JPH0777572A - Feedthrough suppression circuit - Google Patents

Abstract

PURPOSE:To provide a circuit for suppressing wide band feedthrough. CONSTITUTION:In a CW radar having a phased array antenna, the transmission interval is repeated while interposing a pause period for switching the beam. Switches 1, 2 switch an input signal between a feedthrough receiving period present in the initial stage of receiving period and a following target signal receiving period. During the feedthrough receiving period, detecting circuits 3-6 detect a feedthrough and low frequency components extracted by LPFs 7, 8 are digitized by ADCs(A/D converters) 9, 10 and then averaged by adders 11, 12 and memories 13, 14 to produce a suppression data being stored. During a target signal receiving periodal, the suppression data is taken out from the memories 13, 14 and converted by DACs(D/A converters) 15, 16 into an analog data, and a suppression signal is produced in weighting circuits 17-20. It is fed to an adder 21 which outputs a receiving data subjected to feedthrough suppression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a feedthrough suppressing circuit used in a CW radar device having a phased array antenna.

[0002]

2. Description of the Related Art In a CW radar device, feedthrough causes saturation of a receiver, so that suppression thereof is one of important problems. The feedthrough that directly leaks from the transmitting antenna to the receiving antenna can be solved by changing the layout of both antennas, but the feedthrough consisting of reflected waves (clutter component) in a building or the like changes depending on the installation environment of the CW radar device. To do.

Therefore, as shown in FIG. 3, for example, the feedthrough suppressing circuit 34 is connected to the receiving antenna 33 and the receiver 35.
It is provided between the two to suppress the feedthrough consisting of clutter components.

That is, in FIG. 3, the continuous wave transmission signal output from the transmitter 31 is transmitted from the transmission antenna 32, and a part of the transmission signal is given to the feedthrough circuit 34 as a reference signal. Conventional feedthrough suppression circuit 3
4 is configured specifically as shown in FIG. 4, for example, detects the feedthrough amount included in the received signal based on the reference signal, weights the reference signal based on the detected feedthrough amount, and outputs the suppression signal. The suppression signal and the reception signal that have been formed are added, and the addition is applied to the detection circuit to repeat the same operation, and the addition result is output to the receiver 35.

As a result, since the receiver 35 receives the received signal whose feedthrough is suppressed, the receiver 35 can perform the receiving process such as amplification and frequency conversion on the input signal without being saturated, and the signal processor 36 receives the target signal. Information can be detected and output.

Next, a conventional feedthrough suppressing circuit will be described with reference to FIG. In FIG. 4, this feedthrough suppression circuit is basically composed of a feedthrough detection circuit (41 to 44), a loop filter (45, 46), a weight circuit (47 to 50), and a loop circuit of an adder 51. It

The reference signal from the transmitter 31 is a distributor 52.
Is distributed to the distributor 41 of the feed-through detection circuit and the distributor 47 of the weighting circuit, and each becomes a reference signal to which phase information is added. That is, the distributors 41 and 47 have the reference signal of the same phase (0 °) as the output of the transmitter 31 and 9 °, respectively.
And a reference signal phase-shifted by 0 °.

The received signal from the receiving antenna 33 passes through the adder 51 and the distributor 53 into the distributor 42 of the feedthrough detecting circuit.

In the feedthrough detection circuits (41 to 44), the output of the distributor 42 (received signal) and the output of the distributor 41 (reference signal added with phase information) are multiplied (43, 4).
4) Multiplication, that is, so-called quadrature detection is performed, and the fluctuation amount (feedthrough amount) of the feedthrough included in the received signal is detected.

The loop filter (45, 46) takes out the low frequency component of the variation of the feedthrough output from the multiplier (43, 44) and supplies it to the weighting circuit.

In the weight circuit, the loop filters (45, 4
The output of 6) (feedthrough amount) and the output of the distributor 47 (reference signal added with phase information) are multiplied by multipliers (49, 5).
0) and the two multiplication results are vector-combined by the combiner 48 to form a suppressed signal.

