Antenna equipment, transmitters, and radar

Abstract

To provide an antenna device capable of suppressing phase shift in patch antennas. [Solution] The antenna device comprises a series antenna array including a dielectric substrate, a plurality of patch antennas formed on the dielectric substrate and arranged in one direction, and a transmission line connecting adjacent patch antennas among the plurality of patch antennas, wherein the transmission line length is such that the greater the difference between the width of the transmission line and the width of the patch antennas connected to the transmission line, the greater the decrease from half a wavelength of the fundamental wave.

Description

Technical Field

[0001] The present invention relates to an antenna device, a transmitter, and a radar.

Background Art

[0002] Patent Documents 1 and 2 disclose a patch array antenna in which a plurality of patch antennas are arranged in one direction and connected in series.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Among patch array antennas, there is a standing wave excitation type designed so that standing waves are formed throughout the antenna. The inventor of the present application has found that in such a patch array antenna, not only the patch antennas but also the transmission lines connecting the patch antennas themselves are in a resonant state.

[0005] By making the transmission line in a resonant state, it can be expected to suppress the phase shift of the patch antenna and improve the directivity in the front direction.

[0006] However, it has been found that simply adjusting the length of the transmission line to match the half wavelength of the fundamental wave is insufficient to make the transmission line resonate, and the cause is the electromagnetic field disturbance generated at the discontinuity between the patch antenna and the transmission line.

[0007] The present invention has been made in view of the above problems, and its main objective is to provide an antenna device, a transmitter, and a radar capable of suppressing phase shift of a patch antenna. [Means for solving the problem]

[0008] To solve the above problems, an antenna device according to one aspect of the present invention includes a dielectric substrate, a plurality of patch antennas formed on the dielectric substrate and arranged in one direction, and a transmission line connecting adjacent patch antennas among the plurality of patch antennas, wherein the transmission line length is such that the greater the difference between the width of the transmission line and the width of the patch antennas connected to the transmission line, the greater the reduction from half a wavelength of the fundamental wave.

[0009] In the above embodiment, the patch antenna may be narrower towards the end of the unidirectional connection, and the transmission line may be longer towards the end of the connection. This makes it possible to suppress phase shift of the patch antenna.

[0010] In the above embodiment, the length of the transmission line may be shorter than half the wavelength of the fundamental wave by an amount corresponding to the difference between the width of the transmission line and the width of the patch antenna connected to the transmission line. This makes it possible to suppress the phase shift of the patch antenna.

[0011] In the above embodiment, the larger the difference between the width of the transmission line and the width of the patch antenna connected to one end of the transmission line, and the larger the difference between the width of the transmission line and the width of the patch antenna connected to the other end of the transmission line, the larger the reduction from half a wavelength of the fundamental wave. This makes it possible to suppress the phase shift of the patch antenna.

[0012] In the above embodiment, the transmission line length may be determined by calculating S-parameters using a computational model that includes the transmission line, an input line with the same width as the patch antenna connected to one end of the transmission line, and an output line with the same width as the patch antenna connected to the other end of the transmission line, so that the transmission line resonates with the fundamental wave. This makes it possible to suppress the phase shift of the patch antenna.

[0013] In the above embodiment, at least some of the transmission lines may have curved sections that are more curved the longer the transmission line is. This makes it possible to equalize the spacing of the patch antennas while suppressing the phase shift of the patch antennas.

[0014] In the above embodiment, at least some of the transmission lines may have curved sections so that the patch antennas are arranged at equal intervals. This makes it possible to equalize the spacing of the patch antennas while suppressing phase shifts in the patch antennas.

[0015] Furthermore, an antenna device according to another aspect of the present invention includes a series antenna array comprising a dielectric substrate, a plurality of patch antennas formed on the dielectric substrate and arranged in one direction, and a transmission line connecting adjacent patch antennas among the plurality of patch antennas, wherein the line length of the first transmission line is shorter than the line length of the second transmission line when the difference between the width of the first transmission line and the width of the first patch antenna connected to the first transmission line is greater than the difference between the width of the second transmission line and the width of the second patch antenna connected to the second transmission line. This makes it possible to suppress phase shift of the patch antennas.

