JP2009147769A - Circular polarization antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish a waveguide-type circular polarization antenna which is capable of securing a wide band excellent in gain, axis ratio, and VSWR and has a simple structure. <P>SOLUTION: A circular polarization antenna 1 is provided with: a waveguide part 23, probes 5A-5D inserted into the waveguide part 23; and coaxial cables 4A-4D with the probes 5A-5D as center conductors. The waveguide part 23 is constituted of a cylindrical waveguide 2 opened at a zenith side and a semispherical cavity 3 connected to a side opposite to the zenith side of the cylindrical waveguide 2. The probes 5A-5D are disposed at equal angle intervals with a center O of the cylindrical waveguide 2 as a reference. Transmission signals phase-adjusted in accordance with the angle intervals and the arrangement positions are fed to these probes 5A-5D via the coaxial cables 4A-4D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circularly polarized antenna for transmitting and receiving circularly polarized waves, and more particularly to a circularly polarized antenna comprising a waveguide antenna.

  Currently, in GNSS including GPS, there are many applications using circular polarization as an application for receiving radio waves from satellites. For this reason, various circularly polarized antennas have been devised and disclosed. In recent years, antennas are required to have a wide band. For example, in GPS, L1 waves (frequency: 1.57542 GHz), L2 waves (frequency: 1.2276 GHz), and L5 waves (frequency: 1.17645 GHz). An antenna capable of receiving three frequencies is required, and an antenna capable of receiving other GNSS radio waves such as Galileo may also be required.

In response to such a broadening of the bandwidth, the frequency bandwidth is devised by devising the shape of the antenna formed on a single flat plate, and the shape of the elements formed on a flat plate, each of which transmits and receives radio waves of different frequencies An antenna with a widening is disclosed. Various antennas using a waveguide having a wide propagation frequency band are also disclosed. For example, the antenna of Patent Document 1 includes a plurality of receiving units arranged in an array, an array-shaped waveguide installed on the receiving direction side with respect to the plurality of receiving units, and an outside of the waveguide. And a dome-shaped lens unit installed.
JP 2006-29776 A

  As described above, various types of broadband antennas have been devised in the past. However, there are waveguide-type circularly polarized antennas with a simple shape that can take a wide band with good gain, axial ratio, and VSWR. There wasn't.

  Accordingly, an object of the present invention is to realize a waveguide-type circularly polarized antenna having a simple structure that can provide a wide bandwidth with good characteristics with respect to circularly polarized waves.

The present invention relates to a circularly polarized antenna that transmits and receives circularly polarized waves having a plurality of different frequencies within a predetermined frequency bandwidth. This circularly polarized antenna includes a waveguide section having the following characteristics, a plurality of probes, and phase processing means.
The waveguide portion is made of a conductor that opens only the surface on the zenith direction side, and is formed such that the distance from the opening surface of the conductor to the inner wall surface increases in order from the edge side of the opening surface toward the center. The plurality of probes are arranged in the waveguide portion so as to generate electric field vectors that are spatially orthogonal during power feeding. The phase processing means performs phase processing according to the angular intervals of the plurality of probes viewed from the zenith direction at the time of transmission and reception by the plurality of probes.

  In this configuration, for example, when a transmission signal is supplied to each probe during transmission, radio waves are radiated from each probe and guided to the waveguide section. The propagation of radio waves (signals) from the probe to the waveguide section is the same as the principle of signal propagation in a so-called coaxial-waveguide converter.

  FIG. 7 is a schematic configuration diagram for explaining the basic concept of the coaxial-waveguide converter. As shown in FIG. 7, the coaxial-waveguide converter includes a waveguide 101 and a coaxial cable 102 having a probe 103 as a central conductor. The probe 103 has a shape inserted from the wall surface along the signal carrying direction of the waveguide 101 into the waveguide 101. At this time, the probe 103 is installed at a position of about 1/4 wavelength (approximately λ / 4) for carrying transmission with respect to the end face 111 having a plane perpendicular to the radio wave transmission direction of the waveguide 101. With such a configuration, signal mode conversion is performed between the coaxial cable 102 and the waveguide 101, and the signal is transmitted.

