ANTENNA SYSTEM

Abstract

Antenna system, comprehensive: a chamber shielded against electromagnetic waves; a loop-shaped transmitting antenna consisting of a metallic wire and arranged in the chamber shielded against electromagnetic waves such that a loop surface of the loop-shaped transmitting antenna faces a ground plane; a feed cable designed to feed an AM broadcast signal; wherein a feed wire of the feed cable is connected to the transmitting antenna and a ground wire of the feed cable is connected to the ground plane.

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to an antenna device used for a receiver sensitivity evaluation device in an AM radio receiver antenna.

[0002] Priority is claimed over the Japanese patent application No. 2018-056086 filed on March 23, 2018, the contents of which are incorporated herein by reference. Description of the related prior art

[0003] Generally, antenna systems for receiving AM and FM radio broadcasts are installed in vehicles. Vehicle antenna systems are broadly classified into roof-mounted antennas, glass antennas, and film antennas. These antenna systems are designed to improve both reception sensitivity and aesthetics. Reception sensitivity is defined as the "lowest received input power that can ensure the necessary reception quality for communication" and is one of the key parameters that determine a receiver's performance.

[0004] The receiving sensitivity of an antenna system for receiving in-vehicle AM ​​radio (with a carrier frequency of approximately 500 kHz to 2 MHz) must be evaluated not only for the antenna system itself, but also for the vehicle's internal state, where the antenna system is installed. For evaluation in the vehicle's internal state, the vehicle is generally placed in an anechoic chamber shielded from electromagnetic waves to eliminate the influence of external waves and subjected to a receiving sensitivity test. A metallic straight antenna is attached to a transmitting antenna that is in use at the time of evaluation in this vehicle's internal state. This transmitting antenna is positioned on a side wall or similar surface within the anechoic chamber, and the receiving sensitivity of the antenna system installed in the vehicle is measured.Here, electromagnetic waves from actual AM radio broadcasting are plane waves, and it is desirable that the electromagnetic waves radiated by a transmitting antenna have a uniform electric field intensity throughout the entire vehicle.

[0005] For example, the technique described in patent document 1 is known as a receive sensitivity evaluation technique for a conventional AM broadcast receiving antenna. In the conventional technique described in patent document 1, a copper wire with a total length of 10 m is used as a transmitting antenna, and the transmitting antenna is arranged above a vehicle and in a shielded room in which the wall surfaces, other than the actual floor, are insulated from the wall surfaces by an insulator.Furthermore, a coaxial cable with a characteristic impedance of 50 Ω is used to deliver power to a transmitting antenna, and one side of the coaxial cable is connected to the transmitting antenna via a 25 Ω resistor and a coil, the other side of the coaxial cable is connected to the wall surface of the shielded room, and the wall surface of the shielded room is connected to ground using a grounding wire. [Patent documents]

[0006] [Patent document 1] Unexamined Japanese patent application, first publication no. H2-285268 BRIEF DESCRIPTION OF THE INVENTION

[0007] The lengths of a metallic straight antenna, which is the conventional transmitting antenna described above and detailed in Patent Document 1, are determined individually, for example, under the condition that the size of an anechoic chamber is present, such as that possessed by a manufacturer of an AM broadcast transmitting antenna device or a manufacturer of a vehicle with an AM broadcast receiving antenna device installed therein. Furthermore, in the conventional technique described above and detailed in Patent Document 1, it is particularly important to treat the outer conductor of the coaxial cable used to supply power to the metallic straight antenna, which is the transmitting antenna. If the treatment of the outer conductor is not adequate, it is unlikely that a uniform electric field intensity can be obtained in the electromagnetic waves radiated by the transmitting antenna.

[0008] As described above, in the conventional technique described in patent document 1, it is conceivable that the evaluation result for the receive sensitivity of the AM broadcast receiving antenna may vary due to non-uniformity in the length of the metallic straight antenna, which is the transmitting antenna, and improper processing of the outer conductor of the coaxial cable used for power supply. For this reason, it is necessary for an evaluator to optimize the evaluation conditions, such as the location where the receive sensitivity of an AM broadcast receiving antenna is evaluated and the position where an AM broadcast receiving antenna system is installed in a vehicle.

[0009] The present invention was undertaken in view of such circumstances, and one object of the present invention is to provide an antenna device that can form a plane on which an electric field intensity of an AM broadcast wave is uniformized, for example with respect to an evaluation area of ​​the AM broadcast receiving antenna device installed in a device such as a vehicle.

[0010] One aspect of the present invention is an antenna device comprising: a chamber shielded against electromagnetic waves; a loop-shaped transmitting antenna consisting of a metallic wire and arranged in the chamber shielded against electromagnetic waves such that a loop surface of the loop-shaped transmitting antenna faces a ground plane; a feed cable configured to feed an AM broadcast signal; wherein a feed wire of the feed cable is connected to the transmitting antenna and a ground wire of the feed cable is connected to the ground plane.

