Figure 1.

[0073] Fig. 8 is a perspective view of a wideband antenna 10D as another example, and Fig. 9 is an end view of the wideband antenna 10D taken along the line EE in Fig. 8. In Fig. 8, the axial direction is indicated by an arrow X, the radial direction is indicated by an arrow Y, the axial front direction is indicated by an arrow X1, and the axial rear direction is indicated by an arrow X2. In Fig. 9, the thickness direction is indicated by an arrow Z. The wideband antenna 10D in Fig. 8 differs from that in Fig. 5 in that it has a second parasitic element 41, and other configurations are the same as those of the wideband antenna 10C in Fig. 5. Therefore, the same reference numerals as in Fig. 1 are used, and the description of the wideband antenna 10A in Fig. 1 and the wideband antenna 10C in Fig. 5 is used, and the description of other configurations of the wideband antenna 10D is omitted.

[0074] The wideband antenna 10D is formed of an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonance conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, a second parasitic element 41, and a feed element 16. The unbalanced feed material 11, the first parasitic element 15, and the feed element 16 are the same as those in the wideband antenna 10A of Fig. 1, and the resonance conductor 12, the ground conductor 13, and the fixing conductor 14 are the same as those in the wideband antenna 10C of Fig. 5. The second parasitic element 41 is the same as that in the wideband antenna 10B of Fig. 4.

[0075] The first parasitic conductor section 32 of the first parasitic element 15 is formed in a rectangular thin plate shape long in the axial direction and has a predetermined area, and is located between the unbalanced power supply material 11 (parasitic section) 21 and the rectangular thin plate-shaped first ground conductor section 25a, and is spaced radially outward from the unbalanced power supply material 11 and radially inward from the first ground conductor section 25a, and extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply material 11. The first parasitic conductor section 32 is parallel to the rectangular thin plate-shaped first ground conductor section 25a. A high-frequency current flows in the first parasitic conductor section 32 in a direction opposite (the other axial direction) to the direction (one axial direction) of the high-frequency current flowing in the first ground conductor section 25a.

[0076] The second parasitic conductor section 33 of the first parasitic element 15 is formed in a rectangular thin plate shape long in the axial direction and has a predetermined area. The second parasitic conductor section 33 is located on the opposite side of the first parasitic conductor section 32 across the unbalanced power supply material 11 (parasitic section 21), and is located between the unbalanced power supply material 11 and the rectangular thin plate-shaped second ground conductor section 25b, and is spaced radially outward from the unbalanced power supply material 11 and radially inward from the second ground conductor section 25b. The second parasitic conductor section 33 extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply material 11. The second parasitic conductor section 33 is parallel to the parallel portion of the rectangular thin plate-shaped second ground conductor section 25b. A high-frequency current flows in the second parasitic conductor section 33 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing in the second ground conductor section 25b.

[0077] The third parasitic conductor 43 of the second parasitic element 41 is formed in a rectangular thin plate shape long in the axial direction and has a predetermined area. The third parasitic conductor 43 is located between the unbalanced power supply material 11 (parasitic portion 21) and the rectangular thin plate-shaped first ground conductor 25a, and is located in front of the first parasitic conductor 32 in the axial direction, and is spaced radially outward from the unbalanced power supply material 11 and radially inward from the first ground conductor 25a. The third parasitic conductor 43 extends axially backward from the second parasitic fixed portion 42 in parallel with the parasitic portion 21 of the unbalanced power supply material 11. The third parasitic conductor 43 is parallel to the rectangular thin plate-shaped first ground conductor 25a. A high-frequency current flows in the third parasitic conductor 43 in a direction opposite (the other axial direction) to the direction (one axial direction) of the high-frequency current flowing in the first ground conductor 25a.

[0078] The fourth parasitic conductor section 44 of the second parasitic element 41 is formed in a rectangular thin plate shape long in the axial direction and has a predetermined area, and is located on the opposite side of the third parasitic conductor section 43 across the unbalanced power supply member 11 (parasitic section 21), and is located between the unbalanced power supply member 11 and the second ground conductor section 25b, and is located axially forward of the second parasitic conductor section 33. The fourth parasitic conductor section 44 is spaced radially outward from the unbalanced power supply member 11 (parasitic section 21) and radially inward from the second ground conductor section 25b. The fourth parasitic conductor section 44 extends axially backward from the second parasitic fixed section 42 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The fourth parasitic conductor section 44 is parallel to the rectangular thin plate-shaped second ground conductor section 25b. A high-frequency current flows through the fourth parasitic conductor section 44 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the second ground conductor section 25b.

[0079] In the wideband antenna 10D, the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8 to λ / 16, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8 to λ / 16. When the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8, the length (2×L5) obtained by adding the length L5 of the first parasitic conductor portion 32 to the length L5 of the second parasitic conductor portion 33 is λ / 4, and the length (2×L7) obtained by adding the length L7 of the third parasitic conductor portion 43 to the length L7 of the fourth parasitic conductor portion 44 is λ / 4. Furthermore, if the axial length L5 of the first parasitic conductor section 32 and the axial length L5 of the second parasitic conductor section 33 are λ / 16, and the axial length L7 of the third parasitic conductor section 43 and the axial length L7 of the fourth parasitic conductor section 44 are λ / 16, then the length L5 of the first parasitic conductor section 32 plus the length L5 of the second parasitic conductor section 33 (2×L5) is λ / 8, the length L7 of the third parasitic conductor section 43 plus the length L7 of the fourth parasitic conductor section 44 (2×L7) is λ / 8, and the axial length of the first and second parasitic conductor sections 32, 33 (2×L5) plus the axial length of the third and fourth parasitic conductor sections 43, 44 (2×L7) is λ / 4.

[0080] The first and second parasitic elements are arranged in such a manner that the first parasitic conductor section is on top and the third parasitic conductor section is on the bottom, the first parasitic conductor section and the third parasitic conductor section are arranged facing each other at a distance in the thickness direction of the wideband antenna, and the first parasitic conductor section and the third parasitic conductor section partially overlap in the thickness direction. The first and third parasitic conductor sections are slightly spaced apart (1 to 3 mm) in the thickness direction. Also, the second parasitic conductor section is on top and the fourth parasitic conductor section is on the bottom, the second and fourth parasitic conductor sections are arranged facing each other at a distance in the thickness direction of the wideband antenna, and the second and fourth parasitic conductor sections partially overlap in the thickness direction. The second and fourth parasitic conductor sections are slightly spaced apart (1 to 3 mm) in the thickness direction. Furthermore, these conductor sections may be arranged opposite each other and spaced apart in the thickness direction, with the third parasitic conductor section on top and the first parasitic conductor section on the bottom, and the fourth parasitic conductor section on top and the second parasitic conductor section on the bottom.

[0081] 4, the front end 45 of the first parasitic conductor portion 32 of the first parasitic element 15 may be slightly spaced (in the range of 1 to 5 mm) axially rearward from the rear end 46 of the third parasitic conductor portion 43 of the second parasitic element 41, and the front end 45 of the second parasitic conductor portion 33 of the first parasitic element 15 may be slightly spaced (in the range of 1 to 5 mm) axially rearward from the rear end 46 of the fourth parasitic conductor portion 44 of the second parasitic element 41.

