JP2014132729A - Waveguide slot array antenna, method of designing the same, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circularly polarized slot antenna that keeps an axial ratio intact over a wide band.SOLUTION: The waveguide slot array antenna includes: a first plane waveguide circuit 300 for guiding a first polarized wave input through a first feed port 301 and having a direction of vibration in a first direction to radiate the first polarized wave from a first plane waveguide slot disposed at each end portion of a plurality of waveguides arranged isometrically from the first feed port 301; and a second plane waveguide circuit 200 for guiding a second polarized wave input through a second feed port 201 and having a direction of vibration in a direction orthogonal to the first polarized wave to radiate the second polarized wave from a second plane waveguide slot disposed at each end portion of a plurality of waveguides arranged isometrically from the second feed port 201 and over the same length as those of the first plane waveguide circuit 300. The first plane waveguide slot and the second plane waveguide slot are arranged such that a composite wave of the first polarized wave and the second polarized wave radiated is a circularly polarized wave.

Description

  The present invention relates to a slot array antenna that emits circularly polarized waves, a design method thereof, and a manufacturing method thereof.

  From the viewpoint of mobile communication, satellite communication, and effective use of frequency, circularly polarized antennas have attracted attention. Circular polarization is polarization in which the direction of the electric field rotates in a plane perpendicular to the traveling direction of the electromagnetic wave with a period equal to the excitation frequency.

  Linearly polarized waves (horizontal polarization or vertical polarization) are used in terrestrial wireless communication. However, for example, when linearly polarized waves are used for satellite communication or the like, the polarization direction changes depending on the attitude of the satellite, and reception may be difficult because the polarization plane is not determined. If circularly polarized waves are used, reception is possible without determining the plane of polarization.

Various techniques have been proposed in the past for antennas that radiate circularly polarized waves.
For example, Patent Document 1 discloses a rectangular waveguide having a structure in which a rectangular waveguide is bent in the tube axis direction and a radiation slot interval is λg / 2 (λg: wavelength in the tube), and a conventional waveguide having an E-plane slot; A slot antenna that emits circularly polarized waves using these two waveguides is presented.

Non-Patent Document 1 presents a circularly polarized radiation slot antenna in which a slot is provided in a waveguide.
According to this method, circular polarization is realized by shifting the phase of two polarizations by 90 ° with an excitation slot provided at the top of the linear slot.

JP 2008-212326 A

IEICE Transactions on Electronics, vol.94, no.10, pp.1618-1625, Oct. 2011.Yohei Miura, Jiro Hirokawa, Makoto Ando, Kazufumi Igarashi, and GoroYoshida "A high-efficiency circularly-polarized aperture array antennawith a corporate -feed circuit in the 60GHz band "

  According to the method of Patent Document 1, there is a problem that the slot interval depends on the guide wavelength λg, the input of electromagnetic waves of different wavelengths is limited, and the circularly polarized band that can be emitted is narrow. Further, the method of Non-Patent Document 1 has a problem in that the band of circularly polarized light that can be radiated is narrow because the resonance phenomenon of two linearly polarized components orthogonal to each other in the waveguide opening is used.

  A waveguide slot array antenna according to the present invention guides a first polarized wave having a vibration direction in a first direction, which is input from a first feeding port, and is equal in length from the first feeding port. The first surface waveguide circuit that radiates the first polarized wave from the waveguide first surface slot provided at each end of the plurality of waveguides provided in the manner described above and the second power supply port, A second polarized wave having a vibration direction in a direction orthogonal to one polarized wave is guided so as to be equal in length from the second feeding port and the same length as the waveguide length of the first surface waveguide circuit. A second surface waveguide circuit that radiates a second polarization from a waveguide second surface slot provided at each end of a plurality of waveguides provided in the waveguide, the waveguide first surface slot and the waveguide The waveguide second surface slot is installed so that the synthesized wave of the first polarized wave and the second polarized wave is circularly polarized.

  The present invention further includes a bottomed cylindrical circular waveguide having an opening at one end, and the circular waveguide receives linearly polarized light radiated from the first waveguide slot. The first surface slot is formed on the other end surface, and the second surface slot is formed on the side wall so as to input linearly polarized light radiated from the waveguide second surface slot. In addition, circularly polarized waves may be radiated from the opening surface of the circular waveguide.

  The present invention further includes an excitation unit having a circular cavity communicating with the circular waveguide, and the circular cavity of the excitation unit is designed to have a radius so that circularly polarized waves from the waveguide are excited. It may be configured as described.

  Furthermore, in the present invention, the excitation unit is provided so as to close the circular cavity, and has a slot plate in which a plurality of radiation slots are perforated, and the slot plate includes a slot plate in the excitation unit. In the distribution of the excited electromagnetic field, the radiation slot may be formed at a position where the intensity of the cross-sectional electromagnetic field is high, and circularly polarized waves may be emitted from the radiation slot.

  In the present invention, the radiation slot may be circular.

  In the present invention, the radiation slot may be configured to have a cross shape.