[0011] According to the present invention, an effect is achieved in which it is possible to form a plane in which an electric field intensity of an AM radio wave is uniformized with respect to an evaluation area of ​​the AM radio receiving antenna device installed in a device such as a vehicle. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram of a basic structure of an antenna device used for a receiver sensitivity evaluation device in an AM broadcast receiving antenna according to an embodiment of the present invention. Fig. Figure 2 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 3 is a diagram showing an example of an evaluation condition according to the embodiment of the present invention. Fig. Figure 4 is a diagram showing an example of an evaluation condition according to the embodiment of the present invention. Fig. 5A and Fig. Figure 5B shows diagrams that demonstrate the evaluation results of the uniformity of the electric field according to the embodiment of the present invention. Fig. 6A and Fig. Figure 6B shows diagrams that demonstrate the evaluation results of the uniformity of the electric field according to the embodiment of the present invention. Fig. 7A and Fig. 7B are diagrams that show a mirror image principle of an electromagnetic field. Fig. Figure 8 is a diagram showing the uniformity of the electric field under an evaluation condition without a ground plane. Fig. Figure 9 is a diagram showing the uniformity of the electric field under an evaluation condition without mass on a ground plane. Fig. Figure 10 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 11 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 12 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 13 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 14 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 15 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 16 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 17 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 18 is a diagram showing an example of an evaluation condition according to the embodiment of the present invention. Fig. Figure 19 is a diagram showing an example of an evaluation condition according to the embodiment of the present invention. Fig. Figure 20 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. 21A and Fig. Figure 21B shows diagrams that demonstrate the evaluation results of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 22 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 23 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 24 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 25 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 26 is a diagram showing an example of a transmitting antenna according to the embodiment of the present invention. Fig. Figure 27 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 28 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 29 is a diagram showing an example of a mass-equivalent soil according to the embodiment of the present invention. Fig. Figure 30 is a diagram showing an evaluation result of the uniformity of the electric field according to the embodiment of the present invention. Fig. Figure 31 is a diagram showing an application example of an echo-free chamber according to the embodiment of the present invention. Fig. Figure 32 is a diagram showing an example of the construction of a measurement-based system in a receiver sensitivity evaluation device in an AM broadcast receiving antenna according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the present invention are described in detail below with reference to the drawings. [First embodiment]

[0013] Fig. Figure 1 is a schematic diagram of a basic structure of an antenna device used for a receive sensitivity evaluation device in an AM broadcast receiving antenna associated with the present invention. A chamber 7 is a chamber shielded against electromagnetic waves, such as an anechoic chamber or a shielded room. Within the chamber 7, a loop-shaped transmitting antenna formed from a metallic wire 1 is arranged such that one loop surface faces a ground plane 6.

[0014] In the following, the loop-shaped transmitting antenna, which consists of the metallic wire 1, will in some cases be referred to as "a transmitting antenna 1". The loop surface of the transmitting antenna 1 and the ground plane 6 can be parallel. Here, the term "parallel" may imply a certain deviation. The transmitting antenna 1 is positioned at a height h above the ground plane 6.

[0015] Furthermore, a feed line of a feed cable 3, configured to deliver an AM broadcast signal output by an AM broadcast signal source 2, is connected to a feed point 4 of the transmitting antenna 1, and a ground wire of the feed cable 3 is connected to a ground point 5 of the ground plane 6. The carrier frequency of the AM broadcast signal is in the range of approximately 500 kHz to 2 MHz. The feed cable 3 can be a coaxial cable. If the feed cable 3 is a coaxial cable, an inner conductor of the coaxial cable is connected to the feed point 4 of the transmitting antenna 1, and an outer conductor of the coaxial cable is connected to the ground point 5 of the ground plane 6.

[0016] It should be noted that it is desirable for a wall surface of chamber 7 other than the ground plane 6 to be formed from a ferrite tile radio wave absorber or a composite radio wave absorber consisting of a ferrite tile and a dielectric loss body.

[0017] Fig. Figure 2 is a diagram showing an example of the transmitting antenna associated with the present invention. The Fig. The transmitting antenna shown in Figure 2 is formed in a rectangular loop shape using the metallic wire 1. Fig. Figure 2 is a size of a rectangular loop transmitting antenna set such that the length of one side (a side extending in the x-direction in the drawing), where the feed point 4 is located, is set to 9.0 m, and the length of another side (a side extending in the y-direction in the drawing) is set to 10.8 m. Furthermore, AWG3 (one diameter: 5.827 mm), which is an American Wire Gauge standard, is used as the metallic wire 1. [Effect of grounding on a mass plane]

[0018] Here, an effect of grounding on a mass plane is described based on a specific evaluation result.

[0019] Experiments are conducted under the evaluation condition in Fig. 3 and the evaluation condition in Fig. 4. The process is carried out and electric field intensities are evaluated.

[0020] At the in Fig. The evaluation condition shown in section 3 is within the range shown in Fig. 1 shown chamber 7 which in Fig. The rectangular loop transmitting antenna 1, shown above and described above, is arranged parallel to the ground plane 6 at a height (h = 5 m) above the ground plane 6. A coaxial cable is used as the feed cable 3. Hereinafter, a coaxial cable that serves as a feed cable will be referred to as "a coaxial cable 3".

[0021] As in Fig. As shown in Figure 3, an inner conductor of the coaxial cable 3, through which an AM broadcast signal output by the AM broadcast signal source 2 is supplied, is connected to the feed point 4 of the transmitting antenna 1, and an outer conductor of the coaxial cable 3 is connected to the ground point 5 of the ground plane 6.

[0022] Although the in Fig. The evaluation condition shown in section 4 is the same as the one in... Fig. The evaluation conditions shown in section 3 differ from those shown in the previous section. Fig. 4 evaluation conditions shown and those in Fig. The evaluation condition shown in section 3 is that the outer conductor of the coaxial cable 3 is in the Fig. The evaluation condition shown in section 4 is not connected to the mass plane 6.

[0023] A in Fig. 3 and Fig. The electric field intensity evaluation area 8 shown in Figure 4 is an area with the transmitting antenna 1 as its center, at a height of 1.5 m from the ground plane 6, with an area of ​​6 m × 6 m square, and with a grid-like structure where each section of the area is 0.5 m square. A measurement of the maximum electric field intensity in the evaluation area 8 is calibrated to a reference value. A difference is calculated between a measurement of an electric field intensity in a section other than the section with the maximum electric field intensity and the measurement (a reference value) of the maximum electric field intensity. This calculated difference is used as a value indicating the uniformity of the electric field.The uniformity of the electric field refers to a deviation between a maximum and a minimum value of an electric field intensity with respect to an evaluation surface.