  The radio wave guided to the waveguide portion in this manner is radiated to the outside from the surface on the zenith direction side where the waveguide portion is opened. At this time, by adjusting the phase of feeding the transmission signal to each probe in accordance with the angular interval at which the probe is installed, a radio wave having a polarization plane corresponding to the adjusted phase is radiated.

  And, the surface on the side facing the zenith direction in the waveguide portion is formed in a shape that gradually becomes a different distance with respect to the surface on the zenith direction side, so that the surface on the side facing each probe in the zenith direction The distance between and changes gradually. For this reason, the value of λ / 4 of the above-described coaxial-waveguide converter becomes plural, and the matching frequency changes at each position on the surface facing the zenith direction. As a result, a radio wave of a predetermined frequency band including a plurality of frequencies is propagated from the probe into the waveguide with low loss and radiated to the outside.

  In the circularly polarized antenna according to the present invention, the waveguide portion is substantially hemispherical, and the cut surface of the substantially hemispherical surface is the surface on the zenith direction side.

  In this configuration, a circularly polarized antenna is formed only with a simple substantially hemisphere.

  In the circularly polarized antenna according to the present invention, the waveguide portion is composed of a cylindrical portion and a substantially hemispherical portion. The cylindrical portion has one surface of the opposing circular surfaces on the zenith direction side, and the substantially hemispherical portion has a shape in which the cut surface of the substantially hemispherical surface coincides with the surface on the side facing the zenith direction of the cylindrical portion. And the some probe is installed in the cylindrical part.

  In this configuration, the portion where the probe is installed is a cylindrical waveguide, and the surface on the side facing the zenith direction is formed as a simple substantially hemisphere. By providing the probe in the cylindrical waveguide in this way, if the probe is inserted perpendicularly to the side wall surface of the cylindrical waveguide, the extending direction of the probe can be made orthogonal to the signal carrying direction of the waveguide. it can.

  In the circularly polarized antenna according to the present invention, the waveguide portion is filled with a dielectric having a predetermined dielectric constant.

  In this configuration, by setting the relative permittivity to be larger than 1 and setting it appropriately, the antenna can be made smaller than the case where the dielectric is not filled at a desired frequency. Further, if the dielectric constant of the dielectric to be filled is changed without changing the shape of the waveguide, radio waves in a frequency band corresponding to the dielectric constant are transmitted and received.

  Moreover, the circularly polarized wave antenna of this invention is equipped with the flat conductor board connected to a waveguide part along the surface of a zenith direction side.

  In this configuration, the gain is improved by emitting radio waves from the conductor plate.

  According to the present invention, a circularly polarized antenna having a simple and simple structure such as a substantially hemispherical shape or a combined shape of a cylinder and a substantially hemisphere and excellent in various characteristics relating to radio waves such as gain, axial ratio, and VSWR is realized. Can do.

A circularly polarized antenna according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an external perspective view showing the main configuration of the circularly polarized antenna 1 of the present embodiment. 2A and 2B are a top view and a side sectional view of the circularly polarized antenna 1 of the present embodiment, wherein FIG. 2A shows a top view and FIG. 2B shows a side sectional view.

  The circularly polarized wave antenna 1 includes a waveguide portion 23, probes 5A to 5D installed in the waveguide portion 23, and coaxial cables 4A to 4D having the probes 5A to 5D as central conductors. .

