Narrow directional planar antenna

Abstract

To provide a technique for suppressing the deterioration of the axial ratio caused by narrowing the spacing between antenna elements.SOLUTION: Antenna elements 21 to 23 are arranged without contact with each other and at intervals of less than 0.6λ, and λ is the wavelength corresponding to the center frequency of the signal to be transmitted and received. With regard to the antenna elements 21 to 23, the antenna elements located at both ends in the arrangement direction are referred to as the end elements 21 and 23, and the antenna element located in the center in the arrangement direction is referred to as the central element 22. The phase difference of the feed signals supplied to the feed points P1 and P2 of the end elements 21 and 23 is set to 90°. The phase difference of the feed signals supplied to the feed points P1 and P2 of the central element 22 is set to a value other than 90° such that the axial ratio of a narrow directional planar antenna 1 is 0 to 3 dB.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a narrow directional planar antenna. [Background technology]

[0002] In systems that realize communication in a small area, such as an RFID system that reads information on an IC chip embedded in a tag without contact, it is desirable to sharpen the directivity of the antenna. Furthermore, antennas used in RFID systems often use circular polarization so that RFID tags can be read regardless of their orientation. The following Patent Document 1 describes a narrow-directivity planar antenna that narrows the half-power angle and reduces the side lobe level by adjusting the phase and power of the distributed input supplied to multiple antenna elements arranged along the arrangement direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6741503 Summary of the Invention [Problem to be solved by the invention]

[0004] The multiple antenna elements that make up a narrow directivity planar antenna are usually arranged at intervals of 0.6λ to λ, where λ is the wavelength at the center frequency of the radio waves transmitted and received by the narrow directivity planar antenna. In a narrow directivity planar antenna, in order to slightly widen the directivity or to make the planar antenna smaller, it is necessary to make the arrangement interval of the antenna elements narrower than 0.6λ.

[0005] However, when the spacing between antenna elements is narrower than 0.6λ, the axial ratio deteriorates and the deviation from the ideal circular polarization becomes large, resulting in a significant drop in the read rate depending on the orientation of the RFID tag.

[0006] One aspect of the present disclosure provides a technique for suppressing degradation of the axial ratio caused by narrowing the spacing between antenna elements. [Means for solving the problem]

[0007] One aspect of the present disclosure is a narrow-directivity planar antenna, comprising three or more antenna elements, three or more feeding circuits, and a signal supply unit. The three or more antenna elements are arranged along a preset arrangement direction and have the same configuration. The feeding circuit is provided in each of the three or more antenna elements, and is configured to transmit and receive circularly polarized waves by feeding power to two feeding points provided in two directions perpendicular to each other as viewed from the center of the antenna elements. The signal supply unit supplies a feeding signal of the same phase to each of the three or more feeding circuits. The three or more antenna elements are arranged without contacting each other and at intervals of less than 0.6λ, where λ is a wavelength corresponding to the center frequency of the signal to be transmitted and received. Among the three or more antenna elements, the antenna elements located at both ends in the arrangement direction are referred to as end elements, and one or more antenna elements other than the end elements located in a range symmetrical to the center of the arrangement direction are referred to as central elements. In the end feeding circuit, which is a feeding circuit that feeds power to the end elements, the phase difference of the feeding signal supplied to the two feeding points is set to 90°. The central feeding circuit, which is a feeding circuit that feeds power to the central element, is set so that the phase difference between feeding signals supplied to two feeding points is other than 90° so that the axial ratio of the narrow directivity planar antenna is 0 to 3 dB.

[0008] With this configuration, it is possible to suppress the deterioration of the axial ratio caused by narrowing the spacing between the antenna elements. In one embodiment of the present disclosure, three or more antenna elements may be configured to transmit and receive right-handed circularly polarized waves. In this case, the central feed circuit may be configured such that the phase difference between the feed signals supplied to the two feed points is α, and is 90°<|α|<180°.

[0009] In one embodiment of the present disclosure, three or more antenna elements may be configured to transmit and receive left-handed circularly polarized waves. In this case, the central feed circuit may be configured such that the phase difference between the feed signals supplied to the two feed points is α, and is 0°<|α|<90°.

