JP2659640B2 - Side lobe canceller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidelobe canceller (hereinafter referred to as CSLC), and more particularly to an improvement in a correlation loop.

[0002]

2. Description of the Related Art CSLC is mainly used for radar receivers.

The basic function of a radar receiver is to receive a reflected signal from a target object, perform necessary reception processing, and output the signal to a radar target detection device such as an indicator.

[0004] Undesirable waves such as interference waves sometimes enter the radar receiver from side lobes. Therefore, by extracting the correlation component of the unnecessary wave received from the auxiliary antenna with the reference signal, the unnecessary wave component in the received signal from the main antenna is estimated, and the unnecessary wave component is subtracted from the received signal of the main antenna to remove the unnecessary wave component. A CSLC that suppresses wave components is used.

FIG. 6 is a system diagram of a conventional CSLC. FIGS. 2, 3, and 7 are diagrams for explaining the operation.
FIG. 2 is a diagram showing antenna patterns of a main antenna and an auxiliary antenna. FIG. 3 is a conceptual diagram of one-dimensional and two-dimensional phased array antenna beam scanning, and FIG. 7 is a waveform diagram of each signal.

In FIG. 1, reference numeral 1 denotes a main antenna, and 2 denotes an auxiliary antenna. Received signal u received by main antenna 1
Passes through the subtractor 3 to become a z signal. 5, 6 are multipliers to which the signal z is input . The other inputs of the multipliers 5 and 6 include the signal x received by the auxiliary antenna 2 and the signal x
Is input by the π / 2 transfer unit 4 as xQ.
10, 11 in the low-pass filter, the output of the multiplier 5,6 rI
, RQ are input and desired correlation signals tI, tQ are extracted. Reference numerals 40 and 41 denote correlators, which are a combination of multipliers 5 and 6 and low-pass filters 10 and 11. 12,1
A DC amplifier 3 amplifies the correlation signals tI and tQ, and outputs signals wI and wQ. Reference numerals 14 and 15 denote multipliers, and the signal w
I, wQ and the signals x, xQ are input. An adder 16 adds the outputs of the multipliers 14 and 15 to obtain a signal y. The signal y is input to the subtractor 3.

In this configuration, the subtractor 3 to the multiplier 5,
A loop that reaches the subtractor 3 again through 6 is called a correlation loop.

Further, a multiplier 1 is obtained from the outputs of the multipliers 5 and 6.
Up to the input of 4, 15 is a baseband processing area.

Next, the operation will be described. One-dimensional and two
Assuming that the number of unnecessary wave sources incident on the main antenna 1 and the ignoring directional auxiliary antenna 2 which is a dimensional phased array is one, it can be said that the unnecessary waves mutually received have a correlation. From this viewpoint, by adding the output signal z and the unnecessary wave reference signals x and x _Q to the correlators 40 and 41, the correlation of the unnecessary wave, that is, the phase and amplitude difference is extracted.

The signals t _I and t from the correlators 40 and 41 are
_The complex weighted signals w _I and w _Q are generated from _Q and multiplied by the unnecessary wave reference signals x and x _Q from the auxiliary antenna 2 to obtain the same IF as the unnecessary wave component included in the received signal u from the main antenna 1. The signal y is obtained, and the unnecessary wave from the main antenna 1 is removed by the subtractor 3.

The output of the subtractor 3 forms a correlation loop which passes through the multipliers 5 and 6 again and returns to the subtractor 3.

[0012]

Since the conventional CSLC is configured as described above, as shown in FIG. 7, when a pulse-like unnecessary wave is input, the correlation loop receives a pulse wave. When the pulse wave is not input, the closed loop is repeated, and when the pulse wave is not input, the open loop is repeated, and it takes a long time to stabilize, and it takes a long time to suppress the unnecessary wave. In the one-dimensional and two-dimensional phased array main antennas, when the beam is scanned, the antenna pattern in the unwanted wave incident direction changes, and the phase and amplitude of the unnecessary wave change uncorrelatedly. Therefore, there is a problem that it takes a long time until the correlation loop becomes stable, and it takes a long time to suppress the unnecessary wave as described above.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the suppression time of unnecessary waves is short even when a pulse-like unnecessary wave is input or when beam scanning is performed. The purpose is to obtain CSLC.

