Antenna module, antenna system, and radio wave receiving method

Abstract

According to the present invention, each of a plurality of antenna elements includes two ports for receiving two linear polarization waves that are orthogonal to each other. A processing unit processes signals received by the plurality of antenna elements. The polarization directions of the linear polarization waves received through the respective two ports of the plurality of antenna elements are different between the plurality of antenna elements. At the time of arrival of radio waves, the processing unit compares, between the plurality of ports, reception levels of linear polarization wave components received through the plurality of ports included in the plurality of antenna elements, and detects a port that provides the highest reception level.

Description

[Technical Field]

[0001] The present invention relates to an antenna module, an antenna system, and a radio wave receiving method. [Background technology]

[0002] A technique for improving the axial ratio of a circularly polarized array antenna configured by arranging multiple circularly polarized antenna elements is disclosed in Patent Document 1. In the technique disclosed in Patent Document 1, the excitation phase of the multiple circularly polarized antenna elements is determined so as to equalize the radiated field strength of three types of linearly polarized components, and the multiple circularly polarized antenna elements are excited at this phase. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-249807 Summary of the Invention [Problem to be solved by the invention]

[0004] In communications in which the orientation of at least one of the transmitting antenna and the receiving antenna is not fixed, such as communications between a mobile terminal and a base station, a circularly polarized antenna is used for one antenna and a linearly polarized antenna for the other. Radio waves transmitted from a circularly polarized antenna are generally not perfectly circularly polarized but are elliptically polarized. When elliptically polarized waves are received by a linearly polarized antenna, the reception sensitivity varies depending on the major axis direction of the elliptical polarization. If the major axis direction of the incoming elliptical polarization can be detected, it is possible to suppress a decrease in reception sensitivity. An object of the present invention is to provide an antenna module that can obtain information about the major axis direction of the incoming elliptical polarization. Another object of the present invention is to provide a radio wave reception method that can obtain information about the major axis direction of the incoming elliptical polarization.

[0005] Conversely, when a linearly polarized wave is received by a circularly polarized receiving antenna, the receiving sensitivity may decrease depending on the polarization direction of the incoming linearly polarized wave. It is yet another object of the present invention to provide an antenna system that can suppress the decrease in receiving sensitivity when a linearly polarized wave is received by a circularly polarized receiving antenna. [Means for solving the problem]

[0006] According to one aspect of the present invention, a plurality of antenna elements each including two ports for receiving two orthogonal linearly polarized waves; a processing unit that processes signals received by the plurality of antenna elements; Equipped with The polarization directions of the linearly polarized waves received by each of the two ports of the plurality of antenna elements are different among the plurality of antenna elements; The processing unit is an antenna module that compares the reception levels of linearly polarized components received at each of the multiple ports included in the multiple antenna elements when radio waves arrive, and detects the port with the highest reception level.

[0007] According to another aspect of the present invention, A plurality of antenna elements, each having two ports, for transmitting and receiving two linearly polarized waves having different polarization directions via the two ports; and a first antenna module that supplies transmission signals to the plurality of antenna elements and has a processing unit that processes received signals received by the plurality of antenna elements; a second antenna module that receives radio waves transmitted from the first antenna module, measures a reception level, and transmits a signal including information specifying the measured reception level back to the first antenna module; Equipped with The polarization directions of the linearly polarized waves transmitted by the plurality of antenna elements are different among the antenna elements, The processing unit the plurality of antenna elements Included ina process of supplying a transmission signal to one of the plurality of ports to transmit a linearly polarized wave and receiving a return signal returned from the second antenna module, the process being performed for each of the plurality of ports; An antenna system is provided that detects the port of the plurality of ports that was used when the reception level was highest, based on information specifying the reception level contained in the return signal. [Effects of the Invention]

[0008] By detecting the port with the highest reception level from among the multiple ports included in the multiple antenna elements, the major axis direction of the arriving elliptically polarized wave can be identified within a certain range.

[0009] By changing the polarization direction of the linearly polarized wave transmitted from the first antenna module based on the reception level received by the second antenna module, it is possible to suppress a decrease in reception sensitivity at the second antenna module. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an antenna module according to a first embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of processing executed by the processing unit of the antenna module according to the first embodiment. [Figure 3] Figure 3A is a schematic diagram showing the trajectory of the tip of the electric field vector on the xy plane of elliptically polarized waves received by two antenna elements, and Figure 3B is a diagram showing the relationship between the direction of the major axis of the elliptically polarized waves and the port at which the reception level is maximum. [Figure 4] FIG. 4 is a schematic diagram showing the locus of the tip of the electric field vector on the xy plane of linearly polarized waves received by two antenna elements of the antenna module according to a modified example of the first embodiment. [Figure 5] FIG. 5 is a plan view of two antenna elements mounted on an antenna module according to another modification of the first embodiment. [Figure 6]FIG. 6 is a schematic diagram of an antenna module according to a second embodiment. [Figure 7] FIG. 7 is a flowchart showing the procedure of processing executed by the processing unit of the antenna module according to the second embodiment. [Figure 8] FIG. 8 is a schematic diagram for explaining the polarization directions of two antenna elements of the antenna module according to the second embodiment. [Figure 9] FIG. 9 is a flowchart showing the procedure of processing by the processing unit of the antenna module according to the second embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the relationship between the antenna elements of the antenna module according to a modified example of the second preferred embodiment and their polarization directions. [Figure 11] Figure 11A is a schematic diagram showing the relationship between the antenna elements of an antenna module according to another modified example of the second embodiment and their polarization directions, and Figures 11B and 11C are schematic diagrams showing the first antenna element and the second antenna element superimposed on each other. [Figure 12] FIG. 12 is a schematic diagram showing the positional relationship of the polarization directions of linearly polarized waves received at 2N ports when N antenna elements are stacked. [Figure 13] FIG. 13 is a schematic diagram of an antenna system according to a third embodiment. [Figure 14] FIG. 14 is a flowchart showing the procedure of the processing of the first antenna module and the second antenna module of the antenna system according to the third embodiment. [Figure 15] FIG. 15 is a schematic diagram of an antenna system according to a modification of the third embodiment. [Figure 16] 16A to 16D are schematic diagrams of a communication system using an antenna module according to the above-described embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First Example] An antenna module according to a first embodiment will be described with reference to Figures 1 to 3B. Note that the "antenna module" can also be called an "antenna device." 1 is a schematic diagram of an antenna module according to a first embodiment. The antenna module according to the first embodiment includes two antenna elements 20 and a processing unit 30. The two antenna elements 20 receive radio waves transmitted from a transmitting antenna 72. The transmitting antenna 72 is designed to transmit circularly polarized waves, but the radio waves actually transmitted are not perfectly circularly polarized waves but are elliptically polarized waves 80.

