JP2007081648A - Phased-array antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an inexpensive phased-array antenna device with an excellent gain and excellent sidelobe characteristics while reducing shielding by a subreflecting mirror especially even when it is a small antenna. <P>SOLUTION: The phased-array antenna device has a first reflector 43 which reflects a radio wave of a prescribed polarized wave emitted from a primary radiator 41, and has a polarized wave selection function for transmitting a polarized wave orthogonal to the prescribed polarized wave; and a second reflector 42 which reflects the radio wave of the prescribed polarized wave reflected from the first reflector 43 after changing it to an orthogonal polarized wave, and controls the beam orientation by changing the phase of the orthogonal polarized wave. A plurality of antenna elements respectively have a function for converting the radio wave of the prescribed polarized wave to the orthogonal polarized wave, and a phase-shifting function for changing the phase. The antenna elements are arranged into a planar shape as the second reflector 42. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phased array antenna device that controls a beam directing direction by changing radio waves of a predetermined polarization into orthogonal polarizations and changing the phase.

  Conventionally, parabola antennas and cassegrain antennas have been widely used for communication and radar antennas in order to obtain a high gain and a sharp beam.

  FIG. 5 is a perspective view showing a conventional Cassegrain antenna, and FIG. 6 is a diagram for explaining the operation principle of the conventional Cassegrain antenna. As shown in FIG. 5, a primary radiator 12 is provided at the center of the main reflector 11 made of a metal plate, and a sub-reflector 13 made of a metal plate is attached to the front surface of the primary radiator 12. That is, as shown in FIG. 6, the linearly polarized horizontal polarization HP radiated from the primary radiator 12 is reflected by the sub-reflecting mirror 13, then reflected by the main reflecting mirror 11 and emitted to the outside.

  Since these reflector antennas have a simpler structure than the array antenna, there is an advantage that they can be manufactured at low cost to obtain the same gain and beam width. However, since these reflector antennas are primary radiators for parabolic antennas, and secondary reflectors for Cassegrain antennas are in front of the main reflector, the primary radiator, subreflector itself, and the primary radiator and subreflector are mechanical. Since the holding tool that holds the target shields radio waves radiated from the main reflecting mirror, the gain is lowered and the side lobe is deteriorated.

  The dimensions of the primary radiator and the sub-reflector have a property that largely depends on the operating frequency and the shape parameter of the reflector antenna, but not on the size of the main reflector. Therefore, in the case of a small antenna with a small antenna diameter (corresponding to the diameter of the main reflector), the ratio of the size of the primary radiator and the sub reflector is larger than the size of the main reflector, and the radio wave shielding ratio Since it becomes large, there is a disadvantage that the deterioration of gain and side lobe becomes large. The Cassegrain antenna has the advantage that the length of the feed line from the transceiver to the primary radiator can be shortened compared to the parabolic antenna because the primary radiator is located near the main reflector. Since it is generally larger than the primary radiator of the antenna, there is a problem that the shielding ratio of the sub-reflecting mirror becomes very large in a small antenna, and the gain and sidelobe characteristics are deteriorated compared to the parabolic antenna.

  As means for solving the above problems, when the polarization to be used is a linear polarization, it is conceivable to use an antenna system called a twist reflector. Thereby, shielding of the sub-reflecting mirror described above can be reduced, and deterioration of characteristics due to shielding can be prevented.