  A method for designing a waveguide slot array antenna according to the present invention is a method for designing a structure of a radiating element including an excitation unit having a circular cavity and a circular waveguide of the waveguide slot array antenna. A step of determining a radius of the circular waveguide for guiding the circularly polarized wave, a first surface slot for generating a circularly polarized wave by combining the linearly polarized wave incident on the circular waveguide and the second wave; A step of designing a surface slot, a step of designing a radius of an excitation part for exciting the circularly polarized wave radiated from the circular waveguide, and a circularly polarized electromagnetic field portion having a strong circular polarization excited by the excitation part. Designing a radiation slot that emits polarized light.

  Further, in the present invention, a step of designing a first surface waveguide circuit that inputs a horizontally polarized wave to the radiating element, a step of designing a second surface waveguide circuit that inputs a vertically polarized wave to the radiating element, May be further provided.

  A method of manufacturing a waveguide slot array antenna according to the present invention includes a step of creating a radiating element obtained by the design method of the waveguide slot array antenna and a design method of the waveguide slot array antenna. A step of creating the obtained first surface waveguide circuit, a step of producing the second surface waveguide circuit obtained by the design method of the waveguide slot array antenna, and the radiating element on the first surface A step of installing in the waveguide circuit, a step of connecting the radiation element to the second surface waveguide circuit, and a magic T for feeding linearly polarized waves to the first surface waveguide circuit and the second surface waveguide circuit. And a step of performing.

  In the present invention, each of the above steps may be realized by laminating a conductor plate in which a cross-sectional shape of a portion where an electromagnetic wave is guided is formed.

  According to the present invention, it is possible to provide a circularly polarized slot antenna that has a wide band and the axial ratio does not deteriorate.

1 is an overall view of a circularly polarized slot array antenna according to an embodiment of the present invention. It is an exploded view of the apparatus of the circular polarization slot array antenna of embodiment of this invention. It is a top perspective view of a radiating element that radiates circularly polarized waves. It is a bottom perspective view of a radiation element which radiates circular polarization. It is an exploded view of a radiation element. It is a figure of the waveguide circuit of an embodiment of the invention. It is explanatory drawing of slot arrangement | positioning of a circular waveguide. It is a figure of the magic T (branch waveguide) which inputs electromagnetic waves into a 2nd surface waveguide circuit and a 1st surface waveguide circuit. It is the figure which showed the connection part of the magic T and a waveguide circuit. It is the perspective view which showed the connection part of the excitation part 401 provided with the edge part of a waveguide circuit, and a circular waveguide. It is the perspective view which showed the connection part of the excitation part 401 provided with the edge part of a waveguide circuit, and a circular waveguide from the other direction. It is a distribution map in each mode of the electromagnetic field in a circular waveguide. It is the figure shown about the relationship between the Bessel function and the radius of the excitation part 401. FIG. It is the figure which compared the frequency characteristic of a prior art with the frequency characteristic of this Embodiment. It is a figure which shows the modification of embodiment of this invention. It is a figure which shows the modification of embodiment of this invention. It is a flowchart of the design and manufacturing method of the circularly polarized slot array antenna concerning embodiment of this invention. It is a figure of the slot array antenna which discharge | releases the conventional circularly polarized wave relevant to embodiment of this invention. FIG. 3 is an exploded view of a conventional slot array antenna that emits circularly polarized waves related to the embodiment of the present invention. It is a figure which shows the frequency characteristic of the conventional circularly polarized slot array antenna.

  Circular polarization is polarization in which the direction of the electric field is rotating in a plane perpendicular to the traveling direction of the radio wave with a period equal to the excitation frequency. There is polarization. The left-handed circularly polarized wave and the right-handed circularly polarized wave are electrically orthogonal to each other. A circularly polarized wave can be realized by combining two linearly polarized waves having equal amplitude and a phase difference of 90 degrees from each other. However, it is difficult to realize a complete circularly polarized wave, and it is generally an elliptically polarized wave. An axial ratio (AR) is used as an index indicating how close the elliptically polarized wave is to the circularly polarized wave.

  Conversely, an arbitrary elliptically polarized wave can also be expressed as a combination of a left-handed circularly polarized wave and a right-handed circularly polarized wave. When these electric field strengths are EL and ER, respectively, the axial ratio is AR = (| EL | + | ER |) / (| EL | − | ER |). When AR is positive, it becomes a left-handed circularly polarized wave, and when negative, it becomes a right-handed circularly polarized wave. Further, as | AR | is closer to 1, it means closer to circular polarization.

  Actually, the axial ratio is often expressed in dB, and the closer to 0 dB, the closer to circular polarization. The present invention provides a slot array antenna capable of emitting a radio wave with | AR | close to 1.

First, the background of the study conducted until the present invention was conceived will be described.
A related technical example of the slot array antenna that emits circularly polarized waves described in Non-Patent Document 1 is shown in FIGS. FIG. 18 is a diagram of the antenna. FIG. 19 is an exploded view thereof.

