JPS6330588B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing method in a secondary surveillance radar.

Traditionally, secondary surveillance radar (hereinafter referred to as SSR) uses a signal processing method that processes the signal input from the receiver unidirectionally on the circuit and then detects the target based on a uniform standard for all input signals. It was widely adopted. However, this method inevitably causes various problems as described below. That is,
First, since the level of the received signal in SSR weakens in proportion to the square of the distance, the sensitivity of the receiver is automatically controlled (this control is called STC) using ideal characteristics corresponding to this. However, even if the response signals are from the same distance, there are differences in the output of the transponders mounted on each aircraft, changes in the onboard antenna pattern due to the attitude of the aircraft,
Alternatively, the level of the received signal may change by 0 to 15 dB or more due to roving, etc., and if control is applied using a uniform detection standard, a certain response signal may not reach the reference voltage and not be received. be. Second, the SSR signal synchronization signal detection circuit delays the response signal from the transponder by the time of the SSR sweep cycle, matches the response signal of the next cycle in time, and only detects the matched response signal. However, if there is no response signal in continuous synchronization for each sweep, it is inevitable that effective signals will disappear as long as a uniform signal detection algorithm is adopted. Third, SSR
When the sliding window method is adopted, the signal sweep correlation calculation circuit detects the target position (leading edge, trailing edge of the target) from the hit pattern for each sweep using a uniform detection standard K/W. Considering many combinations of modes, mode C
Depending on the conditions, it may not be possible to detect an unequipped aircraft as a target, or even if it is detected, the azimuth accuracy may be poor.

The purpose of the present invention is to differentiate the sensitivity of the receiver in the tracking gate, the signal detection algorithm of the synchronization signal detection circuit, and the detection standard K/W of the sweep correlation calculation circuit (sliding window) from other areas, An object of the present invention is to provide an SSR signal processing method that can solve the problems caused by the prior art and improve target detection performance through independent control.

According to the present invention, by feeding back the target aircraft predictive tracking gate information from the tracking circuit to the receiver STC circuit, the synchronization signal detection circuit, and the sweep correlation calculation circuit, the receiver STC circuit receives information only within the tracking gate. The level reference of the machine STC is changed to increase the receiver sensitivity, and the synchronous signal detection circuit changes the detection algorithm to another algorithm to remove the asynchronous signal, picks up the effective signal in the low hit pattern, and uses the sweep correlation calculation circuit. However, when an aircraft not equipped with Mode C is predicted as a target, a signal processing method in a secondary surveillance radar is obtained, which is controlled to detect the target by changing the detection standard (K/W). It will be done.

By having the above-mentioned features, the present invention has the following features:
By applying a different detection standard or algorithm only to the area (time) that enters the tracking gate and detecting the signal adaptively, it is possible to prevent the loss of valid signals, which was a problem in the past. can. Specifically, by applying the predictive tracking gate information to the receiver's STC circuit, synchronization signal detection circuit, and sweep correlation calculation circuit,
The sensitivity of the receiver is increased only in the tracking gate area, a different detection algorithm is adopted for the tracking gate area, and, for example, signals exhibiting an intermittent hit pattern as shown in Fig. 1 are also picked up. , If information is given that the target aircraft in the tracking gate area is not equipped with Mode C during mode interlacing, a different detection standard value (K/W) is adopted for that area to detect the target. do. In this way, tracking performance can be improved overall.

Next, an embodiment of the present invention will be described with reference to the block diagram of FIG. In the figure, an SSR received video signal 101 is input to an amplifier 11. Further, a conventionally used STC gate signal 102 is input to the STC curve generation circuit 12. On the other hand, the predicted tracking gate information 110 of the target aircraft is transmitted from the automatic tracking circuit 20 to the STC curve generation circuit 1.
2. Feedback is provided to the synchronization signal detection circuit 17 and the sweep correlation calculation circuit (sliding window) 18, respectively. In the STC curve generation circuit 12, when predicted tracking gate information is input during the time when the STC gate is applied, the sensitivity is increased by NdB compared to the standard STC curve signal only during that predicted position (time). Generate a threshold signal with a directionally modified STC curve. This STC curve signal 104,
The amplified received video signal 103 is input to a level comparator 13, which generates a gate signal 105 that allows only the received signal that reaches the reference voltage indicated by the STC curve signal 104 to pass through. The received video signal 103 is
It is gated by a gate signal 105 in an AND circuit 14 and inputted to a bracket pulse pair detection circuit 16 through an amplifier 15. When a pair of bracket pulses (pulses before and after a message break) is detected, the output signal 106 enters the synchronization signal detection circuit 17.