[0024] Fig. 5A and Fig. 5B are diagrams showing the evaluation results of the uniformity of the electric field under the evaluation condition of Fig. Show 3. Fig. Figure 5A shows the uniformity of the electric field in the evaluation area 8 when a carrier frequency of an AM broadcast signal is 500 kHz. Fig. Figure 5B shows the uniformity of the electric field in the evaluation area 8 when a carrier frequency of an AM broadcast signal is 1.75 MHz. Fig. 6A and Fig. 6B are diagrams showing the evaluation results of the uniformity of the electric field under the evaluation condition of Fig. Show 4. Fig. Figure 6A shows the uniformity of the electric field in the evaluation area 8 when a carrier frequency of an AM broadcast signal is 500 kHz. Fig. Figure 6B shows the uniformity of the electric field in the evaluation area 8 when a carrier frequency of an AM broadcast signal is 1.75 MHz.

[0025] At the in Fig. 5A and Fig. 5B shown uniformity of the electric field (the evaluation condition of Fig. 3 with mass on the ground plane 6) the uniformity of the electric field is approximately 5.5 dB when the carrier frequency of Fig. 5A 500 kHz, the uniformity of the electric field is approximately 3.7 dB when the carrier frequency is Fig. 5B is 1.75 MHz and the difference between electric field intensities in the evaluation area 8 is small. On the other hand, in the Fig. 6A and Fig. 6B shown uniformity of the electric field (the evaluation condition of Fig. 4 without mass on the ground plane 6) the uniformity of the electric field approximately 17.7 dB both when the carrier frequency of Fig. 6A 500 kHz is also the case when the carrier frequency is of Fig. 6B is 1.75 MHz and a very large difference between electric field intensities occurs in the evaluation area 8.

[0026] The uniformity of the electric field under the evaluation condition without mass on the ground plane 6 can be determined on the basis of a mirror image principle of a Fig. 7A and Fig. The electromagnetic field shown in 7B will be explained.

[0027] It is assumed that an electric field generated by an electric current flowing through the rectangular-loop transmitting antenna formed by the metallic wire 1 contains a horizontal component E1 parallel to the ground plane 6 and a vertical component E2 perpendicular to the ground plane 6. Furthermore, as with the electric field, it is assumed that a magnetic field generated by an electric current flowing through the rectangular-loop transmitting antenna formed by the metallic wire 1 contains a horizontal component H1 parallel to the ground plane 6 and a vertical component H2 perpendicular to the ground plane 6.

[0028] The horizontal and vertical components of the electromagnetic field generated on the ground plane 6 form a mirror-image electromagnetic field component on a bottom surface of the ground plane 6 in order to satisfy a boundary condition of the ground plane 6.

[0029] The horizontal component of the mirror-image electric field is E3 in opposite phase, and the vertical component is E4 in phase. Similarly, the horizontal component of a mirror-image magnetic field is H3 in phase, and the vertical component is H4 in opposite phase. It should be noted that the amplitudes of mirror-image electromagnetic fields are essentially the same if the ground plane 6 is a metal.

[0030] Here, one imagines an electric field generated by an electric current flowing through the rectangular loop transmitting antenna formed by the metallic wire 1, primarily as a horizontal component. Conversely, one imagines a magnetic field generated by an electric current flowing through the rectangular loop transmitting antenna formed by the metallic wire 1, primarily as a vertical component.

[0031] When the evaluation condition is considered without a mass on the ground plane 6, an inverse electric field and an inverse magnetic field have opposite phases, and electromagnetic fields, combined by the ground plane 6, cancel each other out and become very small. Therefore, in a rectangular loop formed by the metallic wire 1 located near and directly below the feed point 4, the electric field intensity becomes stronger, but in a direction opposite to the feed point 4 from a central axis of the rectangular loop, the electric field intensity becomes very small, and consequently, the uniformity of the electric field is very high.

[0032] Furthermore, according to the idea of ​​the in Fig. 8 and Fig. The uniformity of the electric field under an evaluation condition with mass and an evaluation condition without mass on the mass plane 6 can be explained by the 9 mirror images shown.

[0033] The uniformity of the electric field under an evaluation condition with ground on the ground plane 6 is determined with reference to Fig. 8 described. As in Fig. As shown in Figure 8, an electric current flowing from the AM broadcast signal source 2 of a real image to a rectangular-loop transmitting antenna 9 is assumed to be i. Furthermore, an electric current flowing to a rectangular-loop transmitting antenna 10 of the mirror image through the ground plane 6 is set to i'. The electric currents i and i' flow in a vertical direction, and the electric currents are generated due to a potential difference. Thus, the directions in which the electric currents i and i' flow are consistent with reference to Fig. 7A agree with each other. For this reason, the rectangular loop transmitting antenna 9 of a real image and the rectangular loop transmitting antenna 10 of a mirror image can be considered as parallel-plate capacitors, and an electric field is generated uniformly in the vertical direction. Consequently, the uniformity of the electric field is a small value.

[0034] Next, the uniformity of the electric field under an evaluation condition without mass on the ground plane 6 is examined with reference to Fig. 9 described. As in Fig. As shown in Figure 9, the AM broadcast signal source 2 of a real image has no ground connection to the ground plane 6. Therefore, one direction of an electric current i flowing from the AM broadcast signal source 2 of the real image to the rectangular-loop transmitting antenna 9 is a horizontal direction. For this reason, with reference to Fig. 7A is the direction of an electric current i' flowing from the AM broadcast signal source 11 of the mirror image to the rectangular loop transmitting antenna 10, opposite to the electric current i. That is, a magnetic field generated by the rectangular loop transmitting antenna 9 and a magnetic field generated by the rectangular loop transmitting antenna 10 cancel each other out, and thus the electromagnetic fields are very small. Consequently, the uniformity of the electric field is of a high value.

