JP2707827B2 - SSR signal processing device - Google Patents

Description

The present invention relates to an SSR (Secondary Surveillance Radar) signal processing device, and more particularly to suppressing the use of a pseudo image caused by multiple reflection of radar radio waves. The present invention relates to an SSR signal processing device.

[Conventional technology]

The SSR emits an interrogation signal from the interrogator at the ground station to the space, and the transponder (Tr
Ansponder) decodes the data and returns it to the ground station as a response signal.

The signals received by the ground station are decoded by the signal processor in the SSR, and various types of information from the aircraft can be obtained. These are displayed on a radarscope and used for air traffic control.

The SSR ground station consists of an antenna, an interrogator (transmitter and receiver), a signal processor, and so on. In addition, the SSR antenna has several radiation patterns due to its radio wave radiation characteristics. One is called a main beam pattern and shows a sharp directivity in a horizontal plane. The other is called an omega pattern and has a special directional characteristic that covers the side lobe of the main beam.

The main pattern emits an interrogation signal into space while the antenna continuously rotates in the azimuth plane. The interrogation signal is composed of a plurality of continuous pulse trains, and this pulse train is composed of a pair of pulses (P1) and (P1) having a predetermined time interval.
Formed by 3).

The aircraft present in the main beam receives this interrogation signal, and if the pulse interval between the pair of pulses (P1) and (P3) is a predetermined value, recognizes it as a normal interrogation and automatically emits a response signal.

On the other hand, in addition to the pair of pulses (P1) and (P3), the (P2) pulse is emitted from the omega pattern, and the pulses (P1), (P2),
(P3) is received. In each reception level, the pulse (P2) is larger than the pulse (P1) or (P3).
In this case, the transponder mounted on the aircraft uses a pulse (P
After the reception of 2), a prohibition gate for prohibiting the reception for about 35 μs immediately after that is generated. Therefore, even if the pulse (P3) arrives after the reception of the pulse (P2), the pulse (P3) is suppressed by the above-described inhibition gate and is not received. Therefore, no time correlation is obtained for the time interval between the pulse (P1) and the pulse (P3), and the transponder does not emit a response signal. That is, it is possible to prevent unnecessary response from the aircraft in the side lobe region of the main beam.

Further, as an unnecessary response from the aircraft, there is a pseudo response (similar to an optical image) generated by multiple reflections of radio waves from obstacles existing around the ground station. As a means of improving this kind of image, conventional I ² SLS (Improved
There is a function called Interrogator Sidelobe Suppression).

 The following briefly introduces this principle.

The pulse (P1) is emitted from the main beam of the SSR antenna with half the power of the conventional one, and a pulse (P3) that is the same as the conventional one. On the other hand, the Omega pattern emits a pulse (P1) with the remaining half of the power and a pulse (P2) like the conventional one.
It is assumed that both an electric wave that arrives directly at the shortest distance by an omega pattern and an electric wave that reaches once after being reflected by an obstacle are received on an aircraft that may generate a suspect image. Comparing the former and the latter, the pulse (P1) from the omega pattern arrives at the aircraft earlier than the pulse (P1) of the main beam because the radio wave propagation distance is short. Now, when the aircraft receives radio waves from this Omega pattern, (P1) and (P1)
The pair pulse 2) satisfies the condition for generating the above-described inhibition gate. Therefore, in this case, as in the case of improving the unnecessary response in the side lobe region, the pulse (P
2) Reception of a signal arriving within 35 μs after reception, that is, reception of a signal from a reflector, is prohibited, and generation of a pseudo response can be prevented.

The above-mentioned prior art is described in detail in Avionics System, Nikkan Kogyo Shimbun, Chapter 2.2.2 and others.

[Problems to be solved by the invention]

I ² SLS that provides an improvement over the conventional multiple reflections described above
The method has a drawback that it has the following two performance limitations as can be inferred from its operation principle.

(1). The absolute condition is that the pulse (P1) emitted from the Omega pattern reaches the aircraft, and it is effective only in this range. The antenna gain of the Omega pattern is extremely low with respect to the gain of the main beam, and can be received by an aircraft only in a region very close to the ground station. Therefore, it has no effect on aircraft beyond that.

(2). If the difference between the direct propagation path and the propagation path through the obstacle is other than (5.250 ± 1.500) m (35 ± μs), the pulse (P1), (P1) from the main beam after the prohibition gate of 35μs ends P3) arrives, and the prohibition gate has no effect. Therefore, in this case, the transponder responds to the reflected wave, which is a pseudo response.

[Means for solving the problem]

The device of the present invention is an SSR signal processing device for performing signal processing of a secondary monitoring radar operated for air traffic control,
When a ground station receives and decodes a response signal transmitted from an airborne transponder, it extracts only those signals that match the time intervals of the paired pulses of the response signal as normal signals, and sets the pulse width of the received signal in advance. And determining whether or not the response signal exceeds the set value.

Further, in the apparatus of the present invention, the value set in advance for judging the pulse width of the received signal by the means is such that when the response signal arrives after being once reflected by an obstacle, the pulse width of the received signal is changed. Based on being stretched in accordance with the size of the obstacle, it has a configuration that is set as a scale sufficient to recognize a received signal passing through the obstacle.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention. The embodiment shown in FIG. 1 comprises a transponder 1 mounted on an aircraft 10, an antenna 2 constituting a ground station, and an interrogator 3, and the interrogator 3 is provided with a receiving device 4 and a signal processor directly related to the present invention. Device 5
And a transmission device 6 for transmitting an interrogation signal and a transmission / reception switch 7
FIG. 2 also shows an obstacle 11 to the response signal transmitted from the transponder 1 together.