  As shown in FIG. 19, a waveguide side wall 106 is provided above the lower end plate 107. Then, a cavity side wall 109 having a cavity 101 is provided on an upper part of a waveguide plate 103 including the waveguide 103 and an upper part of a slot plate 110 having a single slot 102 for emitting linearly polarized light. A slot plate 108 having four slots 100 perforated thereon is provided, and each slot 100 is designed to emit linearly polarized waves having the same frequency and the same amplitude. Then, a circularly polarized wave element 105 using a hexagonal opening 104 having two square corners is installed on the slot 100.

  The electromagnetic wave guided by the waveguide 103 is emitted as a linearly polarized wave from the single slot 102. The linearly polarized waves are excited in the cavity 101 and emitted from the slots 100 as linearly polarized waves having the same amplitude and the same phase. The linearly polarized wave emitted from the slot 100 is decomposed into two orthogonally polarized waves orthogonal to each other in the hexagonal opening 104, and between the two orthogonally polarized waves orthogonal to each other while traveling the distance h of the thickness of the element 105. A phase difference of 90 degrees is generated, and circularly polarized light is radiated from the opening 104 of the element 105. A plurality of antenna elements using the circular polarization element 105 are arranged to form an array antenna.

  This method uses a resonance phenomenon of two linearly polarized components orthogonal to each other at the waveguide opening, and can emit circularly polarized waves having a frequency determined at the design stage. However, if it deviates from the design frequency, the polarization speed and phase shift with respect to the distance of the element thickness, and the circularly polarized wave deteriorates.

  Therefore, the band of circularly polarized light emitted by this method is narrowed. FIG. 20 shows the frequency characteristics when this method is used. Ideally, the axial ratio of the circularly polarized antenna is better as it approaches 0 dB in the design frequency band. It is even better that the bandwidth close to 0 dB is wide around the design frequency. However, the axial ratio according to this method has a very narrow band close to 0 dB as shown in FIG. FIG. 20 shows the result that the axial ratio of circularly polarized waves deteriorates when the design frequency (61.5 GHz) of this method is exceeded. In the case of using the resonance phenomenon with the same two polarizations in other aperture shapes as well, narrow-band circularly polarized radiation is similarly obtained.

Embodiment 1
FIG. 1 shows a configuration of a circularly polarized slot array antenna 1 according to an embodiment of the present invention. FIG. 2 is an exploded view of the circularly polarized slot array antenna 1. The circularly polarized slot array antenna 1 includes a two-layer waveguide circuit (200, 300), a radiating element 400, and a feeding unit (201, 301). Although not shown, the magic T700 is connected to the power feeding units (201, 301).

  FIG. 6 shows the configuration of the feed waveguide circuit (200, 300). The feeding waveguide circuit (200, 300) is a waveguide circuit constituted by a two-layer rectangular waveguide. The waveguide is formed of a conductive metal conductor such as copper or aluminum.

  The lower-layer waveguide is a first surface waveguide circuit 300 that emits a horizontal (H) polarized wave (first polarized wave) having a vibration direction in the y direction on the drawing of FIG. The cross section of the waveguide of the first surface waveguide circuit 300 is rectangular, and is short in the z direction. The first surface waveguide circuit 300 is a circuit in which a rectangular waveguide is branched. The phase of the horizontally polarized wave radiated by this branching method becomes the same phase. The first-surface waveguide circuit is configured such that a plurality of waveguides branch from a central power supply opening and equidistant to each terminal end of the circuit branch.

  A waveguide first surface slot 302 that emits a first surface polarized wave is formed in each end portion of the branch. Horizontal (H) polarized light is incident from the central power supply port 301 of the first surface waveguide circuit, and the first waveguide surface on the bottom surface of the circular waveguide at each end of the branch of the circuit equidistant from the central portion. Radiated from the slot 302 as a horizontal (H) polarized wave (first polarized wave).

  The upper-layer waveguide is a second surface waveguide circuit 200 that emits a vertical (V) polarized wave (second polarized wave) having a vibration direction in the x direction on the drawing of FIG. The waveguide cross section of the second surface waveguide circuit 200 is rectangular and is elongated in the z direction. The second surface waveguide circuit 200 is a circuit in which a rectangular waveguide is branched. The phase of the vertically polarized wave radiated by this branching method becomes the same phase. The second surface waveguide circuit 200 is configured such that a plurality of waveguides are branched from the central power supply port 201 and the terminal ends of the circuit branches are equidistant.

  A waveguide second slot 202 that emits the second polarized wave is formed in each end portion of the branch. Vertical (V) polarized light is incident from the central feeding port 201 of the second surface waveguide circuit 200 and is perpendicular (V) from the waveguide second slot 202 at each terminal end of the circuit branch equidistant from the central portion. Radiated as polarization (second polarization).

FIG. 3 shows a perspective view of a radiating element 400 that radiates circularly polarized waves. FIG. 4 shows a perspective view of the radiating element 400 in another direction that radiates circularly polarized waves. FIG. 5 is an exploded view of the radiating element 400.
The radiating element 400 is provided at each end of the feed waveguide (200, 300). The radiating element includes a circular waveguide 500 formed of a thin conductor plate and an excitation unit 401.

