JPH05297130A - Secondary monitoring radar device - Google Patents

Abstract

PURPOSE:To prevent a secondary monitor radar from deterioration in the azimuth accuracy and azimuth resolution by suppressing variation of the blip width. CONSTITUTION:An SLS control pulse P2 to be sent to between a pair of mode pulses P1, P3 is transmitted not only with the SLS beam pattern but also with the differential beam pattern. Therefore, such a configuration is introduced that an electric power distribution switch 6 two-divides the control pulse P, the result being sent off from an aerial 1 for mono-pulse. Therein the response range of transponder is determined only by the ratio of the sum pattern to difference pattern, so that the blip width (response width) is stabilized regardless of the antenna gain and the conditions about transmission of electric waves, which prevents deterioration of the azimuth accuracy and azimuth resolution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a secondary surveillance radar apparatus, and more particularly to a monopulse type secondary surveillance radar apparatus.

[0002]

2. Description of the Related Art A secondary surveillance radar emits an interrogation signal from the ground toward a transponder mounted on an aircraft, receives a response signal from the transponder to acquire a distance and an azimuth angle to the aircraft, Is a device for controlling the aircraft on the ground by acquiring the code information such as the identification altitude of the aircraft based on the information included in the response signal.

FIG. 2 is a block diagram of a conventional secondary surveillance radar of this type, and FIG. 3 is a diagram showing an example of a directivity pattern of a monopulse antenna.

The antenna 1 for monopulse has a pair of mode pulses P1, which are interrogation signals, by a sum beam pattern (pattern of FIG. 3A) which is one directional pattern.
P3 is transmitted, and at the same time, the SLS pattern (SLS pattern of FIG. 3C), which is one omnidirectional beam pattern, causes the SLS (si
delobe Suppression) Transmits control pulse P2.

The reception of the response signal from the aircraft is
Two directional patterns (beam patterns of sum and difference, which are shown in FIGS. 3A and 3B) and one omnidirectional SLS beam pattern are used.
The situation is shown in FIG.

In FIG. 2, the receiver 2 receives a response signal obtained by two directional patterns (sum and difference beam patterns) by the monopulse antenna 1 and one omnidirectional SLS beam pattern. Is. Further, the transmitter 3 has interrogation pulses P1 and P3 and SLS control pulse P2.
Are transmitted to the monopulse antenna 1 respectively.

Reference numerals 4a to 4c denote circulators,
The transmission / reception timing generator 5 controls the operation timing of the receiver 2 and the transmitter 3.

As shown in FIG. 5, a transponder in an aircraft uses one of the mode pulses P1 and P3 to generate a pulse P.
The received signal amplitudes of 1 and the control pulse P2 are compared, and when the pulse P1 is larger (in the case of FIG. 5A), the response signal is sent back. In the case of FIG. 5B, the transponder cannot send back a response signal.

In the above-mentioned conventional secondary surveillance radar, since the transmission is performed with only two beam patterns (the sum pattern and the SLS pattern), the variation in the antenna gain due to the change in the attitude of the aircraft, the sea surface or the ground surface. Due to vertical roving due to reflection and changes in various conditions on radio wave propagation, the blip width (response width determined by the antenna beam width and the strength of the received signal) changes, and the number of hits (the number of responses from the aircraft) increases or decreases. As a result, the azimuth accuracy and the azimuth resolution are deteriorated.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a secondary surveillance radar device which suppresses variations in blip width and reduces deterioration of azimuth accuracy and azimuth resolution.

[0011]

A secondary surveillance radar according to the present invention is a secondary surveillance radar device which sends out a pair of mode pulses having a predetermined interval and an SLS control pulse between the pair of mode pulses. Mode pulse transmitting means for transmitting the mode pulse of the above S by a sum beam pattern;
SLS control pulse sending means for sending the LS control pulse in two patterns of a difference beam pattern and an SLS beam pattern.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and the same portions as those in FIG. 2 are designated by the same reference numerals. In this example, the hit number detection unit 7 and the power distributor switch 6 are provided in addition to the configuration of FIG.

