JPS62230102A - Side lobe canceller - Google Patents

Abstract

PURPOSE:To prevent an undesired radio wave from being left due to dead time cut by reserving a correlation component in a correlation loop during the dead time cut by a sample holding circuit. CONSTITUTION:sample holding circuit 15,16 holding the correlation component are provided in the correlation loop. Outputs rI,rQ of correlation devices 30,31 are inputted to the circuits 15,16. The correlation component before the dead time cut is held aud reserved by the sample hold timing rising before the dead time cut timing and descending as soon as the dead tine cut timing falls down. Outputs SI,SQ of the circuits 15,16 are inputted to band amplifiers 17,18. Then the dead time cut is finished and the time requiring for the correlation loop to be closed again is not required. Thus, the undesired radio wave due to the dead time cut is prevented from being left uneliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a side rope canceller (hereinafter referred to as SLC), and particularly relates to improvement of its correlation loop.

[Conventional technology]

SLC is primarily used in radar receivers. The basic function of a radar receiver is to receive reflected signals from a target object,
It performs the necessary reception processing and outputs it to the radar target detection device such as an indicator.

Unnecessary interference waves and the like are often incident on a radar receiver through a side rope. In order to suppress these unnecessary radio waves, the correlation component between the received signal of the unnecessary radio waves incident from the side rope of the main antenna and the reference signal for the unnecessary radio waves received from the auxiliary antenna is extracted, and the SLC is used to suppress unnecessary radio wave components by estimating the radio wave components and subtracting them from the received signal of the main antenna.

A conventional system diagram of such a system is shown in FIG. FIG. 4 is an explanatory diagram of the operation.

In Fig. 3, 1 indicates the main antenna, 2 indicates the auxiliary antenna, and 3 supplies the transmission pulse Vt of the radio frequency band (hereinafter referred to as RF) to the main antenna 1, and also transmits the received signal ullF from the main antenna 1 to the subsequent stage. This is a transmitter/receiver switch for output.

6 is a local oscillator for the RF band, and the carrier wave is mixed by a mixer 4.5.
converts the received signals uRF and XIIF into an intermediate frequency (hereinafter referred to as IP).

The required time is set by each IF band optical reception signal Ta, resulting in signals u and x. The U signal passes through the subtracter 9,
Two signals are input to mixers 11 and 12. mixer 1
The other inputs of 1.12 are the X signal and the signal converted to xQ by the π/2 phase shifter 10.

The output of this mixer 11.12 is filtered by a low pass filter 13.14.
A desired correlation signal rl+rQ is extracted.

The combination of mixer 11.12 and low-pass filter 13.14 is called correlator 30.31. The correlation signals r and rQ are band-amplified by band-band amplifiers 17 and 18, and then band-amplified by band-band amplifiers 17 and 18, and multipliers 19 and 19, respectively.
The other inputs of the multipliers 19 and 20 are
These are the aforementioned signals x and Xo.

The outputs of the multipliers 19 and 20 are added by an adder 21 and inputted to the subtracter 9 mentioned above as a y signal.

In this configuration, the loop from the subtracter 9 through the mixers 11 and 12 to the subtracter 9 again is called a correlation loop.

Next, the operation will be explained using FIG. 4. The transmission pulse signal Vt (see FIG. 4(a)) passes through the transmitter/receiver switch 3 and the main antenna 1 and is radiated into the air. In addition, the transmitter/receiver switch 3
Due to the isolation of
In addition to F and 7, the reflected signal input from the main rope of the main antenna 1 and the interference wave input from the side rope are input, and these are input to the mixer 4 as a composite signal U□. . In the mixer 4, R from the local oscillator 6
The frequency of the received signal is converted into an IF band reception signal by FF transmission and output to the switch 7 . The purpose of the switch 7 is to cut unnecessary signals during the time (referred to as dead time) from a distance beyond the maximum radar reception distance to a transmission pulse. The unnecessary signal is a leakage signal of the transmission pulse signal Vt, and this signal has a large power, and as the pulse width becomes wider, it adversely affects the subsequent SLC operation. (see FIG. 4(e)) and output to the subtracter 9 as a U signal (see FIG. 4(e)).

The output of subtractor 9 is input to mixer 11.12. The other input of this mixer 11.12 is the received signal from the auxiliary antenna 2. This received signal is
Leakage of transmitted signal as shown in IF.

Consists of reflected waves and interference waves. This RF received signal
□ is processed in the same way as the received signal uRF of the main antenna 1 by the mixer 5 and the switch 8, and the X signal (Fig. 4 (
f)) is outputted to the mixer 11 and the π/2 phase shifter 10.

The π/2 phase shifter 10 has orthogonal I in the correlation loop at the subsequent stage.
(INPIIAsH, in phase) and Q (OUTUADRATU
RI! , orthogonal), the X signal is
The phase is shifted by 2 and added to the mixer 12 as xo.

