JPH0346076B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a coherent side lobe canceller (hereinafter referred to as
This invention relates to a radar receiver equipped with a CSLC (CSLC) circuit, and is concerned with improving the timing of injection of AGC pilot pulse signals or pseudo signals into the radar receiver.

[Conventional technology]

The basic function of a normal radar receiver is to receive the reflected signal from a target object and amplify it by a predetermined amount.
This is to detect the signal, convert it into a video signal, and output it to a radar target detection device such as an indicator.

Especially when the radar target detection device is of an automatic processing type, it is important to deal with various control fluctuation factors and keep the receiver output noise level constant. A circuit is used.

Various AGC methods are known for radar receivers, but one that is relatively commonly used is to send a pilot pulse signal of a specified level from the receiver input terminal during the radar idle period outside the reception area (also called dead time). There is a method in which an automatic gain control loop is constructed so that the pilot pulse signal level is constant at the output end of the receiver.

In addition, for the purpose of suppressing unnecessary interference waves input to the radar equipment, CSLC suppresses unnecessary input signals from the main antenna when there is a correlation between the input signal from the auxiliary antenna and the input signal from the main antenna.
A circuit is used.

A conventional system diagram of such a system is shown in FIG. 1, and FIG. 2 is an explanatory diagram of its operation.

In Figure 1, 1 is an intermediate frequency (hereinafter referred to as IF) band reference signal oscillator, and 2 is a radio frequency (hereinafter referred to as IF) band reference signal oscillator.
This is a local oscillator for the RF band. Output of both
Vc and Vl are mixed in a mixer 3, divided into transmission pulses in a power amplifier 4, and power-amplified to become a transmission pulse signal V _T. The signal passes through a transmission/reception switch 5 and a directional coupler 6a, and then is transmitted as a predetermined transmission pulse. It is radiated into the air from the main antenna 7 at a repetition period T.

The directional couplers 6a, 6b divide the output of the mixer 3 into two pulses, Vpa, Vpb, which are generated by dividing the output into pulses using the pulse generator 9, and divide the pilot pulse signals Vpa, Vpb into two, and send them to the main receiving system 30 at the same time and with the same amplitude. This is a directional coupler for injecting the signal into the auxiliary reception system 40.

The reflected signal and interference wave from the object to the main reception system 30 are received by the main antenna 7 on the opposite path to the transmission pulse signal _VT , and then passed through the directional coupler 6a and the transmission/reception switch 5 to the broadband RF The signal is amplified by an amplifier 10a.

After this, the local oscillator 2 is connected to the receiving mixer 11a.
It is mixed with the local oscillation signal Vl of , and sent to the CSLC 12 as the IF reception signal V _M of the difference frequency.

The reflected signal and interference wave from the object to the auxiliary reception system are received by the auxiliary antenna 8, and then passed through the directional coupler 6b, the RF amplifier 10b, and the mixer 11b to the IF.
It is sent to the CSLC circuit 12 as a received signal _VS.

Here, the IF received signals V _M and V _S are equal to the frequency of the output Vc of the reference signal oscillator 1. The output signal Vo of the CSLC circuit 12 and the output V _S of the mixer 11b are subjected to AGC processing in AGC circuits 13a and 13b, respectively, detected by detection circuits 14a and 14b, and sent to the target detection device 20 as a video signal.

Next, the operation will be explained. Transmission pulse signal
The time relationship between V _T and the pilot pulse signals Vpa and Vpb is set as shown in a and b in FIG. 2.

The pilot pulse signals Vpa and Vpb are injected during the so-called radar pause time corresponding to the radar maximum detection distance immediately before the transmission pulse signal _VT , and do not overlap with the reflected signal from the target. Here, in addition to the reflected signal from the object and the interference wave, pilot pulse signals having the same amplitude at the same time are injected into the auxiliary receiving system 40 and the main receiving system 30 by the directional couplers 6a and 6b. These signals are transmitted to the individual receiving systems 30, 40.
The IF received signals c and d in Figure 2 are received and processed by
The signals are input to the CSLC circuit 12 as V _M and V _S.
The purpose of the CSLC circuit 12 is to suppress unnecessary interference waves input from the main antenna 7 by interference waves input from the auxiliary antenna 8, and the correlated signals between V _M and V _S are The purpose is to suppress unnecessary waves in _VM using _VS.