[0016] Furthermore, a transmitter according to another aspect of the present invention includes the above-described antenna device. This makes it possible to apply an antenna device that suppresses the phase shift of the patch antenna.

[0017] In addition, a radar according to another aspect of the present invention includes the above-described antenna device. According to this, it becomes possible to apply an antenna device in which the phase shift of the patch antenna is suppressed.

Effects of the Invention

[0018] According to the present invention, it becomes possible to suppress the phase shift of the patch antenna.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing an example of a radar. [Figure 2] It is a diagram showing an example of an antenna device. [Figure 3] It is a diagram showing an example of the first embodiment. [Figure 4] It is a diagram showing an example of a line length. [Figure 5] It is a diagram showing an example of a line length. [Figure 6] It is a diagram showing an example of a calculation model. [Figure 7] It is a diagram showing an example of an S parameter. [Figure 8] It is a diagram showing an example of an angle and an output. [Figure 9] It is a diagram showing an example of the second embodiment. [Figure 10] It is a diagram showing an example of a line length. [Figure 11] It is a diagram showing an example of an angle and a gain. [Figure 12] It is a diagram showing an example of the third embodiment.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and each drawing, elements that are the same as those described above with respect to the already shown drawings may be denoted by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0021] [Radar] Figure 1 is a block diagram showing an example configuration of radar 100. Radar 100 is an example of a transmitter. Radar 100 includes an antenna device 10, a transmitting / receiving unit 11, a signal processing unit 12, and a control unit 13.

[0022] The transmitting / receiving unit 11 includes a modulation unit and a magnetron. In response to a trigger signal from the signal processing unit 12, the magnetron is intermittently driven by a pulse voltage generated in the modulation unit to generate a transmission signal. The antenna device 10 transmits the transmission signal from the transmitting / receiving unit 11 as a radio wave pulse.

[0023] Furthermore, the antenna device 10 converts the received reflected wave into a received signal. The received signal from the antenna device 10 passes through the frequency conversion / amplification circuit and detection circuit included in the transmitting / receiving unit 11, is processed by the signal processing unit 12, and sent as a digital signal to the control unit 13.

[0024] The radar 100 is applied, for example, to an in-vehicle radar for obstacle detection or collision avoidance that transmits and receives millimeter waves. However, it is not limited to this, and the radar 100 may also be applied, for example, to a marine radar that transmits and receives microwaves.

[0025] [Antenna equipment] Figure 2 is a plan view showing an example of the configuration of the antenna device 10. The antenna device 10 comprises a dielectric substrate 2, a conductor pattern 3 formed on the first main surface 21 (the surface visible in the figure) of the dielectric substrate 2, and a ground pattern (not shown) formed on the second main surface of the dielectric substrate 2 opposite to the first main surface.

[0026] The conductor pattern 3 comprises a series antenna array 4 and input / output lines 7 for supplying power to the series antenna array 4. "Series antenna array 4" is a general term for the series antenna arrays 4A to 4C of each embodiment described later.

[0027] The series antenna array 4 is a standing wave-excited series-fed patch array antenna, comprising a plurality of patch antennas 51-59 (also called antenna elements) arranged in one direction, and a plurality of transmission lines 61-68 connecting two adjacent patch antennas 51-59. The number of patch antennas 51-59 is not limited to the example shown.

[0028] In other words, in the series antenna array 4, the patch antennas 51-59 and transmission lines 61-68 are arranged alternately in one direction. As a result, the antenna device 10 as a whole has strong directivity. The transmission lines 61-68 are high-impedance lines with higher impedance than the patch antennas 51-59.

