JP2009038459A - Reflector antenna - Google Patents

Abstract

A reflector antenna capable of suppressing a side lobe level within a mechanical constraint of the reflector antenna is obtained.
A primary radiator that radiates radio waves of linearly polarized waves, and a primary radiator that transmits and reflects incident radio waves according to a polarization angle with an incident axis as an axis by providing a conductor grid on a dielectric plate. Sub-reflection of the sub-reflector 3 that reflects the radio wave from the sub-reflector 3 and the dielectric plate 40 that receives and reflects the plane wave reflected by the sub-reflector and has a thickness that is an odd multiple of ¼ of the wavelength of the internal frequency used. A conductor grid of the sub-reflecting mirror and a conductor grid inclined by 45 ° about the mirror axis are provided on the surface facing the mirror, and the back surface is covered with a conductor film, and the combined radio waves reflected by the front and back surfaces are transmitted through the sub-reflecting mirror A rotating quadratic curved surface that includes a main reflecting mirror 4 that reflects the sub-reflecting mirror while changing the polarization angle so that the front and back surfaces of the main reflecting mirror are incident on the surfaces and are focused at different positions. It has a surface shape consisting of a part thereof.
[Selection] Figure 5

Description

  The present invention relates to a reflector antenna, and more particularly to a reflector antenna including a main reflector having a polarization rotation function based on a reflection phase difference between a front surface and a back surface and a sub-reflector having a polarization selection function.

  As this kind of reflector antenna called a twist reflector antenna, for example, a first dielectric having first and second paraboloids and a first paraboloid on the first paraboloid are spaced apart from each other in parallel. A plurality of first linear conductors that reflect radio waves, and a back conductor that is provided on the second paraboloid and reflects between radio waves that have passed through the first dielectric and passed through the first dielectric. A parabolic reflecting mirror (main reflecting mirror), a flat plate-like second dielectric having a facing surface facing the first parabolic surface, and a parallel space spaced apart from each other on the facing surface And a plurality of second linear conductors that reflect radio waves toward the paraboloidal reflecting mirror, and are plane reflecting mirrors (sub-reflecting mirrors) that transmit the radio waves reflected by the parabolic reflecting mirror The primary radiator that radiates radio waves toward the plane reflecting mirror and the parabolic reflecting mirror are moved so that the reflection angle Some have a driving means for changing the degree (see, for example, Patent Document 1).

  When the polarization direction of the radiated radio wave is horizontal, the radio wave radiated from the primary radiator with the vertical polarization is reflected by the second linear conductor and arranged at 45 ° with respect to the second linear conductor. The first linear conductor, that is, the deflected torsional reflection means, changes the polarization direction by 90 ° to become a horizontal polarization and becomes a parallel beam, which is radiated into the air through the second linear conductor. . In order to change the direction of the beam, a parabolic reflecting mirror having a deflecting torsional reflecting means is driven by an actuator.

JP 2001-27646 A

  In general, the radiation characteristics of antennas used for communication and radar are not limited to reflector antennas, and in order to prevent reception of radio waves that interfere with communication and reception of clutter, in particular, the side lobe level relative to the main lobe level is It is required to be sufficiently low. In order to reduce the sidelobe level, for example, there is a method of optimizing the distribution of the aperture (amplitude and phase) of the main reflector due to the irradiation of the primary radiator. Irradiation must be optimized within the mechanical constraints of the antenna device, and the positional relationship between the primary radiator and the main reflector is optimized within these mechanical constraints, and the side lobe level is set to a sufficient level. It is difficult to suppress it.

  Further, as in the above-described conventional example, in order to obtain the maximum radiation efficiency as a reflector antenna, the phase center of the primary radiator is usually arranged at the focal point or in the vicinity thereof. The radiation characteristics of the reflector antenna are specific to the reflector antenna structure, especially the main reflector structure. In the same structure, the aperture (amplitude and phase) distribution of the main reflector by the primary radiator irradiation is adjusted. However, there is a problem that it is difficult to suppress the side lobe level to a desired level.

  The present invention has been made to solve the above-described problems, and provides a reflector antenna that can suppress the side lobe level to a sufficient level within the mechanical constraints of the reflector antenna. With the goal.