[0012] Each of the two antenna elements 20 is, for example, a circular patch antenna and has two ports. The two ports of one antenna element 20 are labeled as ports P0 and P1, and the two ports of the other antenna element 20 are labeled as ports P2 and P3. Linearly polarized waves can be received by each of the two ports of the antenna element 20. An xyz Cartesian coordinate system is defined, with the plane on which the two antenna elements 20 are arranged being the xy plane. When viewing the antenna element 20 from the front, the angle tilted clockwise from the positive direction of the y axis is labeled as the tilt angle θ. When tilted counterclockwise from the positive direction of the y axis, the value of the tilt angle θ is negative.

[0013] The polarization direction of the linearly polarized wave received at port P0 of one antenna element 20 is parallel to the y-axis (tilt angle θ is 0°), and the polarization direction of the linearly polarized wave received at port P1 is parallel to the x-axis (tilt angle θ is 90°). The polarization direction of the linearly polarized wave received at port P2 of the other antenna element 20 has a tilt angle θ of 135°, and the polarization direction of the linearly polarized wave received at port P3 has a tilt angle θ of 45°.

[0014] That is, when focusing on one antenna element 20, the polarization directions of the linearly polarized waves received at one port and the linearly polarized waves received at the other port are orthogonal to each other. Furthermore, the polarization directions of the two linearly polarized waves received at each of the two ports of one antenna element 20 and the polarization directions of the two linearly polarized waves received at each of the two ports of the other antenna element 20 form an angle of 45°.

[0015] The processing unit 30 includes four receivers 31 and a reception level comparison and determination unit 32. The four receivers 31 are each connected to two antenna elements 20, for a total of four ports P0, P1, P2, and P3. The reception signals received at each of the four ports P0, P1, P2, and P3 are input to the four receivers 31. The receivers 31 measure the reception levels of the received signals. The reception levels measured by the receivers 31 correspond to the intensity of the linearly polarized wave component received at each port. The measurement results of the reception levels are input to the reception level comparison and determination unit 32.

[0016] Next, processing executed by the processing unit 30 of the antenna module according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the procedure of processing executed by the processing unit 30 (radio wave receiving method). First, radio waves transmitted from the transmitting antenna 72 (Fig. 1) are received by the two antenna elements 20, and the receiver 31 of the processing unit 30 acquires the received signals received at each of the four ports P0, P1, P2, and P3 (step SA1). The receiver 31 measures the reception levels of the received signals received at each of the four ports P0, P1, P2, and P3 (step SA2). The measurement results of the reception levels are input to the reception level comparison and determination unit 32.

[0017] The reception level comparison / determination unit 32 compares the reception levels of the signals received at the ports P0, P1, P2, and P3, and detects the port that shows the highest reception level (step SA3).

[0018] Next, the excellent effects of the first embodiment will be described with reference to Figure 3A. Figure 3A is a schematic diagram showing the locus 81 of the tip of the electric field vector on the xy plane of the elliptically polarized waves received by the two antenna elements 20 (Figure 1). Even if the transmitting antenna 72 (Figure 1) is designed to transmit circularly polarized waves, the radio waves actually transmitted will generally be elliptically polarized waves. Figure 3A shows an example in which the major axis MA of the elliptically polarized waves is slightly tilted with respect to the y-axis direction.

[0019] Ports P0 and P1 of one antenna element 20 receive linearly polarized waves with polarization directions parallel to the y and x directions, respectively, so reception levels L0 and L1 of the received signals received at ports P0 and P1 correspond to the y-direction and x-direction dimensions, respectively, of locus 81. Ports P2 and P3 of the other antenna element 20 receive linearly polarized waves with polarization direction tilt angles θ of 135° and 45°, respectively, so reception levels L2 and L3 of the received signals received at ports P2 and P3 correspond to the dimensions of locus 81 in the direction D135 where tilt angle θ is 135° and the direction D45 where tilt angle θ is 45°, respectively.

[0020] For example, when the tilt angle θ of the major axis MA of the elliptical polarization is greater than -22.5° and less than 22.5°, the magnitude relationship among the reception levels L0, L1, L2, and L3 is L0>L3>L2>L1. The polarization direction (y direction) of the linearly polarized wave received at port P0, which shows the highest reception level, is closest to the direction of the major axis MA of the elliptical polarization compared to the polarization directions of the linearly polarized waves received at the other ports P1, P2, and P3.

[0021] FIG. 3B is a diagram showing the relationship between the direction of the major axis MA of the elliptical polarization and the port at which the reception level is maximum. When reception level L0 is maximum, the tilt angle θ of the major axis MA of the elliptical polarization can be determined to be greater than -22.5° and less than 22.5°. When reception level L3 is maximum, the tilt angle θ of the major axis MA of the elliptical polarization can be determined to be greater than 22.5° and less than 67.5°. When reception level L1 is maximum, the tilt angle θ of the major axis MA of the elliptical polarization can be determined to be greater than 67.5° and less than 112.5°. When reception level L2 is maximum, the tilt angle θ of the major axis MA of the elliptical polarization can be determined to be greater than 112.5° and less than 157.5°.

[0022] If the tilt angle θ of the major axis MA of the elliptical polarization can be specified within a certain range, it is possible to optimize various processes that depend on the direction of the major axis MA of the elliptical polarization.

[0023] Next, a modified example of the first embodiment will be described with reference to Fig. 4. In the first embodiment, elliptically polarized waves are received by two antenna elements 20, but in the modified example of the first embodiment, linearly polarized waves are received. In this modified example, the polarization direction of the incoming linearly polarized waves is estimated.

[0024] 4 is a schematic diagram showing a locus 81 of the tip of the electric field vector on the xy plane of linearly polarized waves received by two antenna elements 20 (FIG. 1) of an antenna module according to a modified example of the first embodiment. The locus 81 is a straight line extending, for example, in a direction slightly deviated from the y-axis direction. The reception levels L0 and L1 of the reception signal received at ports P0 and P1 (FIG. 1) of one antenna element 20 correspond to the dimensions in the y and x directions of the locus 81, respectively. The reception levels L2 and L3 of the reception signal received at ports P2 and P3 of the other antenna element 20 correspond to the dimensions of the locus 81 in the direction D135 where the tilt angle θ is 135° and the direction D45 where the tilt angle θ is 45°, respectively.