[0035] In the above description of the Fig. 7A, Fig. 7B, Fig. 8 and Fig. 9 according to a first embodiment, as in Fig. 5A and Fig. As shown in Figure 5B, an effect is achieved in which it is possible to form a plane on which an electric field intensity of an AM radio wave is uniformized with respect to an evaluation area of ​​the AM radio receiving antenna device.

[0036] Next, we will show Fig. 10. The uniformity of the electric field (uniformity) of carrier frequencies from 500 kHz to 2 MHz, when sizes of the evaluation area 8 from a square 6 m×6 m to a square 5 m×5 m and a square 4 m×4 m under the in Fig. The evaluation condition shown in point 3 can be changed. Fig. 10 corresponds to a curve line FU1 area1 In a case where one size of the evaluation area 8 is a square 6 m×6 m, a curve FU1 area2 This corresponds to a case where the size of the evaluation area 8 is a square 5 m×5 m, and a curve FU1 area3 This corresponds to a case where the evaluation area 8 is a square of 4 m × 4 m. Each curve represents a maximum value of the uniformity of the electric field in the evaluation area 8.

[0037] The in Fig. The uniformity of the electric field shown in Figure 10 is within 6 dB when the size of the evaluation area 8 is a square of 6 m × 6 m, within 4 dB when the size of the evaluation area 8 is a square of 5 m × 5 m, and within 3 dB when the size of the evaluation area 8 is a square of 4 m × 4 m. Based on the above description, according to the first embodiment, even under the evaluation condition where the carrier frequencies are from 500 kHz to 2 MHz and the sizes of the evaluation area 8 are from a square of 6 m × 6 m to a square of 4 m × 4 m, an effect is achieved in which it is possible to form a plane on which the electric field intensity of the AM broadcast wave is uniform with respect to the evaluation area of ​​the AM broadcast receiving antenna device.

[0038] As described above, according to the first embodiment, it is possible to create a plane on which the electric field intensity of the AM radio wave is uniformed with respect to the evaluation area of ​​the AM radio receiving antenna device, which is installed in a device such as a vehicle. Thus, the present invention can contribute to the precise evaluation of the receiving sensitivity of the AM radio receiving antenna. [Second embodiment]

[0039] A second embodiment associated with the present invention is described below. In the second embodiment, for the purpose of further improving the uniformity of the electric field, various modified examples based on the rectangular loop transmitting antenna formed from the metallic wire 1 are provided. Fig. 2 shown in the first embodiment.

[0040] One in Fig. The transmitting antenna shown in Figure 11 is obtained by further providing a grid-like structure formed from a metallic wire within the rectangular loop consisting of the metallic wire 1. The interval between sections of the grid is p.

[0041] One in Fig. The transmitting antenna shown in Figure 12 is obtained by further providing a cross-shaped structure, wherein opposite angles of the rectangular loop are connected to each other using a metallic wire within a rectangular loop consisting of the metallic wire 1. A Fig. The transmitting antenna shown in Figure 13 is obtained by further providing a rectangular loop structure using a metallic wire within a rectangular loop in the Fig. 12 shown transmitting antennas.

[0042] One in Fig. The transmission antenna shown in section 14 is further enhanced by the provision of several more (in one example of Fig. 14 two) rectangular loop-shaped structures using a metallic wire within a rectangular loop in the in Fig. The transmitting antenna shown in section 12 is obtained. Fig. 13 and Fig. The 14 transmitting antennas shown have several rectangular loops arranged at arbitrary intervals.

[0043] One in Fig. The transmitting antenna shown in Figure 15 is formed in a concave rectangular loop shape using the metallic wire 1. As shown in Figure 15. Fig. As shown in Figure 15, a gap with a width g is provided on one side opposite a side on which the feeding point 4 is located.

[0044] One in Fig. The transmitting antenna shown in Figure 16 is formed in several concave rectangular loop shapes using the metallic wire 1. As shown in Figure 16. Fig. As shown in Figure 16, a gap with a width g is provided on one side opposite a side on which the feeding point 4 is located.

[0045] The second embodiment is described based on a specific evaluation result.

[0046] One of the transmitting antennas used for evaluation is a lattice structure within the transmitting antenna. Fig. In the rectangular loop shown in Figure 11, the length of one side, on which the feed point 4 is located (a side extending in the x-direction in the drawing), is set to 9.1 m, the length of another side (a side extending in the y-direction in the drawing) is set to 10.5 m, and an interval p between sections of a grid is set to 0.7 m. Additionally, AWG 3, which is an American Wire Gauge standard, is used as the metallic wire 1. Sections of the grid are configured to have a structure in which the sections are electrically interconnected.

[0047] One of the transmitting antennas used for this evaluation is the transmitting antenna with a cross-shaped structure within the in Fig. In the rectangular loop shown in Figure 12, the length of one side, where the feed point 4 is located (a side extending in the x-direction in the drawing), is set to 9.0 m, and the length of another side (a side extending in the y-direction in the drawing) is set to 10.8 m. Additionally, AWG 3, which is an American Wire Gauge standard, is used as the metallic wire 1.

[0048] Rectangular loops and crosses are set up so that they have a structure in which the rectangular loops and the crosses are electrically connected to each other.

[0049] One of the transmitting antennas used for this evaluation is the transmitting antenna with a [missing information] Fig. In Figure 15, the concave rectangular loop structure is designed with the length of one outer circumferential side, where feed point 4 is located (a side extending in the x-direction in the drawing), set to 9.0 m, and the length of another outer circumferential side (a side extending in the y-direction in the drawing) set to 10.8 m. Additionally, a concave rectangular loop is formed in which the metallic wire 1 is folded back inwards on a side facing feed point 4, creating a gap with a width g. The conditions "w1=w2=w3=0.9 m" and "g=0.9 m" are both satisfied. Furthermore, AWG3, an American Wire Gauge standard, is used for the metallic wire 1.