  According to the present invention, a primary radiator that radiates linearly polarized radio waves, and a conductor grid in which a plurality of conductor strips are formed in parallel are provided on a dielectric plate, and incident radio waves are used with an incident axis as an axis. A sub-reflector provided so as to reflect the radio wave emitted from the primary radiator, which is selectively transmitted or reflected as a plane wave according to a polarization angle, and a plane wave radio wave reflected by the sub-reflector. The dielectric plate is provided so as to be opposed to the sub-reflecting mirror so as to be reflected, and has a thickness that is an odd multiple of 1/4 of the wavelength of the operating frequency inside. The conductor grid of the sub-reflecting mirror is provided on the front surface with a conductor grid in which a plurality of conductor strips inclined at 45 ° about the mirror axis are formed in parallel, and the back surface is covered with a conductor film. The sub-reflection of radio waves reflected and synthesized on the front and back surfaces And a main reflecting mirror that reflects the sub-reflecting mirror while changing the polarization angle so that it is transmitted at the front surface and the back surface of the main reflecting mirror, respectively, and the plane wave incident on the surface is reflected, respectively. The reflector antenna is characterized in that it has a surface shape formed of a rotating quadratic curved surface converging at different positions or a part thereof.

  In the present invention, the side lobe level can be suppressed within the mechanical constraints of the reflector antenna.

  In particular, the shape of the front and back surfaces of the main reflector is formed so as to shift the position where the plane wave incident on each surface is focused after reflection, and the positional relationship between the focusing position and the phase center of the primary radiator. However, the phase pattern of the secondary radiation obtained by reflecting the radio wave radiated from the primary radiator by the main reflector is made different between the front surface and the back surface of the main reflector. It can be different between the front and back surfaces of the reflector. As a result, the phase pattern of the secondary radiation is made different between the front surface and the back surface of the main reflecting mirror, so that the reflection phases on the front surface and the back surface are the same in the incident polarization direction. Therefore, even if there is a direction where an unnecessary radiation level exists on each of the front surface and the back surface of the main reflecting mirror, it can be suppressed.

  Hereinafter, the present invention will be described in accordance with an embodiment, but regarding the operation of the antenna, the same characteristics are obtained regardless of whether it is used for transmission or reception by the antenna reversibility theorem. Only explained. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the same or corresponding operation in the opposite direction is performed in the operation of the receiving antenna.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of a reflector antenna according to an embodiment of the present invention. First, an outline will be described. In FIG. 1, a sub-reflecting mirror 3 is integrally formed as a part of the case 2 on the transmission / reception surface side of the case 2 of the reflecting mirror antenna 1. A main reflecting mirror 4 is installed in the case 2 so as to face the sub-reflecting mirror 3. The main reflecting mirror 4 is formed, for example, in the shape of a rotating plane with the point F1 as a focal point (details will be described later), and a primary radiation that radiates radio waves toward the sub-reflecting mirror 3 at the center thereof. A vessel 5 is arranged. The primary radiator 5 is an antenna that radiates linearly polarized waves, and here is a pyramid horn antenna. The sub-reflecting mirror 3 is installed at a position that is half the distance from the main reflecting mirror 4 to the focal point F1 of the main reflecting mirror 4 or in the vicinity thereof. Further, the primary radiator 5 is arranged at the position F1r of the mirror image with respect to the sub-reflecting mirror 3 at the focal point F1 of the main reflecting mirror 4 or in the vicinity thereof. As described above, the reflecting mirror antenna 1 includes the primary radiator 5, the sub-reflecting mirror 3, and the main reflecting mirror 4.

  2A and 2B schematically show an example of the structure of the sub-reflecting mirror 3. FIG. 2A is a top view and FIG. 2B is a side view. As shown in FIG. 2, the sub-reflecting mirror 3 has a plurality of thin conductor strips made of a conductor such as metal in parallel on the inner surface of the case 2 made of a flat dielectric plate 30 on the transmission / reception surface side. A conductor grid 31 configured side by side is provided. The extension direction of the conductor of the conductor grid 31 is installed so as to reflect the polarized radio wave of the primary radiator 5 and conversely transmit the polarized radio wave orthogonal thereto. The conductor grid 31 may be provided on the outer surface or inside of the dielectric plate 30. The conductor grid 31 is formed by arranging a plurality of conductor strips having a sufficiently narrow width compared to the wavelength of the operating frequency in parallel at intervals sufficiently narrower than the wavelength.