  FIG. 7 is a diagram for explaining the operation principle of a conventional twist reflector. As shown in FIG. 7, in the twist reflector, the first reflector 23 corresponding to the sub-reflector of the Cassegrain antenna is configured with a special surface having polarization selectivity. This special surface with polarization selectivity produces almost perfect reflection for linear polarization in one direction, and transmits light with almost no effect on linear polarization orthogonal to this polarization. Have. The second reflector 21 corresponding to the main reflector of the Cassegrain antenna has a special property of reflecting the incident linearly polarized wave after converting it into an orthogonal linearly polarized wave. The linearly polarized wave (assumed to be horizontal polarization HP) radiated from the primary radiator 22 is reflected by the first reflector 23 installed so as to reflect the horizontal polarization HP, and the second reflector. 21 is incident. The radio wave incident on the second reflector 21 is reflected as a vertically polarized wave VP by changing the direction of polarization by 90 °. The radio wave reflected by the second reflector 21 is incident on the first reflector 23 placed in the reflection direction of the second reflector 21, and the first reflector 23 corresponds to the vertically polarized wave VP. Since it is transparent, it is emitted without being shielded. From the above, it can be seen that the twist reflector can prevent deterioration of characteristics due to shielding of a sub-reflector such as a Cassegrain antenna.

  FIG. 8 is a diagram for explaining the operating principle of a conventional Cassegrain-type reflective space-feed array antenna. As shown in FIG. 8, the linearly polarized horizontal polarization HP radiated from the primary radiator 32 is reflected by the sub-reflecting mirror 33, then reflected by each element antenna 31 and emitted to the outside. In this case, when the radio wave reflected by each element antenna 31 is further reflected by the sub-reflecting mirror 33, the radio wave is shielded without being emitted to the outside.

  On the other hand, in a phased array antenna capable of high-speed beam scanning, there is a space feeding method as a method for simplifying the feeding to each element antenna 31 of the array antenna. In this system, power is supplied by radiating radio waves from the primary radiator 32 to each element antenna 31 of the array antenna. Usually, a power supply circuit constituted by a distributor is not required, so that the array is inexpensive and lightweight. There is a great advantage that an antenna can be configured. In the reflection type spatially fed array antenna which is one of the spatially fed systems, the radio wave radiated from the primary radiator 32 is once received by the element antenna 31 and given a phase change of a predetermined phase amount by the phase shifter. Radiated from the same element antenna 31. This method can be regarded as a parabolic antenna reflecting mirror replaced with an element antenna group. However, the parabolic antenna cannot perform high-speed beam scanning, but this array antenna can perform high-speed beam scanning by performing phase control using a phase shifter.

Also in the reflection type space feeding type phased array antenna, a system similar to the Cassegrain antenna using the sub-reflection mirror 33 can be used. However, as described in the case of the Cassegrain antenna, the sub-reflecting mirror 33 shields the radio wave radiated from the element antenna 31 and thus has a problem that the antenna characteristics are deteriorated. It is the same as in the case of a Cassegrain antenna that there is a property that becomes larger. Furthermore, in a reflective space-feed type phased array antenna, beam scanning is performed by phase control, but when the beam is scanned in a direction other than the front, the shielding ratio of the holder that mechanically holds the sub-reflecting mirror 33 Is larger than when the beam is scanned in front, which increases the gain and sidelobe degradation.
PWHannan, “Microwave Antennas Derived from the Cassegrain Telescope”, IRE Transactions on Antennas and Propagation, pp140-153, March 1961 D. Piltz and W. Menzel, “Folded reflectaary antenna”, Electronics Letters, Vol. 34, No. 9, pp832-833, April 1998

  As described above, also in the reflective space-feed phased array antenna having the sub-reflecting mirror, the problem of shielding by the sub-reflecting mirror and its holder occurs as in the case of the Cassegrain antenna, and the characteristics are deteriorated.

  The present invention has been made in view of the above circumstances, and is intended to reduce the shielding by the sub-reflecting mirror, and to realize an inexpensive phased array antenna device having good gain and sidelobe characteristics even in the case of a small antenna. Objective.

  In order to achieve the above object, the present invention provides a primary radiator that radiates a radio wave of a predetermined polarization, and a predetermined polarization that is provided at an irradiation position of the radio wave radiated from the primary radiator and radiated from the primary radiator. A first reflector having a polarization selection function that reflects a first polarized wave and transmits a polarized wave orthogonal to the predetermined polarized wave, and a polarized wave orthogonal to the predetermined polarized wave reflected from the first reflector. A phased array antenna apparatus having a second reflector that controls a beam directing direction by changing the phase and changing the phase, and as the second reflector, radio waves of a predetermined polarization are orthogonal to each other A plurality of antenna elements having a function of converting to polarization and a phase shifting function of changing the phase are arranged in a planar shape.