[0010] In one aspect of the present disclosure, the signal supply section may be set so that the power of the feed signal supplied to the edge feed circuit is smaller than the power of the feed signal supplied to the center feed circuit. With this configuration, the side lobes can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a top view showing the appearance of the planar antenna according to the present embodiment. [Diagram 2] FIG. 2 is a rear view showing the appearance of the planar antenna according to the present embodiment. [Diagram 3] FIG. 2 is an explanatory diagram showing a circuit configuration of a power supply circuit. [Figure 4] 1 is a graph showing how the horizontal directivity pattern changes when the spacing between antenna elements of a planar antenna is changed. [Diagram 5] 1 is a graph showing the relationship between the arrangement interval of antenna elements and the axial ratio of a planar antenna. [Figure 6] 1 is a graph showing the relationship between the arrangement interval of antenna elements and the antenna gain of a planar antenna. [Figure 7] This is a graph showing the relationship between the phase difference at the two feed points of the central antenna element and the axial ratio of the planar antenna when the antenna elements of the planar antenna are arranged at an interval of 0.55λ and right-handed circularly polarized waves are transmitted and received. [Figure 8] 1 is a graph showing the relationship between the phase difference at the two feed points of the central antenna element and the antenna gain of the planar antenna when the antenna elements of the planar antenna are arranged at an interval of 0.55λ and right-handed circularly polarized waves are transmitted and received. [Figure 9]1 is a graph showing the relationship between the phase difference at the two feed points of the central antenna element and the axial ratio of the planar antenna when the antenna elements of the planar antenna are arranged at an interval of 0.55λ and left-handed circularly polarized waves are transmitted and received. [Figure 10] 1 is a graph showing the relationship between the phase difference at the two feed points of the central antenna element and the antenna gain of the planar antenna when the antenna elements of the planar antenna are arranged at an interval of 0.55λ and the antenna elements are configured to transmit and receive left-handed circularly polarized waves. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] A narrow directivity planar antenna (hereinafter, referred to as planar antenna) 1 shown in Fig. 1 and Fig. 2 is installed and used, for example, at an RFID communication gate. The RFID communication gate is installed at the entrance of a facility to be monitored, and is used to read identification information from an RFID tag attached to an article carried by a person passing through the entrance. In this embodiment, the planar antenna 1 transmits and receives radio waves of 916.8 MHz to 923.4 MHz.

[0013] The planar antenna 1 includes a reflector 10, three antenna elements 21 to 23, three feed circuits 31 to 33, a distributor / combiner 40, attenuators 61 and 62, and coaxial cables 51 and 52. The planar antenna 1 may be housed in an antenna case made of resin that is permeable to radio waves.

[0014] Reflector 10 includes a metal plate formed into a rectangular shape. Antenna elements 21-23 are disposed on a front surface 10A of reflector 10. Feed circuits 31-33 and a distributor / combiner 40 are disposed on a back surface 10B of reflector 10. Reflector 10 reflects radio waves radiated from antenna elements 21-23.

[0015] The antenna elements 21-23 are patch antennas formed in a substantially square shape with one side having a length X that is smaller than that of the reflector 10. The antenna elements 21-23 are feed elements, and radiate radio waves in a direction opposite to the direction toward the reflector 10. The antenna elements 21-23 are arranged at equal intervals with an arrangement interval W on the surface 10A along the longitudinal direction of the reflector 10. In other words, the antenna elements 21-23 constitute an array antenna.

[0016] Specifically, antenna elements 21 and 23 are arranged on both ends with antenna element 22 at the center. In the following, the side where antenna element 21 is arranged is referred to as the left side, and the side where antenna element 23 is arranged is referred to as the right side, as viewed from antenna element 22. In addition, a plane that is perpendicular to surface 10A of reflector 10 and aligned along the arrangement direction of antenna elements 21 to 23 is referred to as a horizontal plane.

[0017] The wavelength at the center frequency of the radio waves transmitted and received by the antenna elements 21-23 is λ, and the wavelength shortened on the antenna elements 21-23 is λg. The length X of one side of the antenna elements 21-23 is set to X=λg / 2. In this embodiment, the wavelength shortening rate is set to 0.88, and X=143.5 mm. The arrangement interval W of the antenna elements 21-23 is set to W<0.6λ according to the desired directivity on the horizontal plane. In this embodiment, the half-value angle is set to W=0.55λ (=180 mm) in order to expand the half-value angle from about 22°, which is realized when W=0.88λ, to about 33°.