  The excitation unit 401 includes a slot plate 402, a tubular side wall 403 that serves as a side wall of the circular cavity 407, and a lower end plate 404. The slot plate 402 is installed at one end of the side wall 403 so as to close the circular cavity 407. The lower end plate 404 is installed at the other end of the side wall 403 so as to close the circular cavity 407.

  A plurality of radiation slots 405 that radiate circularly polarized waves are formed in the slot plate 402. The lower end plate 404 is provided with an opening 406 for receiving circularly polarized light radiated from the circular waveguide 500.

As shown in FIGS. 4 and 5, the circular waveguide 500 has an opening 503 at one end and is closed at the other end. In FIG. 4, auxiliary lines (504, 505) are drawn on the circular waveguide 500 along the cutting line that appears when the circular waveguide 500 is cut in a virtual plane including the axis for the sake of explanation. Yes.
A first surface slot 502 is formed in the other end so that the first polarized light can enter. The first surface slot 502 is formed so as to be along the y-axis direction shown in FIG. 4 and to be orthogonal to the auxiliary line 504.

  The circular waveguide 500 is provided with a second surface slot 501 on its side surface so that the second polarized wave is incident thereon. The second surface slot 501 is formed so that the center of the slot is along the z-axis direction illustrated in FIG. 4 and passes through the auxiliary line 505. Then, as shown in FIG. 7, the second surface slot 501 is formed so that the center of the second surface slot 501 is located at a distance of about ¼ tube wavelength from the lower end. In this way, the second polarized wave incident from the second surface slot 50 1 and the first polarized wave incident from the first surface slot 502 are combined with each other to form a combined wave.

  However, in this case, the electromagnetic wave incident from the first surface slot 502 goes out to the opening 503 but does not go out to the second surface slot 501. Similarly, the electromagnetic wave incident from the second surface slot 501 goes out to the opening 503 but does not go out to the first surface slot 502. By feeding the first polarization and the second polarization with the same amplitude and a phase difference of 90 degrees, the combined wave becomes a circular polarization.

  The excitation unit 401 and the circular waveguide 500 are joined so that the opening 406 of the circular waveguide 500 communicates with the circular cavity 407. The excitation unit 401 and the circular waveguide 500 are formed of a conductive metal conductor such as copper or aluminum.

  10 and 11 are diagrams showing a connection portion of the radiating element 400 including the end portion of the waveguide circuit (200, 300) and the circular waveguide 500. FIG. A waveguide first surface slot 302 provided at a terminal portion of the first surface waveguide circuit 200 is connected to the first surface slot 502 so that the first polarized wave is incident thereon.

  A waveguide second surface slot 202 provided at the end of the second surface waveguide circuit 200 is connected to the second surface slot 501 so that the second polarization is incident thereon.

  FIG. 8 is a diagram of a magic T700 (branch waveguide) that inputs electromagnetic waves to the second surface waveguide circuit 200 and the first surface waveguide circuit 300. FIG.

  The electromagnetic waves input from the port (1) 701 are emitted from the port (3) 703 and the port (4) 704, respectively, but their directions have a relative phase difference of 90 degrees. And electromagnetic waves are not emitted from the port (2) 702.

  The electromagnetic waves input from the port (2) 702 are emitted from the port (3) 703 and the port (4) 704, respectively, but their directions have a relative phase difference of 90 degrees. And electromagnetic waves are not emitted from the port (1) 701.

  In this case, the phase difference between the electromagnetic waves emitted from the port (3) 703 and the port (4) 704 is opposite to the input of the electromagnetic waves from the port (1) 701. Therefore, when the electromagnetic waves emitted from the port (3) 703 and the port (4) 704 are synthesized so as to be orthogonal depending on whether the input position is the port (1) 701 or the port (2) 702, the right-handed rotation is performed. It is possible to switch between circular polarization and left-handed rotation. The property of the magic T is that the electromagnetic wave is emitted according to the same principle regardless of the frequency of the electromagnetic wave.

  In this embodiment, an example in which electromagnetic waves are input from the power supply ports of the port (1) 701 and the port (2) 702 described above is used. Utilizing the property of this magic T, it is used to feed electromagnetic waves in an antenna whose frequency band of input electromagnetic waves is not limited.

  FIG. 9 shows a connection portion between the magic T700 and the waveguide circuit (200, 300). The radiation port (port (4) 704) of the magic T700 is designed to be connected to the power supply port 301 of the first surface waveguide circuit 300. Further, the radiation port (port (3) 703) of the magic T is designed to be connected to the power supply port 201 of the second surface waveguide circuit 200.

  Then, connecting pipes (705, 706) are provided in the middle so as to be equal in length from the power supply port (ports (701, 702)) to the power supply port (201, 301) of each waveguide (200, 300). That is, the length of the connecting pipe (705, 706) is set so that the distance from the power supply port (701, 702) to the power supply port 201 is equal to the distance from the power supply port (701, 702) to the power supply port 202. adjust. Also, connecting pipes (707, 708) for inputting electromagnetic waves are connected to the power supply ports (ports (701, 702)).

