JPH0349452Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Industrial field of application] This invention mainly relates to antenna devices used in microwave band communication or radar, etc. More specifically, it uses a rotating parabolic mirror and a rotating ellipsoidal mirror. The present invention relates to an improvement of an offset Gregorian antenna having an offset Gregorian antenna.

[Conventional technology]

FIG. 10 is a diagram showing the configuration of a conventional antenna device. In the figure, 1 is a main reflecting mirror of a paraboloid of revolution with F ₂ as the focal point and A ₁ A _1a as the rotation axis, 2 as F ₁ and
The sub-reflector 3 is a part of a rotating ellipsoid with F ₂ as the focal point and A ₂ A _2a as the rotation axis, and 3 is, for example, a primary radiator of a conical horn, and the phase center of the radiated radio wave of this primary radiator 3 is It coincides with one of the focal points F ₁ of the sub-reflector 2. 4 is the radio wave emission direction, 5 is a mount that supports the main reflector 1, 6a is an adjustment mechanism A that determines the relative position of the sub-reflector 2 with respect to the main reflector 1, and 6b is the sub-reflector 2
This is an adjustment mechanism B that determines the relative position of the primary radiator 3 with respect to the primary radiator 3.

The conventional antenna device is configured as above,
When this is considered as a transmitting antenna, the radio waves radiated from the primary radiator 3 are projected as a spherical wave centered on the phase center of the radiated radio waves of this primary radiator, that is, the focal point _F1 , and are reflected by the sub-reflector 2. is,
The light passes through the focal point _F2 , is further reflected by the main reflecting mirror 1, and reaches the direction 4. This antenna type (offset Gregorian type) using a rotating parabolic mirror (main reflector 1) and a rotating ellipsoidal mirror (sub-reflector 2) is used from the primary radiator 3 to the radio wave emission direction 4. It can be constructed without blocking radio waves, and since there is no sidelobe deterioration or reduction in antenna aperture area due to this blocking, it is essentially a high efficiency and low sidelobe antenna, and has become important in recent years as an antenna with a large degree of design freedom. I'm getting used to it.

[Problem that the invention attempts to solve]

However, when realizing low side lobes in the conventional antenna device described above, there are some points to be considered in the relationship between the sub-reflector 2 and the primary radiator 3. That is, FIG. 11 is a view of the sub-reflector 2 and the primary radiator 3 seen from above, and radiation is emitted in the range between the broken lines in the figure in a plane that includes the focal point _F1 and is parallel to the radio wave emission direction 4. The radio waves emitted from the primary radiator 3 are reflected by the sub-reflector 2 and directed toward the main reflector 1, but in the region outside the broken line, the radio waves emitted from the primary radiator 3 go directly into space, resulting in sidelobe characteristics due to so-called spillover. Getting worse. FIG. 12 is an example showing the deterioration of sidelobe characteristics due to this spillover, and the characteristic values exceed the desired characteristics shown by the broken line in the figure in the azimuth range of about 24 to 60 degrees.

Therefore, as a means to achieve low sidelobes, the gain of the primary radiator is increased, the radio wave radiation level around the sub-reflector is lowered, and the circumference of the sub-reflector is extended to a range where spillover can be ignored.
There are improvement measures such as: However, all of these methods have problems such as increasing the size of the primary radiator or sub-reflector and increasing manufacturing costs, which is particularly an obstacle to achieving maximum gain and low side lobes as an antenna. was.

This invention was made to solve this problem, and suppresses the deterioration of sidelobe characteristics due to the spillover without increasing the shape and size.
The purpose is to obtain an economical antenna device.

[Means for solving problems]

The antenna device according to this invention has two sub-reflectors.
A shield whose inner surface is the outer envelope of two pyramids with apexes near each of the two focal points and a conducting wire around the sub-reflector is passed from the primary radiator through the sub-reflector to the main reflector. It is installed between the primary radiator and the sub-reflector without blocking the radio waves reaching the aperture.

[Effect]

In this design, the shield blocks radio waves emitted from the primary radiator to areas other than the sub-reflector, so
Prevents deterioration of sidelobe characteristics due to spillover.

[Implementation diagram]

Fig. 1 is an overall view showing one embodiment of this invention, Fig. 2 is a partial view, and Fig. 3 is a perspective view of a shield.
6 to 6 are completely the same as the above-mentioned conventional device. 7
is a shielding body, which consists of a cone 8 whose apex is a point T ₁ near one of the focal points F ₁ of the sub-reflector 2 and a conductor around the sub-reflector 2, and the other focal point F ₂
Or the sub-reflector 2 with the point T ₂ in the vicinity as the apex
The outer envelope formed by the cone 9 with the conductor around the cone 9 is an inner surface shape, and the cone 8 It has an opening 10 on the side thereof and an opening 11 on the side of the cone 9. FIGS. 4 and 5 are exploded views of the cone 8 and cone 9 constituting the shield 7 when they are manufactured by sheet metal processing.