[0025] In this modified example, the polarization direction of the incoming linearly polarized wave can be identified within a certain range based on the magnitude relationship between the reception levels L0, L1, L2, and L3 of the received signals received at the four ports P0, P1, P2, and P3.

[0026] Next, another modification of the first embodiment will be described with reference to FIG. 5 is a plan view of two antenna elements 20 mounted on an antenna module according to another modification of the first embodiment. In the antenna module according to the first embodiment, a circular patch antenna is used as the antenna element 20. In contrast, in this modification, a square patch antenna is used as the antenna element 20. The two ports of each of the antenna elements 20 are arranged on a line segment having the midpoints of two adjacent sides of the antenna element 20 and the geometric center as its two ends.

[0027] The polarization directions of the linearly polarized waves received by the two antenna elements 20 are shifted by 45° between the two antenna elements 20. In the first embodiment, since the antenna element 20 is circular, the external shape of the antenna element 20 does not appear to rotate even when the polarization direction of the antenna element 20 is rotated. In contrast, if the antenna element 20 is square as in the modified example shown in Fig. 5, the external shape of the antenna element 20 needs to be rotated in the direction of the tilt angle θ in order to rotate the polarization direction of the antenna element 20.

[0028] As in this modification, the shape of the antenna element 20 may be a square. Alternatively, the antenna element 20 may have another shape, provided that the antenna element 20 can receive two linearly polarized waves with mutually orthogonal polarization directions. For example, the antenna element 20 may have a square shape with the four corners cut off to form a square shape.

[0029] Next, a further modification of the first embodiment will be described. In the first embodiment, the polarization directions of the linearly polarized waves received by the two antenna elements 20 (FIG. 1) form an angle of 45° between the antenna elements 20, but the angle formed by the polarization directions of the linearly polarized waves between the antenna elements 20 does not necessarily have to be 45°. A configuration may be adopted in which four linearly polarized waves with different polarization directions can be received at a total of four ports P0, P1, P2, and P3 of the two antenna elements 20. In this case as well, the signal level change amount (the sum of the gain and attenuation amount) and the phase change amount of each port may be set so that the receiving sensitivity of the polarization direction of the linearly polarized waves received at the port where the receiving level of the incoming radio waves is maximum is maximized.

[0030] [Second Example] Next, an antenna module according to a second embodiment will be described with reference to Figures 6 to 9. Below, a description of the configuration common to the antenna module according to the first embodiment described with reference to Figures 1 to 3B will be omitted.

[0031] FIG. 6 is a schematic diagram of an antenna module according to a second embodiment. Like the antenna module according to the first embodiment, the antenna module according to the second embodiment also includes two antenna elements 20 and a processing unit 30. In the first embodiment (FIG. 1), the processing unit 30 includes four receivers 31 and a reception level comparison / determination unit 32. In contrast, in the second embodiment, the processing unit 30 includes a reception amplifier 33, a transmission amplifier 34, a variable attenuator 35, a phase shifter 36, and a combiner / demultiplexer 37 in addition to the receivers 31 and the reception level comparison / determination unit 32. The reception amplifier 33, the transmission amplifier 34, the variable attenuator 35, and the phase shifter 36 are provided corresponding to four ports P0, P1, P2, and P3, respectively. Note that the order in which the reception amplifier 33, the transmission amplifier 34, the variable attenuator 35, and the phase shifter 36 are connected is not limited to the order shown in FIG. 6.

[0032] The reception level comparison and determination unit 32 controls the gain of the reception amplifier 33, the attenuation of the variable attenuator 35, and the phase change amount of the phase shifter 36. By controlling the gain of the reception amplifier 33 and the attenuation amount of the variable attenuator 35, the amount of change in the signal level of the reception signal is controlled.

[0033] When the antenna module receives a signal, the received signal received at each of the four ports P0, P1, P2, and P3 is amplified by the receiving amplifier 33, passes through the variable attenuator 35 and the phase shifter 36, and is input to the combiner / demultiplexer 37. The combiner / demultiplexer 37 combines the four input received signals. The combined received signal is down-converted and input to the baseband signal processing circuit.

[0034] When the antenna module transmits a signal, the signal to be transmitted is split into four signals by the splitter / combiner 37. Each of the split signals passes through the phase shifter 36 and the variable attenuator 35, is amplified by the transmission amplifier 34, and is supplied to each of the four ports P0, P1, P2, and P3. During transmission, the gain of the transmission amplifier 34, the amount of attenuation by the variable attenuator 35, and the amount of phase change by the phase shifter 36 are controlled.

[0035] Next, the processing executed by the processing unit 30 of the antenna module according to the second embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the procedure of the processing (radio wave reception method) executed by the processing unit 30. The procedure from step SA1 to step SA3 is the same as the procedure executed by the processing unit 30 of the antenna module according to the first embodiment (Fig. 2). In step SA3, if there are multiple ports showing the highest reception level, any one port may be set as the port with the maximum reception level. Alternatively, each port may be assigned a priority in advance, and the port with the highest priority among the multiple ports showing the highest reception level may be set as the port with the maximum reception level.

[0036] When the port showing the highest reception level is detected in step SA3, the signal level change amount and phase change amount to be applied to the reception signal received at each of the two ports of the two antenna elements 20 are set so that the reception sensitivity in the polarization direction of the linearly polarized wave received at the port with the highest reception level is maximized (step SA4). In this specification, the signal level change amount and phase change amount to be applied to the reception signal received at each port may also be referred to as the port signal level change amount and port phase change amount. Specifically, the gain of the reception amplifier 33 (FIG. 6), the attenuation of the variable attenuator 35 (FIG. 6), and the phase change amount of the phase shifter 36 (FIG. 6) connected to each port are set. As a result, the signal level of the reception signal received at each port changes by the set signal level change amount, and the phase of the reception signal changes by the set phase change amount, and the reception signal is input to the multiplexer / demultiplexer 37.

[0037] Next, referring to Figure 8, we will explain an example of controlling the amount of change in signal level and the amount of change in phase of the received signal received at each port so that the receiving sensitivity in the polarization direction of the linearly polarized wave received at the port with the maximum receiving level is maximized.

[0038] 8 is a schematic diagram illustrating the polarization directions of two antenna elements 20 of the antenna module according to the second embodiment. Ports P0 and P1 of one antenna element 20 are arranged at tilt angles θ of 180° and 90°, respectively. The tilt angle θ of the polarization direction of the linearly polarized wave received at port P0 is 0°, and the tilt angle θ of the polarization direction of the linearly polarized wave received at port P1 is 90°. Ports P2 and P3 of the other antenna element 20 are arranged at tilt angles θ of -45° and -135°, respectively. The tilt angle θ of the polarization direction of the linearly polarized wave received at port P2 is 135°, and the tilt angle θ of the polarization direction of the linearly polarized wave received at port P3 is 45°.