[0050] An electric field intensity is determined by conducting an experiment from each transmitting antenna under the same evaluation conditions as the one described in [reference to relevant document]. Fig. 3 evaluation condition shown in the first embodiment described above using three in the above described Fig. 11, Fig. 12 and Fig. The data from the transmitting antennas shown in Figure 15 are evaluated. The evaluation area 8 is a region in which a central axis of the transmitting antenna is a center and has a height of 1.5 m from the ground plane 6, wherein the size of a region is a square 6 m × 6 m, and a grid-like structure in which a section in the region is a square of 0.5 m. A value indicating the uniformity of the electric field is the same as in the first embodiment described above.

[0051] Fig. Figure 17 shows the uniformity of the electric field of experimental results from each transmitting antenna under the conditions shown in Fig. 3 shown evaluation conditions.

[0052] A carrier frequency lies between 500 kHz and 2 MHz. In Fig. 17 corresponds to a curve line FU1area1 a case of the transmitting antenna in Fig. 2 in the first embodiment described above, a curve line FU2 area1 corresponds to a case of the transmitting antenna in Fig. 11, a curve line FU3 area1 corresponds to a case of the transmitting antenna in Fig. 12 and a curve line FU4 area1 corresponds to a case of the transmitting antenna in Fig. 15. One value of each curve line is a maximum value of the uniformity of the electric field in the evaluation area. 8.

[0053] In Fig. 17. The uniformity of the electric field of each transmitting antenna lies in Fig. 11, Fig. 12 and Fig. 15 in the second embodiment within 2.5 dB when a carrier frequency is between 500 kHz and 2 MHz. Furthermore, each of the transmitting antennas in Fig. 11, Fig. 12 and Fig. 15 in the second embodiment, the excellent uniformity of the electric field is observed when the carrier frequency is between 500 kHz and 1.75 MHz, compared with the transmitting antenna in Fig. 2 in the first embodiment.

[0054] Based on the evaluation results described above in Fig. 17 According to the second embodiment, it is possible to further improve the uniformity of an electric field intensity if a plane is formed on which an electric field intensity of an AM radio wave is uniformized with respect to an evaluation area of ​​an AM radio receiving antenna device installed in a device such as a vehicle. [Third embodiment]

[0055] A third embodiment associated with the present invention is described below. The objectives of the third embodiment are to evaluate the reception sensitivity of two vehicle-integrated AM radio receiving antennas and to reduce the area of ​​a transmitting antenna in order to improve the efficiency of the evaluation of the reception sensitivity of an AM radio receiving antenna.

[0056] Fig. 18 is a diagram in which a transmitting antenna with a cross-shaped structure is located within the Fig. The rectangular loop shown in 12 in the second embodiment described above serves as a basic structure of the [unclear text]. Fig. The antenna system shown in section 1 is arranged as shown. Fig. As shown in Figure 18, the feed point 4 is located at a corner of a transmission antenna. The transmission antenna is positioned at a height h above the ground plane 6.

[0057] Fig. 19 is a diagram in which two transmitting antennas with a cross-shaped structure are located within the area shown in Fig. 12 rectangular loop shown in the second embodiment described above in the basic structure of the Fig. The antenna system shown in section 1 is provided. As shown in Fig. As shown in Figure 19, the two transmitting antennas are arranged such that loop surfaces of these antennas face the ground plane 6 in order to share a feed point 4. The loop surfaces of the two transmitting antennas and the ground plane 6 can be parallel to each other. Here, the term "parallel" may imply a certain degree of deviation. The two transmitting antennas are positioned at height h above the ground plane 6.

[0058] An electric field intensity is determined by conducting an experiment in each of the setups described above. Fig. 18 and Fig. 19 evaluated. Together with the structures of Fig. 18 and Fig. 19 is the inner conductor of the coaxial cable 3, which is configured to deliver an AM broadcast signal output by the AM broadcast signal source 2, connected to the feed point 4, and the outer conductor of the coaxial cable 3 is connected to the ground point 5 of the ground plane 6.

[0059] The transmitting antennas in the structures of Fig. 18 and Fig. 19 represents a length of 6.5 m for each side extending in the x-direction in the drawings, and a length of 6.5 m for each side extending in the y-direction in the drawings. Furthermore, AWG3, an American Wire Gauge standard, is used to refer to a metallic wire. A structure consisting of a rectangular loop and a cross electrically connected to each other is provided.

[0060] First, the electric field intensity is evaluated by changing the height h of a transmitting antenna to 4 m, 5 m, and 6 m in a setup of Fig. 18 and conducting an experiment. The evaluation area 8 is an area in which a central axis of the transmitting antenna is a center and a height from the ground plane 6 is 1.5 m, wherein a size of the area is a square 6 m × 6 m and a grid-like structure in which a section in the area is a square of 0.5 m. A value indicating the uniformity of the electric field is the same as in the first embodiment described above.

[0061] Fig. Figure 20 shows the uniformity of the electric field of experimental results at each height of the transmitting antenna in the setup of Fig. 18. The in Fig. The uniformity of the electric field shown in Figure 20 is the result of obtaining the uniformity of the electric field of a carrier frequency in a 5 m×5 m square (500 kHz to 2 MHz) from a measured electric field intensity obtained in a 6 m×6 m square of the evaluation area 8. Fig. 20 corresponds to a curve line FU3 h=4m a case of a height “h=4 m” of a transmitting antenna, a curve line FU3 h=5 m This corresponds to a case of a height "h=5 m" of the transmitting antenna, and a curve FU3 h-6 m This corresponds to a case where the transmitting antenna is at a height of "h=6 m".