  The waveguide section 23 includes a cylindrical waveguide 2 and a cavity 3. The cylindrical waveguide 2 has a circular shape with a predetermined diameter when viewed from the zenith direction (top surface direction), and is formed of a cylindrical conductor having two open surfaces perpendicular to the axial direction. Is open to the outside as it is, and the cavity 3 is connected to the opening surface on the side facing the zenith surface. The cavity 3 is made of a conductor formed in a hollow hemispherical shape, and has a shape obtained by cutting the sphere that is the base of the hemispherical shape along a plane that passes through the center of the sphere. The cavity 3 is integrally formed with the cylindrical waveguide 2 so that the cut surface coincides with the opening surface on the side facing the top surface of the cylindrical waveguide 2. At this time, the waveguide portion 23 is formed so that the center O when the cylindrical waveguide 2 is viewed from the zenith side and the center when the cavity 3 is viewed from the zenith side coincide with each other when viewed from the zenith side. . Furthermore, as viewed from the zenith side, from the inner wall surface side of the cylindrical waveguide 2 toward the center O of the cylindrical waveguide 2, the inner wall surface of the cavity 3 from the opening surface on the cavity 3 side of the cylindrical waveguide 2. The cavity 3 is installed such that the distance to (the “surface facing the zenith direction” in the present invention) gradually increases.

  On the outer wall side of the cylindrical waveguide 2, coaxial cables 4 </ b> A to 4 </ b> D are installed at an angular interval of π / 2 with respect to the center O when the cylindrical waveguide 2 is viewed from the zenith side. The coaxial cables 4A to 4D include a center conductor that functions as the probes 5A to 5D, and an outer conductor that has a shape surrounding the center conductor in a form spaced apart by a predetermined distance in a radial direction perpendicular to the axis of the center conductor. The outer conductors of the coaxial cables 4 </ b> A to 4 </ b> D are each electrically connected to the cylindrical waveguide 2. The central conductors of the coaxial cables 4A to 4D are formed so as to protrude from the cylindrical waveguide 2 by a predetermined distance, and these portions function as the probes 5A to 5D. The probes 5A to 5D are installed at positions equidistant from the zenith surface perpendicular to the axial direction of the cylindrical waveguide 2, that is, the cylindrical axial direction. The probes 5A to 5D are arranged so as to be point-symmetric with respect to the center O. At this time, the probes 5A to 5D have π / 2 [rad. ] Are arranged at angular intervals.

  The waveguide portion 23 is filled with a dielectric 6 having a predetermined dielectric constant. Note that the cavity (relative permittivity εr = 1) may be used without filling the dielectric 6, but the circularly polarized antenna 1 can be downsized by filling the dielectric 6 satisfying the relative permittivity εr> 1. be able to. Further, the target frequency band can be changed by making the relative permittivity of the dielectric 6 different.

  The diameter of the cylindrical waveguide 2 in such a circularly polarized antenna 1 is appropriately set according to the frequency band of radio waves transmitted and received by the circularly polarized antenna 1 and the dielectric constant of the dielectric 6. Other dimensions of the polarization antenna 1 are also set as appropriate depending on the frequency band and dielectric constant of the radio wave to be transmitted and received.

  In such a structure, for example, when transmitting radio waves, a power feeding unit (not shown) is connected to the coaxial cables 4A to 4D. The power feeding unit adjusts the phase of the original transmission signal for each of the coaxial cables 4A to 4D and outputs it to the coaxial cables 4A to 4D. In the example of FIGS. 1 and 2, with the transmission signal applied to the coaxial cable 4A as a reference, the phase of the transmission signal applied to the coaxial cable 4B is delayed by π / 2, and the phase of the transmission signal applied to the coaxial cable 4C is delayed by π, By delaying the phase of the transmission signal applied to the coaxial cable 4D by 3π / 2, a transmission signal delayed by π / 2 by the probe 5B is transmitted to each of the probes 5A to 5D based on the transmission signal transmitted to the probe 5A. The transmission signal delayed by π is transmitted by the probe 5C, and the transmission signal delayed by 3π / 2 is transmitted by the probe 5D. These transmission signals are propagated from the respective probes 5A to 5D into the waveguide portion 23, propagated through the waveguide portion 23, and radiated to the outside from the opened zenith surface of the waveguide portion 23. . Since the above-described phase relationship is preserved even if it is propagated to the waveguide section 23, in this case (in the case of FIGS. 1 and 2), a right-handed circularly polarized wave is radiated in the zenith direction. Conversely, with the transmission signal applied to the coaxial cable 4A (probe 5A) as a reference, the phase of the transmission signal applied to the coaxial cable 4B (probe 5B) is advanced by π / 2, and the transmission signal applied to the coaxial cable 4C (probe 5C) By causing the phase to advance by π and the phase of the transmission signal applied to the coaxial cable 4D (probe 5D) to advance by 3π / 2, a left-handed circularly polarized wave is emitted in the zenith direction.