A correlator 30.31 composed of a mixer 11.12 and a low-pass filter 13.14 combines the received signal of unnecessary radio waves incident from the side rope of the main antenna 1 and the reference signal for the unnecessary radio waves received from the auxiliary antenna 2. A correlated component is extracted and its output r.

, r, (see FIG. 4(g)) are amplified by bandpass amplifiers 17 and 18 with a predetermined time constant τ. However, since the unnecessary radio waves are cut off by the switch 7.8, the waveforms ω1 and ω follow the time constant τ. (4th
0 outputted to the multiplier 19.20 as (see figure (h))
The other input of the multiplier 19.20 is the output X of the switch 8.
signal, the output X of the π/2 phase shifter 10, and the signal. This multiplier 19°20 converts the reference signal of unnecessary radio waves from the auxiliary antenna 2 to ω1. ω. The phase shift and amplitude are matched to the unnecessary radio waves from the main antenna 1.

The outputs of the multipliers 19 and 20 are converted into vector quantities by the adder 21, and then added to the subtracter 9, where unnecessary radio waves from the main antenna 1 are subtracted.

The output of the subtracter 9 passes through the mixer 11, 12 again and returns to the subtracter 9, forming a correlation loop.

[Problem that the invention seeks to solve]

Since the conventional SLC is configured as described above, the correlation loop becomes an open loop in the region where the dead time has been cut, the correlation component changes according to the time constant τ, and the correlation is restored when the signal is input again after the dead time cut is canceled. The problem was that it took time for the loop to close, and unnecessary radio waves remained.

This invention was made to solve the above-mentioned problems, and reduces the time required to re-close the correlation loop when a signal is input again after canceling the dead time cut, thereby reducing the amount of unnecessary radio waves remaining. The purpose is to obtain SLC that can be prevented.

[Means for solving problems]

The SLC according to the present invention is provided with a sample hold circuit in the correlation loop to hold the correlation component before the dead time cut.

[Effect]

In this invention, the correlation component is held by the sample hold timing that rises slightly before the put time cut timing in the sample hold circuit, and oven loop of the correlation loop due to the dead time cut is prevented. The time required to reclose the correlation loop can be eliminated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, the same reference numerals as in FIG. 3 indicate the same parts. 15.16 is the output signal 'l+rQ of the correlator 30.31
There is a sample-and-hold circuit that holds this at sample-and-hold timing Tb.

Next, the operation will be explained with reference to FIG. The operation is similar to that of the prior art until the correlation components I+rQ of the correlators 30 and 31 are obtained.

and the outputs rl and r of the correlators 30 and 31. is input to sample and hold circuits 15 and 16.

Here, the rise of the dead time cut timing is L”
Due to the sample hold timing Tb which rises before the dead time cut timing (the point where it changes from "H" to "L") and falls at the same time as the falling edge of the dead time cut timing (the point where it changes from "H" to "L"),
The correlation components before the dead time cut are retained and saved (see FIG. 2(d), (hl)).

Output of sample and hold circuit 15.16 “In5Q
(see FIG. 2(1)) is input to bandpass amplifiers 17 and 18. Thereafter, operations similar to those of the prior art are performed.

In the above embodiment, a sample and hold circuit is provided at the output of the correlator, but even if a sample and hold circuit is provided at the output of the mixer 11 and 12, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the correlation component in the correlation loop is stored by the sample and hold circuit during the put-time cut, so the time required for the correlation loop to close again after the put-time cut is completed is This eliminates the need for dead time cutting, which has the effect of providing SLC with no unnecessary radio waves left undisappeared.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an SLC according to an embodiment of the present invention, and FIG.
The figure shows a timing chart of the signals of each component part to explain its operation, FIG. 3 is a system diagram of a conventional SLC, and FIG. 4 shows a timing chart of signals of each component part to explain its operation. FIG. 1 is the main antenna, 2 is the auxiliary antenna, 3 is the transmitter/receiver switch,
4.5 mixer, 6 local oscillator, 7.8 switch, 9
is a subtracter, 10 is a π/2 phase shifter, 11.12 is a mixer,
13.14 is a low-pass filter, 15.16 is a sample and hold circuit, 17.18 is a band amplifier, 19.20 is a multiplier, 21 is an adder, and 30.31 is a correlator. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] It has a correlation loop for suppressing the received signal of unnecessary radio waves incident from the side rope of the main antenna, and the correlation component between the received signal of the unnecessary radio wave and the reference signal for the unnecessary radio wave received from the auxiliary antenna. In the sidelobe canceller, which extracts unnecessary radio wave components from the received signal from the main antenna and suppresses them by subtracting them from the received signal from the main antenna, the correlation component is removed in the correlation loop. A side rope canceller characterized by being equipped with a sample hold circuit.