Because of this effect, when the CSLC ON/OFF control signal Vae in FIG. Since it has a correlation, it is suppressed together with the interference wave. However, the reflected signal has no correlation due to the difference in each antenna pattern, and is not _suppressed .
supplied to The other V _S is supplied to the AGC circuit 13b and subjected to AGC processing.

In the AGC circuits 13a and 13b, the
Pilot pulse signals Vpa, Vpb of V _O and V _S at the timing of AGC timing pulses pa, pb
It operates to perform gain control of the difference between the level and the IF reference value VR, but when the CSLC control signal Va is ON, the pilot pulse signals of the IF reception signals V _M and V _S are suppressed by the CSLC circuit 12. normal
AGC cannot operate. Therefore in this case
An operation is performed to hold the AGC correction value before the CSLC control signal Va turned ON. Then h, i in Figure 2
Vba and Vbb are detected by the detection circuits 14a and 14b, respectively, and sent to the target detection device 20 for transmission processing.

Conventional radar receivers are configured as described above, so when the CSLC circuit is turned on under interference, the AGC pilot pulse signal that is injected as the same signal is suppressed by the CSLC circuit 12 along with unnecessary interference waves. Since the reference signal for AGC operation is lost, there is no other option but to stop AGC operation. For this reason, while the CSLC circuit is operating, gain compensation of the receiving system cannot be performed, which has the disadvantage of degrading the performance of the radar device. In addition, when injecting pseudo signals that are injected into the radar reception area corresponding to the radar's maximum detection distance and used to measure the performance of the radar receiver, they are similarly suppressed, making it impossible to measure the performance of the receiving system at the subsequent stage. It was hot.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional systems as described above, and by shifting the injection timing of the AGC pilot pulse signal or pseudo signal between the main reception system and the auxiliary reception system, the time axis can be adjusted. under interference as uncorrelated signals in
To provide a radar receiver capable of outputting a pilot pulse signal to a subsequent stage without being suppressed even when a CSLC circuit is operated.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. The differences in Figure 3 from the conventional Figure 1 are as follows:
The point is that a delay circuit 15 is provided to delay the AGC pilot pulse signal Vpb to be injected into the auxiliary reception system 40 from Vpa by a time t.
AGC pilot pulse signal delayed by
Vpb' is input to the directional coupler 6b of the auxiliary reception system.

Next, the operation will be explained with reference to the operation explanatory diagram of FIG.

Transmission pulse signal V _T and pilot pulse signal
The time relationship between Vpa and Vpb' is set as shown in Figure 3 a, b, and c. Pilot pulse signal Vpa,
Vpb' is injected during radar downtime. Here, in the main receiving system 30 and the auxiliary receiving system 40, in addition to the reflected signal and interference wave from the object, pilot pulse signals Vpa and Vpb', which are different in the time axis and have the same amplitude, are transmitted through directional couplers 6a and 6b, respectively. Injected. These signals are received and processed by the individual receiving systems 30 and 40, and the IF signals V _M and V _S shown in FIGS. 3d and 3e are input to the CSLC circuit 12. Under interference, Fig. 3 f
Turn the CSLCON/OFF control signal Va ON (“H”),
The CSLC circuit 12 is operated.

As a result, the interference waves are suppressed because they have correlation. However, the pilot pulse signal Vpa,
Vpb' differs on the time axis, and the reflected signal has no correlation due to the difference in each antenna pattern, and is not suppressed and is supplied to the next stage AGC circuit 13a as V _O in g in Fig. 3. . The other auxiliary receiving system 40
The IF received signal V _S is also supplied to the AGC circuit 13a and individually performs AGC processing to keep the receiver gain constant.