[0018] 2, the feed circuits 31-33 are formed on separate substrates 71-73, respectively. The feed circuits 31-33 are disposed at positions facing the antenna elements 21-23 across the reflector 10. The feed circuits 31-33 are connected from the rear surface 10B of the reflector 10 to the antenna elements 21-23 on the front surface 10A, and are circuits that excite the antenna elements 21-23 to transmit and receive circularly polarized waves.

[0019] The distribution / combiner 40 is a circuit that divides the transmission input, which is a high-frequency signal input to the planar antenna 1, equally or unequally into three and generates three distribution inputs S1 to S3 that are supplied to the power supply circuits 31 to 33. Further, the distribution / combiner 40 is a circuit that combines the reception signals R1 to R3 received by the antenna elements 21 to 23 and supplied via the power supply circuits 31 to 33 equally or unequally and outputs the combined signal. The distribution / combiner 40 may be formed on the same substrate 72 as the power supply circuit 32 disposed near the center in the longitudinal direction of the planar antenna 1.

[0020] Since the power supply circuits 31 to 33 all have the same configuration, when not specifying any one of them, they are denoted as the power supply circuit 3. Also, the antenna element to be powered by the power supply circuit 3 is denoted as the antenna element 2, the substrate on which the power supply circuit 3 is mounted is denoted as the substrate 7, the signal supplied from the distribution / combiner 40 to the power supply circuit 3 is denoted as the distribution input S, and the signal supplied from the power supply circuit 3 to the distribution / combiner 40 is denoted as the reception signal R.

[0021] As shown in FIG. 3, the power supply circuit 3 includes a distribution / combiner DM using a Wilkinson circuit. The power supply circuit 3 divides the distribution input S into two by the distribution / combiner DM and supplies the divided signals to two power supply points P1 and P2 provided on the antenna element 2 via the transmission lines L1 and L2. The power supply circuit 3 generates the reception signal R by combining the signals from the two power supply points P1 and P2 by the distribution / combiner DM, and supplies the generated reception signal R to the distribution / combiner 40.

[0022] The feed point P1 is provided near the midpoint between the center C of the antenna element 2 and the right end side Er of the antenna element 2. The feed point P2 is provided near the midpoint between the center C of the antenna element 2 and the upper end side Eu of the antenna element 21. The transmission lines L1 and L2 extending from the distributor / synthesizer DM to the feed points P1 and P2 are set to different lengths so that a phase difference occurs between the two feed points P1 and P2 for the divided input S divided into two by the distributor / synthesizer DM. The phase difference between the two feed points P1 and P2 is set in the feed circuits 31 and 33 so that the phase at the feed point P2 is -90° with the feed point P1 as the reference (i.e., 0°). In the feed circuit 32, the phase at the feed point P2 is set to -95° to -165° (for example, -130°). That is, the feed circuits 31 and 33 are configured to operate the antenna elements 21 and 23 as right-handed circularly polarized antennas, and the feed circuit 32 is configured to operate the antenna element 22 as a right-handed elliptically polarized antenna. A method for setting the phase difference between the feed points P1 and P2 by the feed circuit 32 will be described later.

[0023] In FIG. 3 , of the transmission line L2 extending from the distributor-synthesizer DM to the power feed point P2, the transmission line L2a indicated by a solid line is applied to the power feed circuit 32, and the transmission line L2b indicated by a dotted line using a shortcut is applied to the power feed circuits 31 and 33.

[0024] Returning to FIG. 2, the distributor-combiner 40 is individually connected to each of the power feed circuits 31-33. The distribution input S2 generated by the distributor-combiner 40 is supplied to the power feed circuit 32 that drives the antenna element 22 via a line 53 that transmits a high-frequency signal formed on the substrate 72. The distribution input S1 is supplied to the power feed circuit 31 that drives the antenna element 21 via an attenuator 61 and a coaxial cable 51, and the distribution input S3 is supplied to the power feed circuit 33 that drives the antenna element 23 via an attenuator 62 and a coaxial cable 52. The coaxial cables 51 and 52 are cables of the same length. The power feed circuits 31-33 receive the distribution inputs S1-S3 and excite the antenna elements 21-23. The excited antenna elements 21-23 radiate radio waves.

