JPS633266B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to air traffic control equipment, and particularly to secondary surveillance radar (hereinafter referred to as SSR) in radar control systems.
It concerns an equivalent sidelobe suppression scheme that occurs in the antenna radiation pattern in a system called

[Conventional technology]

In SSR used for air traffic control, radio waves propagate between the SSR device on the ground and the transponder on the aircraft, in addition to normal direct propagation, as well as reflection propagation paths, which can cause roving and false targets. In particular, pseudo targets pose a major obstacle to SSR control using automatic data processing.

Conventionally, transponders have generally been equipped with a function that can suppress interrogation pulses below the second pulse ( _P3 pulse) of the mode pulse for a certain period of time in order to suppress interrogation caused by side lobes of the SSR antenna.
There is a method that utilizes this to perform sidelobe suppression. This system has two antennas, a ground station interrogation antenna 1 and a control (omnidirectional) antenna 2, as shown in Fig. 5, and each transmits mode pulses P ₁ and P ₃ and control pulse P ₂ to the target 3. Send.
The transponder compares the levels of the P ₁ and P ₂ pulses, and in response to sidelobe interrogations, a 35 μs suppression gate is generated inside the transponder to suppress subsequent interrogation pulses. FIG. 6a shows the relationship between the beam pattern and each pulse, and FIG. 6b shows the received waveform of the transponder, where A shows the response and B shows the case of suppression, which is a diagram of the operating principle of the 3-pulse SLS system. In addition, Figures 7a and b show the operating principle diagram of the improved SLS method. When the transponder receives an interrogation signal, if the amplitude ratio of P ₁ and P ₂ is P ₁ /P ₂ ≦0 dB, the suppression gate of 35 μs is applied. generated and suppresses the response to the interrogation pulse. Using this response suppression function, P ₁ is added to P ₂ transmitted from the control antenna for 2 μs.
By transmitting _a pair _of pulses with an interval of Even if a strong reflected wave were to arrive, a pair of pulses would arrive directly from the control antenna before that and generate a suppression gate, so it would not respond to the reflected wave. In the main lobe direction, the gain of the interrogation antenna is much larger than the gain of the control antenna, so P ₁ >>P ₂ and normal operation is performed. Figure 7a shows that when there is a normal question, the 7th
Figure b shows the case where there is a signal S _R from the interrogation antenna due to reflection by the improved SLS, S _C represents the signal from the control antenna, and S _R is suppressed.

[Problem that the invention seeks to solve]

However, the conventional sidelobe suppression and false target suppression functions due to reflections cannot be achieved due to differences in roving patterns due to differences in the installation positions of the two antennas, and disturbances in the pattern radiated from the control antenna due to the rotation of the primary radar reflector. This method has the disadvantage that the levels of P ₁ /P ₂ , which are the criteria for generation of suppression gates, are not constant and unnecessary questions cannot be suppressed reliably. Another drawback is that the effective range of suppression is short.

Regarding the problems of the conventional I-SLS mentioned above, please refer to the literature (J. Zatkalik, DLSengupta and C-T Tai
“Improved Sidelobe Suppression Mode
Performance of ATCRBS With Various
Antenna”Technical Report, Contract−TSC
−717, Interim Report.July 1973−June 1974,
Report NO, FAARD-75-32).

[Means for solving problems]

The present invention uses an antenna capable of emitting three types of beams to emit the interrogation pulse P ₁ and the control pulse P ₂ from the same antenna, thereby suppressing fluctuations in the level ratio of P ₁ /P ₂ and emitting two types of control pulses. The present invention provides an equivalent sidelobe suppression method that eliminates the above-mentioned drawbacks and suppresses the generation of false targets due to reflection by emitting a combined beam.

According to the present invention, a mode pulse consisting of a first pulse and a second pulse having a constant time interval, and a control pulse being sent out between the first pulse and the second pulse, and a level comparison between the first pulse and the control pulse. In the sidelobe suppression method that suppresses the generation of false targets by The signal level of the omega beam of the control pulse is set below the signal level of the omega beam of the control pulse, and the second
A sidelobe suppression method is obtained in which the pulses have a sum beam pattern and are each transmitted from the same antenna.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

The present invention uses three types of beams using the same antenna to transmit a 2μs pair pulse of an interrogation pulse _P1 and a control pulse _P2 , which were conventionally transmitted from an interrogation antenna and a control antenna respectively, and suppresses sidelobes and suppresses reflections. This realizes the stability of pseudo target suppression. Furthermore, a beam with omnidirectional or Ω-like characteristics and a directional beam are combined with an appropriate phase shift difference, and an interrogation pulse P ₁ or a control pulse is generated from both beams.
This is an improved SLS method that suppresses false targets over a long distance in the nose direction of the pattern by emitting _P2 . However, in the directional beam, the directivity of the beam that emits the control pulse is adjusted in comparison with the beam that emits the interrogation pulse so as to give a necessary level difference to the transponder response.

In the method according to the present invention, there are three types of patterns: sum, difference,
By applying the antenna with omega, sum and omega,
Figures 1a to 1c show radiation patterns in which power is supplied to the differential and omega patterns with appropriate phase shifts.

Here, excitation of the antenna for transmitting the above-mentioned beam pattern from the same antenna will be explained.