[0014]

According to a first aspect of the inventions, the main antenna
Suppresses unwanted wave reception signals incident from the side lobe
A correlation loop for compensating for the suppression in the correlation loop.
Using reference signal for unwanted wave received from auxiliary antenna
In the side lobe canceller, the unnecessary wave received from the auxiliary antenna is detected, and the unnecessary wave is reset.
A pulse generating circuit for generating a sample-and-hold pulse from the Toparusu, is controlled by the pulse forming circuit, placed at the output side of the sample-and-hold circuit and the sample and hold circuit for holding the correlation component in said <br/> correlation loop ,Up
Band limiting means reset by the reset pulse .

[0015]

[0016]

According to the present invention, there is provided a pulse generating circuit for detecting an unnecessary wave received from an auxiliary antenna to generate a sample and hold pulse, a sample and hold circuit controlled by the pulse generating circuit and holding a correlation component in a correlation loop. Therefore, the correlation loop does not become an open loop even when there is no unnecessary wave, the correlation loop can be focused in a short time, and the suppression can be performed in a short time.

On the output side of the sample and hold circuit,
A band limiting means reset by a reset pulse is provided.
Having location, when it becomes necessary new correlation operation by beam scanning, and reset by the beam scanning interval, it is the initial turn into Rukoto correlation loop voltage in correlation loop. for that reason,
Can Rukoto focuses the correlated loop in a short time. The result
As a result, it is possible to improve the unnecessary wave suppressing ability.

[0018]

FIG. 1 is a system diagram of a CSLC according to an embodiment of the present invention. FIG. 4 is a waveform diagram of each signal.

In the figure, the same reference numerals as those in FIG. 6 denote the same or corresponding parts, and reference numeral 9 denotes a pulse generation circuit for detecting an unnecessary wave from a signal received by the auxiliary antenna 2 and generating a sample hold pulse Tb. Reference numerals 7 and 8 denote sample and hold circuits, which input the sample and hold pulse Tb and the signals r _I and r _Q and output the signals s _I and s _Q. Low-pass filter 1
0 and 11 receive the signals s _I and s _Q and the reset pulse Ta. The reset pulse Ta is a signal for resetting the time constant circuits of the low-pass filters 10 and 11 and the pulse generation circuit 9 at the beam scanning interval. Reference numerals 30 and 31 denote correlators, which are multipliers 5 and 6 and sample and hold circuits 7 and 8.
And low-pass filters 10 and 11 in combination.
Desired correlation signals t _I and t _Q are extracted by the correlators 30 and 31.

In this configuration, the subtractor 3 to the multiplier 5,
A loop that passes through 6 and reaches the subtractor 3 again is called a correlation loop. Also, the outputs of the multipliers 5 and 6 are used to calculate the multipliers 14 and 15.
Until the input, the area is the baseband processing area.

Next, the operation will be described. Multipliers 5, 6
The operation is the same as that of the prior art up to obtaining the baseband orthogonal components r _I and r _Q as the output of.

The pulse generation circuit 9 detects the signal received by the auxiliary antenna 2 and converts it from analog to digital. The sample signal is set to "H" when there is an unnecessary wave, and is set to "L" when there is no more unnecessary wave. Then, the sample-and-hold pulse Tb is generated by performing a logical sum (or) with the reset pulse Ta for each beam scanning interval.

The outputs r _I , r _Q of the multipliers 5, 6 are supplied to sample-hold circuits 7, 8. The sample-hold circuits 7, 8 convert r _I , r _Q by the sample-hold pulse Tb of the pulse generation circuit 9. The signal is held for a predetermined time and output to the low-pass filters 10 and 11.

That is, as shown in FIG. 4, the signals r _I , r
_Q is sampled by the sample and hold circuits 7 and 8 by the sample and hold pulse Tb for the time when the unnecessary wave is present, and an unnecessary wave component immediately before the unnecessary wave disappears, that is, the final voltage when the unnecessary wave is present is held. Thus, as shown in FIG. 4, the signal s _I, s _Q is obtained, the correlation loop avoids the open even when there is no unnecessary wave, the signal w _I,
w _Q stands up. After that, the same operation as in the related art is performed.