In the synchronization signal detection circuit 17, a standard detection algorithm is used to extract the synchronization signal for each sweep, while when tracking gate information is input to this circuit,
Only in the corresponding area (time), signal detection is performed by changing the standard detection algorithm to another algorithm that can discriminate even if an intermittent hit pattern is received. In addition, in this synchronization signal detection circuit, if the standard detection algorithm is to detect a hit in the same range bin in two consecutive sweeps as a hit, then another algorithm is, for example, a hit in two consecutive sweeps. This means that when a sweep hit occurs, it is detected as a hit. A signal 107 detected at the output side of this circuit is input to a sweep correlation calculation circuit (sliding window) 18.
This circuit detects the signal from the target aircraft using the standard detection standard (K/W), and also uses the tracking gate information to determine whether the target aircraft is equipped with Mode C (altitude information) along with the tracking gate signal. information is given. Based on this information, if the target aircraft is not equipped with mode C and does not respond with mode C, the detection reference K/W is changed according to the state of mode interlace and the target is detected. In this sweep correlation calculation circuit, the standard detection criteria (K/W) are K ₁ /W, K ₂ /W W: window size (specifically, the number of sweeps that fall within the window size) K ₁ : leading edge K2: Detection standard for trailing edge (specifically, it indicates the accuracy and quality of the sweep correlation after the start of detection, and if it exceeds the standard, it is established as a leading edge) _K2 : Detection standard for trailing edge (specifically, (This indicates the degree of uncertainty in the sweep correlation after detection is about to disappear, and if it exceeds the standard, it is established as a trailing edge.) If it turns out that the aircraft is not equipped with Mode C, the Mode C question will be asked. Since there is no response, the detection reference value for K ₁ is lowered and the detection reference value for K ₂ is set higher. The signal 108 detected by the sweep correlation calculation circuit 18 is given as a control signal to the target aircraft information generation circuit 19, and the input signal 107
The location, code, and other incidental information of the target aircraft are extracted from the The target aircraft information 109 extracted by the target aircraft information generation circuit 19 is input to the automatic tracking circuit 20, and error-free automatic tracking is performed.

As is clear from the above description, according to the present invention, in SSR, effective information on response signals from target aircraft can be prevented from being lost, and adaptive target detection can be performed, thereby ensuring reliable tracking of moving target aircraft. Of course, error-free tracking is also possible for aircraft not equipped with Mode C, and this has a great effect on improving target detection performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a hit pattern for explaining signal detection by a synchronization signal detection circuit, and FIG. 2 is a block diagram showing the main parts of the configuration of an embodiment according to the present invention. In the figure, 11 is an amplifier, 12 is an STC curve generation circuit,
13 is a level comparator, 14 is an AND circuit, 15 is an amplifier, 16 is a bracket pulse pair detection circuit,
17 is a synchronization signal detection circuit, 18 is a sweep correlation calculation circuit, 19 is a target aircraft information generation circuit, and 20 is an automatic tracking circuit.

Claims (1)

[Claims] 1 By feeding back the target aircraft predictive tracking gate information from the tracking circuit to the receiver STC circuit, the synchronization signal detection circuit, and the sweep correlation calculation circuit, the receiver STC circuit can adjust the level of the receiver STC only within the tracking group. The receiver sensitivity is increased by changing the reference, and the synchronous signal detection circuit changes the detection algorithm to another algorithm to remove the asynchronous signal, picks up the effective signal in the low hit pattern, and further includes a sweep correlation calculation circuit. However, when predicting an aircraft not equipped with Mode C as a target, the detection standard (K/
W) A signal processing method in a secondary surveillance radar, characterized in that the signal processing method is controlled to detect a target by changing.