[0082] Fig. 10 is a perspective view of a wideband antenna 10E shown as another example, Fig. 11 is an end view taken along line FF in Fig. 10, and Fig. 12 is an end view taken along line GG in Fig. 10. In Fig. 10, the axial direction is indicated by arrow X, the radial direction is indicated by arrow Y, the axial front direction is indicated by arrow X1, and the axial rear direction is indicated by arrow X2. In Figs. 11 and 12, the thickness direction is indicated by arrow Z. In Fig. 10, the central axis S1 is indicated by a dotted line. The wideband antenna 10E is formed of a dielectric substrate 47, an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonance conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, and a feed element 16.

[0083] The dielectric substrate 47 is made of glass epoxy having a predetermined dielectric constant. The dielectric substrate 47 is formed into a plate having a predetermined thickness, and its planar shape is a square (rectangle) long in the axial direction. The dielectric substrate 47 has one surface 48 (upper surface) on which the unbalanced feed material 11 is located, and the other surface 49 (lower surface) located on the opposite side. The dielectric substrate 47 functions as a capacitance (capacitor) that accumulates electric charge in the wideband antenna 10E. The dielectric substrate 47 can be made of a thermoplastic synthetic resin or a thermosetting synthetic resin having a predetermined dielectric constant, in addition to glass epoxy.

[0084] The unbalanced power supply 11 is the same as that of the wideband antenna 10A of FIG. 1. The resonant conductor 12 is formed of a first resonant conductor 22a and a second resonant conductor 22b arranged radially apart from each other with the power supply unit 20 of the unbalanced power supply 11 sandwiched therebetween. The first resonant conductor 22a is made of a conductive metal (aluminum, copper, alloy, etc.) and is formed into a rectangular thin plate having a predetermined area. The base end of the first resonant conductor 22a is electrically connected (fixed) to the fixing conductor 14, is spaced radially outward from the unbalanced power supply 11 (power supply unit 20), and extends axially forward from the fixing conductor 14 in parallel with the power supply unit 20. The first resonant conductor 22a resonates with the power supply unit 20 (first conductor 17 (center metal conductor)) of the unbalanced power supply 11.

[0085] The second resonant conductor 22b is made of a conductive metal (aluminum, copper, alloy, etc.) and is formed into a rectangular thin plate having a predetermined area. The second resonant conductor 22b has a base end electrically connected (fixed) to the fixing conductor 14, is located on the opposite side of the first resonant conductor 22a across the unbalanced power supply material 11 (power supply unit 20), is spaced radially outward from the unbalanced power supply material 11, and extends axially forward from the fixing conductor 14 in parallel with the power supply unit 20. The second resonant conductor 22b resonates with the power supply unit 20 (first conductor 17 (central metal conductor)) of the unbalanced power supply material 11.

[0086] The first resonant conductor 22a and the second resonant conductor 22b are joined (fixed) to one surface 48 (upper surface) of a dielectric substrate 47. The first and second resonant conductors 22a, 22b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the power supply unit 20), have the same planar shape and size, and have the same axial length L1. Furthermore, the radial separation dimension L2 of the first resonant conductor 22a (inner edge) and the second resonant conductor 22b (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the power supply unit 17) are the same. The power supply portion 17 of the unbalanced power supply material 11 has a parallel portion 23 extending parallel to the first and second resonant conductor portions 22a, 22b, and an extension portion 24 connected to the parallel portion 23 and extending axially forward from the first and second resonant conductor portions 22a, 22b.

[0087] The ground conductor 13 is formed of a first ground conductor portion 25a and a second ground conductor portion 25b arranged radially and spaced apart from each other with the parasitic portion 21 in between. The first ground conductor portion 25a is made of a conductive metal (aluminum, copper, an alloy, etc.) and is formed into a rectangular thin plate shape that is long in the axial direction and has a predetermined area. The base end of the first ground conductor portion 25a is electrically connected (fixed) to the fixing conductor 14, is spaced radially outward from the unbalanced power supply material 11 (parasitic portion 21), and extends axially backward from the fixing conductor 14 in parallel with the parasitic portion 21. The first ground conductor portion 25a resonates with the parasitic portion 21 (second conductor 19 (outer metal conductor)) of the unbalanced power supply material 11.

[0088] The second ground conductor portion 25b is made of a conductive metal (aluminum, copper, an alloy, etc.) and is formed into a rectangular thin plate having a predetermined area and elongated in the axial direction. The second ground conductor portion 25b has a base end electrically connected (fixed) to the fixing conductor 13, is located on the opposite side of the first ground conductor portion 25a across the unbalanced power supply material 11 (parallel portion 21), is spaced radially outward from the unbalanced power supply material 11, and extends axially backward from the fixing conductor 14 in parallel with the parallax portion 21. The second ground conductor portion 25b resonates with the parallax portion 21 (second conductor 19 (outer metal conductor)) of the unbalanced power supply material 11.

[0089] The first ground conductor 25a and the second ground conductor 25b are joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47. The first and second ground conductors 25a, 25b are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic section 21), have the same planar shape and size, and have the same axial length L3. Furthermore, the radial separation dimension L4 of the first ground conductor 25a (inner edge) and the second ground conductor 25b (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic section 21) are the same.

[0090] The parasitic section 21 of the unbalanced power supply member 11 has a parallel section 28 extending in parallel with the first and second ground conductors 25a, 25b, and an extending section 29 connected to the parallel section 28 and extending axially rearward from the first and second ground conductors 25a, 25b. A connector 30 is attached to the rear end of the extending section 29 of the parasitic section 21 (the rear end of the unbalanced power supply member 11). In the wideband antenna 10E, the axial length of the first ground conductor 25a and the second ground conductor 25b is longer than the axial length of the first resonant conductor 22a and the second resonant conductor 22b, and the axial length of the first ground conductor 25a and the second ground conductor 25b is about four times the axial length of the first resonant conductor 22a and the second resonant conductor 22b.

[0091] The fixing conductor 14 is made by forming a conductive metal (aluminum, copper, alloy, etc.) into a rectangular thin plate of a predetermined area, and its planar shape is a rectangle that is long in the radial direction. The fixing conductor 14 is located between the resonance conductor 12 (first and second resonance conductor parts 22a, 22b) and the ground conductor 13 (first and second ground conductor parts 25a, 25b), and is fixed (coupled) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the non-power supply part 21 located near the boundary between the power supply part 20 and the non-power supply part 21) by welding (soldering, etc.) (fixing means), and is electrically connected to the unbalanced power supply material 11. The fixing conductor 14 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47.