[0039] The following describes the case where the reception level of the linearly polarized wave received at port P0 is maximum. Because the tilt angle θ of the polarization direction of the linearly polarized wave received at port P0 is 0°, the signal level change amount and phase change amount at each port are controlled so that the reception sensitivity of the linearly polarized wave with a polarization direction tilt angle θ of 0° is maximized. In Figure 8, the polarization direction with a tilt angle θ of 0° is represented by a thick arrow. To maximize the signal level of the combined signal obtained by combining the received signals received by two antenna elements 20, not only the polarization direction but also the phase of the linearly polarized wave received by the two antenna elements 20 must be matched. To take the phase into consideration, the polarization direction of the linearly polarized wave is represented by a single arrow in Figure 8.

[0040] In this explanation, we use a pass rate instead of the amount of signal level change controlled by the receiving amplifier 33 and variable attenuator 35. If the power of the input signal to the receiving amplifier 33 is denoted as Pin and the power of the output signal from the variable attenuator 35 is denoted as Pout, the pass rate is defined as Pout / Pin. The phase of port P0 is used as the reference for the amount of phase change at the other ports P1, P2, and P3. In other words, the phases of ports P1, P2, and P3 are specified by a phase change amount α based on the phase of port P0.

[0041] First, the control in the antenna element 20 provided with ports P0 and P1 will be described. The transmittance of port P0 is set to G. The phase change amount α of port P0 is 0°. By setting the transmittance of port P1 to 0, the receiving sensitivity to linearly polarized waves with a polarization direction tilt angle θ of 0° is maximized. Because the transmittance of port P1 is 0, the phase change amount α of port P1 is arbitrary.

[0042] Next, we will explain the control of the antenna element 20 provided with ports P2 and P3. When the transmission rate of port P2 is set to G and the phase shift amount α is set to 180°, and the transmission rate of port P3 is set to G and the phase shift amount α is set to 0°, the receiving sensitivity for linearly polarized waves with a polarization direction tilt angle θ of 0° is maximized. Furthermore, with these settings, the phases of the linearly polarized received signals received by the two antenna elements 20 can be matched.

[0043] Next, the processing procedure of the processing unit 30 (FIG. 6) when performing communication using the antenna module according to the second embodiment will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the processing procedure (radio wave receiving method) of the processing unit 30 (FIG. 6).

[0044] Before communication begins, the signal level change amount and phase change amount α of each port are set so that the receiving sensitivity is maximized (step SB1). The signal level change amount and phase change amount α can be set using the procedure shown in FIG. 7. After the signal level change amount and phase change amount α are set, communication is actually performed (step SB2). Until communication ends, the processing unit 30 determines whether the reception level of the received signal combined by the combiner / demultiplexer 37 (FIG. 6) is equal to or greater than the determination threshold (steps SB3 and SB4). If the reception level is equal to or greater than the determination threshold, communication continues (steps SB4 and SB2). When the reception level becomes less than the determination threshold, the signal level change amount and phase change amount α of each port are reset so that the receiving sensitivity is maximized (steps SB4 and SB1). In other words, the procedure shown in FIG. 7 is executed again.

[0045] Next, the excellent effects of the second embodiment will be described. In the second embodiment, the signal level change amount and phase change amount of the four ports P0, P1, P2, and P3 of the two antenna elements 20 are set so that the receiving sensitivity in the polarization direction of linearly polarized waves received at the port where the receiving level of the incoming radio waves is maximum is maximized. Therefore, even if the incoming radio waves are elliptically polarized waves, the radio waves can be received with high receiving sensitivity.

[0046] Furthermore, as explained with reference to Figure 4, the antenna module according to the second embodiment can adjust the polarization direction of multiple antenna elements 20 (Figure 6) so as to maximize the receiving sensitivity even when the incoming radio waves are linearly polarized and the polarization direction is unknown.

[0047] In a conventional antenna module that receives linearly polarized waves, when receiving linearly polarized waves in a certain polarization direction, the reception level can be maximized by optimizing the orientation of the antenna module. However, if the orientation of the antenna module changes for some reason, the reception level fluctuates significantly. In the antenna module of the second embodiment, if the orientation of the antenna module changes and the reception level decreases, the signal level change amount and phase change amount for each port are reset in steps SB4 and SB1 shown in Figure 9, thereby suppressing the decrease in reception level.

[0048] Next, an antenna module according to a modification of the second embodiment will be described with reference to Fig. 10. Fig. 10 is a schematic diagram showing the relationship between the antenna elements 20 of the antenna module according to the modification of the second embodiment and their polarization directions. While the antenna module according to the second embodiment has two antenna elements 20 (Fig. 6), the antenna module according to this modification has three antenna elements 20. The first antenna element 20 has ports P0 and P1, the second antenna element 20 has ports P2 and P3, and the third antenna element 20 has ports P4 and P5.

[0049] Ports P0 and P1 of the first antenna element 20 are positioned at tilt angles θ of 180° and 90°, respectively. Ports P2 and P3 of the second antenna element 20 are positioned at tilt angles θ of -150° and -60°, respectively. Ports P4 and P5 of the third antenna element 20 are positioned at tilt angles θ of -120° and -30°, respectively.

[0050] The polarization directions of the linearly polarized waves received at one port P0, P2, and P4 of each of the three antenna elements 20 differ by 30°. For example, the tilt angle θ of the polarization direction of the linearly polarized wave received at port P0 of the first antenna element 20 is 0°, the tilt angle θ of the polarization direction of the linearly polarized wave received at port P2 of the second antenna element 20 is 30°, and the tilt angle θ of the polarization direction of the linearly polarized wave received at port P4 of the third antenna element 20 is 60°.

[0051] In the modification shown in Fig. 10, the processing unit 30 (Fig. 6) compares the reception levels of linearly polarized waves received at a total of six ports and detects the port with the maximum reception level. The signal level change amount and phase change amount are set for each of the two ports of the multiple antenna elements 20 so that the reception sensitivity in the polarization direction corresponding to the port with the maximum reception level is maximized.

[0052] The optimal signal level change and phase change will be explained below using the example of the case where the reception level at port P4 of the third antenna element 20 is maximized. In this case, it is sufficient to maximize the reception sensitivity in the polarization direction when the tilt angle θ is 60°. The phase at port P4 is used as the phase reference, and the transmission rate of port P4 is set to G.