  In the case of reception, the right-handed circularly polarized wave and the left-handed circularly polarized wave can be received by performing phase processing on each probe 5A to 5D according to the signal to be received based on the above-described phase relationship. it can.

  Furthermore, with the above-described structure, the distance D (for example, D1 to D3 in FIG. 2B) between each probe 5A to 5D and the inner wall surface of the cavity 3 is in the axial direction of the probes 5A to 5D. Gradually change along. As the distance D changes in this way, as can be understood with reference to the description of FIG. 7 described above, the band of the frequency to be matched expands according to the change width of the distance D, and a predetermined band for transmission and reception A width can be secured.

  Thereby, it is possible to realize a circularly polarized antenna having a wide band characteristic with a simple structure including a waveguide having a simple structure including a cylindrical waveguide and a hemispherical cavity and a plurality of probes.

  FIG. 3 is a diagram showing simulation results of each frequency characteristic of the circularly polarized antenna according to the present embodiment. (A) is a gain frequency characteristic, (B) is an axial ratio frequency characteristic, and (C) is a VSWR frequency characteristic. Show. In this simulation, the waveguide portion 23 having the dimensions shown in FIG. 4, the probes 5A to 5D, and the dielectric having the relative dielectric constant shown in FIG. .42 MHz. FIG. 4 is an indication diagram of the external dimensions and relative permittivity of the circularly polarized antenna for which the simulation of FIG. 3 was performed.

  As shown in FIG. 3, by using the configuration of the present embodiment, the 3 dB bandwidth, that is, the frequency bandwidth at which a gain within −3 dB is obtained with respect to the gain of the target frequency is about 50% in the specific band, A wide bandwidth can be secured. The bandwidth with an axial ratio of 1 dB or less includes the GPS L1 wave, L2 wave, and L5 wave frequency bands of 1.176 GHz to 1.575 GHz, and the bandwidth is 67% or more of the target frequency. A bandwidth can be obtained, and a very wide bandwidth can be secured as a circularly polarized antenna. Furthermore, the bandwidth at which VSWR is 2 or less is about 45% of the bandwidth relative to the target frequency, and a wide bandwidth can be secured.

  As described above, by using the configuration of the present embodiment, it is possible to realize a circularly polarized antenna having a simple structure that is excellent in various characteristics as a circularly polarized antenna in a wide band.

In addition to the above-described embodiment, a flat conductor plate may be installed on the top surface of the cylindrical waveguide that is the radiation surface.
FIG. 5 is a top view and a side sectional view showing the configuration of the circularly polarized antenna 1 ′ having the conductor plate 7. FIG. 6 is a diagram showing the gain frequency characteristics of the circularly polarized antenna 1 ′ configured as shown in FIG.
A circularly polarized antenna 1 ′ shown in FIG. 5 is provided with a conductor plate 7 having a predetermined diameter along an opening surface on the zenith side of the cylindrical waveguide 2 of the circularly polarized antenna 1 shown in FIGS. It consists of a structure. The conductor plate 7 is configured to be electrically connected to the cylindrical waveguide 2, and is integrally formed with the cylindrical waveguide 2, for example. The conductor plate 7 has a donut shape when viewed from the zenith side, and the end on the center side is connected to the cylindrical waveguide 2. In addition, the area of the conductor plate 7 viewed from the zenith side is set to an area that optimizes the characteristics of the radiated radio waves. For example, this area may be determined in advance by simulation or the like.