[0025] The output of the planar antenna 1 is a composite output obtained by combining the outputs of the antenna elements 21 to 23. In other words, the planar antenna 1 radiates a composite radio wave obtained by combining the radio waves radiated by the antenna elements 21 to 23. Due to the characteristics of the array antenna, when the outputs of the antenna elements 21 to 23 are all in phase, the half-value angle of the planar antenna 1 is narrower than the half-value angle when there is only one antenna element. Therefore, in order to obtain narrow directivity, the phases of the three distributed inputs S1 to S3 are adjusted so that the outputs of the antenna elements 21 to 23 are in phase.

[0026] Specifically, the phase of the distributed inputs S1 and S3 is adjusted by the lengths of the coaxial cables 51 and 52. With the central feed circuit 32 as the reference circuit, the phase change amount of the distribution input S2 that changes during transmission from the distributor / combiner 40 to the feed circuit 32 is set to θa [°]. The phase change amount θb of the distribution inputs S1 and S3 that changes during transmission from the distributor / combiner 40 to the feed circuits 31 and 33 must be set to θa+2Nπ, where N is an integer equal to or greater than 0. In this case, if the wavelength shortening rate of the coaxial cables 51 and 52 is b [%], the speed of light is c, and the center frequency of the distribution inputs S1 to S3 is F [Hz], the length L of the coaxial cables 51 and 52 that gives the phase change amount θb=θa+2Nπ is expressed as L=(c / F)×[(θa+2Nπ) / (2π)]×(b / 100) [m]. In other words, by setting the length of the coaxial cables 51 and 52 to a value that satisfies the above formula for L, the outputs of the antenna elements 21 to 23 can be made in phase.

[0027] Here, when the outputs of the antenna elements 21 to 23 are combined, the half-power angle of the main lobe can be narrowed, but side lobes appear. In order to reduce the side lobe level, the power of the three distributed inputs S1 to S3 is adjusted so that the output of the antenna elements 21 and 23 located at the outermost positions of the array is smaller than the output of the antenna element 22 at the center. However, the more the output of the antenna elements 21 and 23 is reduced, the more the side lobe level is reduced, but the function as an array antenna is degraded and the half-power angle increases. Therefore, the reduction amount of the output of the antenna elements 21 and 23 may be selected so as to obtain a good narrow directivity according to the half-power angle and side lobe level required in the system in which the planar antenna 1 is installed. Specifically, the attenuation amount in the attenuators 61 and 62 is adjusted taking into account the loss in the coaxial cables 51 and 52. In this embodiment, the lengths of the coaxial cables 51, 52 and the attenuation amounts of the attenuators 61, 62 are made equal to make the powers of the distributed inputs S1, S3 equal, and the central antenna element 22 is used as a reference element to adjust the powers of the distributed inputs S1 to S3 to be symmetrical with respect to the reference element. For example, the output of the antenna elements 21, 23 is set to be 5 dB lower than the output of the antenna element 22.

[0028] [3. Method for Setting Phase Difference at Feed Points P1, P2 of Antenna Element 22] First, FIG. 4 shows the results of a simulation performed to determine whether the directivity in the horizontal plane can be expanded by changing the arrangement interval W of the antenna elements 21 to 23 in a conventional device.

[0029] The conventional device here refers to a planar antenna in which in-phase distributed inputs S1 to S3 are supplied to each of the antenna elements 21 to 23, and the phase difference of feed point P2 relative to feed point P1 is -90°, i.e., the antenna elements 21 to 23 are all configured to function as right-hand circularly polarized antennas.

[0030] Figure 4 shows the characteristics of a conventional device with a center frequency of 920 MHz, where W=0.88λ (=287 mm) is set so that the half-angle representing the directivity is about 22°, and the characteristics of a conventional device with W=0.55λ (=180 mm) set so that the half-angle is about 33°, i.e., W<0.6λ. In other words, it can be seen that the half-angle of the directivity can be set arbitrarily by adjusting the arrangement interval W. However, when W<0.6λ is set, the axial ratio and the antenna gain of the planar antenna decrease, as shown in Figures 5 and 6.