[0092] The first parasitic element 15 is made of a conductive metal (aluminum, copper, an alloy, etc.) and is located between the first ground conductor 25a and the second ground conductor 25b. The first parasitic element 15 is formed of a first parasitic fixed part 31, a first parasitic conductor part 32, and a second parasitic conductor part 33. The first parasitic element 15 (the first parasitic fixed part 31, the first parasitic conductor part 32, and the second parasitic conductor part 33) is joined (fixed) to one surface 48 (the upper surface) of the dielectric substrate 47. The first parasitic fixed portion 31 is shaped like a radially elongated rectangular thin plate having a predetermined area, is located between the first ground conductor portion 25a and the second ground conductor portion 25b, and is fixed (connected) to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic portion 21) by welding (soldering, etc.) (fixing means), and is electrically connected to the unbalanced power supply material 11 (the second conductor 19 (outer metal conductor) of the parasitic portion 21)).

[0093] The first parasitic conductor 32 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located between the parasitic part 21 of the unbalanced power supply material 11 and the first ground conductor 25a, and is spaced radially outward from the unbalanced power supply material 11 (parasitic part 21) and radially inward from the first ground conductor 25a. The first parasitic conductor 32 has a base end connected to the first parasitic fixed part 31 and extends axially forward from the first parasitic fixed part 31 in parallel with the parasitic part 21 of the unbalanced power supply material 11. The first parasitic conductor 32 has an axial length L5 of λ / 8 to λ / 16 and is parallel to the first ground conductor 25a. A high-frequency current flows in the first parasitic conductor 32 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing in the first ground conductor 25a (the other axial direction).

[0094] The second parasitic conductor section 33 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located on the opposite side of the first parasitic conductor section 32 with the unbalanced power supply member 11 (parasitic section 21) sandwiched therebetween, and is located between the unbalanced power supply member 11 (parasitic section 21) and the second ground conductor section 25b, and is spaced radially outward from the unbalanced power supply member 11 and radially inward from the second ground conductor section 25b. The second parasitic conductor section 33 has a base end connected to the first parasitic fixed section 31 and extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The second parasitic conductor section 33 has an axial length L5 of λ / 8 to λ / 16. The second parasitic conductor section 33 is parallel to the second ground conductor section 25b. A high-frequency current flows through the second parasitic conductor portion 33 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the second ground conductor portion 25b.

[0095] The first parasitic conductor section 32 and the second parasitic conductor section 33 are in a line-symmetric (plane-symmetric) relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the parasitic section 21), and have the same cross-sectional shape (same shape and same size) and the same axial length L5. Furthermore, the radial separation dimension L6 of the first parasitic conductor section 32 (inner edge) and the radial separation dimension L6 of the second parasitic conductor section 33 (inner edge) with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the power supply section 21) are the same. In the first parasitic element 15, the axial length L5 of the first parasitic conductor section 32 plus the axial length L5 of the second parasitic conductor section 33 is λ / 4.

[0096] The power supply element 16 is made of a conductive metal (aluminum, copper, alloy, etc.) and is formed into a thin plate having a predetermined area. The power supply element 15 is located (separated) axially forward of the resonance conductor 12 (the first resonance conductor portion 22a and the second resonance conductor portion 22b) and is disposed to face the front end portion 34 of the unbalanced power supply material 11 (power supply section 20). The power supply element 16 is formed of a power supply fixing portion 35, a first power supply conductor portion 36, and a second power supply conductor portion 37. The power supply fixing portion 15 (power supply fixing portion 35, first power supply conductor portion 36, second power supply conductor portion 37) is joined (fixed) to the other surface 48 (lower surface) of the dielectric substrate 47, and the power supply fixing portion 135 is electrically connected to the unbalanced power supply material 11 (the first conductor 17 (center metal conductor) of the power supply section 20).

[0097] The first power supply conductor 36 is formed in a thin plate shape having a predetermined area and is long in the radial direction, and is located (separated) axially forward of the resonant conductor 12 (the first resonant conductor 22a and the second resonant conductor 22b), and extends radially outward from the power supply fixing portion 35 (the front end portion 34 of the unbalanced power supply material 11). The first power supply conductor 36 resonates with the first resonant conductor 22a of the resonant conductor 12. The second power supply conductor 37 is formed in a thin plate shape having a predetermined area and is long in the radial direction, and is located (separated) axially forward of the resonant conductor 12 (the first resonant conductor 22a and the second resonant conductor 22b), and extends radially outward from the power supply fixing portion 35 (the front end portion 34 of the unbalanced power supply material 11). The second power supply conductor 37 resonates with the second resonant conductor 22b of the resonant conductor 12. The first power supply conductor portion 36 and the second power supply conductor portion 37 are in an axis-symmetric relationship with respect to the central axis S1 of the unbalanced power supply material 11 (the center of the power supply portion 20), and their planar shapes are identical (same shape and same size) and their areas are identical.

[0098] Fig. 13 is a perspective view of a wideband antenna 10F as another example. In Fig. 13, the axial direction is indicated by an arrow X, the radial direction is indicated by an arrow Y, the axial front direction is indicated by an arrow X1, and the axial rear direction is indicated by an arrow X2. The wideband antenna 10F in Fig. 13 differs from that in Fig. 10 in that it has a second parasitic element 41, and other configurations are the same as those of the wideband antenna 10E in Fig. 10. Therefore, the same reference numerals as in Fig. 10 are used, and the description of the wideband antenna 10E in Fig. 10 is used to omit the description of other configurations of this wideband antenna 10F.

[0099] The wideband antenna 10F is formed from an unbalanced feed material 11 (coaxial cable or semi-rigid cable), a resonance conductor 12, a ground conductor 13, a fixing conductor 14, a first parasitic element 15, a second parasitic element 41, and a feed element 16. The unbalanced feed material 11, the resonance conductor 12, the ground conductor 13, the fixing conductor 14, the first parasitic element 15, and the feed element 16 are the same as those of the wideband antenna 10E in FIG.

[0100] The first parasitic fixed part 31 of the first parasitic element 15 is shaped like a rectangular thin plate that is long in the radial direction and has a predetermined area, is located between the first ground conductor part 25a and the second ground conductor part 25b, and is fixed (coupled) to the unbalanced power feed material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21) by welding (soldering, etc.) (fixing means), and is electrically connected to the unbalanced power feed material 11 (the second conductor 19 (outer metal conductor) of the parasitic part 21). The first parasitic fixed part 31 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47.

[0101] The first parasitic conductor section 32 of the first parasitic element 15 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located between the unbalanced power supply material 11 (parasitic section 21) and the rectangular thin plate-shaped first ground conductor section 25a, and is spaced radially outward from the unbalanced power supply material 11 and radially inward from the first ground conductor section 25a, and extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply material 11. The first parasitic conductor section 32 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47. The first parasitic conductor section 32 is parallel to the rectangular thin plate-shaped first ground conductor section 25a. A high-frequency current flows in the first parasitic conductor section 32 in a direction opposite (the other axial direction) to the direction (one axial direction) of the high-frequency current flowing in the first ground conductor section 25a.

[0102] The second parasitic conductor section 33 of the first parasitic element 15 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located on the opposite side of the first parasitic conductor section 32 across the unbalanced power supply member 11 (parasitic section 21), and is located between the unbalanced power supply member 11 (parasitic section 21) and the rectangular thin plate-shaped second ground conductor section 25b, and is spaced radially outward from the unbalanced power supply member 11 and radially inward from the second ground conductor section 25b. The second parasitic conductor section 33 extends axially forward from the first parasitic fixed section 31 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The second parasitic conductor section 33 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47. The second parasitic conductor section 33 is parallel to the parallel portion of the rectangular thin plate-shaped second ground conductor section 25b. A high-frequency current flows through the second parasitic conductor portion 33 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the second ground conductor portion 25b.

