JPH0283483A - Jamming wave removing apparatus - Google Patents

Abstract

PURPOSE:To erase a pulse jamming wave within a short time by setting the time constant of a digital filter to a high speed when a jamming wave pulse is detected and setting the same to an ultralow speed when not detected. CONSTITUTION:The signal inputted to a main antenna 1 is inputted a subtractor 3 through a frequency converter circuit 2 to be outputted through a power divider 4. The signal inputted to an auxiliary antenna 6 is inputted to a coupler 8 through a frequency converter circuit 7 and the output of said coupler 8 is inputted to 90 deg. hybrids 9, 16. The output of the 90 deg. hybrid 16 becomes signals changed in amplitude and phase by mixers 15a, 15b and said signals are synthesized by a power combiner 17 to be applied to the subtractor 3. An auxiliary circuit for matching the amplitude and phase of the jamming signal of the main antenna and those of the jamming signal of the auxiliary antenna is provided. The presence of the jamming signals is detected by a pulse detection circuit 19 and the time constants of the digital filters 13a, 13b of the auxiliary circuit are changed over through a time constant setting circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention eliminates unnecessary interference waves mixed in the side lobe region of a main antenna in a radar device.

The present invention relates to an interference wave removal device that uses an auxiliary antenna to remove interference waves.

[Conventional technology]

FIG. 3 is a configuration diagram showing a conventional interference wave removal device of this type, and the configuration will be explained along the flow of signals.

The signal input to the main antenna (1) is converted into an IF multiplied signal of the main channel by a frequency conversion circuit (2), then passes through a subtracter (3), and then is converted into an IF multiplied signal of the main channel by a power divider (hereinafter abbreviated as PD) (4). part is taken out, and further P D (
5) will be divided into equal parts.

On the other hand, the signal input to the auxiliary antenna (6) is converted into an IF multiplied signal of the auxiliary channel by the 2-frequency conversion circuit (7), and is converted into a 90° hybrid signal (90°) via the PD (8).
° IQ times signals with different phases are divided. The two same-amplitude and in-phase signals output from the IQ multiplied signal main channel P D (5) are multiplied by the mixer (10a) (10b) to obtain two baseband signals V iVq and Q. These baseband signals 1'i, Vq are.

Each is amplified by an amplifier (l la) (1lb) and A
It is converted into a digital signal by a D converter (12a) (12b). This digital signal is transmitted by the 1 time constant setting switch (21
) with a time constant set by a digital filter (+3
a) It is input to (13b) and integrated. The integrated results are again converted into analog values by the DA converter (14aX14b) and become modulation signals Ti and Yq of the modulators (15a) and (15b).

IF of the auxiliary channel divided by the other P D (8)
After the double signal is divided into IQ double signals by the 90° hybrid (16), it is modulated by the modulation signals Wi and llq in the modulator (15a) (tsb). The signal after modulation.

Power is combined by a power combiner (hereinafter abbreviated as PC) (17) and input to a subtracter (3).

The interference wave removal device configured as described above operates as follows.

First, a correlator in the baseband circuit from the mixer (18) to the DA converter (14) obtains information on the amplitude and phase of the interference wave components of the main channel and the auxiliary channel. Next, the modulator (15) modulates the interference wave component of the auxiliary channel so that it has the same amplitude and phase as the interference wave component of the main channel, and this modulated signal is sent to the subtracter (3) at the IF of the main channel.
By subtracting from the doubled signal, the interference wave component of the main channel is canceled. The remaining interference wave component is P D (4) (
5) to the correlator, and thereafter the same closed-loop operation as above is performed.

[Problem to be solved by the invention]

Here, as an expression expressing the response characteristic of the above closed loop, (1)
The formula is:

1+KGX B= ・・・・・・(
1) In formula (1), B is the loop bandwidth, is a constant, G is the loop gain, and X is the input power of the auxiliary channel.

In the conventional interference wave removal device, the loop bandwidth B is selected according to the interference wave characteristics, and the time constant T for this purpose is manually set using a time constant setting switch. For this reason, the time constant for pulse interference waves is the same whether there is a pulse or no two pulses, and the cancellation characteristics of the pulse interference wave become as shown in Figure 4, which poses the problem that it takes time to completely cancel the interference wave. there were.

[Means to solve the problem]

The interference wave removal device according to the present invention includes a pulse detection circuit that detects the presence or absence of an interference wave pulse, and a time constant setting circuit that switches the time constant of a digital filter depending on whether there is a pulse or no pulse based on the pulse detection result. It is equipped with the following.

[Effect]

In this invention, the presence or absence of an interference wave pulse is detected,
By setting the time constant of the digital filter to be fast in case of a pulse emergency, and to set the time constant of the digital filter to be extremely slow in case of no pulse, the cancellation characteristics of the pulse interference wave will be as shown in Figure 2, and it will be completely canceled in a short time. can do.

〔Example〕

FIG. 1 shows an embodiment of the present invention (1) to
(17) is exactly the same as the conventional device described above.

(18) is a coupler, (19) is a pulse detection circuit, (2
0) is a time constant setting circuit.

In the interference wave removal device configured as described above.

The IF multiplied signal of the auxiliary channel extracted by the coupler (18) is input to a pulse detection circuit (19) to detect the presence or absence of an interference wave pulse. Next, upon receiving this result, the time constant circuit (20) sets the time constant of the digital filter to a high speed when there is a pulse, and to a very low speed when there is no pulse, so that the pulse interference wave cancellation characteristic becomes as shown in FIG.

〔Effect of the invention〕

As explained above, this invention detects the presence or absence of an interference wave pulse, and sets the time constant of the digital filter to a high speed when there is a pulse, and sets the time constant of the digital filter to an ultra-slow speed when there is no pulse, thereby eliminating the pulse interference wave. Can be completely erased in a short time

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an embodiment of the invention.
The canceling characteristics of pulse interference waves in the above embodiment, Fig. 3 is a block diagram showing a conventional interference wave removal device of this type, and Fig. 4 shows the pulse interference wave in a conventional interference wave removal device of this type. is the cancellation property of In Figures 1 and 3, (1) is the main antenna, (2)
(7) is a frequency conversion circuit, (3) is a subtracter, (4)
(5) (8) is a power divider, (6) is an auxiliary antenna, (9) and (16) are 90° hybrid, (10
) (15) is the mixer, (II) is the amplification HL (12) is A
D converter, (13) is a digital filter. (14) is a DA converter, (17) is a power combiner,
(18) is a coupler, (+9) is a pulse detection circuit, (2
0) is a time constant setting circuit, and (21) is a time constant setting switch. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] It has a main antenna, an auxiliary antenna for removing interference waves, and a closed loop circuit connected to both antennas, and removes interference waves mixed in the side lobe region of the main antenna using the auxiliary antenna and the closed loop circuit. In the interference wave removal device, a pulse detection circuit uses a digital filter with a variable time constant as an integrating circuit located at the baseband of the closed loop circuit, and switches the time constant of the digital filter depending on the presence or absence of an interference wave pulse. An interference wave removal device characterized by comprising: and a time constant setting circuit.