The adder 51 subtracts the output (suppression signal) of the combiner 48 from the received signal from the receiving antenna 33, that is, reduces a predetermined amount of feedthrough. The output of the adder 51 is given to the distributor 42 of the feedthrough detection circuit via the distributor 53.

When the above loop operation is repeated and the feedthrough amount contained in the received signal can be suppressed to the extent that the receiver is not saturated, the distribution direction of the distributor 53 is changed and the output of the adder 51 is changed. It is provided to the receiver 35.

In this conventional feedthrough suppressing circuit,
The loop band cannot be widened so as not to extinguish the Doppler signal, but for narrow band feedthrough, it can adaptively cope with the radar installation environment, that is, even if the feedthrough environment changes to some extent. Can be suppressed.

[0015]

By the way, the CW radar device is characterized by being excellent in concealment because of its low peak power, and has a phased array antenna.
In the radar device, it is considered to use a wideband signal such as a spread spectrum signal in order to improve the confidentiality, but as described above, the conventional feedthrough suppression circuit cannot expand the loop band,
Sufficient suppression can be performed only in a specific feedthrough environment,
Improvement is desired.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a feedthrough suppressing circuit which enables use of a wideband signal in a CW radar device having a phased array antenna.

[0017]

In order to achieve the above object, the feedthrough suppressing circuit of the present invention has the following structure. That is, the feedthrough suppression circuit of the present invention is
A CW having a phased array antenna, and a reception period for a transmission period in a certain direction is divided into a feedthrough reception period for receiving only feedthrough in the initial stage of reception and a target signal reception period for thereafter receiving a reflected wave from a target. In a radar device, a feedthrough suppressing circuit that uses a transmitter output as a reference signal and suppresses a feedthrough included in a receiving antenna to suppress the feedthrough contained in the signal, and feeds the received signal from a received signal based on the reference signal during a feedthrough reception period. A circuit for detecting a quantity, averaging it and storing it as suppression data; forming a suppression signal by weighting a reference signal based on the suppression data in the target signal reception period, and forming the suppression signal and the reception signal. And a circuit for adding and outputting to the receiver.

[0018]

Next, the operation of the feedthrough suppressing circuit of the present invention constructed as described above will be described. As is well known, CW
With radar equipment, the first few μ after the start of transmission in a certain direction
During the second period, the reflected wave at the target is not received, but only the feedthrough is received. Here, in the CW radar device having the parabolic antenna, the pointing direction is changed by rotating the antenna, but at that time, since the transmission is continuously performed without interruption, the received feedthrough also changes with the rotation of the antenna. To do.

However, in the CW radar device having the phased array antenna, the control of the pointing direction is performed by stopping the transmission, so that the transmission is performed for a certain period in an arbitrary direction with the beam direction switching pause period interposed. Therefore, the content of the feedthrough initially received in the reception period with respect to the transmission period in a certain direction is constant. The present invention focuses on such fact.

That is, the feedthrough amount is detected during the feedthrough reception period, the averaged amount is stored as suppression data, and the feedthrough in the reception signal is suppressed based on the suppression data during the subsequent target signal reception period.

In short, since only the feedthrough can be suppressed by the open loop control method, it is possible to adaptively suppress the feedthrough without suppressing the target signal even for the wideband feedthrough.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the feedthrough suppression circuit of the present invention. In FIG. 1, this feedthrough suppressing circuit includes a switch (1, 2) and a feedthrough detecting circuit (3-6).
, Low-pass filter (LPF: 7, 8), analog-digital converter (ADC: 9, 10), adder (11, 12), memory (13, 14), digital-analog converter ( DAC: 15, 16), a weighting circuit (17 to 20), an adder 21, and a timing control circuit (not shown) are basically provided.

