JPH02121506A - Antenna having revolution-body reflector - Google Patents

Abstract

PURPOSE: To reduce a loss of the gain due to the surface tolerance of a rotating paraboloidal reflector by forming the reflector from a material having a liquid phase and a solid phase, centrifuging the material in the liquid phase state and then transiting the centrifuged liquid phase to the solid phase. CONSTITUTION: The antenna is constituted of a primary source 10 consisting of a single pole source having an access flange 11 and a single reflector antenna having a reflector 12 obtained by centrifuging a material in a liquid phase state and solidifying the centrifuged material as it is. The source 10 is held on a fixed position by a supporting rod 13, the cross section of the rod is a triangle and the vertex of the triangle is opposed to the recessed parabolic face of the reflector 12. In the invention, a paraboloidal antenna obtained by centrifuging a liquid phase substance such as melted plastic or a melted metal (e.g. copper or aluminum) and having extremely small surface tolerance is substituted for a conventional rotating paraboloidal reflector manufactured from laminated glass or metal.

Description

[Detailed description of the invention] Product 1 The present invention relates to an antenna having a rotating body reflector.

There are several types of such antennas, such as single reflector antennas.

Nhu BIJI HAI's literature "Microwave antennas (^ntennes m1cro-ondes)" (1
978, Masson),
This type of antenna with a reflector illuminated by a primary source placed at the focal point is commonly used in frequency bands above 400 MHz.

Such antennas are generally of the dipole type with a reflector, which is a rotating body, and -ffi, if the operating wavelength is in the range of senna meters, it is of the horn type, and if the operating wavelength is in the range of decimeters, it is of the dipole type. It is in harmony with the primary source.

The efficiency of an antenna with a rotating parabolic reflector with a surface tolerance of approximately ±λ/16 (λ being the operating wavelength) and a horn-shaped primary source is in the range 0.45-0.55.

One of the factors that has a significant effect on antenna efficiency is the loss of gain due to surface tolerances of the rotating parabolic reflector. By the way, the surface tolerance of ±λ/16 is approximately 0.4 dB.
loss and the diffuse radiation level increases by about 15 dB.

The present invention aims to significantly reduce these effects.

An example of such an antenna is a Cassegrain optical antenna.

Cassegrain optical antennas with rotating body reflectors are well known. The antenna includes a parabolic main reflector;
It includes a hyperboloid or ellipsoid sub-reflector and a -order source.

Listing the characteristic performances of this antenna, in non-cross polarized waves, the level of the first secondary lobe is approximately -16 dB/maximum, the efficiency is approximately 0.55 to 0.65, and the level of the distant lobe is below the isotropic level. -5 dB to -15 dB, and in cross-polarized waves, the in-axis level is about -35 dB, and the maximum level is -22 to -22 dB.
-30clB/max.

- The performance of a Cassegrain antenna mainly depends on the mechanical quality of the reflector, i.e. the main reflector and the sub-reflector, assuming that the secondary source has very good performance (e.g. a wavy horn with an exponential profile). and the accuracy of the relative positioning between these two reflectors, as well as the shape, quality and positioning accuracy of the support arms of the sub-reflectors.

The worse these performances become, the more the antenna
The performance of the Cassegrain antenna having a rotating body reflector is as described above.

Such performance met requirements when only analog radio waves were used. When digital radio waves are used, the performance of crossed single-plane waves becomes delicate. The performance is particularly dependent on the modulation quality, i.e. 4.16.64 or 2564QAM (
quadrature amplitude modulation).

For a given modulation form, the corresponding cross-polarization value is e.g. 16QAM→-22 to -32dB/up to 64QAM→-
28~-38dB/fi large 256QAM→-35~-4
It can be up to 5dB/max.

Therefore, even with 64QAM digital radio waves, it is necessary to select antenna components so that the cross-polarization is lower than that of existing antennas. Furthermore, with 256QAM digital radio waves, the cross-polarization performance of existing antennas is completely inadequate.