[0029] The X1-X2 directions shown in the diagram represent the arrangement direction of patch antennas 51-59, the extension direction of transmission lines 61-68, and the transmission direction of radio waves in series antenna array 4. Hereafter, the X1-X2 directions will also be simply referred to as the "X direction." Furthermore, one side of the X direction (left in the diagram) will be referred to as the "X1 side," and the other side (right in the diagram) will be referred to as the "X2 side."

[0030] The Y1-Y2 direction, perpendicular to the X direction, corresponds to the width direction of patch antennas 51-59 and transmission lines 61-68. Hereafter, the Y1-Y2 direction will also simply be referred to as the "Y direction." Furthermore, one side of the Y direction (upward in the diagram) will be referred to as the "Y1 side," and the other side (downward in the diagram) will be referred to as the "Y2 side."

[0031] The patch antennas 51-59 are formed in a rectangular shape and have a transmission direction length X that corresponds to half a wavelength of the fundamental frequency used. That is, the transmission direction length X of the patch antennas 51-59 is approximately equal to half a wavelength of the fundamental frequency.

[0032] The input / output line 7 is connected to the feed point 9 and supplies power from the feed point 9 to the end of the series antenna array 4 (so-called end feed). However, the input / output line 7 may also supply power from the feed point 9 to the middle of the series antenna array 4 (so-called center feed). The feed point 9 is formed by a through-hole formed in the dielectric substrate 2.

[0033] The conductor pattern 3 is formed by patterning a metal foil provided on the first main surface 21 of the dielectric substrate 2 using photolithography technology. Therefore, the patch antennas 51-59, transmission lines 61-68, and input / output lines 7 are formed integrally.

[0034] Although only one series antenna array 4 is shown in the example in Figure 2, the antenna device 10 may be provided with multiple series antenna arrays 4 arranged in the width direction Y. Furthermore, some of the series antenna arrays 4 may be used for transmission, and the remaining series antenna arrays 4 may be used for reception.

[0035] By the way, in conventional patch array antennas, the patch antennas are basically arranged at equal intervals, and the length of the transmission lines is the same for all of them.

[0036] The inventors of this application have found that in a patch array antenna, the transmission lines connecting the patch antennas are also in a resonant state, and therefore, the influence of electromagnetic field disturbances occurring in the discontinuities between the patch antennas and the transmission lines should be considered. These electromagnetic field disturbances are caused by the difference in width between the patch array antenna and the transmission line, and in a patch array antenna where the width of the patch antennas varies depending on the position, the degree of influence will differ.

[0037] In a patch array antenna, the length of the transmission line affects the radiation phase of the patch antennas; if there is a phase shift in the patch antennas, a shift in the directivity in the forward direction will occur.

[0038] Therefore, in this embodiment, by designing the transmission line length as described below, the transmission line is brought into a resonant state, suppressing the phase shift of the patch antenna and improving the directivity in the forward direction.

[0039] [First Embodiment] Figure 3 shows an example of a series antenna array 4A according to the first embodiment. Figures 4 and 5 show examples of the transmission line lengths 61 to 68 in the series antenna array 4A. In the embodiments described below, the dielectric substrate 2 of the antenna device 10 is formed of a material with a relative permittivity of 3.35 and a thickness of 0.4 mm. The half wavelength of the fundamental wave when using 24 GHz radio waves corresponds to 4.04 mm.

[0040] In the series antenna array 4A, the lengths of the transmission lines 61-68 are set such that the greater the difference between the width of the transmission lines 61-68 and the width of the patch antennas 51-59 connected to them, the greater the reduction from half a wavelength of the fundamental wave.

[0041] Patch antennas 51-59 are narrower towards the ends in the X direction and wider towards the center in the X direction. Therefore, transmission lines 61-68 are longer towards the ends in the X direction and shorter towards the center in the X direction. The width of transmission lines 61-68 is the same.