[0062] In Fig. 20. When the height h of the transmitting antenna increases to 4 m, 5 m, and 6 m, the uniformity of the electric field increases. This tendency is particularly noteworthy when the carrier frequency is around 500 kHz and the uniformity of the electric field is approximately 2 dB when the transmitting antenna height is 4 m, approximately 4 dB when the transmitting antenna height is 5 m, and approximately 6 dB when the transmitting antenna height is 6 m. In one case, when the carrier frequency is 500 kHz, the uniformity is significantly increased. Therefore, the design of Fig. 18 the height h at which the transmitting antenna is arranged, preferably in a range of 4 m to 5 m.

[0063] Next, the construction of Fig. 19 an experiment with the height h of the transmitting antenna, which is located at the best 4 m in the setup of Fig. The procedure is performed and an electric field intensity is evaluated. Since the two transmitting antennas are arranged symmetrically, the evaluation area 8 is a region in which a central axis of one of the transmitting antennas is a center and has a height of 1.5 m from the ground plane 6, wherein the area is a square 6 m × 6 m, and has a grid-like structure in which a section in the region is a square of 0.5 m. A value indicating the uniformity of the electric field is the same as in the first embodiment described above.

[0064] Fig. Figure 21A shows the uniformity of the electric field of the experimental results using the two transmitting antennas in the setup of Fig. 19. Furthermore, for comparison, it shows Fig. 21B the uniformity of the electric field of the experimental results using a transmitting antenna in the setup of Fig. 18. The in Fig. 21A and Fig. 21B shown uniformity of the electric field is obtained by detecting the uniformity of the electric field, in which a carrier frequency in a square of 6 m×6 m of the evaluation area is 8 500 kHz, from a measured value of an electric field intensity in the square of 6 m×6 m.

[0065] Furthermore, it shows Fig. 22 the uniformity of the electric field of the experimental results in the setup of Fig. 18 (a transmitting antenna) and the construction of Fig. 19 (two transmitting antennas). The in Fig. The uniformity of the electric field shown in Figure 22 is obtained by detecting the uniformity of the electric field, where a carrier frequency in a 5 m × 5 m square is 500 kHz to 2 MHz, from a measured value of an electric field intensity obtained in a 6 m × 6 m square of the evaluation area 8. Fig. 22 corresponds to a curve line FU3 Paira case of two transmitting antennas, and a curve line FU3 Single This corresponds to a case of a transmitting antenna.

[0066] When comparing the case of two transmitting antennas of Fig. 21A with the case of a transmitting antenna from Fig. 21B shows that in the case of the two transmitting antennas, one of the two transmitting antennas is influenced by the other adjacent transmitting antenna. Furthermore, according to the result of the uniformity of the electric field of Fig. 22 In a case where the carrier frequency is 500 kHz, the uniformity of the electric field is 3.2 dB in the case of two transmitting antennas and 2 dB in the case of one transmitting antenna. Thus, in the case of two transmitting antennas, one of the two transmitting antennas is influenced by the other adjacent transmitting antenna in such a way that the uniformity of the electric field is about 1 dB greater than that of a single transmitting antenna.

[0067] Next, an experiment is conducted for various modified examples of the transmitting antenna, and an electric field intensity is evaluated.

[0068] One of the transmitting antennas used for this evaluation is located in Fig. 23 shown. At the in Fig. The 23 shown transmitting antennas are two in Fig. The 13 transmitting antennas shown are arranged side by side. A feed point 4 is provided at one corner of a rectangular loop of an outer circumference, and the two transmitting antennas are arranged side by side to share the feed point 4. "11=6.5m" and "12=4m" are both satisfied. Furthermore, AWG3, an American Wire Gauge standard, is used as the metallic wire 1. Rectangular loops and crosses are configured to have a structure in which the rectangular loops and crosses are electrically interconnected.

[0069] One of the transmitting antennas used for this evaluation is located in Fig. 24 shown. The in Fig. The transmitting antenna shown in section 24 is obtained by combining two in Fig. The 14 transmitting antennas shown are arranged side by side. A feed point 4 is provided at one corner of a rectangular loop of an outer circumference, and the two transmitting antennas are arranged side by side to share the feed point 4. "11=6.5 m" is satisfied, as is "12=4 m" and "13=2 m". Furthermore, AWG3, which is an American Wire Gauge standard, is used as a metallic wire 1. Rectangular loops and crosses are arranged to have a structure in which the rectangular loops and the crosses are electrically interconnected.

[0070] One of the transmitting antennas used for this evaluation is located in Fig. 25 shown. The in Fig. The transmitting antenna shown in Figure 25 is obtained by arranging two transmitting antennas with a concave rectangular loop-shaped structure side by side. As shown in Fig. As shown in Figure 25, a feed point 4 is provided at one corner of a rectangular loop, and the two transmitting antennas are arranged side by side to share the feed point 4. A gap of width g is provided at one corner of a transmitting antenna opposite the corner where the feed point 4 is located. The conditions "11=6.5 m" and "12=2 m" are met, and g=0.5 m is met. Furthermore, AWG 3, an American Wire Gauge standard, is used as the metallic wire 1.

[0071] One of the transmitting antennas used for this evaluation is located in Fig. 26 shown. The in Fig. The transmitting antenna shown in Figure 26 is obtained by arranging two transmitting antennas with multiple concave rectangular loop-shaped structures side by side. As shown in Fig. As shown in Figure 26, a feed point 4 is provided at a corner of a rectangular loop of an outer circumference, and the two transmitting antennas are arranged side by side to share the feed point 4. A gap of width g is provided on each concave rectangular loop of a transmitting antenna. The conditions "11=6.5 m" are met, "12=4 m" is met, "13=2 m" is met, and g=0.5 m is met. Furthermore, AWG3, which is an American Wire Gauge standard, is used as the metallic wire 1.