[0031] Fig. 5 shows the results of a simulation of the relationship between the arrangement interval W of the antenna elements 21-23 and the axial ratio in a conventional device. Fig. 6 shows the results of a simulation of the relationship between the arrangement interval W of the antenna elements 21-23 and the antenna gain of the planar antenna 1 in a conventional device. Both Fig. 5 and Fig. 6 show the cases where the center frequency is 920 MHz and ±10 MHz (i.e., 910 MHz, 930 MHz).

[0032] As can be seen from Figure 5, when W≧0.6λ, the axial ratio can be set to 0 to 3 dB, when W is smaller than 0.6λ, the axial ratio deteriorates rapidly, and when W=0.55λ, the axial ratio exceeds 3 dB. Also, as can be seen from Figure 6, when W is smaller than 0.55λ, the antenna gain decreases rapidly. In other words, when W=0.55λ, the decrease in antenna gain is within the allowable range, but the deterioration of the axial ratio is outside the allowable range.

[0033] Next, in the planar antenna 1 of this embodiment, the relationship between the phase difference α of the feed point P2 relative to the feed point P1 of the antenna element 22 located at the center and the axial ratio and antenna gain of the planar antenna 1 was obtained by simulation, and the results are shown in Figures 7 and 8.

[0034] The planar antenna 1 according to this embodiment refers to a planar antenna in which, for the antenna element 22, the phase difference between the feed point P2 and the feed point P1 is not limited to -90°. 7 and 8, the phase difference α of the antenna elements 21 and 23 located at both ends of the planar antenna 1 is maintained at -90°, and the phase difference α of the antenna element 22 located at the center is changed between 0° and -180°. Also, Figs. 7 and 8 show the cases where the frequencies are 910 MHz, 920 MHz, and 930 MHz.

[0035] From FIG. 7, it can be seen that the axial ratio is improved by changing the phase difference α, and in particular, when the phase difference α is in the range of -95° to -165°, the axial ratio is 0 to 3 dB, and the best point for the axial ratio is around α = -130°.

[0036] 8, in the range of α=-95° to -165° where the axial ratio can be set to 0 to 3 dB, the antenna gain decreases as |α| increases. In other words, the phase difference α is set so as to obtain the best balance between the axial ratio and the antenna gain in the range of α=-95° to -165°.

[0037] 7 and 8 have been described for the case where the planar antenna 1 transmits and receives right-handed circularly polarized waves, but the case where the planar antenna 1 transmits and receives left-handed circularly polarized waves will be described with reference to FIGS. 9 and 10. FIG. 9 and 10, in-phase distributed inputs S1 to S3 are supplied to the antenna elements 21 to 23. The antenna elements 21 and 23 located at both ends are set so that the phase difference α of the feed point P2 relative to the feed point P1 is 90°, and the antenna element 22 located in the center changes the phase difference of the feed point P2 relative to the feed point P1 between 0° and 180°.

[0038] FIG. 9 shows the results of a simulation of the relationship between the phase difference α and the axial ratio of the planar antenna 1, and FIG. 10 shows the results of a simulation of the relationship between the phase difference α and the antenna gain of the planar antenna 1.

[0039] From Figure 9, we can see that even in the case of left-handed circularly polarized waves, the axial ratio is improved by changing the phase difference α, and in particular, when the phase difference α is in the range of 0° to 70°, the axial ratio is 0 to 3 dB, and the best point for the axial ratio is around α = 30°.

[0040] 10, in the range of α=10° to 80° where the axial ratio can be set to 0 to 3 dB, the smaller α is, the lower the antenna gain becomes. In other words, the phase difference α is set so as to obtain the best balance between the axial ratio and the antenna gain in the range of α=10° to 80°.