  The electromagnetic waves input from the port (1) 701 or the port (2) 702 of the magic T are distributed to the port (3) 703 and the port (4) 704 so as to have a phase difference of 90 degrees with the same amplitude.

  The electromagnetic waves that are guided by the second surface waveguide circuit 200 and the first surface waveguide circuit 300 and output from each end portion have a phase difference of 90 degrees and become a composite wave inside the circular waveguide 500, and the circular waveguide It is output from the opening 503 of the wave tube 500. In this way, the electromagnetic wave output from the circular waveguide 500 is circularly polarized.

  Further, as described above, the phase difference between the input from the port (1) 701 and the input from the port (2) 702 is reversed. By selecting this input method, the input from the port (1) 701 or the input of the electromagnetic wave from the port (2) 702 is changed, and the rotation direction of the circularly polarized wave output from the circular waveguide 500 is right-handed or left-handed. Output is possible.

  A plurality of radiating elements 400 are installed at a plurality of ends of the second surface waveguide circuit 200 and the first surface waveguide circuit 300 in the same manner as described above, and magic T700 is provided at each power supply port (201, 301). The circularly polarized slot array antenna of FIG. 1 is assembled by connecting the radiation ports (703, 704) of the first and second radiation ports (703, 704) using connecting pipes (705, 706). (In FIG. 1, the state where the magic T700 is not connected is shown.)

Next, the layout design of each part in the present embodiment will be described.
The electromagnetic wave propagating in the circular waveguide 500 of the present embodiment is circularly polarized, and its electric field vector is perpendicular to the direction in which the electromagnetic wave is transmitted, and is in the TE mode. The TE mode is a way of transmitting radio waves traveling in the pipe, and there are the following two expression methods depending on how the radio waves are transmitted. A TE (Transverse Electric Wave) wave is an electrical transverse wave having a magnetic field component in the propagation direction. A TM (Transverse Magnetic Wave) wave is a magnetic transverse wave and has an electric field component in the propagation direction.

  In the TEmn mode and the TMmn mode of the circular waveguide, m is the number of electric field peaks in the circumferential direction (one wavelength is two electric field peaks). n represents the number of peaks of the electric field in the radial direction. FIG. 12 shows a distribution diagram in each mode of the electromagnetic field in the circular waveguide. The solid line in the figure indicates the electric field, and the dotted line indicates the magnetic field. The numerical value of each mode is a value proportional to the cutoff wavelength, and is a value at the extreme value of the Bessel function (cylindrical function) in the TE mode, and the zero point of the Bessel function in the TM mode.

  In the present embodiment, the electromagnetic wave is designed to travel in the circular waveguide 500 in the TE11 mode. As described above, the electromagnetic waves output from the second surface slot 501 and the first surface slot 502 become a composite wave inside the circular waveguide 500. Then, the light is output from the opening 503 of the circular waveguide 500. At this time, the distribution of the electromagnetic field in the circular waveguide 500 is designed to be the TE11 mode of FIG. Hereinafter, the design method is the same as the method of the excitation unit 401.

  The radius of the excitation unit 401 is designed so that the TE12 mode is excited with respect to the propagation of the electromagnetic wave in the excitation unit 401.

  FIG. 13 shows a graph of a Bessel function used to determine the radius of the excitation unit 401 in this embodiment. The x = ρ direction distribution of the φ component of the cross-sectional electric field at φ = 0 ° in the TE mode is given by the differentiation of the Bessel function. A portion where the slope of the Bessel function is large is a position where the cross-sectional electromagnetic field is strong.

  On the other hand, a portion where the slope of the Bessel function is 0 is a portion where the intensity of the cross-sectional electromagnetic field is 0.

  FIG. 12 shows the excitation state of the electromagnetic wave in the excitation unit 401 designed so that the electromagnetic wave is excited in each mode. Regarding TE12 in FIG. 12, a thick dotted line portion indicates a position where the cross-sectional electromagnetic field is strong. The radius R of the excitation unit 401 that excites the TE12 mode is determined. According to FIG. 13, the value normalized by the wave number at the design frequency may be 5.331 or more which is the second extreme value of the first-order Bessel function.

  Similarly, as shown in the lower part of FIG. 13, the value obtained by normalizing the radius r of the circular waveguide 500 by the wave number at the design frequency is larger than 1.841 which is the first extreme value of the Bessel function. design.

  Then, a radiating slot 405 is formed in the slot plate 402 above the portion where the cross-sectional electromagnetic field excited in the excitation unit 401 is strong. Hereinafter, a setting method of the radiation slot 405 will be described. A circular radiation slot 405 is provided in the slot plate 402 on the upper surface of the excitation unit 401. If the slot 401 is not provided and the cavity 401 is opened, circularly polarized light is not emitted with uniform intensity, and the aperture efficiency is reduced. Therefore, if the slot is provided, the circularly polarized wave can be radiated from the slot with uniform intensity, and the aperture efficiency can be kept high. By making each slot position symmetrical, circularly polarized waves are emitted from each slot with the same amplitude.