[0072] An experiment with transmitting antennas will be conducted under the same conditions as the setup described above. Fig. 19 using the above described, in Fig. 23, Fig. 24, Fig. 25 and Fig. The four transmitting antennas shown in Figure 26 are used, and the electric field intensity is evaluated. The heights of the transmitting antennas are set to "h=4 m". Since the two transmitting antennas are as shown in the setup of Fig. The evaluation area 8, where 19 are symmetrically arranged, is an area in which a central axis of one of the transmitting antennas is a center and has a height of 1.5 m from a ground plane 6, wherein the area has a size of 6 m × 6 m and a grid-like structure in which a section in the area is a square of 0.5 m. A value indicating the uniformity of the electric field is the same as in the first embodiment described above.

[0073] Fig. Figure 27 shows the uniformity of the electric field from experimental results of the transmitting antennas of Fig. 23 and Fig. 24. Fig. Figure 28 shows the uniformity of the electric field from experimental results of the transmitting antennas of Fig. 25 and Fig. 26. Furthermore, for comparison, it shows Fig. 27 the uniformity of the electric field of experimental results in the two transmitting antennas (one height of the transmitting antenna fulfills “h=4 m”) in the setup of Fig. 19. The in Fig. 27 and Fig. The uniformity of the electric field shown in Figure 28 is obtained by detecting the uniformity of the electric field, in which a carrier frequency in a 5 m×5 m square is 500 kHz to 2 MHz, from a measured value of an electric field intensity obtained in a 6 m×6 m square of the evaluation area 8. Fig. 27 corresponds to a curve line FU3 Pair a case of two transmitting antennas in the setup of Fig. 19, a curve line FU5 Pair corresponds to a case of the transmitting antenna of Fig. 23 and a curve line FU6 Pair corresponds to a case of the transmitting antenna of Fig. 24. In Fig. 28 corresponds to a curve line FU7 Pair a case of the transmitting antenna of Fig. 25, and a curve line FU8 Pair corresponds to a case of the transmitting antenna of Fig. 26.

[0074] In Fig. 27 the uniformity of the electric field of the transmitting antennas of Fig. 23 and Fig. 24 and the uniformity of the electric field of the two transmitting antennas in the setup of Fig. 19 within 3.2 dB at a carrier frequency of 500 kHz to 2 MHz. Furthermore, in Fig. 28 the uniformity of the electric field of the transmitting antennas of Fig. 25 and Fig. 26 and the uniformity of the electric field of the two transmitting antennas in the setup of Fig. 19 within 3.6 dB at a carrier frequency of 500 kHz to 2 MHz.

[0075] As described above, according to the third embodiment, it is possible to improve the efficiency of evaluating the reception sensitivity of the two vehicle-integrated AM radio receiving antennas, since an evaluation task can be performed in parallel. Because it is possible to create a plane on which the electric field intensity of an AM radio wave can be uniformized using a transmitting antenna with a size of approximately 6.5 × 6.5 m per vehicle-integrated AM radio receiving antenna, it is possible to reduce the area of ​​the transmitting antenna. [Fourth embodiment]

[0076] A fourth embodiment associated with the present invention is described below. In the fourth embodiment, a mass-equivalent base, configured to simulate mass, is provided on a mass plane 6. The mass-equivalent base has a surface impedance equivalent to mass. Fig. Figure 29 shows the mass-equivalent base according to this embodiment. The one in Fig. The mass-equivalent base shown in Figure 29 is obtained by laminating a ferrite tile 12 with a thickness of 5.5 mm and a resistive film 13 with a surface resistance of about 400 Ω over the mass plane 6.

[0077] An attempt at the transmitting antenna of Fig. 23 is constructed under the same conditions as the setup described above. Fig. 19 using the in Fig. The measurement is carried out on the mass-equivalent ground shown in Figure 29 and described above, and an electric field intensity is evaluated. The height of the transmitting antenna is set to "h=4 m". An evaluation area 8 is an area where the central axis of a transmitting antenna is the center point and the height from the mass plane 6 is 1.5 m, the area is a square of 6 m x 6 m, and it has a grid-like structure where each section in the area is a square of 0.5 m. A value indicating the uniformity of the electric field is the same as in the first embodiment described above.

[0078] Fig. Figure 30 shows the uniformity of the electric field of experimental results when the mass-equivalent ground described above is used. Fig. 29 is used. The in Fig. The uniformity of the electric field shown in Figure 30 is obtained by detecting the uniformity of the electric field, in which a carrier frequency in a 5 m×5 m square is 500 kHz to 2 MHz, from a measured value of an electric field intensity obtained in a 6 m×6 m square of the evaluation area 8. Fig. 30 corresponds to a curve line FU5 EEGP a case where the mass-equivalent soil of Fig. 29 is used. Furthermore, for comparison, it shows... Fig. 30 a curve line FU5 GP the uniformity of the electric field of experimental results in a case where the mass plane 6 is used without the mass-equivalent ground of Fig. 29 to use.

[0079] In Fig. 30 The uniformity of the electric field lies in a case where the mass-equivalent ground of Fig. 29 is used, within 3 dB at a carrier frequency of 500 kHz to 2 MHz. Furthermore, the uniformity of the electric field in a case where the mass-equivalent ground of Fig. 29 is used, at a carrier frequency of 500 kHz to 750 kHz slightly different from the uniformity of the electric field in a case where the ground plane 6 is used, without the mass-equivalent ground of Fig. 29 to use.

[0080] As described above, according to the fourth embodiment, even if the mass-equivalent ground is provided above the ground plane, an effect is achieved in which a plane is formed on which an electric field intensity of an AM radio wave is uniformized with respect to an evaluation area of ​​an AM radio receiving antenna device installed in a device such as a vehicle.