In the AGC circuits 13a and 13b, h in FIG.
V _O corresponding to the AGC timing Pa and Pb of i
An operation is performed to control the gain of the difference between the levels of the pilot pulse signals Vpa and Vpb' of V _S and the IF reference value VR. By shifting the time of the pilot pulse signal in this way, the ON/OFF state of the CSLC circuit 12 can be controlled.
AGC processing can be performed regardless of whether it is OFF. Thereafter, Vba and Vbb in FIG. 3j and k are detected by detection circuits 14a and 14b, respectively, and sent to target detection device 20 for signal processing.

In the above embodiment, the timing of injection of pilot pulses for AGC has been described, but FIG. 5 shows another embodiment of the present invention, which is applied to the injection of pseudo signals used to measure the performance of a radar receiver. .

In FIG. 5, the time relationship between the transmission pulse signal V _T and the pseudo signals Vga and Vgb is set as shown in FIG. 6 a, b, and c. In this case, the pseudo signal Vga,
Vgb' is injected into the radar reception area (within the maximum radar detection distance). Here, the main receiving system 30 and the auxiliary receiving system 40 receive a reflected signal from an object and an interference wave, as well as pseudo signals Vga, which are different on the time axis and have the same amplitude.
Vgb' is injected from the directional couplers 6a and 6b, respectively, and is received and processed by each receiving system, and the IF reception signals V _M and V _S shown at d and e in FIG. 3 are input to the CSLC circuit 12. The CSLC circuit in Figure 6 f is ON/under interference.
When the OFF control signal Va is turned ON (“H”), the interference waves are suppressed because they have a correlation. However, the pseudo signals are different on the time axis, and the reflected signals are different due to the difference in the patterns of the main and auxiliary antennas 7 and 8, so the pseudo signals of the main receiving system are
The signal is sent to the next-stage detection circuit 14a as V _O shown in FIG. 6g without being suppressed, and after being detected, is sent to the target detection device 20 as a video signal. This makes it possible to measure the performance of the main receiving system 30 using a pseudo signal regardless of whether the CSLC circuit 12 is ON or OFF.

V _S of the auxiliary reception system 40 is also connected to the detection circuit 14b.
The signal is detected by the target detection device 20 as a video signal.
Performance measurements are performed using pseudo signals sent to

In the above embodiment, the case where the injection time of the pilot pulse signal or pseudo signal is set in the auxiliary receiving system after the main receiving system is explained.
The same effect can be obtained even if the injection is performed in the opposite time relationship.

〔Effect of the invention〕

As described above, according to the present invention, by making the times of the pilot pulse signals or pseudo signals injected into the auxiliary reception system and the main signal system different,
Even if the CSLC circuit is operated in a radar device having a CSLC circuit, it is possible to perform AGC processing or measure the performance of the radar receiver.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a conventional radar receiver, Fig. 2 is an explanation diagram of the operation of Fig. 1, Fig. 3 is a system diagram showing an embodiment of the present invention, and Fig. 4 is an explanation of the operation of Fig. 3. 5 is a system diagram showing another embodiment of the present invention, and FIG. 6 is an explanatory diagram of the operation of FIG. 5. In the figure, 1 is a reference signal oscillator, 2 is a local oscillator,
3 is a mixer, 4 is a power amplifier, 5 is a transmission/reception switch,
6a, 6b are directional couplers, 7 is a main antenna, 7 is an auxiliary antenna, 9 is a pulsing circuit, 10a, 11b
is an RF amplifier, 11a and 11b are mixers, and 12 is an RF amplifier.
CSLC circuit, 13a, 13b are AGC circuits, 14
a, 14b are detection circuits, 15 is a delay circuit, 20 is a target detection device, 31 is a main reception system, and 40 is an auxiliary reception system. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Radar reception having a receiving section consisting of two systems, main and auxiliary, and a coherent sidelobe canceller (CSLC) section that suppresses unnecessary interference waves by utilizing the correlation between both received signals. a pulse generator that generates a pilot pulse signal for automatic gain control during a period equal to the radar transmission pulse period and outside the radar reception area or a test pseudo pulse signal during a period within the radar reception area;
A radar receiver comprising a delay circuit that delays the output pulse of the pulse generator for a predetermined time, and injects the output pulse of the pulse generator and the delay circuit into the reception input side of the main receiver and the auxiliary receiver. Machine.