[0103] The second parasitic element 41 is made of a conductive metal (aluminum, copper, an alloy, etc.), and is located between the first ground conductor 25a and the second ground conductor 25b, axially forward of the first parasitic element 15, and faces the first parasitic element 15. The second parasitic element 41 is formed of a second parasitic fixed part 42, a third parasitic conductor part 43, and a fourth parasitic conductor part 44. In the second parasitic element 41, the second parasitic fixed part 42, the third parasitic conductor part 43, and the fourth parasitic conductor part 44 are integrally formed. The second parasitic fixed part 42 is formed in a rectangular thin plate shape that is elongated in the radial direction and has a predetermined area, and is located between the rectangular thin plate-shaped first ground conductor part 25a and the rectangular thin plate-shaped second ground conductor part 25b. The second parasitic fixed portion 42 is fixed (coupled) to the unbalanced power feed material 11 (the second conductor 19 (outer metal conductor) of the parasitic portion 21) by welding (soldering, etc.) (fixing means), and is electrically connected to the unbalanced power feed material 11 (the second conductor 19 (outer metal conductor) of the parasitic portion 21). The second parasitic fixed portion 42 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47.

[0104] The third parasitic conductor section 43 of the second parasitic element 41 is formed in a rectangular thin plate shape having a predetermined area and elongated in the axial direction, and is located between the unbalanced power supply member 11 (parasitic section 21) and the rectangular thin first ground conductor section 25a, and is located in front of the first parasitic conductor section 32 in the axial direction, and is spaced radially outward from the unbalanced power supply member 11 (parasitic section 21) and radially inward from the first ground conductor section 25a. The third parasitic conductor section 43 extends axially backward from the second parasitic fixed section 42 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The third parasitic conductor section 43 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47. The third parasitic conductor section 43 is parallel to the rectangular thin first ground conductor section 25a. A high-frequency current flows through the third parasitic conductor portion 43 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the first ground conductor portion 25a.

[0105] The fourth parasitic conductor section 44 of the second parasitic element 41 is located on the opposite side of the third parasitic conductor section 43 across the unbalanced power supply member 11 (parasitic section 21), and is located between the unbalanced power supply member 11 (parasitic section 21) and the second ground conductor section 25b, and is located axially forward of the second parasitic conductor section 33. The fourth parasitic conductor section 44 is spaced radially outward from the unbalanced power supply member 11 (parasitic section 21) and radially inward from the second ground conductor section 25b. The fourth parasitic conductor section 44 extends axially backward from the second parasitic fixed section 342 in parallel with the parasitic section 21 of the unbalanced power supply member 11. The fourth parasitic conductor section 44 is joined (fixed) to one surface 48 (upper surface) of the dielectric substrate 47. The fourth parasitic conductor section 44 is parallel to the rectangular, thin-plate-shaped second ground conductor section 25b. A high-frequency current flows in the fourth parasitic conductor section 44 in a direction opposite to the direction of the high-frequency current flowing in the second ground conductor section 25b (one axial direction).

[0106] In the wideband antenna 10F, the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8 to λ / 16, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8 to λ / 16. When the axial length L5 of the first parasitic conductor portion 32 and the axial length L5 of the second parasitic conductor portion 33 are λ / 8, and the axial length L7 of the third parasitic conductor portion 43 and the axial length L7 of the fourth parasitic conductor portion 44 are λ / 8, the length (2×L5) obtained by adding the length L5 of the first parasitic conductor portion 32 to the length L5 of the second parasitic conductor portion 33 is λ / 4, and the length (2×L7) obtained by adding the length L7 of the third parasitic conductor portion 43 to the length L7 of the fourth parasitic conductor portion 44 is λ / 4. Furthermore, if the axial length L5 of the first parasitic conductor section 32 and the axial length L5 of the second parasitic conductor section 33 are λ / 16, and the axial length L7 of the third parasitic conductor section 43 and the axial length L7 of the fourth parasitic conductor section 44 are λ / 16, then the length L5 of the first parasitic conductor section 32 plus the length L5 of the second parasitic conductor section 33 (2×L5) is λ / 8, the length L7 of the third parasitic conductor section 43 plus the length L7 of the fourth parasitic conductor section 44 (2×L7) is λ / 8, and the axial length of the first and second parasitic conductor sections 32, 33 (2×L5) plus the axial length of the third and fourth parasitic conductor sections 43, 44 (2×L7) is λ / 4.

[0107] In the wideband antenna 10F, a front end 45 of the first parasitic conductor portion 32 of the first parasitic element 15 is slightly spaced (in a range of 1 to 5 mm) axially rearward from a rear end 46 of the third parasitic conductor portion 43 of the second parasitic element 41, and a clearance (slight gap) is formed between the front end 45 of the first parasitic conductor portion 32 and the rear end 46 of the third parasitic conductor portion 43. A front end 45 of the second parasitic conductor portion 33 of the first parasitic element 15 is slightly spaced (in a range of 1 to 5 mm) axially rearward from a rear end 46 of the fourth parasitic conductor portion 44 of the second parasitic element 41, and a clearance (slight gap) is formed between the front end 45 of the second parasitic conductor portion 33 of the first parasitic element 15 and the rear end 46 of the fourth parasitic conductor portion 44 of the second parasitic element 41.

[0108] 8, the first and third parasitic conductors may be arranged facing each other with a space in the thickness direction of the wideband antenna with the first parasitic conductor on top and the third parasitic conductor on the bottom, and the second and fourth parasitic conductors may be arranged facing each other with a space in the thickness direction of the wideband antenna with the second parasitic conductor on top and the fourth parasitic conductor on the bottom. In this case, an insulator is interposed between the first and third parasitic conductors, and an insulator is interposed between the second and fourth parasitic conductors.

[0109] In the wideband antennas 10A to 10F, it is possible to freely set the axial length L1 of the first and second resonant conductor portions 22a, 22b of the resonant conductor 12 relative to the feed portion 20 of the unbalanced feed material 11 and the axial length L3 of the first and second ground conductor portions 15a, 15b of the ground conductor 13 relative to the parasitic portion 21 of the unbalanced feed material 11. In the wideband antennas 10A to 10F, only the length L1 of the first and second resonant conductor portions 22a, 22b relative to the feed portion 20 can be changed, and only the length L3 of the first and second ground conductor portions 25a, 25b relative to the parasitic portion 21 can be changed, or both of these lengths L1 and L3 can be changed.