First, basic features of the present invention will be described with reference to FIG.

The feature of the present invention resides in that an operation principle completely different from that of the above-mentioned conventional I ² SLS system is applied, and provides a means for overcoming the conventional performance limit. The means for making this possible are described below.

Now, the response signal emitted from the aircraft 10 arrives at the ground station from the aircraft 10 via a route that is exactly the same as the radio wave that reaches the ground station directly and from the ground station to the aircraft 10 via the obstacle 11. It is assumed that two routes are taken with the radio wave. If the ground station receiver detects a direct wave from the aircraft 10, the pulse width of this signal will be relatively close to the ICAO-specified transponder output pulse width of 0.45μs. Should be.

On the other hand, the response signal that is reflected from the terrestrial obstacle 11 having a finite size and reaches the ground station once has a pulse width of 1.0 μs per 150 m when it is constant in proportion to the size of this obstacle. Spreads. The present invention focuses on the spread of the pulse width due to obstacles, and when an input signal that is longer than the pulse width detected as a direct wave is detected, these signals are transmitted through an obstacle. It is determined whether or not the input signal is a pseudo signal.

Returning to FIG. 1, the operation of this embodiment will be described.

Pulse width of 0.45 transmitted from Transponder 1 mounted on aircraft 10
The response signal of μs hits the obstacle 11 and is reflected here, so that its pulse width becomes wider than the original width. This signal is received by the antenna 2. The receiving device 4 of the interrogator 3 inputs a received signal via the transmission / reception switch 7, and the received signal is amplified and detected, and an SSR video having a pulse width somewhat wider than a normal response signal is obtained.

FIG. 2 is a configuration diagram showing the signal processing circuit 5 of FIG. 1 in detail.

The signal processing circuit 5 shown in FIG.
A waveform shaping circuit (1) 5-1 for shaping a pulse width of an R video into a fixed value, and detecting a pulse width of an SSR video input and outputting only those having a pulse width not less than a predetermined pulse width. A pulse width detection circuit 5-2, a waveform shaping circuit (2) 5-3 for shaping and converting the output of the pulse width detection circuit 5-2 into a signal having a constant pulse width, and a time interval of a pulse train from among the received signals. A pulse interval discriminating circuit 5-4 for selectively outputting only a pair pulse equal to the time interval of the response pulse transmitted from the transponder 1, and a pair pulse having the time interval of the received pulse train equal to the time interval of the response pulse emitted from the transponder 1 And a pulse interval discriminating circuit (2) 5-5 for prohibiting the output of the output A when the output B appears.

In FIG. 2, an SSR video input having a correct pulse width is supplied to a waveform shaping circuit 5-1 and a pulse interval identification circuit 5-1.
-4 is output as output A. The output A obtained by the pulse interval discriminating circuit 5-4 is processed in exactly the same system as in the conventional system, and includes both a response signal received on the direct path from the aircraft and a pseudo response signal passing through the obstacle 11. ing.

On the other hand, as for the output B output from the pulse interval discriminating circuit 6-5, only the signal whose pulse width is expanded via the obstacle 11 appears.

By using these two outputs A and B and prohibiting the output of the signal of the output A only when the output B appears, the improvement on the suppression of the use of the pseudo response, which is the original purpose, is realized.

In this embodiment, the method of inhibiting the output of the signal of the output A when the output B appears is adopted. However, without such prohibition, the code analysis of the response signal is performed and the radar scope is analyzed. In displaying, there may be various kinds of modified applications in which an output B from the reflection path is used to add a sign indicating a suspected image, and these applications do not limit the scope of the present invention.

〔The invention's effect〕

As described above, the present invention detects the pulse width extension due to obstacle reflection to the SSR signal processing circuit, and when this detection output appears, suppresses the output of the multipath signal included in the received signal or adds a label. By adding the function, the use of the pseudo response signal can be fundamentally eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram showing the signal processing device of FIG. 1 in detail. DESCRIPTION OF SYMBOLS 1 ... Transponder, 2 ... Antenna, 3 ... Interrogator, 4 ... Receiver, 5 ... Signal processor, 5-1 ... Waveform shaping circuit (1), 5
-2: pulse width detection circuit, 5-3: waveform shaping circuit (2), 5-4: pulse interval identification circuit (1), 5-5 ...
Pulse interval discriminating circuit (2), 6: transmitting device, 7: duplexer, 10: aircraft, 11: obstacle.

Claims (1)

(57) [Claims] An SSR signal processing device for performing signal processing of a secondary surveillance radar used for air traffic control, wherein the response signal transmitted from a transponder mounted on an aircraft is received and decoded by a ground station. And extracting only a signal whose time interval of the paired pulses matches as a normal signal, and determining whether or not the pulse width of the received signal exceeds a preset value. A value set in advance for determining the pulse width of the received signal by the suppressing means is a pulse width of the received signal when the response signal arrives after being reflected once by hitting an obstacle. Based on the fact that it is stretched according to the size of the object, it is set as a scale sufficient to recognize the received signal via the obstacle. SSR signal processing apparatus according to symptoms.