In the CW radar device having the phased array antenna, the control of the directivity direction is performed by stopping the transmission. Therefore, for example, as shown in FIG. 2, there is a transmission period 23 across a beam switching pause period 22. Period 23
Is divided into a feed-through reception period (referred to as "feed-through listen") 24 in which only the initial feed-through is received and a target signal reception period 25 in which a reflected wave from the target is received thereafter. It

The period of the feedthrough listen 24 defines the shortest detection distance of the device and is determined by the device, but a timing control circuit (not shown) manages the feedthrough listen 24 and the target signal reception period 25. , And gives timing signals to each part for control.

The switch 1 which receives the reference signal from the transmitter 31 gives the reference signal to the distributor 3 of the feedthrough detection circuit during the period of the feedthrough listen 24 and supplies the reference signal of the weighting circuit during the target signal reception period 25. Distributor 1
Give to 7.

The switch 2 which receives the reception signal from the reception antenna 33 gives the reception signal to the distributor 4 of the feedthrough detection circuit during the period of the feedthrough listen 24,
In the target signal reception period 25, the reception signal is given to one input of the adder 21.

During the feedthrough listen 24 period, the following operations are performed. First, the feedthrough detection circuit (3
The feedthrough amount is detected as described above in 6) to 6). Next, the low frequency component of the detected feed-through fluctuation is extracted by the LPF (7, 8). Up to this point, it is almost the same as the conventional one, but in the present invention, the low frequency component of the extracted feed-through fluctuation is converted into the ADC (9, 1).
0) digitized and stored in the memory (13, 14) via the adder (11, 12), and at the same time by the loop circuit of the adder (11, 12) and the memory (13, 14). , 14) stores the averaged suppression data.

Next, in the target signal reception period 25, the memories (13, 14) and thereafter are activated. That is, the memory (1
The suppression data of (3, 14) are analogized by the DAC (15, 16) and given to the multiplier (19, 20) of the weighting circuit, the reference signal is weighted as described above, and the combiner 18 outputs the vector. The combined suppression signal becomes the other input of the adder 21, and the reception signal in which the feedthrough is suppressed is output.

The weighting circuit multipliers (19, 20)
Needless to say, may be composed of an attenuator.

[0030]

As described above, in the feedthrough suppression circuit of the present invention, attention is paid to the operating characteristics of the CW radar device having the phased array antenna, suppression data is formed in the period when the feedthrough is received, and the target is obtained. When the signal is received, only the feedthrough can be suppressed by using the generated suppression data. Therefore, the wideband feedthrough can be adaptively suppressed without affecting the target signal, and the phased array antenna. There is an effect that it is possible to provide a feedthrough suppression circuit suitable for a CW radar device having.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a feedthrough suppression circuit according to an embodiment of the present invention.

FIG. 2 is a time chart explaining a transmission operation of a CW radar device having a phased array antenna.

FIG. 3 is a configuration block diagram of a CW radar device including a feedthrough suppression circuit.

FIG. 4 is a configuration block diagram of a conventional feedthrough suppression circuit.

[Explanation of symbols]

 1, 2 Switching device 3, 4, 17 Distributor 5, 6, 19, 20 Multiplier 7,8 Low-pass filter (LPF) 9,10 Analog-digital converter (ADC) 11, 12 Adder 13, 14 Memory 15 , 16 Digital-analog converter (DAC) 18 Combiner 21 Adder 22 Idle period of beam switching 23 Transmission period 24 Feedthrough listen 25 Target signal reception period

Claims (1)

[Claims] 1. A feedthrough receiving period having a phased array antenna, wherein a receiving period for a transmitting period in a certain direction receives only a feedthrough at an initial stage of reception, and a target signal receiving period thereafter for receiving a reflected wave from a target. In the CW radar device classified into 1., a feedthrough suppressing circuit that suppresses the feedthrough contained in the received signal of the receiving antenna and supplies it to the receiver by using the transmitter output as a reference signal based on the reference signal in the feedthrough receiving period. A circuit for detecting a feedthrough amount from a received signal, averaging it, and storing it as suppression data; a reference signal is weighted based on the suppression data in the target signal reception period to form a suppression signal, and the suppression signal thus formed And a circuit for adding the received signal to the receiver and outputting the result to the receiver. Idosuru suppression circuit.