  3A and 3B schematically show an example of the structure of the main reflecting mirror 4. FIG. 3A is a top view and FIG. 3B is a side view. As described above, the main reflecting mirror 4 is configured by molding the dielectric plate 40 in the shape of a rotating paraboloid (surface shape obtained by rotating a parabola), for example, with the point F1 as a focal point (details will be described later). Here, the thickness of the dielectric plate 40 is selected to be an odd multiple of about ¼ of the wavelength in the dielectric plate 40 with respect to the use frequency (radio frequency) of the antenna. Further, as shown in FIG. 3, the main reflector 4 has a dielectric plate 40 on the front surface (surface on which radio waves are incident) and the conductor grid 31 of the sub-reflector 3 with its mirror axis as an axis. In a direction inclined by 45 °, a conductor grid 41 provided with a plurality of thin conductor strips made of a conductor such as metal is provided in parallel, and the back surface of the dielectric plate 40 (opposite the front surface). The conductor film 42 is provided on the entire opposite surface. In the conductor grid 41, a plurality of conductor strips having a sufficiently narrow width compared to the wavelength in the dielectric plate 40 with respect to the use frequency of the antenna (frequency of radio waves) are arranged in parallel at a sufficiently narrow interval compared to the above-mentioned wavelength, and As described above, the conductor strip of the sub-reflecting mirror is installed in a direction inclined by 45 ° about the mirror axis. An opening 43 serving as a radiation port of the primary radiator 5 is formed at the center of the dielectric plate 40.

  FIG. 4 shows the direction of the electric field with respect to the extending direction of the conductor of the conductor grid 31 of the sub-reflecting mirror 3. E1 represents the direction of the electric field of the radio wave radiated from the primary radiator 5. The subscript “in” indicates the direction of the electric field of the radio wave reflected by the conductor grid 31. The subscript out indicates the direction of the electric field of the radio wave transmitted through the conductor grid 31.

  The radio wave radiated from the primary radiator 5 is reflected by the conductor grid 31, that is, the sub-reflecting mirror 3 because the direction of the electric field is E1in. This reflected wave enters the main reflecting mirror 4. The main reflecting mirror 4 rotates the polarization of the incident wave by 90 ° around the incident axis depending on the direction of the conductor grid 31 and the distance between the front and back surfaces of the reflecting mirror (the thickness of the dielectric plate 40). It has a polarization rotation function structure of reflecting. The radio wave whose polarization direction is rotated by 90 ° by the main reflecting mirror 4 has an electric field direction E1out and reaches the sub-reflecting mirror 3. Since the electric field direction E1out is perpendicular to the conductor extension direction of the conductor grid 31, it passes through the conductor grid 31 as it is. That is, it is radiated to the space without being reflected by the sub-reflecting mirror 3.

  In the conventional reflector antenna, both the front surface and the back surface of the main reflector 4 are, for example, a rotating paraboloid focusing on the point F1 in FIG. By installing the primary radiator 5 at the position F1r, the center feed parabolic antenna functions as a reflector antenna that is folded back in the direction of the mirror axis.

  FIG. 5 is a diagram showing an operation concept of the present embodiment. FIG. 6 is a diagram showing the radiation pattern characteristics of the reflector antenna via the sub-reflector 3 and the main reflector 4 for explaining the present embodiment. The horizontal axis represents the angle from the main radiation direction (beam direction), and the vertical axis. The axis indicates the radiation power value in each direction normalized by the radiation power value in the main radiation direction. (A) shows a phase pattern, (b) shows an amplitude pattern, A shows a front surface pattern, B shows a back surface pattern, and C in (b) shows a composite pattern.

  Hereinafter, the operation of the reflector antenna according to the present embodiment will be described. In FIG. 5, when the radio wave radiated from the primary radiator 5 is reflected by the sub-reflecting mirror 3 and further reflected by the main reflecting mirror 4, the electric field direction is changed by the polarization rotation function of the reflecting mirror 4 described above. From E1in shown in FIG. 4 to E1out, the auxiliary reflector 3 is reached. As a result, the radio wave in the electric field direction E1out is transmitted through the conductor grid 31 without being reflected by the sub-reflecting mirror 3, and is radiated to the space.

  Here, in the reflector antenna according to the present embodiment, the conductor grid 41 and the conductor film 42 installed on the front surface and the back surface of the dielectric plate 40 both have a paraboloidal shape. As shown, the conductor grid 41 and the conductor film 42 are formed so that the focal position F1 of the conductor grid 41 installed on the front surface is different from the focal position F2 of the conductor film 42 installed on the back surface ( For example, the main reflector 4 has a surface shape in which the curvatures of the front surface and the back surface of the main reflecting mirror 4 and the conductor grid 41 and the conductor film 42 are changed. Therefore, as shown in FIG. 5, the focal position F1 of the conductor grid 41 and the focal position F2 of the conductor film 42 are positively shifted to make them different, so that the mirror images of the focal positions F1 and F2 with respect to the sub-reflecting mirror 3 are obtained. The positional relationship between the positions F1r and F2r and the phase center O of the primary radiator 5 can be made different. Thereby, the radiation pattern formed by the front surface (that is, the conductor grid 41) and the back surface (that is, the conductor film 42) of the main reflecting mirror 4 is positively made to have a particularly different shape. Thus, it is possible to suppress radiation in a desired angular direction as a radiation pattern by combining the front surface and the back surface.