Further, when a new correlation operation is required for each beam scanning in the one-dimensional or two-dimensional phased array antenna, the correlation loop is initialized (reset) by the reset pulse Ta, the loop is released, and the new loop is released. make. That is, the outputs s _I ,
The s _Q is applied to the low-pass filters 10 and 11, where the correlation components are processed and output as signals t _I and t _Q. The low-pass filters 10 and 11 are configured by op-amps and
It has a time constant circuit based on R and determines the response time of the correlation loop. An operation is performed to reduce the time constant of this time constant circuit by a reset pulse Ta for each beam scanning,
Initialize the correlated loop voltage. And the correlators 30, 3
After output to 1, the same operation as in the prior art is performed.

As described above, according to the present embodiment, the pulse generation circuit 9 for detecting an unnecessary wave received from the auxiliary antenna and generating a sample and hold pulse, and the sample and hold circuits 7 and 8 operating with the sample and hold pulse Tb are provided. A reset pulse Ta for resetting the time constants of the low-pass filters 10 and 11 and the pulse generation circuit 9 for each beam scanning.
, The correlation component in the correlation loop immediately before the pulse of the unnecessary unnecessary pulse disappears can be maintained, the response of the correlation loop can be accelerated, and the beam scanning in the one-dimensional or two-dimensional phased array antenna can be performed. When a new correlation operation is required every time, a new loop can be created by initializing (resetting) the correlation loop, converging the correlation loop in a short time, and improving the CSLC unwanted wave suppression ability. Can be planned.

FIG. 5 shows a CSL according to another embodiment of the present invention.
1 is a system diagram of C, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

In the above-described embodiment, the input of the pulse generating circuit 9 is the received signal x, but may be x _Q , and the same effect is obtained.

[0029]

As described above, according to the CSLC according to the present invention, a pulse generating circuit for detecting an unnecessary wave received from the auxiliary antenna and generating a sample hold pulse, and a pulse control circuit controlled by the pulse generating circuit for controlling a correlation loop And a sample-and-hold circuit that holds the correlation component of the signal. It has the effect of improving.

On the output side of the sample and hold circuit,
A band limiting means reset by a reset pulse is provided.
Having location, when it becomes necessary new correlation operation by beam scanning, and reset by the beam scanning interval, in correlation loop
It is possible to initialize the correlation loop voltage, the results can Rukoto focuses the correlated loop in a short period of time, suppress unnecessary waves
There is an effect that the pressure capacity can be improved .

[Brief description of the drawings]

FIG. 1 is a system diagram of a CSLC according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of FIGS. 1 and 6;

FIG. 3 is a diagram for explaining the operation of FIGS. 1 and 6;

FIG. 4 is a waveform diagram of a CSLC according to an embodiment of the present invention.

FIG. 5 is a system diagram of a CSLC according to another embodiment of the present invention.

FIG. 6 is a system diagram of a conventional CSLC.

FIG. 7 is a waveform diagram of a conventional CSLC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main antenna 2 Auxiliary antenna 3 Subtractor 4 π / 2 phase shifter 5, 6, 14, 15 Multiplier 7, 8 Sample hold circuit 9 Pulse creation circuit 10, 11 Low-pass filter 12, 13 DC amplifier 16 Adder

Claims (1)

(57) [Claims] 1. A correlation loop for suppressing a reception signal of an unnecessary wave incident from a side lobe of a main antenna,
In a side lobe canceller for performing suppression in the correlation loop using a reference signal for an unnecessary wave received from an auxiliary antenna, an unnecessary wave received from the auxiliary antenna is detected , and
A pulse generation circuit that generates a sample-and-hold pulse from a wave and a reset pulse; a sample-and-hold circuit that is controlled by the pulse-generation circuit and holds a correlation component in the correlation loop ; and is disposed on an output side of the sample-and-hold circuit. , Above
A band limiting means reset by a reset pulse .