  In the phased array antenna device according to the present invention, the shape of the reflecting surface of the first reflector is a curved surface.

  According to the present invention, in the phased array antenna device, the shape of the reflection surface of the first reflector is a flat surface.

  According to the present invention, in the phased array antenna device, an orthogonally polarized microstrip patch antenna is used as the antenna element of the second reflector.

  According to the present invention, in the phased array antenna device, a cross dipole antenna is used as an antenna element of the second reflector.

  In the phased array antenna apparatus of the present invention, the polarization direction of the radio wave that is given a phase change of a predetermined phase amount corresponding to the beam scanning angle radiated from the second reflector is transmitted through the first reflector. Therefore, since the light is transmitted and radiated without being shielded by the first reflector, the characteristics are not deteriorated due to the shielding of the first reflector. Therefore, even in the case of a small antenna in particular, it has good gain and sidelobe characteristics.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a phased array antenna apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining an operation principle of the phased array antenna apparatus according to the embodiment of the present invention. As shown in FIG. 1, the primary radiator 41 is provided at the center of the disc-shaped second reflector 42 and radiates radio waves of a predetermined polarization. A first reflector 43 is provided at the irradiation position of the radio wave radiated from the primary radiator 41 in front of the primary radiator 41. The first reflector 43 has a polarization selection function that reflects radio waves of a predetermined polarization radiated from the primary radiator 41 and transmits orthogonal polarizations in directions different from the predetermined polarization by 90 °. The second reflector 42 receives a radio wave of a predetermined polarization reflected from the first reflector 43, changes the radio wave of the predetermined polarization by 90 °, converts it to an orthogonal polarization, reflects it, and changes the phase. The beam directing direction is controlled by changing.

  The second reflector 42 is configured by arranging a plurality of antenna elements on the surface of a plurality of elements having a function of converting radio waves of a predetermined polarization into orthogonal polarizations and a phase shifting function of changing the phase. For example, a plurality of antenna elements are arranged vertically and horizontally to form a disk shape.

  FIG. 3 is a configuration explanatory view showing an example of the antenna element of the second reflector according to the embodiment of the present invention. FIG. 3 shows a microstrip patch antenna 51 of orthogonal polarization feeding, and the phase of the linearly polarized horizontal polarization HP inputted to the input terminal 52 of the microstrip patch antenna 51 is changed to a predetermined phase by the phase shifter 53. At the same time, the linearly polarized horizontal polarization HP is converted into a linearly polarized vertical polarization VP in a direction different by 90 ° and radiated from the output terminal 54.

  FIG. 4 is a configuration explanatory view showing an example of the first reflector according to the embodiment of the present invention. As shown in FIG. 4, the first reflector 43 is configured by arranging a plurality of rod-shaped antenna members 62 in a circular frame 61 at equal intervals in the horizontal direction. That is, the linearly polarized horizontal polarized wave HP is reflected, but the linearly polarized vertical polarized wave VP is transmitted.

  As shown in FIG. 2, the linearly polarized wave (assumed to be horizontal polarization HP) radiated from the primary radiator 41 has a polarization selectivity that reflects the horizontal polarization HP and transmits the vertical polarization VP. It reaches the antenna element group that constitutes the second reflector 42 that is reflected by the first reflector 43 and has the polarization conversion function that is opposed to the first reflector 43. The radio waves of the horizontally polarized wave HP that have reached the orthogonally polarized microstrip patch antenna 51, which is each antenna element in the antenna element group, are once received by the terminal 52 on the input side of the microstrip patch antenna 51, A predetermined phase change corresponding to the beam scanning direction is given by the phase shifter 53 connected between the input and output terminals of the strip patch antenna 51, and the output side terminal 54 of the microstrip patch antenna 51 is reached. Since the output-side terminal 54 generates a polarization that is orthogonal to the input side by 90 °, a radio wave of a vertically polarized wave VP is radiated from each microstrip patch antenna 51. A radio wave radiated from each microstrip patch antenna 51 travels in the set beam direction, but a part of the radio wave enters the first reflector 43.