[0053] In the first antenna element 20, the transmission rate of port P0 is set to (1 / (3 1 / 2 ))G, the phase shift amount α is set to 0°, the transmission rate of port P1 is set to G, and the phase shift amount α is set to 180°. In the second antenna element 20, the transmission rate of port P2 is set to G, the phase shift amount is set to 0°, and the transmission rate of port P3 is set to (1 / (3 1 / 2))G, the phase change amount α should be set to 0°. In the third antenna element 20, the transmission rate of port P5 should be set to 0. The phase change amount α of port P5 is arbitrary.

[0054] As in the modified example of the second embodiment shown in Fig. 10, the number of antenna elements 20 may be three. More generally, the number of antenna elements 20 may be N, where N is an integer equal to or greater than 2. In this case, it is preferable that the linearly polarized waves received at one port of each of the N antenna elements 20 have polarization directions that differ by 180 / (2N) degrees between the antenna elements 20.

[0055] In the modified example of the second embodiment shown in Fig. 10, the transmittance of both port P0 and port P3 may be set to G. In this case, the first antenna element 20 and the second antenna element 20 will also be sensitive to linearly polarized waves (cross-polarized waves) that are orthogonal to the polarization direction of the linearly polarized waves received at port P4. However, if the intensity of the cross-polarized waves is small, the decrease in sensitivity to linearly polarized waves in the polarization direction received at port P4 can be ignored.

[0056] In other words, to maximize the receiving sensitivity for linearly polarized waves in the polarization direction received at port P4, the phase change amount of each port should be set so that the phase of the linearly polarized wave component in the polarization direction received at port P4 is in phase with port P4 and the other ports P0, P1, P2, and P3.

[0057] Next, an antenna module according to another modification of the second embodiment will be described with reference to FIGS. 11A, 11B, and 11C.

[0058] 11A is a schematic diagram showing the relationship between the antenna elements 20 of an antenna module according to another modification of the second embodiment and their polarization directions. The antenna module according to this modification also has three antenna elements 20, similar to the modification shown in FIG. 10. The arrangement of the ports of the three antenna elements 20 is also the same as in the modification shown in FIG.

[0059] 10, the receiving sensitivity of each antenna element 20 is maximized by adjusting the transmittance and the phase shift amount of the two ports for each antenna element 20. In contrast, in this modification, the receiving sensitivity of the three antenna elements 20 as a whole is maximized.

[0060] As in the modified example described with reference to Fig. 10, the optimal transmission rate and phase change amount will be described below using as an example the case where the reception level at port P4 of the third antenna element 20 is maximized. The transmission rate at port P5 is set to 0, as in the modified example shown in Fig. 10.

[0061] 11B and 11C are schematic diagrams showing the first antenna element 20 and the second antenna element 20 superimposed on each other. Two ports are selected to receive linearly polarized waves in two polarization directions such that the absolute values ​​of the tilt angles with respect to the polarization direction of the linearly polarized wave received at port P4, where the reception level is maximum, are equal. For example, as shown in FIG. 11B, port P1 of the first antenna element 20 and port P2 of the second antenna element 20 are selected. When the polarization direction of the linearly polarized wave received at port P4 is used as a reference, the tilt angle of the polarization direction of the linearly polarized wave received at port P1 is 30°, and the tilt angle of the polarization direction of the linearly polarized wave received at port P2 is -30°, and the absolute values ​​of both are equal.

[0062] Next, we will explain a method for combining signals received at ports P1 and P2 to maximize the receiving sensitivity of linearly polarized waves received at port P4, which has the highest receiving level. In the following explanation, we assume that radio waves arrive from the boresight direction of an array antenna consisting of multiple antenna elements 20. The phase shifts of ports P1 and P2 are set so that the phases of the polarization direction components (indicated by the thick arrow in FIG. 11B) of the linearly polarized waves received at port P4 are in phase at ports P1, P2, and P4. Specifically, with the phase shift α of port P4 as the reference, the phase shift α of port P1 is set to 180°, and the phase shift α of port P2 is set to 0°. The transmission rates of ports P1 and P2 are set to the maximum values ​​of the transmission rates of each port P1 and P2. This setting maximizes the receiving sensitivity when the signals received at ports P1 and P2 are combined.

[0063] The following describes the case where it is assumed that the antenna gains of ports P1 and P2 are the same. When the maximum values ​​of the transmission rates of ports P1 and P2 are equal, and the transmission rates and phase shifts of ports P1 and P2 are set as described above, the radio waves radiated from the two antenna elements 20 become linearly polarized waves in the far field that are parallel to the polarization direction of the linearly polarized waves received at port P4. Conversely, under the above-described transmission rate and phase shift conditions, when radio waves regarded as plane waves are received at ports P1 and P2, the receiving sensitivity for linearly polarized waves in the polarization direction received at port P4 is maximized, and the receiving sensitivity for cross-polarized waves is zero.

[0064] Next, we will explain the case where the antenna gains of ports P1 and P2 are different. When the maximum values ​​of the transmission coefficients of ports P1 and P2 are equal, even if the transmission coefficients and phase shifts of ports P1 and P2 are set as described above, the radio waves radiated from the two antenna elements 20 will not be parallel to the polarization direction of the linearly polarized waves received at port P4 in the far field. Conversely, when radio waves regarded as plane waves are received at ports P1 and P2 under the above-described transmission coefficient and phase shift conditions, the receiving sensitivity for cross-polarized waves of the linearly polarized waves received at port P4 will not be zero. However, even in this case, the receiving sensitivity for linearly polarized waves in the polarization direction received at port P4 will be maximized.

[0065] The transmission rates of ports P1 and P2 may be set so that the product of the antenna gain of port P1 and the transmission rate of port P1 is equal to the product of the antenna gain of port P2 and the transmission rate of port P2. For example, the transmission rate of the port with the smaller antenna gain is set to the maximum, and the transmission rate of the other port is set so that the product of the antenna gain and the transmission rate of the two ports is equal. In this case, the receiver sensitivity for linearly polarized waves in the polarization direction received at port P4 is maximized, and the receiver sensitivity for cross-polarized waves is zero. This prevents degradation of the main polarization receiver signal due to the cross-polarized received signal. Reducing the transmission rate of one port below the maximum value is equivalent to reducing the gain of the receiver amplifier 33 (Figure 6). This allows the receiver sensitivity to be maximized while suppressing the effects of cross-polarized waves, and power consumption to be reduced.