Furthermore, in order to increase the illumination efficiency of Cassegrain antennas with rotating body reflectors, attempts have been made to make the amplitude distribution within the aperture even and in phase, while continuing to use a primary source that provides gradual illumination. There is. For this purpose two new reflector profiles, namely [adaptive (co
nformal)” profile is defined. The main reflector has a pseudo-parabolic shape, and the sub-reflector has a pseudo-hyperboloid shape. By adapting the sub-reflector profile,
The illumination of the main reflector can be made uniform, and by "adapting" the main reflector, the illumination within the aperture of the antenna can be brought into phase. However, when using a pseudo-hyperboloid sub-reflector, a source must be placed at a focal point placed between the main reflector and the sub-reflector, and the source shields, so to speak, the radio waves transmitted or received by the antenna. It turns out.

It is therefore an object of the present invention to solve these various problems.

One arc to one method The present invention provides an antenna including at least one rotating body reflector, in which the reflector is formed of a material having a liquid phase and a solid phase, and the material is made of a material having a liquid phase. It can be obtained by centrifugation in this state and then transitioning to a solid phase.

Such an antenna with a centrifuged reflector can obtain the following improvements: a gain of about 0.3 dB, a spread radiation level of about 10 dB, a reduction in cross-polarization level of about 10 dB to 15 dB, and these performances are obtained using the same primary source.

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

A first embodiment of the antenna of the invention, shown in FIGS. 1 and 2, comprises a primary source 10 consisting of a unipolar source with an access flange 11, and a method in which the material is centrifuged in the liquid phase.
Reflector 12 obtained by solidifying as it is
It consists of a single reflector antenna with The source 10 is held in place by a support rod 13, which may be triangular in cross-section, the vertex of the triangle facing the concave parabolic surface of the reflector 12.

Accordingly, the present invention replaces conventional rotating parabolic reflectors made from laminated glass or metal with surfaces such as those obtained by centrifuging liquid phase materials such as molten plastic or molten metal (e.g. copper or aluminum). It replaces parabolic reflectors with extremely small tolerances.

The reflector is made of plastic material (e.g. polyester)
The reflector is then coated with a metal layer (for example by depositing a zinc layer with a thickness of a few tens of pm using the 5 hoop method).

The radius of curvature and focal length of such a reflector depends on the speed of the centrifugation process. The tolerance of the reflector thus obtained is approximately 0.11.

As shown in Fig. 3, the flat radome 16 is equipped with an absorbing material so as to obtain good wind resistance and at the same time reduce the maximum level of radiation of 80@ or more from the axis by 10 to 15 dB.
A single reflector antenna with a ring 15 closed around it may also be used.

This embodiment improves the radio performance of the antenna of the present invention.

Similarly, as shown in FIG. 3, the support rod 13 of the -order source may be coated with a high frequency absorbing material 17 to further increase cross-polarization performance. Depending on the angle of interest, the cross-polarized radiation level may be reduced by several decibels, approximately 10 dB.

Advantageously, even if a conventional parabolic reflector is replaced in the antenna by a centrifugally processed parabolic reflector of the present invention having the same diameter and the same focal length, the fixing and mounting system remains unchanged.

The only change is that the radio performance of the antenna is significantly improved.

To take advantage of the improved cross-polarization performance, it is advantageous to use a corrugated horn type primary source.

According to one embodiment, an antenna with a centrifugal parabolic reflector illuminated by a primary source located at the focal point, the antenna diameter being 3.60 meters, the focal length to diameter ratio 0,43, the surface tolerance of the centrifuging reflector ≦±
0.11, and frequency band 5.925GHz to 6.425
One can envisage having characteristics of GHz.

The resulting curve 20 is the envelope of the non-cross-polarized radiation pattern as shown in FIG.
is the angle (°)), whereas the same curve obtained with an antenna using a conventional parabolic reflector is denoted by 21, where old represents the isotropic level.