[0110] The axial length L1 of the first and second resonant conductor parts 22a, 22b relative to the power supply part 20 may be changed by changing the lengths of the first and second resonant conductor parts 22a, 22b of the resonant conductor 12, by moving the fixing position of the fixing conductor 14 relative to the unbalanced power supply material 11 axially forward or backward, or by using both of them in combination. The axial length L3 of the first and second ground conductor parts 25a, 25b relative to the parasitic part 21 may be changed by changing the lengths of the first and second ground conductor parts 25a, 25b of the ground conductor 13, by moving the fixing position of the fixing conductor 14 relative to the unbalanced power supply material 11 axially forward or backward, or by using both of them in combination.

[0111] In the wideband antennas 10A to 10F, the relative band (used frequency band) can be freely shifted to a higher or lower side by changing at least one of the axial length L1 of the first and second resonant conductors 22a and 22b relative to the power supply unit 20 and the axial length L3 of the first and second ground conductors 25a and 25b relative to the parasitic unit 21. For example, when the length L1 is made longer than that shown in the figure, the resonance point between the power supply unit 20 and the resonant conductor 12 moves higher, and the relative band of the antennas 10A to 10F can be shifted to a higher side (higher position). Conversely, when the length dimension L1 is made shorter than that shown in the figure, the resonant wavelength between the power supply unit 20 and the resonant conductor 12 becomes longer, and the relative band of the antennas 10A to 10F can be shifted to a lower side (lower position). Furthermore, if the length L3 is made longer than that shown in the figure, the resonant wavelength between the parasitic section 21 and the ground conductor 13 becomes longer, and the relative bandwidth of the antennas 10A to 10F can be shifted lower (lower). Conversely, if the length L3 is made shorter than that shown in the figure, the resonance point between the parasitic section 21 and the ground conductor 13 moves higher, and thus the relative bandwidth of the antennas 10A to 10F can be shifted higher (higher).

[0112] In the wideband antennas 10A to 10F, by increasing the size (area) of the first and second power supply conductor sections 36, 37 of the power supply element 16, the shift of the resonance point between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b of the resonant conductor 12 to a higher level is made greater, and by reducing the size (area) of the first and second power supply conductor sections 36, 37 of the power supply element 16, the shift of the resonance point between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b of the resonant conductor 12 to a higher level is made smaller.

[0113] In the wideband antennas 10A to 10F, by increasing the size (area) of the first and second power supply conductor sections 36, 37 of the power supply element 16, the resonance point between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b of the resonant conductor 12 can be shifted significantly to a higher level, and by reducing the size (area) of the first and second power supply conductor sections 36, 37 of the power supply element 16, the resonance point between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b of the resonant conductor 12 can be shifted slightly to a higher level, thereby making it possible to fine-tune the shift of the fractional bandwidth to a higher level.

[0114] In the wideband antennas 10A to 10F, the radial separation dimension L2 between the central axis S1 (center of the power supply section 20) of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b (inner edges) of the resonant conductor 12 is in the range of 2 to 9 mm. If the separation dimension L2 is less than 2 mm, resonance between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b becomes insufficient, making it impossible to obtain multiple resonant frequencies, and making it impossible to widen the frequency band available in the antennas 10A to 10F. If the spacing dimension L2 exceeds 9 mm, not only will the fractional bandwidth (used frequency band) of the wideband antennas 10A to 10F saturate at its widest state, and the fractional bandwidth of the antennas 10A to 10F cannot be widened any further, but if the spacing dimension L2 is made too large, the resonance between the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b will become unstable within the frequency band, and it may not be possible to resonate the power supply section 20 of the unbalanced power supply material 11 and the first and second resonant conductor sections 22a, 22b.

[0115] By changing the separation dimension L2 within the above range, the wideband antennas 10A to 10F can freely adjust the width of the fractional bandwidth (used frequency band) of the antennas 10A to 10F, and can stabilize the frequency band in which the antennas resonate. Specifically, by increasing the separation dimension L2, the fractional bandwidth can be widened, and by decreasing the separation dimension L2, the fractional bandwidth can be narrowed, and the VSWR within the resonance band can be stabilized. In the wideband antennas 10A to 10F, the fractional bandwidth increases sharply as the separation dimension L2 increases from 2 mm, and the fractional bandwidth is widest when the separation dimension L2 is 9 mm. Even if the separation dimension L2 increases beyond that, the fractional bandwidth of the antennas 10A to 10F remains approximately constant. By setting the spacing dimension L2 in the range of 2 to 9 mm, the wideband antennas 10A to 10F optimize the resonance efficiency of radio waves between the power supply section 20 and the first and second resonant conductor sections 22a, 22b, allowing the power supply section 20 and the first and second resonant conductor sections 22a, 22b to resonate efficiently and significantly widening the relative bandwidth of the antennas 10A to 10F.

[0116] In the wideband antennas 10A to 10F, the distance L4 between the central axis S1 (center of the parasitic portion 21) of the unbalanced power supply member 11 and the first and second ground conductors 25a, 25b (inner edges) is in the range of 3 to 10 mm. In the antennas 10A to 10F, the distance L4 is set to be larger than the distance L2, or the distance L4 is set to be the same as the distance L2. If the distance L4 is less than 3 mm, resonance between the parasitic portion 21 of the unbalanced power supply member 11 and the first and second ground conductors 25a, 25b becomes insufficient, making it impossible to obtain multiple resonant frequencies, and making it impossible to widen the frequency band available in the antennas 10A to 10F. If the spacing dimension L4 exceeds 10 mm, not only will the usable frequency band of the antennas 10A-10F saturate at its widest state, and the frequency band of the antennas 10A-10F cannot be expanded any further, but if the spacing dimension L4 is made too large, the resonance between the non-power-fed portion 21 of the unbalanced power supply material 11 and the first and second ground conductor portions 25a, 25b will become unstable within the frequency band, and it may not be possible to resonate the power supply portion 21 of the unbalanced power supply material 11 and the first and second ground conductor portions 25a, 25b.

[0117] By changing the separation dimension L4 within the above range, the wideband antennas 10A to 10F can freely adjust the width of the fractional bandwidth (used frequency band) of the antennas 10A to 10F, and can stabilize the frequency band in which the antennas resonate. Specifically, by increasing the separation dimension L4, the fractional bandwidth can be widened, and by decreasing the separation dimension L4, the fractional bandwidth can be narrowed, and the VSWR within the resonance band can be stabilized. In the wideband antennas 10A to 10F, the fractional bandwidth increases sharply as the separation dimension L4 increases from 3 mm, and the fractional bandwidth is widest when the separation dimension L4 is 10 mm. Even if the separation dimension L4 increases beyond that, the fractional bandwidth of the antennas 10A to 10F remains approximately constant. By setting the spacing dimension L4 in the range of 3 to 10 mm, the wideband antennas 10A to 10F optimize the resonance efficiency of radio waves between the parasitic section 21 and the first and second ground conductor sections 25a, 25b, allowing the parasitic section 21 and the first and second ground conductor sections 25a, 25b to resonate efficiently and significantly widening the relative bandwidth of the antennas 10A to 10F.