  FIG. 6 (a) shows a front surface pattern A and a back surface pattern B, which are radiation phase patterns when radio waves are radiated into the space on the front surface and the back surface of the main reflecting mirror 4, respectively. Show. However, the radiation phase patterns on the front surface and the back surface shown in FIG. 6A are the characteristics in the polarization direction of the primary radiator 5, and are displayed in alignment with the common polarization direction. Yes. In FIG. 6A, the phase difference between the front surface pattern A and the back surface pattern B is about 180 ° in the front direction (θ = 0 ° direction). Compared with the reflected wave from the surface, the phase is rotated by 180 ° by extra reciprocating propagation in the dielectric plate 40. Therefore, the polarization direction of the incident wave is determined by combining the reflected waves on the front surface and the back surface. It represents the polarization rotation itself, which is reflected by rotating 90 ° around the incident axis. That is, if the reflection phase difference between the front surface and the back surface is an integral multiple of 180 °, polarization rotation functions (polarization rotation function structure), so that gain in a desired polarization direction can be obtained. Can do.

  On the other hand, on the contrary to the above, when the reflection phase difference between the front surface and the back surface is only an integer multiple of 0 ° or 360 ° (that is, in the same phase), the polarization rotation is completely completed. Since it does not function, a gain in a desired polarization direction cannot be obtained. In the present embodiment, an unnecessary radiation level in the radiation direction can be suppressed by positively making the reflection phase on the front surface and the back surface in the same phase in any desired direction. It is something that can be done.

  FIG. 6B shows a front surface pattern A, a back surface pattern B, which are radiation amplitude patterns when radio waves are radiated into the space on the front surface and the back surface of the main reflector 4, respectively. In addition, these synthesis patterns C are shown. As shown in FIG. 6 (b), in the front surface pattern A and the back surface pattern B by the front surface and the back surface of the main reflecting mirror 4, there are main lobes such that the 0 ° direction is the maximum radiation direction. You can see that it exists.

  Further, in the radiation pattern of only the front surface and the back surface, there is a portion (= hereinafter referred to as a shoulder) having a relatively high radiation level in the angular direction (± 5 ° direction) which is the base on both sides of the main lobe. It has occurred. The shoulder generated in this way becomes a factor that deteriorates the angle measurement performance, particularly in the radar function, when the reflector antenna of the present embodiment is applied to the radar function.

  However, in the present embodiment shown in FIG. 6B, as described in the description of the phase pattern in FIG. 6A, the front surface of the main reflecting mirror 4, that is, the conductor grid 41 is provided. Even if the focal position F1 and the back surface of the main reflecting mirror 4, that is, the focal position F2 of the conductor film 42 are positively changed, even in an angular direction in which a shoulder is generated only on the front surface and the back surface. If the reflection phase is in-phase in that direction, the radiation in the angular direction in which the shoulder is generated can be reduced as shown by the composite pattern C in FIG.

  As described above, in the present embodiment, the focal positions of the front surface and the back surface of the main reflecting mirror 4 are positively changed, so that it is not necessary for each of the front surface and the back surface of the main reflecting mirror 4. Even if a high radiation level exists, this unnecessary radiation can be suppressed as the combined pattern of the reflected waves by both sides, that is, the radiation pattern of the reflector antenna in the present embodiment.

  It should be noted that unnecessary radiation can be generated by making the focal positions of the front and back surfaces of the main reflector 4 positively different so that the reflection amplitude patterns on the front and back surfaces of the main reflector 4 are different. Concerning suppression, in particular, it is configured so that a null (an output decreasing direction region in directivity) is generated on the other surface with respect to the direction in which unnecessary radiation is generated on one surface of the front surface and the back surface. Therefore, unnecessary radiation can be suppressed.

  In the above description, the shape of the front surface and the back surface of the main reflecting mirror 4 has been described as a rotating paraboloid. However, this shape is such that at least one of the front surface and the back surface is a rotating paraboloid. The shape may be a part, and the shape may be a rotating quadratic surface (surface shape obtained by rotating a quadratic curve) having any desired reflection characteristic or a part thereof. When the shape is an arbitrary rotating quadric surface, the focal position may not be fixed to one point as in the case of a rotating paraboloid, and in this case, the plane wave incident on each surface is focused at a different position. That is, it is only necessary to shift the focusing position (region).