Similarly, a curve 22 is obtained representing the envelope E'=f(θ) of the cross-polarized radiation pattern as shown in FIG. The curve is represented by 23.

A second embodiment of the antenna of the invention is a Cassegrain optical antenna as shown in FIG. 110 and 111.

The main reflector 110 is obtained by the centrifugal process described above, using metals such as copper or aluminum, or by applying metal deposits 126 to polyester, for example. The sub-reflector 111 is obtained by processing it as a solid. The accuracy of the parabolic profile is therefore excellent, with a peak-to-peak error of less than ±0.1+nm.

Comparing this accuracy with existing reflectors manufactured by molding, metal spinning, or stamping of Wt layer polyester, the accuracy of reflectors obtained by conventional methods is generally 4.
The peak-to-peak error is 1 mm or more for a reflector with a diameter of 1 meter. These parameters are highly related to the reduction of the cross leakage value.

The primary source 112 is an undulating horn type 118 with an exponential profile. The source is defined to have a phase center O that is as fixed as possible, thus making it possible to obtain excellent cross-plane performance over a wide frequency band. A polarization transmitting/receiving switch 113 is arranged at the free end of the wavy horn 118 .

This wave transmitter/receiver 113 operates with two orthogonal polarizations, vertical and horizontal, and includes a portion 114 in the form of a circular waveguide;
two accesses 115 and 116 in the form of rectangular waveguides, the second access 116 being in the form of a circular waveguide 11
4 and between the level of the first access 115 and the second access 116 is a reflector plate 11.
7 is placed.

The duplexer thus functions to combine these two orthogonal horizontal and vertical linear polarizations. When the bipolar wave reaches the entrance of the circular waveguide 114, the horizontally polarized wave hits a reflector plate 117 parallel to the circular waveguide. The horizontally polarized wave is reflected into the first access 115, while the vertically polarized wave crosses the reflector plate 117 in the normal direction and reaches the second access 116. Reciprocity applies so that waves arriving through the first access 115 are reflected at the reflector plate 117 and exit through the circular waveguide 114. second access 116
Since the wave coming from enters the center of the circular waveguide 114,
The second access is, so to speak, "balanced".
It is J. On the other hand, the first access 115 connected to the side surface of the circular waveguide 114 is “asymmetric (asyn+met)”.
rical)” and is not symmetrical.

A lens 119 is placed in the aperture of the wavy horn 118 . The lens functions to convert spherical waves from the wavy horn into plane waves. The lens has a parabolic surface and a plane, and the focal point of the lens 119 coincides with the phase center O of the wavy horn 118.

The lens is made from a dielectric material, such as polytetrafluoroethylene or "Teflon."

Most existing high-efficiency Cassigrain antennas (efficiency 0.70-0.75) are “adaptive”.
med) J profile, that is, the irradiation phase reflected from the main reflector 110 becomes actually very small (several 10
The main reflector 110 and the auxiliary reflector 111 have a profile that is deformed so that the amplitude reflected by the sub-reflector 111 is uniform.

On the other hand, in the antenna of the present invention, the main reflector 11
The zero profile is necessarily parabolic due to the centrifugal process. Using such centrifugation may cause deformation or
It is not possible to obtain a "adaptive" profile. On the other hand, since the sub-reflector 111 is fabricated as a solid body, it can be adapted to have a different profile. The efficiency of this antenna is approximately 0.65-0.70.

In this embodiment, in order to obtain an antenna with improved efficiency, the two reflectors 110 and 111 are maintained, and the lens 119 is modified to modify the phase pattern so that the main reflector 110 is illuminated with as many phases as possible.
"Adapt" the profile of.

This improves the efficiency slightly, about 0.67-0.72
That is, the main reflector 11 created by centrifugation
0 and an adaptive sub-reflector 111, the antenna of the present invention adapts the lens so that in the waves transmitted or received by the main reflector 110 the shape of the lens is substantially equal to that of the main reflector 110. Such an embodiment can in particular be manufactured in two different ways. The first aspect consists of a centrifugal main reflector 110, which necessarily has a parabolic profile, and a sub-reflector 1, which is processed as a solid and has an adaptive profile.
11, but this solution is only partially applicable (
half-conformed) Corresponds to the J method.