FIG. 4 shows the configuration of an embodiment of the present invention, which includes a plurality of antenna elements 5, an antenna center element 6, power distribution sections 7, 7', a transfer device 8, a switching control section 9, and distributors 10, 10. ′. Here, in order to form the beam pattern mentioned above, power is supplied as follows.
Emitted from the antenna element.

First, the "sum + omega" beam pattern emits a P ₁ pulse. Therefore, a part of the _P1 pulse power is first distributed by the distributor 10, and inputted to the switch of the switching control section 9, and then passed through the phase shifter 8 and the power distribution sections 7, 7' to the antenna element 5. A specified power is supplied to each to form a "sum" beam pattern. On the other hand, the other power distributed by the distributor 10 is supplied to the antenna central element 6 under switch control of the switching control section 9 to form an "omega" beam pattern. These two beam patterns are combined in space to form the "sum+omega" beam pattern shown in FIG. 1a. The "sum" pattern shown in FIG. 1c is formed by cutting off the power supplied to the antenna center element 6 by controlling the switch from the power distributed to the switch of the switching control section 9 in the same manner as described above. "Difference + Omega" beam pattern is
Emit P ₂ pulses. Therefore, the power of P ₂ pulse is
First, a portion of the electric power is distributed by the distributor 10' and inputted to the switch of the switching control section 9, and a prescribed electric power is supplied to each of the antenna elements 5 via the phase shifter 8 and the power distribution sections 7 and 7'. Form a “difference” pattern. Here, the power is supplied to the power distribution unit 7' with the phase delayed by 180 degrees by the phase shifter 8. On the other hand, distributor 1
The power distributed by 0' is supplied only to the antenna center element 6 under the switch control of the switching control section 9 to form an "omega" beam pattern. Both beam patterns are combined in space to form the "difference+omega" beam pattern of FIG. 4b.

P ₁ pulse in sum and omega pattern as shown,
Also, P ₂ is transmitted at each timing from the difference and omega patterns. This pattern is shown in FIG. 2, and the signal from the Wa-difference Omega antenna 4 reaches the target 3 in the same process in all three patterns.

Furthermore, as shown in Figure 3, in the area surrounded by the difference + omega pattern, the P ₁ P ₂ pair of pulses reaches the transponder first, and since P ₁ /P ₂ ≦0 dB, it takes 35 μs depending on the characteristics of the transponder. Since a suppression gate is generated and the signal does not respond to the reflected signal, the false target due to reflection is suppressed. This suppressed area is effective over a long distance in the direction of the antenna's nose, as shown in the figure.
In Fig. 3, it responds when P ₁ /P ₂ ≧9 dB (shaded area), and is suppressed when P ₁ /P ₂ ≦0 dB, and 0<P ₁ /P ₂ <
It responds or is suppressed when it is 9dB. This is in accordance with the transponder performance specified by the International Convention on Civil Aviation (ICAO).
CIVIL AVIATION ORGANIZATION
“INTERNATIONAL STANDARDS AND
RECOMMENDED PRACTICES
AERONAVITICAL
TELECOMMUNICATION ANNEX 10 TO
THE CONVENTION ON
INTERNATIONAL CIVIL AVIATION”
THIRD EDITION OF VOLUME JULY
1972, page 3.8.5 (page 39) and Fig. 13-4 (page 92)
(page). In other words, the permissible performance range of the aircraft-mounted transponder device is defined as above, and the last condition indicates the response/suppression transition period (tolerance range), and it is possible to respond or suppress without responding. have meaning. Furthermore, the phase relationship between the interrogation and control pulsed radiation beams is constant, and the sidelobe suppression operation is stable, so that sidelobe suppression problems due to topography are considerably improved. Therefore, the target is stable and it is possible to provide stable good news to the automated processing of air traffic control, which is useful for processing.

〔Effect of the invention〕

As described above, the present invention has the effect of suppressing the occurrence of pseudo targets, reliably suppressing unnecessary questions, and widening the effective range of suppression.

[Brief explanation of the drawing]

Figures 1 a to c are power distribution diagrams when sum, difference, and omega antennas are combined; a shows (sum + omega), b shows (difference + omega), and c shows (sum), respectively. Figure 3 is a diagram showing the influence of ground reflection on the SLS method according to the present invention, Figure 3 is an operational diagram of the principle of expanding the effective range of the SLS method according to the present invention, Figure 4 is a diagram showing an example of the configuration of the present invention, Figure 5 is a diagram showing the propagation path of radio waves in the conventional SLS method, and Figure 6 a and b are the conventional 3-pulse
7a and 7b are diagrams showing the operating principle of the conventional improved SLS method. 1...Question antenna, 2...Control antenna, 3...
...Target, 4...Was difference omega antenna, 5...
Antenna element, 6... Antenna central element, 7, 7'...
...Power distribution section, 8... Phase shifter, 9... Switching control section, 10, 10'... Distributor.

Claims (1)

[Claims] 1 A mode pulse consisting of a first pulse and a second pulse with a fixed time interval;
In a sidelobe suppression method that sends a control pulse between pulses and suppresses the generation of false targets by comparing the levels of the first pulse and the control pulse, the first pulse has a (sum + omega) beam pattern. , the control pulse is a (difference + omega) beam pattern, the signal level of the omega beam of the first pulse is set to be less than the signal level of the omega beam of the control pulse, and the second pulse is a sum beam pattern, each of which is the same. A sidelobe suppression method characterized by transmission from an antenna.