[0066] If a sufficient signal level can be ensured for the received signal without setting the transmission rate to the maximum, there is no need to set the transmission rate of the port with the smaller antenna gain to the maximum. Even in this case, it is advisable to set the transmission rate of the other port so that the product of the antenna gain and the transmission rate of the two ports is equal.

[0067] 11C, the transmittance of ports P0 and P3 are both set to G, and the phase shift amount α is both set to 0°. In this case, when radio waves regarded as plane waves are received at the two ports P0 and P3, the receiving sensitivity to the linearly polarized wave in the polarization direction of the linearly polarized wave received at port P4 (the direction indicated by the thick arrow in FIG. 11C) is maximized.

[0068] As in this modification, the transmittance and the amount of phase change may be adjusted to maximize the receiving sensitivity for two ports arranged across two antenna elements 20 as a set. In this case, the receiving sensitivity can be maximized by setting the transmittance (amount of signal level change) of all ports to the same value except for the port (port P5 in the example shown in FIG. 11A) that receives linearly polarized waves in a polarization direction orthogonal to the polarization direction that maximizes the receiving sensitivity, and adjusting only the amount of phase change.

[0069] In the above explanation, it is assumed that radio waves arrive from the boresight direction of an array antenna consisting of multiple antenna elements 20. When tilting the main beam of an array antenna consisting of multiple antenna elements 20 from the boresight direction, beam tilt control can be performed in addition to control to maximize receiving sensitivity according to the polarization direction. For example, multiple phase conditions are determined based on the phase change amount for maximizing receiving sensitivity according to the polarization direction and the phase change amount set according to the direction of the main beam. One phase condition can be selected based on the direction of the main beam and the polarization direction, and the phase change amount to be applied to each port can be determined based on the selected phase condition.

[0070] Next, an antenna module according to yet another modification of the second embodiment will be described with reference to Fig. 12. In the modifications shown in Figs. 11A, 11B, and 11C, three antenna elements 20 are arranged. In contrast, in the modification shown in Fig. 12, N antenna elements are arranged, where N is an integer equal to or greater than 2.

[0071] Figure 12 is a schematic diagram showing the positional relationship of the polarization directions of linearly polarized waves received at 2N ports when N antenna elements are stacked. When N antenna elements are stacked, the 2N ports are arranged so that the 2N polarization directions differ by 180 / (2N) degrees. The polarization directions are numbered consecutively, starting from 0, in order of increasing clockwise tilt angle θ from the reference polarization direction, and the i-th polarization direction is denoted as D(i). Here, i is an integer between 0 and (2N-1).

[0072] We will explain the case where the polarization direction that maximizes the receiving sensitivity is the ith polarization direction D(i). The 2N polarization directions are distributed so that the angular difference is constant, so there are two polarization directions D(i+k) and D(ik) that are tilted at the same angle clockwise and counterclockwise from the polarization direction D(i). Here, k is an integer between 1 and (N-1). If i+k is greater than or equal to N, the value obtained by subtracting N from i+k is considered to be the value of i+k. If ik is negative, the value obtained by adding N to ik is considered to be the value of ik.

[0073] The two ports that receive linearly polarized waves in the two polarization directions D(i+k) and D(ik) are considered as a pair, and the transmittance and phase shift of the two ports are set so that the receiving sensitivity of the linearly polarized wave in the polarization direction D(i) is maximized. Specifically, the transmittance of the two ports is made equal. The phase shift is set to 0° or 180° so that it matches the phase of the port that receives the linearly polarized wave in the polarization direction D(i).

[0074] For a port that receives a linearly polarized wave in a polarization direction D(i+N) orthogonal to the polarization direction D(i), the transmission rate is set to 0.

[0075] As in the modified example shown in FIG. 12, it is possible to set the transmittance and phase change amount of 2N ports so as to maximize the reception sensitivity of the linearly polarized or elliptically polarized incoming radio waves.

[0076] As an example of the modification shown in Fig. 12, the amount of transmission (i.e., the amount of change in signal level) of all ports may be made the same, and only the amount of phase change of each port may be adjusted. In this case, the amount of phase change α may be controlled so that the linearly polarized wave component parallel to the polarization direction D(i) of the linearly polarized wave received at the port with the highest reception level is in phase with each port.

[0077] Next, another modification of the second embodiment will be described. In the second embodiment and the modification described above, the polarization directions of the multiple antenna elements do not match, but the polarization directions of at least some of the multiple antenna elements may match. For example, multiple sets of two antenna elements 20 shown in FIG. 6 may be arranged, or multiple sets of three antenna elements 20 shown in FIG. 10 may be arranged.

[0078] Of the multiple antenna elements with different polarization directions, multiple antenna elements with only some of the polarization directions may be arranged. For example, in the example shown in Figure 10, only the first antenna element 20 with ports P0 and P1 may be arranged two times.

[0079] When multiple antenna elements with the same polarization direction are arranged, N antenna elements 20 with different polarization directions are extracted from all the antenna elements 20, and only N antenna elements 20 are operated to detect the long axis direction of the arriving elliptically polarized wave.

[0080] In the second embodiment (FIG. 6), the receiver 31 and the receiving amplifier 33 are provided separately, but the functions of the receiver 31 may be realized by the receiving amplifier 33. For example, the received signal after being amplified by the receiving amplifier 33 but before being combined by the combining / demultiplexing filter 37 may be input to the receiving level comparison / determination unit 32. In this case, the gains of the multiple receiving amplifiers 33 must be set to the same. When receiving signals attenuated by the variable attenuators 35 are input to the receiving level comparison / determination unit 32, the attenuation amounts of the multiple variable attenuators 35 must be set to the same.

[0081] In FIG. 6, the power supply lines from each of the four ports P0, P1, P2, and P3 are branched and the branched power supply lines are connected to the processing unit 30, but each power supply line may also be branched inside the processing unit 30.

[0082] [Third Example] Next, an antenna system according to a third embodiment will be described with reference to Figures 13 and 14. Below, a description of the configuration common to the antenna module according to the second embodiment described with reference to Figures 6 to 9 will be omitted. In the second embodiment, a decrease in reception sensitivity is suppressed when a circularly polarized wave transmitted from a transmitting antenna is received by a linearly polarized antenna element. In contrast, in the third embodiment described below, a decrease in reception sensitivity is suppressed when a linearly polarized wave transmitted from a transmitting antenna is received by a circularly polarized antenna element.

[0083] 13 is a schematic diagram of an antenna system according to a third embodiment. The antenna system according to the third embodiment includes a first antenna module 45 and a second antenna module 46.