In the antenna device configured as described above, the radio waves radiated from the primary radiator 3 to the sub-reflector 2 are directed to the shield 7 along the line marked with an arrow in FIG.
It propagates through the inside of F 2 and is reflected by the sub-reflector 2 to the focal point F ₂
and then reaches the main reflecting mirror 1. However, the primary radiator 3
The radio waves radiated from the auxiliary reflector 2 to other than the sub-reflector 2, that is, the radio waves that became a spillover in the conventional device, are blocked by the cone 9 or the cone 8 of the shielding body 7, and
As shown in the figure, deterioration of sidelobe characteristics can be suppressed. This allows a greater degree of freedom in designing the main reflecting mirror 1, the sub-reflecting mirror 2, and the primary radiator 3. Further, as shown in the above embodiments, this shielding body 7 can be manufactured by an inexpensive method such as sheet metal processing, so it is much more economical than an improvement by changing the shape of the primary radiator or the sub-reflector.

In the above embodiment, the shielding body 7 blocked radio waves that would spill over, but as shown in FIG. Similar effects can be expected.

Furthermore, in FIG. 8, a dielectric hollow spherical crown 13 is provided in the opening 11 of one cone 9 of the shielding body 7, and the hollow spherical crown 13 of dielectric material is centered on one focal point _F2 of the sub-reflector 2.
The thickness of 3 is set to 1/2 of the wavelength within the dielectric of the emitted radio waves, and the inner surface of the primary radiator 3 and the sub-reflector 2 are protected from snow and foreign matter adhesion without affecting the radiation characteristics. can be protected. Similarly the 9th
The figure shows an aperture 11 provided with a dielectric thin film 14 that is sufficiently thin compared to the wavelength.

[Effect of idea]

As explained above, this idea has a simple structure in which a shield whose inner surface is the outer envelope of two pyramids is attached between the primary radiator and the sub-reflector.
This has the effect of suppressing deterioration of sidelobe characteristics due to spillover and realizing an antenna device with good characteristics at a low cost.

[Brief explanation of the drawing]

Figure 1 is an overall view showing one embodiment of this invention, Figure 2 is a partial view, Figure 3 is a perspective view of the shield, Figures 4 and 5 are developed views of the shield, and Figure 6 is a partial view. A radiation characteristic diagram, FIGS. 7, 8, and 9 are partial views showing still other embodiments of this invention, FIG. 10 is an overall view showing a conventional antenna device, and FIG. 11 is a partial top view. FIG. 12 is a radiation characteristic diagram. In the figure, 1 is the main reflecting mirror, 2 is the sub-reflecting mirror, and 3 is the main reflecting mirror.
is the primary radiator, 4 is the radio wave emission direction, 5 is the mount, 6
1 is an adjustment mechanism, 7 is a shield, 8 and 9 are cones, 10 and 11 are openings, 12 is a radio wave absorber, 13 is a hollow spherical crown, and 14 is a dielectric thin film. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A main reflecting mirror of a paraboloid of revolution, a sub-reflecting mirror of a part of an ellipsoid of revolution whose focal point is the focal point of this main reflecting mirror, and the above-mentioned sub-reflecting mirror. In an antenna device including a primary radiator whose radio wave phase center is at the other focal point of the secondary reflecting mirror, the vertices are located near the two focal points of the secondary reflecting mirror, and the periphery of the secondary reflecting mirror is A shielding body whose inner surface is the outer envelope of two pyramids of the conductor is provided so as not to block radio waves from the primary radiator to the aperture of the main reflecting mirror via the sub-reflecting mirror. An antenna device characterized by: (2) The antenna device according to claim (1) as a utility model, characterized in that a radio wave absorber is attached to the inner surface of the shield. (3) Utility model registration claim (1) characterized in that the shielding body is equipped with a dielectric hollow spherical crown centered on the focal point of the main reflecting mirror of the sub-reflecting mirror. or the antenna device described in paragraph (2). (4) Claims (1) or (2) of the utility model registration claim characterized in that a dielectric thin film is attached to the main reflecting mirror side of the sub-reflecting mirror of the shielding body, both near the focal point. Antenna device as described in section.