[0118] In the wideband antennas 10A to 10F, the separation dimensions L2 and L4 are within the above-mentioned ranges, a high-frequency current is induced in the first and second resonant conductors 22a, 22b and the power supply section 20, so that the high-frequency current flows in the axial direction between the first and second resonant conductors 22a, 22b and the power supply section 20, a high-frequency current is induced in the first and second ground conductors 25a, 25b and the parasitic section 21, so that the high-frequency current flows in the axial direction between the first and second ground conductors 25a, 25b and the parasitic section 21, and a high-frequency current is induced between the first and second resonant conductors 22a, 22b (resonant conductor 12) and the unbalanced power supply material 11. The power supply section 20 resonates efficiently and reliably due to the axial high-frequency current induced in the conductor sections 22a, 22b and the power supply section 20, and the first and second ground conductor sections 25a, 25b (ground conductor 13) and the unbalanced power supply section 21 of the unbalanced power supply material 11 resonate efficiently and reliably due to the axial high-frequency current induced in the conductor sections 25a, 25b and the unbalanced power supply section 21, thereby obtaining multiple resonant frequencies that are adjacent to each other in succession in one direction and that partially overlap with each other.

[0119] In the wideband antennas 10A to 10F, a high-frequency current flows in the axial direction of the first feed conductor section 36 of the feed element 16, and a high-frequency current flows in the axial direction of the second feed conductor section 37 of the feed element 16, so that the first feed conductor section 36 of the feed element 15 and the first resonant conductor section 22a of the resonant conductor 12 resonate due to the axial high-frequency current induced in those conductor sections 22a, 36, and the second feed conductor section 37 of the feed element 16 and the second resonant conductor section 22b of the resonant conductor 12 resonate due to the axial high-frequency current induced in those conductor sections 22b, 37, thereby stabilizing the resonant frequency band.

[0120] In the wideband antennas 10A, 10C, and 10E, a high-frequency current is induced in the first ground conductor portion 25a, causing the high-frequency current to flow in one axial direction of the first ground conductor portion 25a, and a high-frequency current is induced in the first parasitic conductor portion 32 extending in the axial direction of the first parasitic element 15, causing the high-frequency current to flow in the other axial direction of the first parasitic conductor portion 32. A high-frequency current flows in the first parasitic conductor portion 32 in a direction opposite to the direction of the high-frequency current flowing in the first ground conductor portion 25a (one axial direction). Therefore, the high-frequency current flowing in one axial direction of the first ground conductor portion 25b and the high-frequency current flowing in the other axial direction of the first parasitic conductor portion 32 cancel each other out.

[0121] In the wideband antennas 10A, 10C, and 10E, a high-frequency current is induced in the second ground conductor portion 25b, causing the high-frequency current to flow in one axial direction of the second ground conductor portion 25b, and a high-frequency current is induced in the second parasitic conductor portion 33 extending in the axial direction of the second parasitic element 15, causing the high-frequency current to flow in the other axial direction of the second parasitic conductor portion 33. A high-frequency current flows in the second parasitic conductor portion 33 in a direction opposite to the direction of the high-frequency current flowing in the second ground conductor portion 25b (one axial direction). Therefore, the high-frequency current flowing in one axial direction of the second ground conductor portion 25b and the high-frequency current flowing in the other axial direction of the second parasitic conductor portion 33 cancel each other out.

[0122] In the wideband antennas 10B, 10D, and 10F, a high-frequency current is induced in the first ground conductor portion 25a, causing the high-frequency current to flow in one axial direction of the first ground conductor portion 25a, a high-frequency current is induced in the first parasitic conductor portion 32 extending in the axial direction of the first parasitic element 15, causing the high-frequency current to flow in the other axial direction of the first parasitic conductor portion 32, and a high-frequency current is induced in the third parasitic conductor portion 43 extending in the axial direction of the second parasitic element 41, causing the high-frequency current to flow in the other axial direction of the third parasitic conductor portion 43, causing the high-frequency current to flow in the first Because a high-frequency current flows through the parasitic conductor section 32 and the third parasitic conductor section 43 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the first ground conductor section 25a, the high-frequency current flowing in one axial direction of the first ground conductor section 25a and the high-frequency current flowing in the other axial direction of the first parasitic conductor section 32 cancel each other out, and the high-frequency current flowing in one axial direction of the first ground conductor section 25a and the high-frequency current flowing in the other axial direction of the third parasitic conductor section 43 cancel each other out.

[0123] In the wideband antennas 10B, 10D, and 10F, a high-frequency current is induced in the second ground conductor portion 25b, causing the high-frequency current to flow in one axial direction of the second ground conductor portion 25b, a high-frequency current is induced in the second parasitic conductor portion 33 extending in the axial direction of the first parasitic element 15, causing the high-frequency current to flow in the other axial direction of the second parasitic conductor portion 33, and a high-frequency current is induced in the fourth parasitic conductor portion 44 extending in the axial direction of the second parasitic element 41, causing the high-frequency current to flow in the other axial direction of the third parasitic conductor portion 44, A high-frequency current flows through the parasitic conductor section 33 and the fourth parasitic conductor section 44 in a direction opposite to the direction (one axial direction) of the high-frequency current flowing through the second ground conductor section 25b. Therefore, the high-frequency current flowing in one axial direction of the second ground conductor section 25b and the high-frequency current flowing in the other axial direction of the second parasitic conductor section 33 cancel each other out, and the high-frequency current flowing in one axial direction of the second ground conductor section 25b and the high-frequency current flowing in the other axial direction of the fourth parasitic conductor section 44 cancel each other out.

[0124] Fig. 14 is a diagram showing the correlation between VSWR (Voltage Standing Wave Ratio) and the band used in the wideband antennas 10A to 10F, and Fig. 15 is a Smith chart showing the impedance of the wideband antennas 10A to 10F. Figs. 16 and 17 are diagrams showing the electric field strength measured in the circumferential direction of three planes (XY plane, YZ plane, ZX plane) of the wideband antennas 10A to 10F. Fig. 16 shows the measurement result of the electric field strength in the circumferential direction (0° to 360°) of the XY plane antenna characteristic, and Fig. 17 shows the measurement result of the electric field strength in the circumferential direction (0° to 360°) of the YZ plane or ZX plane antenna characteristic.

[0125] As shown in Fig. 14, the wideband antennas 10A to 10F have a reflection coefficient VSWR (voltage standing wave ratio) of 2 to 3 in the fractional bandwidth (used frequency band) of about 100 MHz to about 10.0 GHz, and have a wide fractional bandwidth while maintaining a low VSWR (voltage standing wave ratio). As shown in Fig. 15, the impedance of the wideband antennas 10A to 10F is 50Ω, as shown in Fig. 16, the electric field strength (radio wave strength) in the circumferential direction (0° to 360°) of the XY plane antenna characteristic draws a nearly perfect circle, and as shown in Fig. 17, the electric field strength (radio wave strength) in the circumferential direction (0° to 360°) of the YZ plane or ZX plane antenna characteristic draws a glasses shape, and it is understood that the wideband antennas 10A to 10F have good omnidirectionality.