  Further, the phase center position of the primary radiator 5 is set between the respective positions of the mirror image with respect to the sub-reflecting mirror 3 at the focal position of the rotary paraboloid constituting the front surface and the back surface of the main reflecting mirror 4, or By setting between each position (region) of the mirror image with respect to the sub-reflecting mirror 3 at a position (region) where the plane wave incident on the rotating quadratic surface constituting the front surface and the back surface of the main reflector 4 is focused Since the radiation phase pattern formed by both surfaces can be made different, the angle at which the reflection phase is in phase, that is, the angle at which radiation is suppressed can be easily controlled.

1 is a schematic configuration diagram of a reflector antenna according to an embodiment of the present invention. It is a figure which shows roughly an example of the structure of the sub-reflecting mirror of FIG. It is a figure which shows roughly an example of the structure of the main reflective mirror of FIG. It is a figure for demonstrating the relationship between the extension direction of the conductor of the conductor grid of the sub-reflecting mirror of FIG. 1, and the direction of an electric field. It is a figure for demonstrating operation | movement of the reflector antenna by one Embodiment of this invention. It is a figure which shows the example of the radiation pattern characteristic of the reflector antenna by one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Reflector antenna, 2 Case, 3 Sub reflector, 4 Main reflector, 5 Primary radiator, 30 Dielectric board, 31 Conductor grid, 40 Dielectric board, 41 Conductor grid, 42 Conductor film, 43 Opening.

Claims (9)

A primary radiator that radiates linearly polarized radio waves;
The primary radiation is provided with a conductor grid in which a plurality of conductor strips are formed in parallel on a dielectric plate, and selectively reflects incident radio waves as transmission waves or plane waves according to a polarization angle about the incident axis. A sub-reflector provided to reflect radio waves emitted from the vessel,
It is provided opposite to the sub-reflecting mirror so as to receive and reflect the plane wave radio wave reflected by the sub-reflecting mirror, and the thickness is an odd multiple of 1/4 of the wavelength of the internal frequency used. Provided on the front surface of the dielectric plate facing the sub-reflecting mirror is a conductor grid in which a plurality of conductor strips inclined at 45 ° about the mirror axis are formed in parallel with the conductor grid of the sub-reflecting mirror A main reflecting mirror whose back surface is covered with a conductor film, and whose reflected wave is reflected by the sub-reflecting mirror so as to transmit the radio wave reflected and synthesized by the front and back surfaces by the sub-reflecting mirror; ,
With
A reflecting mirror characterized in that the front surface and the back surface of the main reflecting mirror each have a surface shape composed of a rotating quadratic curved surface or a part thereof that reflects and focuses plane waves incident on the surface. antenna.   The reflector antenna according to claim 1, wherein the reflection amplitude patterns of radio waves by the front surface and the back surface of the main reflector are different.   The reflector antenna according to claim 2, wherein the null generation direction in one of the reflection amplitude patterns of the radio waves by the front surface and the back surface of the main reflection mirror is the generation direction of the other unnecessary radio wave radiation.   2. The reflector antenna according to claim 1, wherein a reflection phase pattern of radio waves differs between the front surface and the back surface of the main reflector.   The phase center of the primary radiator is misaligned with the position of the mirror image relative to the sub-reflecting mirror at each position where plane waves incident on the front and back surfaces of the main reflecting mirror are reflected and converged. The reflector antenna according to claim 4.   The phase center of the primary radiator is located between the positions of the mirror image with respect to the sub-reflecting mirror at each position where plane waves incident on the front and back surfaces of the main reflecting mirror are reflected and converged. The reflector antenna according to claim 5, wherein   2. The reflector antenna according to claim 1, wherein at least one of a front surface and a back surface of the main reflector has a surface shape formed of a paraboloid of revolution or a part thereof.   The position and position of the mirror image with respect to the sub-reflector at the position where the phase center of the primary radiator reflects and focuses the incident plane waves on the front and back surfaces of the main reflector. The reflector antenna according to claim 7, wherein the mirror antenna is misaligned.   Between the position where the phase center of the primary radiator reflects and focuses the incident plane waves on the front surface and the back surface of the main reflector or the position of the mirror image with respect to the sub-reflector at the focal position. The reflector antenna according to claim 8, wherein

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