  With such a configuration, the radiation efficiency is improved, and as shown in FIG. 6, the gain in the desired frequency band, in this case, the gain in the above-mentioned GPS use band is 2 dB to It improves about 3dB. In this way, by using the configuration as shown in FIG. 5, a circularly polarized antenna having a simple structure in which a conductor plate is simply added to the circularly polarized antenna 1 shown in FIG. Can be realized.

  In the above description, the case where the cavity 3 is a hemisphere has been described as an example, but it may be an elliptical hemisphere, and further, the center O from the inner wall surface side of the cylindrical waveguide 2 when viewed from the zenith side. As long as the distance between each of the probes 5A to 5D and the wall surface of the cavity 3 gradually increases, another shape may be used.

  In the above description, the case where the number of probes is four is shown as an example. However, the probes may be arranged so that the electric field vectors generated from the probes are spatially orthogonal. The number may be two or more. For example, the arrangement angle interval may be set to 2π / N in accordance with the number of probes N, and the phase of the transmission signal fed to each probe may be shifted by 2π / N.

  In the above description, an example using a cylindrical waveguide is shown. However, the cylindrical waveguide may be omitted, and the waveguide portion may be formed only by a hemispherical or elliptical hemispherical cavity. Thereby, the waveguide portion has a simpler structure.

  In the above description, an example using a cylindrical waveguide has been shown. However, a rectangular waveguide or the like may be used. In this case, the cavity may be a quadrangular pyramid, for example.

1 is an external perspective view showing a main configuration of a circularly polarized antenna 1 according to an embodiment of the present invention. It is the top view and side sectional drawing of the circularly polarized antenna 1 of embodiment of this invention. It is a figure which shows the simulation result of each frequency characteristic of the circularly polarized wave antenna 1 of embodiment of this invention. FIG. 4 is a diagram showing the external dimensions and relative permittivity of the circularly polarized antenna for which the simulation of FIG. 3 was performed. It is the top view and side sectional view showing the composition of the circular polarization antenna which has a conductor board. It is a figure which shows the gain characteristic of the circularly polarized antenna of the structure shown in FIG. It is a schematic block diagram for demonstrating the basic concept of a coaxial-waveguide converter.

Explanation of symbols

1-circularly polarized antenna, 2-cylindrical waveguide, 3-cavity, 23-waveguide section, 4A-4D-coaxial cable, 5A-5D-probe, 6-dielectric, 7-conductor plate, 101- Waveguide, 111-end face of waveguide 100, 102-coaxial cable, 103-probe

Claims (5)

A circularly polarized antenna that transmits and receives circularly polarized waves having different frequencies within a predetermined frequency bandwidth,
A waveguide portion formed of a conductor that opens only the surface on the zenith direction side, and a waveguide portion formed such that the distance from the opening surface of the conductor to the inner wall surface increases in order from the edge side of the opening surface toward the center;
In the waveguide section, a plurality of probes arranged to generate electric field vectors spatially orthogonal at the time of feeding,
Phase processing means for performing phase processing according to the angular interval of the plurality of probes viewed from the zenith direction at the time of transmission and reception by the plurality of probes;
Circularly polarized antenna with   The circularly polarized wave antenna according to claim 1, wherein the waveguide portion is formed of a substantially hemisphere, and a cut surface of the substantially hemisphere is a surface on the zenith direction side. The waveguide portion is composed of a cylindrical portion and a substantially hemispherical portion,
The cylindrical portion has one surface of the opposing circular surface as the surface on the zenith direction side,
The substantially hemispherical portion has a shape in which the cut surface of the substantially hemispherical surface coincides with the surface of the cylindrical portion facing the zenith direction,
The circularly polarized antenna according to claim 1, wherein the plurality of probes are installed in the cylindrical portion.   The circularly polarized wave antenna according to any one of claims 1 to 3, wherein the waveguide portion is filled with a dielectric having a predetermined dielectric constant.   The circularly polarized wave antenna according to any one of claims 1 to 4, comprising a flat conductor plate connected to the waveguide portion along a surface on the zenith direction side.

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