[0126] In the wideband antennas 10A to 10F, a high-frequency current is induced in the first and second resonant conductors 22a, 22b and the power supply section 20, so that the high-frequency current flows in the axial direction between the first and second resonant conductors 22a, 22b and the power supply section 20, a high-frequency current is induced in the first and second ground conductors 25a, 25b and the parasitic section 21, so that the high-frequency current flows in the axial direction between the first and second ground conductors 25a, 25b and the parasitic section 21, and a high-frequency current is induced in the first and second resonant conductors 22a, 22b and the power supply section 20. While first and second ground conductor parts 25a, 25b and parasitic part 21 resonate due to the axial high-frequency current induced in conductor parts 25a, 25b and parasitic part 21, a plurality of resonant frequencies can be obtained. Since the obtained plurality of resonant frequencies are adjacent to each other in a continuous manner in one direction and partially overlap with each other, the fractional bandwidth (from about 100 MHz to about 10.0 GHz) of antennas 10A to 10F can be significantly widened.

[0127] The wideband antennas 10A to 10F can be made to have a high radiation gain with a VSWR (voltage standing wave ratio) of 2 or more and 3 or less, and can transmit and receive radio waves in all bands of the relative band (approximately 100 MHz to approximately 10.0 GHz) in which they can be used. Therefore, it is possible to make the antennas 10A to 10F usable in broadband and capable of transmitting and receiving broadband radio waves using only one antenna.

[0128] In the wideband antennas 10A to 10F, a high-frequency current is induced in the first feed conductor portion 36 of the feed element 16, which is formed with a plurality of step-like first step portions 39, so that the high-frequency current flows in the axial direction from the rear end to the front end of the first feed conductor portion 36, and a high-frequency current is induced in the second feed conductor portion 37 of the feed element 16, which is formed with a plurality of step-like second step portions 40, so that the high-frequency current flows in the axial direction from the rear end to the front end of the second feed conductor portion 37. The first step portions 39 of the first power supply conductor portion 36 and the first resonant conductor portion 22a of the resonant conductor 12 resonate in multiple resonances due to the axial high-frequency current induced in the conductor portions 22a and 36, and the second step portions 40 of the second power supply conductor portion 37 and the second resonant conductor portion 22b of the resonant conductor 12 resonate in multiple resonances due to the axial high-frequency current induced in the conductor portions 22b and 37, and the conductor portions 22a, 22b, 36, and 37 resonate in multiple resonances. By this resonance, multiple resonant frequencies with strong electric field strength (radio wave strength) in different bands can be obtained, and not only can wideband radio waves be transmitted over a wide range and long distances while maintaining a predetermined electric field strength (increasing radiation gain), but also the first and second feed conductor portions 36, 37 of the feed element 16, in which multiple first and second step portions 39, 40 are formed, resonate with the first and resonant conductor portions 22a, 22b of the resonant conductor 12, thereby stabilizing the resonant frequency band. Even if an obstacle made of a conductor such as metal is close to or present near the antennas 10A-10F, the resonance point of the antennas 10A-10F will not fluctuate, and changes in the frequency band of the antennas 10A-10F can be prevented, the conversion efficiency of converting high-frequency current into radio waves can be maintained, and radio waves in the frequency band as designed can be transmitted and received.

[0129] In the wideband antennas 10A, 10C, and 10 shown in FIGS. 1, 5, and 10, a high-frequency current is induced in the first ground conductor portion 25a, so that the high-frequency current flows in one axial direction of the first ground conductor portion 25a, a high-frequency current is induced in the first parasitic conductor portion 32, so that the high-frequency current flows in the other axial direction of the first parasitic conductor portion 32, and the high-frequency current flowing in one axial direction of the first ground conductor portion 25a and the high-frequency current flowing in the other axial direction of the first parasitic conductor portion 32 cancel each other out, a high-frequency current is induced in the second ground conductor portion 25b, so that the high-frequency current flows in one axial direction of the second ground conductor portion 25b, and a high-frequency current is induced in the second parasitic conductor portion 33, so that the high-frequency current flowing in one axial direction of the second ground conductor portion 25b cancels out. Since a high-frequency current flows in the other axial direction of antenna 3, and the high-frequency current flowing in one axial direction of second ground conductor portion 25b and the high-frequency current flowing in the other axial direction of second parasitic conductor portion 33 cancel each other out, unwanted currents are cancelled out and the radiation gain in antennas 10A, 10C, 10E is improved. A strong electromagnetic field of linear polarization can be generated in which the vibration direction of the electric field is parallel to the axial direction of antennas 10A, 10C, 10E. This allows antennas 10A, 10C, 10E to have high radiation gain and to transmit wideband radio waves over a wide range and long distances while maintaining a predetermined electric field strength (radio wave strength) (increasing radiation gain).

[0130] In the wideband antennas 10B, 10D, and 10F shown in FIGS. 4, 8, and 13, a high-frequency current is induced in the first ground conductor portion 25a, causing the high-frequency current to flow in one axial direction of the first ground conductor portion 25a; a high-frequency current is induced in the first parasitic conductor portion 32, causing the high-frequency current to flow in the other axial direction of the first parasitic conductor portion 32; a high-frequency current is induced in the third parasitic conductor portion 43, causing the high-frequency current to flow in the other axial direction of the third parasitic conductor portion 43; the high-frequency current flowing in one axial direction of the first ground conductor portion 25a and the high-frequency current flowing in the other axial direction of the first parasitic conductor portion 32 and the third parasitic conductor portion 43 cancel each other out; a high-frequency current is induced in the second ground conductor portion 25b, causing the high-frequency current to flow in one axial direction of the second ground conductor portion 25b; and a high-frequency current is induced in the second parasitic conductor portion 33, causing the high-frequency current to flow in the other axial direction of the second parasitic conductor portion 33. As a result, a high-frequency current flows in the other axial direction of antenna 10B, 10D, 10F, and a high-frequency current is induced in fourth parasitic conductor part 44, causing a high-frequency current to flow in the other axial direction of fourth parasitic conductor part 44. The high-frequency current flowing in one axial direction of second ground conductor part 25b and the high-frequency current flowing in the other axial direction of second parasitic conductor part 33 and fourth parasitic conductor part 44 cancel each other out, thereby canceling out unnecessary currents and improving the radiation gain in antennas 10B, 10D, 10F. A strong electromagnetic field of linear polarization whose electric field vibration direction is parallel to the axial direction of antennas 10B, 10D, 10F can be generated. This allows antennas 10B, 10D, 10F to have high radiation gain and to transmit wideband radio waves over a wide range and long distances while maintaining a predetermined electric field strength (radio wave strength) (increasing radiation gain).