The second aspect consists of a centrifugal main reflector 110, which necessarily has a parabolic profile, and a sub-reflector 11, which is fabricated as a solid body and has an adaptive profile.
1 and a lens 119 with a phase-adapted profile.
Equipped with.

As shown in FIGS. 6 and 7, the sub-reflector support 111 is composed of four rods 120 (or arms) that accurately position and support the sub-reflector 111. These rods are advantageously arranged in a "cruciform" manner. Four arms 120 are fixed around the main reflector 110. In this way, the main reflector profile maintains perfect parabolic continuity and thus
The profile does not change where the four arms are fixed as in prior art antennas. Additionally, the four arms have a "cruciform" profile rather than an X-shaped profile, so that each electric field is
The influence on cross-polarized waves converging at an angle of 5° can be avoided. Furthermore, the cross section of each arm 120 is preferably triangular (isosceles triangle), with the apex facing the parabolic surface of the main reflector 110. In this way, reflection of the radiated electric field off arm 120 is minimized. Therefore, cross-polarization is reduced.

According to the embodiment of the duplexer as shown in FIGS. 8 and 9, the first access 115 is formed into two diametrically opposed rectangular accesses 124 and 1 around the circular waveguide 114.
25 is obtained by a "magic T" having two arms 122 and 123 connecting the two arms 122 and 123. This device is symmetrical.

To reduce the space taken up by the primary source 112, the wavy horn may be bent by a 45° plane, as shown in FIG. 10, so that the horn assumes a vertical position.

During the operation implied in Figure 11, when transmitting, the horn 1
A spherical wave Σ1 is formed within the 18 apertures.

After passing through the lens 119, the spherical wave is converted into a plane wave Σ2. The plane wave Σ2 is reflected by the parabolic sub-reflector 111, becomes a spherical wave Σ3, and the parabolic main reflector 11
0 and becomes a plane wave Σ4 at the exit of the antenna.

Naturally, reception is based on the reciprocity principle (repro
ity principles) apply. plane wave Σ
4 is reflected by the parabolic main reflector 110. After the plane wave is reflected, it becomes a spherical wave Σ3 and hits the parabolic sub-reflector 111. After leaving the sub-reflector, it becomes a plane wave Σ2 and hits the lens 119. The lens converts this plane wave into a spherical wave Σ1, and the steep wave forms a wavy horn 118.
and exits through the access of the polarization transmitter/receiver 113.

One operational example of this second embodiment of the invention considers the following values.

One frequency band: 6.43 GHz to 7.1111:llz.

-1 diameter of reflector 10 D-4 m.

- Diameter d of sub-reflector 11 = 0.60 m.

- Focal length to diameter ratio of 0.45° - The main reflector 110 is manufactured by centrifugal processing, for example by centrifuging a plastic material and then depositing a metal layer on the plastic.
For example, it can be obtained by depositing a zinc layer with a thickness of several tens of pm using the 5-hoop method (or spraying with a molten metal flame gun).

- The sub-reflector 111 is obtained by processing a solid piece of metal, such as aluminum.

Reflector profile tolerance is ±0.1 mm.

- The next source 112 has a diameter of 0.60 mm and a length of 0.90 m.
It is an exponential profile wavy horn with an aperture of .

The diameter of the horn aperture lens 119 is 0.60 m.
Yes.

Fixed around the main reflector are four triangular cross-section support arms 120 arranged in a "cruciform" configuration.

- The difference polarization value is better than 42 dB.

- Efficiency is better than 0.65.

It is to be understood that the above description is merely a preferred embodiment of the invention, and elements may be replaced by equivalent elements within the scope of the invention.

For example, the -order source 112 may be square, rectangular, or circular and may be provided by a waveguide of square, rectangular, or circular cross-section, respectively.