  The center of the circular radiating slot 405 is the position where the TE12 mode cross-sectional electromagnetic field is strong (the value normalized by the wave number at the design frequency is the first zero of the Bessel function 3.832: TE12 thick dotted line at the bottom of FIG. Part) Design to be near. In the present embodiment, four circular radiating slots 405 are provided with the position where the cross-sectional electromagnetic field is strong as the center point. Here, the slot shape is circular, but other shapes may be used as long as the shape can radiate circularly polarized waves. For example, a cross-shaped slot may be used. In addition, the number of slots is not limited to four as long as slots are provided with the position where the cross-sectional electromagnetic field is strong as a center point.

  On the other hand, in the design of the circular radiating slot 405, it is necessary that the excitation from the circular radiating slot 405 due to a propagation mode other than m = 1 in the cavity is not so large. The excitation by propagation modes other than m = 1 in the cavity becomes a grating lobe at a wide angle (a phenomenon in which an electromagnetic wave having the same intensity as the front direction appears in the wide angle direction) when the array of radiation slots is arranged. However, in the front direction, excitation due to a propagation mode other than m = 1 in the cavity is offset by the symmetry, so that the axial ratio of circularly polarized waves does not deteriorate.

  The distance from each end of the branch circuit of the first surface waveguide circuit 300 and the second surface waveguide circuit 200 in FIG. 6 is the same as the electrical length from the power supply port (201, 301) to the branch end. design. This is to prevent a phase difference between the electromagnetic waves emitted from the terminal portions even when electromagnetic waves having different frequencies are input.

  FIG. 14 is a diagram comparing the frequency characteristics of the prior art and the frequency characteristics of the present embodiment. FIG. 14 shows that the present embodiment has a broadband frequency characteristic as compared with the related technology. That is, in FIG. 14, the thick line portion indicates the axial ratio in the present embodiment, and indicates that circularly polarized light having an axial ratio (dB) of 0 dB is radiated over a wide band.

Next, a method for manufacturing a waveguide slot array antenna having such a radiating element and a circular slot will be described.
FIG. 24 is a flowchart showing the procedure of the design and manufacturing method of the waveguide slot array antenna 1 according to the present embodiment.

In order to manufacture the waveguide slot array antenna 1, first, the circular waveguide 500 of the radiating element 400, the excitation unit 401, and the radiating slot 405 are designed.
In designing the circular waveguide 500, first, the in-tube wavelength of the electromagnetic wave propagating through the circular waveguide 500 and the propagation mode of the electromagnetic wave are determined, and the radius is designed (S100). For example, the electromagnetic wave propagating in the circular waveguide 500 is set to the TE11 mode, and the radius r that is equal to or larger than the cutoff obtained using the Bessel function is determined.

Further, the tube length of the circular waveguide 500 is set to a length of about an integral multiple of half of the in-tube wavelength from the bottom surface so that the amplitude of the circularly polarized wave radiated from the upper opening 503 is maximized.

  Next, the first surface slot 502 and the second surface slot 501 are designed (S110). For example, as shown in FIG. 7, the first surface slot 502 is drilled on the bottom surface, and the second surface slot 501 is drilled on the side wall at a height of about 1/4 of the in-tube wavelength from the bottom surface. The combined wave of the electromagnetic wave incident from the first surface slot 502 and the electromagnetic wave incident from the first surface slot 502 is circularly polarized.

Next, the excitation unit 401 that excites the circularly polarized light incident from the circular waveguide 500 is designed.
In designing the excitation unit 401, first, the propagation mode of the electromagnetic wave excited in the excitation unit 401 is determined, and the radius is designed (S120). For example, the main mode of the electromagnetic wave excited in the excitation unit 401 is set to TE12, and the radius R that is equal to or greater than the cutoff obtained using the Bessel function is determined.

Next, a circular radiation slot 405 that radiates circularly polarized waves to the slot plate 402 on the upper surface of the excitation unit 401 is designed (S130). For example, as shown in the lower part of FIG. 16, in the TE12 mode excitation state, the radiation slot 405 is formed in a circular shape with the vicinity of the upper part of the strong electromagnetic field portion as the center point. The arrangement of the radiation slots 405 is designed to have symmetry so that the circularly polarized radiation is symmetric. In the present embodiment, the number of slots is four.
This completes the design of the excitation unit 401.

  When the circularly polarized band is set, the design of the radiating element 400 is completed, and the size of the radiating element 400 is obtained, the process shifts to the design of the waveguide slot array antenna 1 as the entire apparatus.

  First, the first surface waveguide circuit 300 in which the radiation element is installed at the end of the waveguide is designed (S140). And the length of the waveguide which installs the radiation element 400 in both ends is determined. The length of the waveguide is such that the distance between both central portions of the waveguide first surface slot 302 is longer than twice the radius R of the excitation portion 401, and linearly polarized waves input from the central portion of the waveguide are at both ends. The maximum amplitude is designed when output from the first waveguide slot 302 of the waveguide. And the waveguide 1st surface slot 302 is drilled in both ends.