[0084] The first antenna module 45 includes two antenna elements 20, a processing unit 30, and a baseband processing unit 40. The configuration of the two antenna elements 20 is the same as the configuration of the two antenna elements 20 of the antenna module according to the second embodiment (FIG. 6), and transmits linearly polarized waves 82. The processing unit 30 includes a receiving amplifier 33, a transmitting amplifier 34, a variable attenuator 35, a phase shifter 36, and a multiplexer / demultiplexer 37, just like the antenna module according to the second embodiment (FIG. 6). The processing unit 30 of the first antenna module 45 according to the third embodiment includes a transmission control unit 39 instead of the receiver 31 and the reception level comparison / determination unit 32 of the processing unit 30 of the antenna module according to the second embodiment (FIG. 6). The transmission control unit 39 selects a port from which to transmit a transmission signal and adjusts the signal level of the transmission signal.

[0085] The baseband processing unit 40 includes a demodulation unit 41 and a reception level comparison unit 42. The demodulation unit 41 demodulates the received signal combined by the combiner / demultiplexer 37. The reception level comparison unit 42 extracts reception level information included in the received signal and compares multiple reception levels. The detailed function of the reception level comparison unit 42 will be described later with reference to FIG. 14. Note that the processing unit 30 and the baseband processing unit 40 do not correspond to hardware (integrated circuit elements) that realize these functions. For example, the function of the demodulation unit 41 may be distributed between a radio frequency integrated circuit element (RFIC) that processes signals in the high frequency range and a baseband integrated circuit element (BBIC) that processes signals in the baseband frequency range.

[0086] The second antenna module 46 includes a transceiver 75 and a transmitting / receiving antenna 76 that transmits and receives circularly polarized waves. If the transmitting / receiving antenna 76 has the characteristic of receiving circularly polarized waves, when linearly polarized waves arrive, the receiving sensitivity is constant regardless of the polarization direction. However, in reality, the transmitting / receiving antenna 76 has the characteristic of having the greatest sensitivity to elliptically polarized waves with the major axis in a certain direction. Therefore, the receiving sensitivity of the transmitting / receiving antenna 76 depends on the polarization direction of the incoming linearly polarized waves. In order to maintain high receiving sensitivity, it is preferable that the first antenna module 45 transmits linearly polarized waves in a polarization direction that increases the receiving sensitivity of the transmitting / receiving antenna 76.

[0087] When the transceiver 75 receives the radio wave, it measures the reception level and transmits a reply signal including information specifying the reception level from the transmitting / receiving antenna 76 .

[0088] Next, the procedure of the process performed by the first antenna module 45 and the second antenna module 46 will be described with reference to Fig. 14. Fig. 14 is a flowchart showing the procedure of the process performed by the first antenna module 45 and the second antenna module 46.

[0089] First, the first antenna module 45 selects one port P0 from the four ports of the two antenna elements 20 (FIG. 13), and supplies a test transmission signal to the selected port P0, thereby exciting the antenna element 20 (step SC1). As a result, a linearly polarized wave 82 is transmitted in the polarization direction corresponding to the port P0 to which the test transmission signal has been supplied.

[0090] The second antenna module 46 receives the linearly polarized wave 82 arriving from the first antenna module 45 and measures the reception level (step SD1). Thereafter, the second antenna module 46 transmits a reply signal 83 including information specifying the measured reception level (step SD2). The first antenna module 45 receives the reply signal 83 from the second antenna module 46 and stores the information specifying the reception level included in the reply signal 83 (step SC2). More specifically, the demodulator 41 (FIG. 13) demodulates the reply signal 83, and the reception level comparator 42 (FIG. 13) stores the information specifying the reception level.

[0091] The processes of steps SC1, SD1, SD2, and SC2 are executed for all remaining ports P1, P2, and P3, while the signal level of the transmission signal transmitted from the first antenna module 45 is kept constant.

[0092] The reception level comparator 42 (FIG. 13) of the first antenna module 45 detects the port at which the reception level of the linearly polarized wave received by the second antenna module 46 is maximized (step SC3). Information specifying the port at which the reception level is maximized is input to the transmission control unit 39 (FIG. 13). The transmission control unit 39 sets the signal level change amount and phase change amount for the four ports P0, P1, P2, and P3 so that the polarization direction of the linearly polarized waves transmitted from the two antenna elements 20 is the same as the direction of the linearly polarized wave at the port at which the reception level is maximized (step SC4). The signal level change amount is set by adjusting the gain of the transmission amplifier 34 and the attenuation of the variable attenuator 35.

[0093] After setting the signal level change amount and phase change amount for each port, the processing unit 30 transmits linearly polarized waves from each of the two antenna elements 20 using the set signal level change amount and phase change amount (step SC5). The second antenna module 46 receives the linearly polarized waves transmitted from the first antenna module 45 (step SD3).

[0094] Next, the excellent effects of the third embodiment will be described. In the third embodiment, the polarization direction of the linearly polarized wave 82 transmitted by the first antenna module 45 is adjusted to a direction that maximizes the receiving sensitivity of the second antenna module 46. This improves the stability of communication from the first antenna module 45 to the second antenna module 46.

[0095] Next, an antenna system according to a modification of the third embodiment will be described with reference to Fig. 15. Fig. 15 is a schematic diagram of an antenna system according to a modification of the third embodiment. In the third embodiment (Fig. 13), the functions of a demodulator 41 and a reception level comparator 42 are realized by a baseband processor 40 separate from the processor 30 that processes the high frequency range.

[0096] 15, the demodulator 41 and the reception level comparator 42 are included in the processing unit 30. For example, an integrated circuit element that performs signal processing in the high frequency range has the functions of the demodulator 41 and the reception level comparator 42. In this way, the functions of the demodulator 41 and the reception level comparator 42 may be provided in the integrated circuit element that performs signal processing in the high frequency range.

[0097] [Application of the antenna module according to the embodiment] Next, a communication system to which the antenna module and antenna system according to each of the first to third embodiments is applied will be described with reference to Figures 16A to 16D. Figures 16A to 16D are schematic diagrams of a communication system using the antenna module according to the above-mentioned embodiments.

[0098] The communication system shown in Fig. 16A includes a mobile terminal 51 such as a smartphone and a base station 52. For example, mobile terminal 51 transmits and receives linearly polarized waves, and base station 52 transmits and receives circularly polarized waves. The communication system shown in Fig. 16B includes a terrestrial base station 53 and a communication satellite 54. Communication satellite 54 transmits and receives linearly polarized waves, and terrestrial base station 53 transmits and receives circularly polarized waves. Note that the communication system may be configured with a mobile terminal moving on the ground and communication satellite 54 instead of terrestrial base station 53.