[0081] It should be noted that in the Fig. In the mass-equivalent soil shown in Figure 29, the ferrite tile and the resistive film are arranged above the mass plane, but the mass-equivalent soil can be one in which only a ferrite tile is arranged above the mass plane. [Fifth embodiment]

[0082] A fifth embodiment associated with the present invention is described below. Fig. Figure 31 is a diagram showing an example of an application in an anechoic chamber according to the fifth embodiment. As in Fig. As shown in 31, the basic structure of the in Fig. In the antenna arrangement shown in Figure 1, a non-metallic frame 14 is provided on the outer circumference of a loop of a transmitting antenna within a chamber 7, which is an anechoic chamber. A winch 16 (a drive device) is further provided, configured to drive the non-metallic frame 14 in a direction in which the non-metallic frame 14 faces the ground plane 6, using a non-metallic cable 15. The winch 16 is located on a ceiling surface of the chamber 7. A wall surface of the chamber 7 is configured as a radio wave absorber 17. A transmitting antenna attached to the non-metallic frame 14 is moved from the ceiling surface of the chamber 7 by the winch 16 via the non-metallic cable 15 in a direction in the direction of the ground plane 6, thus allowing the transmitting antenna to be arranged parallel to the ground plane 6 and at an arbitrary height h.

[0083] Although it is necessary that an arbitrary height h at which the transmitting antenna is arranged be higher than the height of a device such as a vehicle in which the AM broadcast receiving antenna is installed, it is desirable to adjust the height from ground plane 6, taking into account the transmit output of the AM broadcast wave and the interference of ground plane 6 of the AM broadcast wave, in a range of 4 m to 5 m.

[0084] It should be noted that the transmitting antenna can be mounted using a wall surface of an anechoic chamber owned by a manufacturer of the AM broadcast receiving antenna system or by a manufacturer of a system with the AM broadcast receiving antenna installed therein. Furthermore, although a loop shape for the transmitting antenna is not restricted, a simple shape such as a rectangular loop is preferable, considering the labor and manufacturing costs of fabricating a non-metal frame to support the transmitting antenna. [Sixth embodiment]

[0085] A sixth embodiment associated with the present invention is described below. Fig. Figure 32 is a diagram showing an example of the construction of a measurement-based system in a receiver sensitivity evaluation device of an AM broadcast receiving antenna associated with the present invention. Fig. 32 A vehicle with an internal antenna 23, which is an AM broadcast receiving antenna installed therein, is placed above a ground plane 6. As in Fig. Figure 32 shows a matching network 21 for impedance matching of a loop-shaped transmitting antenna, formed from a metallic wire 1, connected to a coaxial cable 3 (a feed cable). More precisely, in Fig.32 A built-in RF broadband signal analyzer 18 is connected to the matching network 21 via the coaxial cable 3, and a splitter 22 is also connected to the matching network 21 via the coaxial cable 3. Furthermore, an inner conductor of the coaxial cable 3 is connected through the splitter 22 to a feed point 4 of the transmitting antenna, and the outer conductor of the coaxial cable 3 is connected to a ground point 5 of the ground plane 6. To perform measurement control on the built-in RF broadband signal analyzer 18, a measurement control personal computer (measurement control PC) 19 is also connected via a communication control cable 20.

[0086] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific structure is not limited to these embodiments and includes design changes and the like, without deviating from the core of the present invention. EXPLANATION OF THE REFERENCES 1 metallic wire 2 AM broadcast signal source 3 power cables 4 Feeding point 5 Mass point 6. Mass plane 7th Chamber 8 Evaluation area 9 Transmitting antenna of a real image 10 Transmitting antenna of a mirror image 11 AM broadcast signal source of the mirror image 12 Ferrite tiles 13 Resistive Film 14 Non-metallic frame 15 Non-metallic rope 16 winches (drive unit) 17 radio wave absorbers 18 built-in RF broadband signal analyzers 19 Measurement control PCs 20 communication control cables 21 Adaptation network 22 distributors 23. Vehicle-internal antenna

Claims

[1] Antenna system, comprising: a chamber shielded against electromagnetic waves; a loop-shaped transmitting antenna consisting of a metallic wire and arranged in the chamber shielded against electromagnetic waves such that a loop surface of the loop-shaped transmitting antenna faces a ground plane; a feed cable designed to feed an AM broadcast signal; wherein a feed wire of the feed cable is connected to the transmitting antenna and a ground wire of the feed cable is connected to the ground plane. [2] Antenna device according to claim 1, wherein the transmitting antenna is formed in a rectangular loop shape using the metallic wire. [3] Antenna device according to claim 2, wherein a grid-like structure is further provided within a rectangular loop of the transmitting antenna using a metallic wire. [4] Antenna device according to claim 2, wherein a cross-shaped structure in which opposite angles of the rectangular loop are connected to each other using a metallic wire is further provided within a rectangular loop of the transmitting antenna. [5] Antenna device according to claim 4, wherein one or more rectangular loop-shaped structures are further provided within the rectangular loop using a metallic wire. [6] Antenna device according to claim 1, wherein the transmitting antenna is formed using the metallic wire in one or more concave rectangular loop shapes. [7] Antenna arrangement according to one of claims 1 to 6, wherein another loop-shaped transmitting antenna, which is designed for the common use of a feed point connecting the feed line to the transmitting antenna, is further provided such that a loop surface faces the ground plane. [8] Antenna device according to one of claims 1 to 7, wherein a ferrite tile or a ferrite tile and a resistive film having a surface impedance equivalent to the mass are arranged on the ground plane. [9] Antenna device according to any one of claims 1 to 8, further comprising: A control device with a non-metallic frame, provided on an outer circumference of a loop of the transmitting antenna and designed to cause the non-metallic frame to move in a direction in which the non-metallic frame faces the ground plane, using a non-metallic rope. [10] Antenna device according to one of claims 1 to 9, wherein an impedance matching network for matching the transmitting antenna is connected to the feed cable.

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