Further, the sub-reflector 111 does not need to have the same focal point as the main reflector 110, and may be a hyperboloid or an ellipsoid. In both cases the primary source is a horn without a lens. In this case, the antenna efficiency is reduced, but its characteristics are maintained very well due to the centrifugal main reflector.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views and front views, respectively, of a first embodiment of the antenna of the present invention, and FIG. 3 shows the first embodiment of the present invention of FIG. 1 together with other components. 4 and 5 are graphs showing the performance of the first embodiment of the antenna of the present invention. FIG. 6 is a partial vertical sectional view of the second embodiment of the antenna of the present invention, and FIG. The figure is a front view of a second embodiment of the antenna of the present invention, and FIGS. 8 and 9 are front views of an embodiment of a polarization transmitter/receiver switch used in the second embodiment of the antenna of the present invention, respectively. and a side view, FIG. 10 is a vertical sectional view showing an embodiment of the source of the second embodiment of the antenna of the present invention, and FIG. 11 is an operational diagram of the second embodiment of the antenna of the present invention. 10.112... Source, 12,110,11
DESCRIPTION OF SYMBOLS 1... Reflector, 13... Support rod, 15... Ring, 16... Radome, 113... Transmission/reception switch, 114. ...
...Circular waveguide, 115.116,124,125...
...Rectangular access, 117...Reflector plate, 118...Horn, 119...
・Lens, 120.122,123...Arm.

Claims (21)

[Claims] (1) An antenna equipped with at least one rotating reflector, in which the reflector is formed from a material having a liquid phase and a solid phase, in which the material is centrifuged in the liquid phase and then converted into the solid phase. Antenna obtained by transitioning. (2) The antenna according to claim 1, wherein the material is plastic. (3) The antenna according to claim 2, wherein a metal deposit is attached to the plastic after centrifugation. (4) An antenna according to claim 3, wherein the metal deposit is obtained by depositing zinc using the Shoop method. (5) The antenna according to claim 1, wherein the material is metal. 6. The antenna of claim 1 including a source carried by a support rod. (7) The antenna according to claim 6, wherein each rod has a triangular cross section, and the vertex of the triangle faces the concave parabolic surface of the reflector. (8) The antenna according to claim 6, wherein the rod is coated with a microwave absorbing material. (9) The antenna according to claim 1, wherein the reflector comprises a microwave absorbing ring comprising a radome that transmits microwaves. (10) The antenna according to claim 1, comprising two rotating body reflectors and a source, and wherein the main reflector is a parabolic reflector obtained by centrifugation. (11) The antenna according to claim 10, wherein a lens is arranged at the aperture of the source. (12) The antenna of claim 11, wherein the lens has an adaptive profile. (13) An antenna according to claim 10, comprising two parabolic reflectors that are cofocal, ie, have the same focal length to diameter ratio. (14) The focal length to diameter ratio of the two reflectors is approximately 0.
14. The antenna according to claim 13, wherein the antenna is 45. (15) The antenna according to claim 10, wherein the sub-reflector has a support constituted by four arms arranged in a cross shape and fixed around the main reflector. (16) The antenna according to claim 10, wherein the source is of a wavy horn type with an exponential profile. (17) The antenna of claim 16, wherein the wavy horn is bent through a 45° plane. (18) The antenna according to claim 10, wherein the sub-reflector is a parabolic reflector processed as a solid. (19) The antenna according to claim 16, wherein a polarization transmitting/receiving switch is disposed at the free end of the wavy horn. (20) a polarization transmitter/receiver including a circular waveguide section and two rectangular waveguide accesses, the second access aligned with the circular waveguide, the first access and the rectangular waveguide access; 20. An antenna according to claim 19, wherein a reflector plate is arranged between the two accesses. 21. The antenna of claim 20, wherein the first access is provided by a "magic T" having two arms connected to two diametrically opposed rectangular accesses around the circular waveguide.