[0042] In other words, the width of patch antenna 55 located in the center in the X direction is wider than the widths of patch antennas 54 and 56 adjacent to it in the X direction. The widths of patch antennas 54 and 56 are wider than the widths of patch antennas 53 and 57 adjacent to them in the X direction. The widths of patch antennas 53 and 57 are wider than the widths of patch antennas 52 and 58 adjacent to them in the X direction. The widths of patch antennas 52 and 58 are wider than the widths of patch antennas 51 and 59 adjacent to them in the X direction.

[0043] Therefore, the line lengths D4 and D5 of transmission lines 64 and 65, which are in the center in the X direction, are shorter than the line lengths D3 and D6 of transmission lines 63 and 66, which are located outside of them in the X direction. The line lengths D3 and D6 of transmission lines 63 and 66 are shorter than the line lengths D2 and D7 of transmission lines 62 and 67, which are located outside of them in the X direction. The line lengths D2 and D7 of transmission lines 62 and 67 are shorter than the line lengths D1 and D8 of transmission lines 61 and 68, which are located outside of them in the X direction.

[0044] For example, if we focus on transmission line 64 located near the center of the direct antenna row 4 and transmission line 61 located near the end, the difference between the width of transmission line 64 and the width of the patch antennas 54 and 55 connected to it is greater than the difference between the width of transmission line 61 and the width of the patch antennas 51 and 52 connected to it. Therefore, the line length D4 (=3.75mm) of transmission line 64 is shorter than the line length D1 (=4.04mm) of transmission line 61, resulting in a larger reduction from half the wavelength of the fundamental wave (=4.04mm).

[0045] The difference between the width of the transmission line 64 and the widths of the patch antennas 54 and 55 connected to it may be the sum of the differences between the width of the transmission line 64 and the width of the patch antenna 54 connected to its X1 end, and the differences between the width of the transmission line 64 and the width of the patch antenna 55 connected to its X2 end, or it may be the average.

[0046] As described above, electromagnetic field disturbance occurs at the boundary between patch antennas 51-59 and transmission lines 61-68. This electromagnetic field disturbance increases with the difference between the width of patch antennas 51-59 and the width of transmission lines 61-68. When such electromagnetic field disturbance exists, the effective length of transmission lines 61-68 for radio waves propagating through them becomes longer by the amount of the electromagnetic field disturbance.

[0047] In order to bring transmission lines 61-68 into a resonant state, that is, to bring the effective line length of transmission lines 61-68 to be close to half a wavelength of the fundamental wave, the actual line length of transmission lines 61-68 must be shorter than half a wavelength of the fundamental wave. Therefore, in this embodiment, the actual line length of transmission lines 61-68 is made shorter than half a wavelength of the fundamental wave by an amount corresponding to the difference between the width of transmission lines 61-68 and the width of the patch antennas 51-59 connected to them.

[0048] Figures 6 and 7 illustrate the method for determining the line lengths of transmission lines 61 to 68. Figure 6 shows an example of a calculation model CM for determining the line length of transmission line 63.

[0049] The calculation model CM represents a one-input, one-output circuit that includes a transmission line 63, an input line IL with the same width as the patch antenna 53 connected to the X1 end of the transmission line 63, and an output line OL with the same width as the patch antenna 54 connected to the X2 end of the transmission line 63.

[0050] The length of the transmission line 63 is determined by calculating the S-parameters using the computational model CM, so that the transmission line 63 resonates at the fundamental frequency. That is, as shown in Figure 7, the length of the transmission line 63 is determined so that S11 is minimized at the design frequency (24 GHz).

[0051] The length of the transmission line 63 determined in this way takes into account the electromagnetic field disturbance at the boundary between the transmission line 63 and the patch antennas 53 and 54. In other words, the effective length of the transmission line 63 for the design frequency radio wave is half the wavelength of the fundamental wave.

[0052] Furthermore, as shown in Figure 5, the line lengths D1 and D8 (=4.04 mm) of transmission lines 61 and 68 are the same as half the wavelength of the fundamental wave (=4.04 mm). This is because the reduction due to electromagnetic field disturbances is negligibly small.

