JPS608647B2 - Antenna device for tracking radar - Google Patents

Description

Detailed Description of the Invention This invention has a primary radiator system consisting of a rotationally symmetrical reflector system and four or five horn antennas, and synthesizes the signals output from the four outer horn antennas to generate an arbitrary signal. This invention relates to a radar antenna that tracks the direction of polarized radio waves.

Conventionally, as this type of antenna, there has been a Gregorian type antenna as shown in FIG.

1 has four horn antennas A and B as shown in figure b.
, C, D are arranged in the primary radiator system, 2 is the main reflecting mirror, 3
is a sub-reflector, and the main reflector 2 and sub-reflector 3 constitute a rotationally symmetrical reflector system, and the signals taken out from the horn antennas A, B'C, and D outside the primary radiator system 1 are They were combined to obtain a tracking signal.

That is, the tracking signal E^z in the Az (Azimu 5) direction,
A tracking signal E8 in the E-evation direction is obtained from the outputs a, b, c, and d of the horns A to D according to the following equation. When a radio wave arrives from a certain direction in the plane, E
It must be 8 or 0.

In the case of direct polarization or horizontal polarization, it is clear that a=b and c=d due to the symmetry of the structure, so EE=0. However, in the case of 45o polarization, generally the polarities are a, b, c, and d, so E8〆=0 is not necessarily true. That is, there was a drawback that cross-coupling occurred. This often occurs, for example, when other frequency bands are shared and the primary radiator system needs to be provided on the sub-reflector. This invention was made to eliminate these drawbacks.
An object of the present invention is to provide a tracking radar antenna device with less cross-coupling.

An embodiment of the present invention shown in FIG. 2 will be described below. Figure 2a shows the outer horn antenna A~ which detects the tracking signals in the horizontal and vertical directions forming the primary radiator system 1.
On the Sekiguchi plane 4 of D, the intersection of the central axis of the reflecting mirror system consisting of the main reflecting mirror 2 and the sub-reflecting mirror 3 and the Sekiguchi plane of the primary radiator system 1 and the center of the opening □ of each outer horn antenna A to D. A metal piece 5 made of a metal band or wire is provided in parallel to the direction y connecting the two. In addition, the Sekiguchi surface of the primary radiator system 1 here refers to the plane containing each Sekiguchi surface 4 of the outer horn antennas A to D. The metal piece 5 provided on the open □ surface 4 as described above
affects the polarization in the y direction, but not the polarization in the C direction, which is orthogonal to it. Therefore, by providing the metal piece 5 in an appropriate range on the open surface 4, the shape of the radiation pattern of the polarized wave in the y direction can be changed, and the secondary radiation characteristics in the horizontal or vertical plane can be changed to that of the C polarized wave. You can get close. In this case, any polarization of the outer horn antennas A to D is represented by a combination of y-polarization and C-polarization, so the secondary radiation pattern in the horizontal or vertical plane for any polarization is It is possible to realize a tracking radar antenna with almost the same shape and less cross-coupling.

Although the above description is based on the case where the metal strip is provided in the y direction, it is clear that the same effect can be obtained even if the metal strip is provided in the c direction as shown in FIG. 2b.

A similar effect can also be obtained by providing metal fins parallel to the y direction or the C direction inside the outer horn antennas A to D. Although the primary radiator system 1 has been described above as being composed of four horn antennas A to D, a horn antenna is also arranged in the center of the horn antennas A to D, so that the primary radiator system 1 is composed of five horn antennas. In this case, the same effect can be obtained by disposing metal pieces on the outer horn antennas A to D as described above.

As described above, according to the present invention, the secondary polarization for polarized waves in the direction parallel or perpendicular to the direction connecting the intersection of the central axis of the reflector system and the closed surface of the primary radiator system and the closed center of each horn antenna is achieved. Since the radiation characteristics can be made equal, there are advantages such as less cross-coupling.

[Brief explanation of the drawing]

FIG. 1 shows a conventional tracking radar antenna, FIG. 1A shows a side view showing its configuration, FIG. Figure b is a diagram showing another embodiment. In the figure, 1 is a primary radiator system, 2 is a main reflecting mirror, 3 is a sub-reflecting mirror, A to D are horn antennas, and 5 is a metal piece.
Note that the same reference numerals in the figures indicate the same or corresponding parts. Bag l figure 2

Claims (1)

[Claims] 1. A tracking radar antenna comprising a rotationally symmetrical reflector system and a primary radiator system having four horn antennas for detecting horizontal and vertical tracking signals,
A metal piece is arranged in each horn antenna in a direction parallel or perpendicular to the direction connecting the intersection of the central axis of the reflector system and the aperture surface of the primary radiator system and the center of the aperture of each horn antenna. Features of tracking radar antenna device. 2. The tracking radar antenna device according to claim 1, wherein the metal piece is disposed on a part of the aperture surface of the horn antenna. 3. The tracking radar antenna device according to claim 2, wherein the metal piece is strip-shaped or linear. 4. The tracking radar antenna device according to claim 1, wherein the metal piece is disposed inside the horn antenna. 5. The tracking radar antenna device according to claim 4, wherein the metal piece is fin-shaped.