[0041] That is, in the case of right-handed circularly polarized waves, the axial ratio is improved by adjusting the phase difference to be wider than -90°, i.e., by delaying the phase of feed point P2 with respect to feed point P1 as the reference. Also, in the case of left-handed circularly polarized waves, the axial ratio is improved by adjusting the phase difference to be narrower than 90°, i.e., by advancing the phase of feed point P2 with respect to feed point P1 as the reference. [4. Correspondence of terminology] In this embodiment, the planar antenna 1 corresponds to the narrow directivity antenna of the present disclosure. The antenna elements 21 and 23 correspond to the end elements of the present disclosure, and the antenna element 22 corresponds to the center element of the present disclosure. The power feed circuits 31 and 33 correspond to the end feed circuit of the present disclosure, and the power feed circuit 32 corresponds to the center feed circuit of the present disclosure. The coaxial cables 51 and 52, the line 53, and the attenuators 61 and 62 correspond to the signal supply unit of the present disclosure. The distribution inputs S1 to S3 correspond to the power feed signals of the present disclosure.

[0042] [5. Effects] According to the planar antenna 1 described above in detail, even if the arrangement interval W of the antenna elements 21-23 is narrower than 0.6λ, it is possible to suppress deterioration of the axial ratio. Therefore, it is possible to arbitrarily set the arrangement interval W of the antenna elements 21-23 and the half-value angle of the main lobe while maintaining the axial ratio characteristic.

[0043] 6. Other embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0044] (a) In the above embodiment, the case where three antenna elements 21 to 23 are used has been described, but the number of antenna elements may be four or more. When the number of antenna elements is four or more, the antenna elements for which the phase difference between the feed points P1 and P2 is set to a value other than |90|° may be all antenna elements located other than at both ends. In addition, the antenna elements may be part of the antenna elements located other than at both ends, and may be antenna elements located in a range symmetrical to the center of the arrangement direction of the antenna elements 21 to 23.

[0045] (b) Multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0046] (c) In addition to the above-described planar antenna 1, the present disclosure can also be realized in various forms, such as a system including the planar antenna 1 as a component, and a method for improving an axial ratio. [Explanation of symbols]

[0047] 1...narrow-directivity planar antenna (planar antenna), 2 (21-23)...antenna element, 3 (31-33)...feed circuit, 7...substrate, 10...reflector, 10A...front surface, 10B...back surface, 40...distributor / combiner, 51, 52...coaxial cable, 53...line, 61, 62...attenuator, 71-73...substrate, DM...distributor / combiner, L1, L2...transmission line, P1, P2...feed point.

Claims

1. A narrow directional planar antenna, Three or more antenna elements having the same configuration and arranged along a preset arrangement direction; Three or more feeding circuits are provided in each of the three or more antenna elements, and are configured to transmit and receive circularly polarized waves by feeding power to two feeding points provided in two directions perpendicular to each other as viewed from a center of the antenna element; A signal supply unit that supplies in-phase power supply signals to each of the three or more power supply circuits; Equipped with The three or more antenna elements are arranged without contact with each other and at intervals of less than 0.6λ, where λ is a wavelength corresponding to a center frequency of a signal to be transmitted or received; Among the three or more antenna elements, the antenna elements located at both ends in the arrangement direction are defined as end elements, and one or more antenna elements other than the end elements located in a range symmetrical to the center of the arrangement direction are defined as a central element, The edge feeding circuit, which is the feeding circuit that feeds power to the edge element, is set so that the phase difference of the feeding signals supplied to the two feeding points is 90°, The central feed circuit, which is the feed circuit that feeds power to the central element, is configured so that the phase difference of the feed signals supplied to the two feed points is set to a value other than 90° so that the axial ratio of the narrow directivity planar antenna is 0 to 3 dB. Narrow directional planar antenna.

2. 2. The narrow directional planar antenna according to claim 1, the three or more antenna elements are configured to transmit and receive right-handed circularly polarized waves; The central feeding circuit is set so that a phase difference between the feeding signals supplied to the two feeding points is α and is 90°<|α|<180°. Narrow directional planar antenna.

3. 2. The narrow directional planar antenna according to claim 1, the three or more antenna elements are configured to transmit and receive left-handed circularly polarized waves; The central feeding circuit is set so that the phase difference between the feeding signals supplied to the two feeding points is α and is 0<|α|<90°. Narrow directional planar antenna.

4. The narrow directional planar antenna according to any one of claims 1 to 3, The signal supply unit is set so that the power of the feed signal supplied to the edge feed circuit is smaller than the power of the feed signal supplied to the center feed circuit. Narrow directional planar antenna.

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