[0099] The communication system shown in Figure 16C includes a virtual reality / augmented reality terminal 55 and a repeater 56. One of the virtual reality / augmented reality terminal 55 and the repeater 56 transmits and receives linearly polarized waves, and the other transmits and receives circularly polarized waves. Instead of the repeater 56, communication may be performed between a game console or a smartphone and the virtual reality / augmented reality terminal 55. The communication system shown in Figure 16D includes a mobile terminal 57 such as a smartphone and a drone 58 (unmanned aerial vehicle). One of the mobile terminal 57 and the drone 58 transmits and receives linearly polarized waves, and the other transmits and receives circularly polarized waves.

[0100] In the various communication systems shown in Figures 16A to 16D, by adopting the antenna module or antenna system according to the above-mentioned embodiments, it is possible to suppress a decrease in reception sensitivity and ensure stable communication.

[0101] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0102] 20 antenna elements 30 Processing section 31 Receiver 32 Reception level comparison and judgment unit 33 Receiving amplifier 34 Transmitting amplifier 35 Variable Attenuator 36 Phase shifter 37 Synthetic demultiplexer 38 Transceiver 39 Transmission control section 40 Baseband processing section 41 Demodulation section 42 Reception level comparison section 45 First Antenna Module 46 Second Antenna Module 51 Mobile devices 52 Base station 53 Terrestrial base stations 54 Communications satellite 55 Virtual reality / augmented reality devices 56 Repeater 57 Mobile Devices 58 Drone 72 transmitting antenna 75 Transceiver 76 Transmitting and receiving antenna 80 Elliptical Polarization 81 Polarized electric field vector tip locus 82 Linearly polarized 83 Reply Signal

Claims

1. a plurality of antenna elements each including two ports for receiving two orthogonal linearly polarized waves; a processing unit that processes signals received by the plurality of antenna elements; Equipped with The polarization directions of the linearly polarized waves received by each of the two ports of the plurality of antenna elements are different among the plurality of antenna elements, The processing unit is an antenna module that compares the reception levels of linearly polarized components received at each of a plurality of ports included in the plurality of antenna elements when radio waves arrive, and detects the port with the highest reception level.

2. 2. The antenna module according to claim 1, wherein the number of the plurality of antenna elements is N (N is an integer greater than or equal to 2), and the antenna module receives linearly polarized waves whose polarization directions differ by 180 / (2N) degrees at each port of each of the plurality of antenna elements.

3. The antenna module according to claim 1 or 2, wherein the processing unit controls the amount of phase change of the received signal output from the multiple ports so that the phase of the polarization direction component of the linearly polarized wave received at the port with the highest reception level among the multiple ports is in phase among the multiple ports included in the multiple antenna elements.

4. the processing unit includes a plurality of phase shifters connected to a plurality of ports of the plurality of antenna elements, respectively; 4. The antenna module according to claim 3, wherein each of the plurality of phase shifters controls the amount of phase change of the received signals output from the plurality of ports.

5. The antenna module described in claim 3, wherein the processing unit controls the amount of change in signal level of the received signal output from the two ports of each of the plurality of antenna elements so that the polarization direction of the radio waves received by each of the plurality of antenna elements is parallel to the polarization direction of the linearly polarized wave received by the port among the plurality of ports with the highest reception level.

6. the processing unit includes at least one of a plurality of receiving amplifiers and a plurality of variable attenuators connected to the plurality of ports of the plurality of antenna elements, 6. The antenna module according to claim 5, wherein the amount of change in signal level is controlled by controlling at least one of the gain of each of the plurality of receiving amplifiers and the attenuation of each of the plurality of variable attenuators.

7. A plurality of antenna elements each having two ports, and transmitting and receiving two linearly polarized waves having different polarization directions via the two ports; and a first antenna module that supplies transmission signals to the plurality of antenna elements and has a processing unit that processes received signals received by the plurality of antenna elements; a second antenna module that receives radio waves transmitted from the first antenna module, measures a reception level, and transmits a signal including information specifying the measured reception level back to the first antenna module; Equipped with The polarization directions of the linearly polarized waves transmitted by the plurality of antenna elements are different among the antenna elements, The processing unit a process of supplying a transmission signal to one port of a plurality of ports included in the plurality of antenna elements to transmit a linearly polarized wave, and receiving a return signal returned from the second antenna module, for each of the plurality of ports; An antenna system that detects the port among the plurality of ports that was used when the reception level was highest, based on information that specifies the reception level contained in the return signal.

8. The antenna system according to claim 7, wherein the processing unit controls the amount of change in signal level and the amount of change in phase of the transmission signal supplied to the two ports of each of the plurality of antenna elements so that the plurality of antenna elements radiate linearly polarized waves having the same polarization direction as the linearly polarized wave radiated by the port used when the reception level is highest among the plurality of ports.

9. the processing unit includes a plurality of phase shifters connected to the plurality of ports, respectively; 9. The antenna system according to claim 8, wherein each of the plurality of phase shifters controls the amount of phase change of the received signals output from the plurality of ports.

10. the processing unit includes at least one of a plurality of receiving amplifiers and a plurality of variable attenuators connected to the plurality of ports, 10. The antenna system according to claim 8, wherein the amount of change in signal level is controlled by controlling at least one of the gain of each of the plurality of receiving amplifiers and the attenuation of each of the plurality of variable attenuators.

11. A method for receiving radio waves with a plurality of antenna elements, each of which includes two ports for receiving two orthogonal linearly polarized waves, wherein the polarization directions of the linearly polarized waves received by each of the two ports differ among the plurality of antenna elements, Acquiring received signals of the incoming radio waves received at each of the two ports of the plurality of antenna elements; A radio wave receiving method for comparing the reception levels of linearly polarized components received at each of a plurality of ports included in the plurality of antenna elements between the plurality of ports, and detecting the port with the highest reception level.

12. 12. The radio wave receiving method according to claim 11, wherein communication is performed by setting the signal level change amount and phase change amount of each of the two ports of the plurality of antenna elements so that the receiving sensitivity of the linearly polarized wave received at the port with the highest receiving level among the plurality of ports is maximized.

13. The radio wave receiving method according to claim 12, wherein when the reception level of the received signal falls below a judgment threshold during the period in which the communication is being performed, the steps of detecting the port with the highest reception level and setting the signal level change amount and phase change amount for each of the two ports of the plurality of antenna elements are executed again.

Images