[0131] In the wideband antennas 10E, 10F shown in Figures 9 and 12, the dielectric substrate 47 having a predetermined dielectric constant functions as a capacitive element, so that the first and second resonant conductors 22a, 22b and the power supply section 20 joined to the dielectric substrate 47 easily resonate due to the axial high-frequency current induced in the conductors 22a, 22b and the power supply section 20, while the first and second ground conductors 25a, 25b and the non-power-fed section 21 joined to the dielectric substrate 47 resonate due to the axial high-frequency current induced in the conductors 25a, 25b and the non-power-fed section 21, thereby making it possible to obtain multiple resonant frequencies. The obtained multiple resonant frequencies are adjacent to each other in a continuous manner in one direction and partially overlap with each other, so that the fractional bandwidth (usable frequency band) of the antennas 10E, 10F can be significantly widened. [Explanation of symbols]

[0132] 10A Wideband Antenna 10B Wideband Antenna 10C Wideband Antenna 10D Wideband Antenna 10E Wideband Antenna 10F Wideband Antenna 11 Unbalanced feed material 12 Resonant conductor 13 Ground Conductor 14 Fixed conductor 15 First parasitic element 16 Feed element 17 First Conductor 18 First Insulator 19 Second Conductor 20 Power supply unit 21 Unpowered section 22a First resonant conductor 22b Second resonant conductor 23 Parallel part 24 Extending part 25a First ground conductor 25b Second ground conductor 26a Slope section 26b Slope section 27a Straight section 27b straight part 28 Parallel part 29 Extending part 30 Connectors 31 First parasitic fixed part 32 First non-powered conductor section 33 Second non-powered conductor section 34 Front end 35 Power supply fixed part 36 First power supply conductor section 37 Second power supply conductor section 38 Rear end 39 1st step part 40 2nd step part 41 Second parasitic element 42 Second parasitic fixed part 43 Third non-powered conductor section 44 Fourth non-powered conductor section 45 Front end 46 Rear end 47 Dielectric Substrate 48 One side (top) 49 Other side (bottom) L1 Axial length L2 Radial spacing L3 Axial length L4 Radial spacing L5 Axial length L6 Radial clearance dimension L7 Axial length L8 Radial clearance dimension S1 center axis

Claims

1. The unbalanced power supply member has a power supply section of a predetermined length and a parasitic section of a predetermined length connected to the power supply section and extending axially rearward from the power supply section, a resonant conductor that resonates with the power supply section of the unbalanced power supply member, a grounding conductor that resonates with the parasitic section of the unbalanced power supply member, and a fixing conductor that is located between the resonant conductor and the grounding conductor and is electrically connected to the unbalanced power supply member via a fixing means, the resonant conductor being spaced radially outward from the unbalanced power supply member and extending axially forward from the fixing conductor in parallel with the power supply section, a second resonant conductor located at a position opposite to the first ground conductor across the unbalanced power supply member, spaced radially outward from the unbalanced power supply member, and extending axially forward from the fixing conductor in parallel to the power supply section, the ground conductor being formed from a first ground conductor located at a position opposite to the first ground conductor across the unbalanced power supply member, spaced radially outward from the unbalanced power supply member, and extending axially rearward from the fixing conductor in parallel to the power supply section, the wideband antenna comprising: a first parasitic element located between the first ground conductor and the second ground conductor, the first parasitic element being formed from: a first parasitic fixed part electrically connected to the unbalanced feed material via a fixing means; a first parasitic conductor located between the unbalanced feed material and the first ground conductor and extending axially forward from the first parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the first ground conductor; and a second parasitic conductor located between the unbalanced feed material and the second ground conductor and extending axially forward from the first parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the second ground conductor.

2. 2. The wideband antenna according to claim 1, wherein the first and second resonant conductor portions of the resonant conductor are in an axisymmetric relationship with respect to a central axis of the unbalanced power feed material, the first and second ground conductor portions of the ground conductor are in an axisymmetric relationship with respect to the central axis of the unbalanced power feed material, and the first and second parasitic conductor portions of the first parasitic element are in an axisymmetric relationship with respect to the central axis of the unbalanced power feed material.

3. 3. The wideband antenna according to claim 1, wherein the axial length of the first parasitic conductor portion and the second parasitic conductor portion of the first parasitic element is λ / 8 to λ / 16.

4. 4. The wideband antenna according to claim 1, further comprising: a second parasitic element located axially forward of the first parasitic element between the first ground conductor and the second ground conductor and facing the first parasitic element, the second parasitic element being formed from: a second parasitic fixed part electrically connected to the unbalanced feed material via a fixing means; a third parasitic conductor located between the unbalanced feed material and the first ground conductor and extending axially rearward from the second parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the first ground conductor; and a fourth parasitic conductor located between the unbalanced feed material and the second ground conductor and extending axially rearward from the second parasitic fixed part in parallel to the parasitic part while being spaced radially outward from the unbalanced feed material and radially inward from the second ground conductor.

5. 5. The wideband antenna according to claim 4, wherein the third parasitic conductor portion and the fourth parasitic conductor portion of the second parasitic element are in an axis-symmetric relationship with respect to a central axis of the unbalanced feed material, and in the wideband antenna, the axial lengths of the first parasitic conductor portion and the second parasitic conductor portion of the first parasitic element are λ / 8 to λ / 16, and the axial lengths of the third parasitic conductor portion and the fourth parasitic conductor portion of the second parasitic element are λ / 8 to λ / 16.

6. 6. The wideband antenna according to claim 4 or 5, wherein a first parasitic conductor portion of the first parasitic element and a third parasitic conductor portion of the second parasitic element are arranged opposite and spaced apart in a thickness direction of the wideband antenna, with one of the conductor portions being on top and the other being on the bottom, and a second parasitic conductor portion of the first parasitic element and a fourth parasitic conductor portion of the second parasitic element are arranged opposite and spaced apart in a thickness direction of the wideband antenna, with one of the conductor portions being on top and the other being on the bottom.

7. 7. A wideband antenna according to claim 4, wherein a front end of a first parasitic conductor section of the first parasitic element faces a rear end of a third parasitic conductor section of the second parasitic element at a slight axial rearward distance, and a front end of a second parasitic conductor section of the first parasitic element faces a rear end of a fourth parasitic conductor section of the second parasitic element at a slight axial rearward distance.

8. 8. The wideband antenna according to claim 1, further comprising a power supply element shaped like a plate having a predetermined area and positioned axially forward of the resonant conductor, the power supply element having a power supply fixing part electrically connected to the power supply part, a first power supply conductor part of a predetermined area extending radially outward from the power supply fixing part and positioned axially forward of a first resonant conductor part of the resonant conductor, and a second power supply conductor part of a predetermined area extending radially outward from the power supply fixing part and positioned axially forward of a second resonant conductor part of the resonant conductor.

9. 9. The wideband antenna according to claim 8, wherein the first power supply conductor is formed with a plurality of first step portions arranged in a stepped shape from the rear end to the front end of the first power supply conductor, and the second power supply conductor is formed with a plurality of second step portions arranged in a stepped shape from the rear end to the front end of the second power supply conductor.

10. 10. The wideband antenna according to claim 9, wherein the first and second feed conductors of the feed element are in an axisymmetric relationship with respect to a central axis of the unbalanced feed material.

11. 11. The wideband antenna of claim 10, wherein the unbalanced power supply material is formed from a first conductor extending in the axial direction, an insulator covering the outer peripheral surface of the first conductor, and a second conductor covering the outer peripheral surface of the insulator and extending in the axial direction, the power supply portion of the unbalanced power supply material is formed from the first conductor, the non-power supply portion of the unbalanced power supply material is formed from the first and second conductors and the insulator, the fixing conductor is electrically connected to the second conductor, and the power supply element is electrically connected to the first conductor.

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