  In the present embodiment, eight waveguides on which the radiating elements 400 are installed are arranged at both ends (16 radiating elements 400). The central part of each waveguide is further connected by using a waveguide. At this time, the phase of the linearly polarized wave is in phase so that the power supply port 301 installed in the central part is equidistant from each end. Design to be

  Next, the second surface waveguide circuit 200 is designed to connect the radiating element to the end of the waveguide (S150). And the length of the waveguide which connects the 2nd surface slot 501 of the radiation element 400 to the waveguide 2nd surface slot 202 installed in both ends is determined.

  The length of the waveguide is such that the distance between the center portions of the waveguide second surface slot 202 is the same length as the waveguide at the end of the first surface waveguide circuit 300. Is designed so that the linearly polarized wave input from the central portion of the antenna has the maximum amplitude when output from the waveguide second surface slot 202 at both ends. And the waveguide 2nd surface slot 202 is installed in both ends.

  In this embodiment, eight waveguides having the radiating elements 400 connected to both ends are arranged. The central part of each waveguide is further connected using a waveguide. At this time, the phase of the linearly polarized wave is in phase so that the power supply port 201 installed in the central part is equidistant from each end. Design to be

  With the above method, the design of the radiation element 400, the first surface waveguide circuit 300, and the second surface waveguide circuit 200 is completed. As described above, after the design of the radiation element 400, the first surface waveguide circuit 300, and the second surface waveguide circuit 200 is completed, the process proceeds to a specific manufacturing process.

  First, the radiation element 400 designed in S100 to S130 is created (S200). Next, the first surface waveguide circuit 300 designed in S140 is created (S210). Then, the V-plane waveguide circuit 200 designed in S150 is created (S220). Then, the waveguide first surface slot 302 at each end of the first surface waveguide circuit 300 and the first surface slot 502 of the radiating element 400 are radiated so that the first polarized wave enters the circular waveguide 500. The element 400 is installed (S230).

Then, the second polarization is incident on the circular waveguide 500 through the waveguide second surface slot 202 at each end of the second surface waveguide circuit 200 and the second surface slot 501 at the bottom surface of the radiating element 400. The radiating element 400 is installed in (S240). Finally, the second surface and the first surface waveguide of the magic T are connected to the power supply ports (201, 301) of the waveguide (200, 300) (S250).
In this way, the waveguide slot array antenna 1 is obtained.

The above manufacturing method can also be realized by the following method.
In order to realize the above-described waveguide slot array antenna 1, it is only necessary that a conductor having the same shape as the internal space of the waveguide slot array antenna 1 is constructed of a conductor.
The waveguide slot array antenna 1 of FIG. 1 is cut into a plurality of stages along a virtual plane parallel to the xy plane of FIG. And the part (cross-sectional shape of internal space) where electromagnetic waves are guided among the cut surface figures which appeared on the end surface of the cut piece is transferred to a large rectangular conductor plate having the same thickness as the cut piece. In this case, for example, the following rectangular conductor plates (1) to (9) can be formed.
(1) A conductor plate in which desired radiation slots 405 are formed in a 4 × 4 arrangement.
(2) A conductor plate in which circular cavities 407 are perforated with a 4 × 4 cross-sectional shape.

(3) A conductor plate having openings 406 formed in a 4 × 4 array.
(4) A conductor plate in which orthogonal projection shapes of the 4 × 4 array of openings 503, the second surface waveguide circuit 200, and the connecting pipes 705 and 706 on the xy plane of FIG.
(5) In the above (4), an orthogonal projection shape of the 4 × 4 array of second surface slots 501 (in this case, the same as the waveguide second surface slots 301) onto the xy plane of FIG. Conductor plate.
(6) The same conductor plate as in (4) above.

(7) A 4 × 4 waveguide first surface slot 302 (in this case, the same as the first surface slot 502) and an orthogonal projection shape on the xy plane of FIG. Conductor plate.
(8) A conductor plate in which the orthogonal projection shape of the first surface waveguide circuit 300, the magic T700, and the connecting pipe 706 on the xy plane of FIG.
(9) A conductor plate in which orthographic projection shapes of the connecting pipes 707 and 708 on the xy plane in FIG. 1 are formed.

  A plurality of conductor plates (1) to (9) are duplicated depending on the location, and the waveguide slot antenna 1 is manufactured by sequentially stacking from (1) or (9). Each said conductor board can be manufactured by the etching process of a copper plate, for example.

Modification 1
In the first embodiment, a circular radiation slot is used to radiate circularly polarized waves. However, as long as circularly polarized light can be emitted, the shape is not limited to a circular shape. For example, a circularly polarized wave may be realized by using a cross-shaped slot and radiating a second plane polarization and a first plane polarization. Further, as long as circularly polarized waves can be radiated, the shape is not limited to the above shape, and any shape slot can be used. FIG. 15 shows a modification thereof.