[0053] Figure 8 shows an example of the calculation results showing the relationship between angle and gain. The horizontal axis of the graph represents the angle, and the vertical axis represents the gain. 0 degrees is the front (direction perpendicular to the X and Y directions).

[0054] The embodiment is a series antenna array 4A in which the line lengths of transmission lines 61 to 68 are set as described above. The comparative example is a series antenna array in which the line lengths of the transmission lines are equal, and the dimensions other than the line lengths are the same as those of series antenna array 4A.

[0055] According to this, in the comparative example, the direction of maximum gain is 1.6 degrees away from the front, whereas in the embodiment, the direction of maximum gain is 0.4 degrees, indicating that the radiation is almost directly in front.

[0056] [Second Embodiment] Figure 9 shows an example of a series antenna array 4B according to the second embodiment. The series antenna array 4B comprises 41 patch antennas 5 and 40 transmission lines 6. Figure 10 shows an example of the line length of the transmission lines 6 in the series antenna array 4B.

[0057] In Figure 10, the "Transmission Line" row indicates which patch antenna 5 the transmission line 6 is connected to. For example, "1-2" indicates that the transmission line 6 connects the first patch antenna 5 and the second patch antenna 5 from the X1 side.

[0058] Furthermore, Figure 10 only shows the line length of the transmission line 6 on the X1 side relative to the central 21st patch antenna 5. The line length of the transmission line 6 on the X2 side is the same as the line length of the transmission line 6 on the X1 side, which is symmetrically positioned with respect to the 21st patch antenna 5.

[0059] For example, the transmission line 6 connecting the 40th and 41st patch antennas 5 has the same line length as the transmission line 6 connecting the 1st and 2nd patch antennas 5. Also, the transmission line 6 connecting the 21st and 22nd patch antennas 5 has the same line length as the transmission line 6 connecting the 20th and 21st patch antennas 5.

[0060] In the series antenna array 4B, the length of the transmission line 6 is set such that the larger the difference between the width of the transmission line 6 and the width of the patch antenna 5 connected to it, the greater the reduction from half a wavelength of the fundamental wave.

[0061] Figure 11 shows an example of the calculation results for the relationship between angle and gain for a series antenna array 4B. According to this, the direction of maximum gain is close to 0 degrees, indicating high directivity in the forward direction.

[0062] [Third Embodiment] Figure 12 shows an example of a series antenna array 4C according to the third embodiment. In the series antenna array 4C, some of the transmission lines 61-63, 66-68 have curved sections 81-83, 86-88 that are more curved the longer the line length.

[0063] Transmission lines 61-68 have longer lengths closer to the ends in the X direction and shorter lengths closer to the center in the X direction. Therefore, the curved sections 81-83 and 86-88 are more curved closer to the ends in the X direction and less curved closer to the center in the X direction.

[0064] The transmission lines 64 and 65 closest to the center in the X direction, i.e., the transmission lines with the shortest length, are not curved.

[0065] In this way, by having the transmission lines 61-63 and 66-68 have curved sections 81-83 and 86-88, the line lengths of the transmission lines 61-68 can be set as described above, while the patch antennas 51-59 can be placed closer to being at equal intervals.

[0066] In other words, the transmission lines 61-63 and 66-68 have curved sections 81-83 and 86-88 such that the patch antennas 51-59 are arranged at equal intervals. This makes it possible to narrow the beam width and improve directivity.

[0067] In the illustrated example, the curved sections 81-83 and 86-88 are curved in a U-shape, but they are not limited to this and may be curved in an S-shape, for example.

[0068] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are of course possible for those skilled in the art.

[0069] The following lists representative embodiments of the present invention.