The hit detection unit 7 counts the number of hits of the transponder response signal from the receiver 2 and sends a detection signal to the transmission / reception timing generation unit 5 when the number of hits reaches a predetermined number. The transmission / reception timing generation unit 5 receiving this detection signal issues a command to the power distributor switch 6,
In response to this, the power distributor 6 controls so that the control pulse P2 from the transmitter 3 is transmitted not only by the SLS beam pattern but also by the difference beam pattern.

This state is shown in FIG. 4B, and the other transmission pulses P1 and P3 and reception are shown in FIG.
It is the same as (a).

As mentioned above, the transponder is shown in FIG.
As shown in (a), the received amplitudes of pulse P1 and control pulse P2 are compared, and when pulse P1 is larger (4.5 dB
If it is larger than the above), the response signal is sent back. Utilizing the transponder function as described above, the control pulse P2 is SLS.
By transmitting not only the beam pattern but also the difference beam pattern, the blip width indicated by the width T in FIG. 4B becomes stable.

That is, the received signal of the transponder at the point A within the width T of FIG. 4 (b) is as shown in FIG. 5 (a). However, the received signal of the transponder at the points B and C outside the width T of FIG. 4B is as shown in FIG. 5B. Therefore, the response range of the transponder is limited to the width T other than the points B and C, so that the blip width T becomes extremely stable.

Here, the reason why the control pulse P2 is transmitted not only from the SLS beam pattern but also from the difference beam pattern when the number of hits exceeds a predetermined number is as follows.

When the transmission output of the control pulse P2 is divided into two by the power divider switch 6 and transmitted from two patterns of the difference beam pattern and the SLS beam pattern, the transmission power of each control pulse P2 becomes 1/2. Will end up. Therefore, only half the transmission power is supplied to the SLS beam pattern, and the side lobe suppressing function, which is a conventional function, deteriorates.

Therefore, in order to minimize this deterioration,
The power of the control pulse P2 is distributed only in the necessary direction to stabilize the blip width.

As another method, when the number of hits reaches a predetermined number, the transmission power of the control pulse P2 is doubled as compared with the conventional one, and is distributed and supplied to both the difference beam pattern and the SLS beam pattern. It may be done.

[0022]

As described above, according to the present invention, by transmitting the control pulse P2 by not only the SLS beam pattern but also the difference beam pattern, the response range of the transponder can be obtained only by the ratio between the sum pattern and the difference pattern. Since the blip width (response width) is stable regardless of the antenna gain and various conditions on radio wave propagation, there is an effect that azimuth accuracy and azimuth resolution are not deteriorated.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional secondary surveillance radar device.

FIG. 3 is a diagram showing a directivity pattern of a monopulse antenna, where (a) is a sum beam pattern, (b) is a difference beam pattern, and (c) is an SLS beam pattern.

FIG. 4 (a) is a transmission / reception beam pattern of each pulse P1 to P3 in a conventional secondary surveillance radar, and FIG. 4 (b) is a diagram showing a transmission / reception beam pattern of each pulse P1 to P3 in the embodiment of the present invention. is there.

FIG. 5 is a diagram showing an example of receiving respective pulses P to P3 of a transponder.

[Explanation of symbols]

 1 Antenna for monopulse 2 Receiver 3 Transmitter 5 Transmission timing generator 6 Power distribution switch 7 Hit number detector

Claims (2)

[Claims] 1. A secondary surveillance radar device for transmitting a pair of mode pulses having a predetermined interval and an SLS control pulse between the pair of mode pulses, wherein the pair of mode pulses are transmitted in a sum beam pattern. And a SLS control pulse sending means for sending the SLS control pulse in two patterns of a difference beam pattern and an SLS beam pattern. 2. A means for detecting the number of hits of a response signal from an aircraft, and a means for operating the SLS control pulse sending means when the number of hits reaches a predetermined number. The secondary surveillance radar device according to 1.