Modification 2
In the first embodiment, the number of radiation slots is four. However, the number of slots is not limited to the above four as long as circularly polarized waves can be radiated efficiently, and any number of slots can be used. For example, it is good also as a shape which provides a slot in the upper part along the part (dotted line part) where the electromagnetic field intensity of TE12 mode of FIG. 10 is strong. For example, six slots may be used as shown in FIG.

DESCRIPTION OF SYMBOLS 1 Waveguide slot array antenna 100 Excitation slot 101 Cavity 102 Single slot 103 Waveguide 104 Hexagonal opening 105 Circular polarization element 106 Waveguide side wall 107 Lower end plate 108 Slot plate 109 Cavity side wall 110 Slot plate 200 Second surface wave guide Circuit 201 Power supply port 202 Waveguide second surface slot 300 First surface waveguide circuit 301 Power supply port 302 Waveguide first surface slot 400 Radiating element 401 Excitation portion 402 Slot plate 403 Side wall 404 Lower end plate 405 Radiation slot 406 Opening portion 407 Circular shape Cavity 500 Circular waveguide 501 Second surface slot 502 First surface slot 503 Opening 504 Auxiliary line 505 Auxiliary line 700 Magic T
701 Feed port 702 Feed port 703 Radiation port 704 Radiation port 705 Connection tube 706 Connection tube 707 Connection tube 708 Connection tube 709 Connection tube

Claims (10)

Provided at each end of a plurality of waveguides that are input from the first power supply port, guide the first polarized wave having the vibration direction in the first direction, and have the same length from the power supply port. A first surface waveguide circuit that radiates a first polarization from the waveguide first surface slot formed;
A second polarized wave having a vibration direction in a direction orthogonal to the first polarized wave is guided from the second feeding port, is equal in length from the second feeding port, and is guided by the first surface. A second surface waveguide circuit that radiates a second polarization from a waveguide second surface slot provided at each end of a plurality of waveguides provided to have the same length as the waveguide length of the circuit;
With
The waveguide first surface slot and the waveguide second surface slot are installed such that the combined wave of the first and second polarized waves to be radiated is a circularly polarized wave,
Waveguide slot array antenna. Further comprising a bottomed cylindrical circular waveguide having an opening on one end side;
The circular waveguide has a first surface slot drilled to input linearly polarized light radiated from the waveguide first surface slot on the other surface, and the waveguide second surface slot. Having a second surface slot in the side wall drilled to input more linearly polarized radiation,
Radiating circularly polarized waves from the opening surface of the circular waveguide,
The waveguide slot array antenna according to claim 1. An excitation unit having a circular cavity communicating with the circular waveguide;
The radius of the circular cavity of the excitation unit is designed so that circularly polarized waves from the waveguide are excited,
The waveguide slot array antenna according to claim 1 or 2. The excitation unit includes a slot plate provided to close the circular cavity and having a plurality of radiation slots formed therein.
In the slot plate, the radiation slot is formed at a position where the intensity of the cross-sectional electromagnetic field is high in the distribution of the electromagnetic field excited in the excitation unit, and circularly polarized waves are radiated from the radiation slot.
The waveguide slot array antenna of any one of Claims 1-3. The radiating slot is circular;
The waveguide slot array antenna of any one of Claims 1-4. The radiating slot is cross-shaped,
The waveguide slot array antenna of any one of Claims 1-4. A method of designing a structure of a radiating element including an excitation unit having a circular cavity and a circular waveguide of the waveguide slot array antenna according to any one of claims 1 to 5,
Determining a radius of a circular waveguide that guides circularly polarized waves;
Designing a first surface slot and a second surface slot for generating a circularly polarized wave by combining a linearly polarized wave incident on the circular waveguide; and
Designing a radius of an exciter for exciting the circularly polarized wave radiated from the circular waveguide;
Designing a radiation slot for radiating circularly polarized light from the circularly polarized strong magnetic field portion excited by the excitation unit;
A method for designing a waveguide slot array antenna. Designing a first surface waveguide circuit for inputting a horizontally polarized wave to the radiating element;
Designing a second surface waveguide circuit for inputting vertical polarization to the radiating element;
The waveguide slot array antenna design method of claim 6, further comprising: Creating a radiating element obtained by the method for designing a waveguide slot array antenna according to claim 7;
Creating a first surface waveguide circuit obtained by the waveguide slot array antenna design method according to claim 8;
Creating a second surface waveguide circuit obtained by the waveguide slot array antenna design method according to claim 8;
Installing the radiating element in the first surface waveguide circuit;
Connecting the radiating element to a second surface waveguide circuit;
Connecting a magic T for feeding linearly polarized waves to the first surface waveguide circuit and the second surface waveguide circuit;
A method for manufacturing a waveguide slot array antenna. Each step of claim 9 is realized by laminating a conductor plate in which a cross-sectional shape of a portion where electromagnetic waves are guided is formed.
A method for manufacturing a waveguide slot array antenna according to claim 9.