[0070] (1) Dielectric substrate and The series antenna array includes a plurality of patch antennas formed on the dielectric substrate and arranged in one direction, and a transmission line connecting adjacent patch antennas among the plurality of patch antennas, wherein the transmission line length is such that the greater the difference between the width of the transmission line and the width of the patch antennas connected to the transmission line, the greater the decrease from half a wavelength of the fundamental wave, An antenna device equipped with the following features.

[0071] (2) The patch antennas are narrower the closer they are to the end of the one-way direction. The transmission lines have longer lengths as they are closer to the end. (1) The antenna device described above.

[0072] (3) The length of the transmission line is shorter than half the wavelength of the fundamental wave by an amount corresponding to the difference between the width of the transmission line and the width of the patch antenna connected to the transmission line. The antenna device described in (1) or (2).

[0073] (4) The transmission line is such that the larger the difference between the width of the transmission line and the width of the patch antenna connected to one end of the transmission line, and the larger the difference between the width of the transmission line and the width of the patch antenna connected to the other end of the transmission line, the greater the decrease from half the wavelength of the fundamental wave. An antenna device as described in any of (1) to (3).

[0074] (5) The length of the transmission line is determined by calculating S-parameters using a computational model that includes the transmission line, an input line with the same width as the patch antenna connected to one end of the transmission line, and an output line with the same width as the patch antenna connected to the other end of the transmission line, so that the transmission line resonates with the fundamental frequency. An antenna device as described in any of (1) through (4).

[0075] (6) At least some of the transmission lines have a curved section that is more pronounced the longer the transmission line is. An antenna device as described in any of (1) through (5).

[0076] (7) At least some of the transmission lines have curved sections such that the patch antennas are arranged at equal intervals. An antenna device as described in any of (1) through (6).

[0077] (8) A transmitter equipped with an antenna device as described in any of (1) through (7).

[0078] (9) A radar equipped with an antenna device as described in any of (1) through (7). [Explanation of Symbols]

[0079] 2 Dielectric substrate, 21 First main surface, 3 Conductor pattern, 4 Antenna row, 5, 51-59 Patch antenna, 6, 61-68 Transmission line, 7 Input / output line, 81-83, 86-88 Curved section, 10 Antenna device, 11 Transceiver unit, 12 Signal processing unit, 13 Control unit, 100 Radar

Claims

1. Dielectric substrate and The series antenna array includes a plurality of patch antennas formed on the dielectric substrate and arranged in one direction, and a transmission line connecting adjacent patch antennas among the plurality of patch antennas, wherein the transmission line length is such that the greater the difference between the width of the transmission line and the width of the patch antennas connected to the transmission line, the greater the decrease from half a wavelength of the fundamental wave, An antenna device equipped with the following features.

2. The patch antennas are narrower the closer they are to the end of the one-way direction. The transmission lines have longer lengths as they are closer to the end. The antenna device according to claim 1.

3. The length of the transmission line is shorter than half the wavelength of the fundamental wave by an amount corresponding to the difference between the width of the transmission line and the width of the patch antenna connected to the transmission line. The antenna device according to claim 1.

4. The transmission line is such that the larger the difference between the width of the transmission line and the width of the patch antenna connected to one end of the transmission line, and the larger the difference between the width of the transmission line and the width of the patch antenna connected to the other end of the transmission line, the greater the decrease from half the wavelength of the fundamental wave. The antenna device according to claim 1.

5. The length of the transmission line is determined by calculating S-parameters using a computational model that includes the transmission line, an input line with the same width as the patch antenna connected to one end of the transmission line, and an output line with the same width as the patch antenna connected to the other end of the transmission line, so that the transmission line resonates with the fundamental wave. The antenna device according to claim 1.

6. At least some of the transmission lines have a curved section that is more pronounced the longer the transmission line is. The antenna device according to claim 1.

7. At least some of the transmission lines have curved sections such that the patch antennas are arranged at equal intervals. The antenna device according to claim 1.

8. A transmitter comprising the antenna device described in claim 1.

9. A radar comprising the antenna device described in claim 1.

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