  However, since the first reflector 43 has a characteristic of transmitting the vertically polarized wave VP, the radio wave radiated from each microstrip patch antenna 51 travels without being shielded by the first reflector 43, and is caused by the shielding. A beam can be generated without being deteriorated in characteristics.

  In the above embodiment, the shape of the first reflector 43 is not particularly mentioned, but the shape of the reflecting surface may be any one of a rotational hyperboloid, a spheroidal surface, and a plane, and any other curved surface. It does not matter. In the case of a flat surface, the diameter of the first reflector 43 is half of the diameter of the second reflector 42, and can be smaller than half in the case of a rotational hyperboloid or a spheroidal surface. Further, the antenna element group constituting the second reflector 42 may be planar or any curved surface.

  The antenna element having the polarization conversion function that constitutes the second reflector 42 may be an orthogonal polarization element such as a square patch antenna or a cross dipole antenna. Anything can be used.

  In the above embodiment, the case of linear polarization is shown, but the present invention can also be applied to circular polarization. In this case, a primary radiator that radiates circularly polarized waves is used, and the first reflector reflects circularly polarized waves in the same swiveling direction as the primary radiator, and is in the opposite direction, that is, electrically orthogonal. Use one that transmits circularly polarized waves. The second reflector uses a circularly polarized wave in the same turning direction as that of the primary radiator, and converts the circularly polarized wave into an electrically orthogonal circularly polarized wave and gives the same amount of phase change as in the case of the linearly polarized wave.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiment examples may be appropriately combined.

It is a perspective view which shows the phased array antenna apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the operation principle of the phased array antenna apparatus which concerns on embodiment of this invention. It is composition explanatory drawing which shows an example of the antenna element used for the 2nd reflector which concerns on embodiment of this invention. It is composition explanatory drawing which shows an example of the 1st reflector which concerns on embodiment of this invention. It is a perspective view which shows the conventional Cassegrain antenna. It is a figure for demonstrating the principle of operation of the conventional cassegrain antenna. It is a figure for demonstrating the principle of operation of the conventional twist reflector. It is a figure for demonstrating the operation principle of the reflection type space feeding array antenna of the conventional Cassegrain system.

Explanation of symbols

  41 ... primary radiator, 42 ... second reflector, 43 ... first reflector.

Claims (5)

A primary radiator that emits radio waves of a predetermined polarization;
Provided at the irradiation position of the radio wave radiated from the primary radiator, has a polarization selection function of reflecting a radio wave of a predetermined polarization radiated from the primary radiator and transmitting a polarization orthogonal to the predetermined polarization A first reflector;
A phased array antenna apparatus comprising: a second reflector that reflects a wave of a predetermined polarization reflected from the first reflector by changing the radio wave to an orthogonal polarization and changes a phase to control a beam directing direction. There,
As the second reflector, antenna elements having a function of converting radio waves of a predetermined polarization into orthogonal polarizations and a phase shifting function of changing the phase are arranged in a plurality of element planes. Phased array antenna device.   The phased array antenna device according to claim 1, wherein the reflection surface shape of the first reflector is a curved surface.   The phased array antenna device according to claim 1, wherein a shape of a reflection surface of the first reflector is a flat surface.   2. The phased array antenna apparatus according to claim 1, wherein a microstrip patch antenna of orthogonal polarization feeding is used for the antenna element of the second reflector.   The phased array antenna apparatus according to claim 1, wherein a cross dipole antenna is used as an antenna element of the second reflector.

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