JPS6013147B2 - radar receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar receiver that is designed to improve the deterioration of S/N (signal-to-noise ratio) with respect to a sea surface reflection interference suppression device in a radar device.

In the past, interference with radar equipment due to reflections from the sea surface, that is, interference with sea surface reflections, has caused problems such as difficulty in detecting targets or loss of radar detection functions due to targets disappearing. Ta.

One method for suppressing this sea surface reflection disturbance is to use a radar receiving device configured with a circuit consisting of a logarithmic intensifier and a Takagi reactor wave generator with a fixed cutoff frequency for blocking the interference signal component caused by the sea surface reflection disturbance. has been used. However, in such a radar receiver, the signal-to-noise ratio (hereinafter referred to as SNO) in the reception area where there is no interference signal component due to sea surface reflection
) and the target detection ability deteriorates. The present invention has been devised in view of the above-mentioned drawbacks of the radar receiving device, and is designed to reduce the cutoff frequency of the Takagi wave generator in a radar receiver equipped with a logarithmic intensifier and a Takagi wave generator. By changing the S/N ratio, the interference removal effect in the area where interference signal components due to sea surface reflection exist is not impaired, and the S/N ratio is maintained in the received signal area where sea surface reflection does not exist.
An object of the present invention is to provide a radar receiving device that can improve the deterioration of the radar.

In a radar receiving device consisting of a logarithmic intensifier and a Takagi reactor waver used in radar equipment, the cut-off frequency of the Takagi reactor waver is set at a certain point during the pulse of the transmitted pulse in order to suppress sea surface reflection interference. Then, in general, ra3 and kogom are selected.

By using the cutoff frequency given by equation {1), the signal-to-sea reflection interference ratio (hereinafter S/
However, in areas where there is no sea surface reflection, S/N deteriorates. In order to improve the deterioration of SNO in areas where there is no sea surface reflection,
It has been experimentally confirmed that it is sufficient to select the cutoff frequency of the Takagi reactor in {21}.

That is, in a region where there is no sea surface reflection, when the cutoff frequency fo according to equation [1} is used, the S/N decreases by about x.

However, if we use the cutoff frequency et al. according to the formula (■), the S/N
It was confirmed that there is a decline (almost no decline) in terms of aging. However, the pulse width of the transmission pulse is 80 [nS]
``250 [nS] or 1.2 [〆S].

Based on this technical background, the present invention attempts to control the cutoff frequency of the Takagi wave generator in areas where it is subject to sea surface reflection interference and areas where it is not.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a circuit outline of a radar device equipped with a radar receiving device of the present invention, in which pulse-modulated radio waves are radiated into space by a transmitter 1 and an antenna 2.

Radio waves reflected from people, the sea surface, etc. are input to a radar receiving device 3 via an antenna 2. The signal received from the antenna 2 is first detected by a logarithmic intensifier 4, and the output of the logarithmic intensifier nose is applied to a Takagi reactor waver 5. The blast reactor wave generator 5 is configured such that its cutoff frequency is varied by a control signal from a controller 6, and the controller 6 obtains the output of the logarithmic intensifier 4 and produces a control signal output. In the area {
Control is performed to vary the cut-off frequency of the Takagi wave generator 5 to a cut-off frequency that satisfies the formula 1} and a cut-off frequency that satisfies the formula (2) above in a region where there is no sea surface reflection. FIG. 2 shows an example of the circuit of the Takagi furnace wave generator 5 shown in FIG.
In a four-terminal circuit having output terminals 8 and 1', a Takagi reactor is configured with a capacitor Co and a field effect transistor Tr.

A control signal terminal 9 is connected to the gate terminal G of the field effect transistor Tr. If the conduction resistance of the field effect transistor Tr, that is, the resistance between the drain and the source is Ro, the transfer function Y(S) of this circuit is given by ``SCoRo Y(S)=▽Earball Rain, and the cutoff frequency is different=cross; 3}.

Therefore, by varying the conduction resistance Ro of the field effect transistor Tr with the control signal applied to the control signal terminal 9, the cutoff frequency etc. can be varied, as is clear from the second equation. FIG. 3 is a circuit block diagram showing one embodiment of the controller 6 shown in FIG. 1.

In FIG. 3, when the controller 6 receives a received signal that has been intensified detected by a logarithmic intensifier and is given to one input terminal, the controller 6 transmits a control signal from an output terminal 16 to a control signal terminal 9 shown in FIG. give. The low frequency detector 12 has a predetermined low cutoff frequency for extracting the low frequency component Ec of the sea surface reflection disturbance from the received signal Eb subjected to the intensification detection, and the determiner 14 has a predetermined low cutoff frequency for extracting the low frequency component Ec of the sea surface reflection disturbance from the received signal Eb subjected to the intensification detection. A predetermined function value for the output signal Ec of the area wave generator 12 is used as a comparison standard, and a rectangular signal in the pulse corresponding to the time period in which the signal Ec exceeding the threshold value is given is output as the determination signal Ed.

The waveform shaping circuit 15 inputs the determination signal Ed, and in order to prevent transient influences on the Takagi wave generator 5, such as eliminating generation of unnecessary signals and sudden changes in the cut-off frequency, the waveform shaping circuit 15 inputs the determination signal Ed. The waveform is converted into a signal in which the falling edge of green attenuates at a predetermined constant slope, and the signal is output from the output terminal 16 to the control signal terminal 9 of the Takagi wave generator 5 as a control signal Ee.
FIG. 4 shows the signal waveforms Ea to Ee of each part of the controller 6 configured in this way and the output signal waveform of the radar receiver 3 shown in FIG. 1. In FIG. 4, a is the transmitted pulse Ea, b is the received signal Eb, c is the output signal Ec of the low frequency wave generator 12, d is the judgment output signal Ed, and e is the control signal Ee.
is expressed corresponding to FIG. 3, and f represents the output signal Ef of the radar receiving device 3 of FIG.

Here, the operation of the controller 6 shown in FIG. 3 will be explained using the signal waveform shown in FIG. 4. The received signal Eb in FIG. 4b, which is detected by a logarithmic intensifier via an antenna as a reflected wave of the pulse-modulated transmission output, includes an interference signal component due to sea surface reflection in a range indicated by time tc, and this The reflected signal component of the target object superimposed on the signal is included, and this is repeated with the transmission period of the transmission pulse Ea.

This received signal Eb is passed through the low-pass wave generator 12 to remove the reflected signal from the target object, and only the low-frequency component of interference due to reflection from the sea surface is extracted. given to 14. The determiner 14 has a determination reference value S as a threshold value, and provides a determination output signal Ed that is a rectangular pulse with respect to the output signal Ec. This discrimination output signal Ed is converted by a waveform shaping circuit 15 into a control signal Ee whose falling edge becomes a trapezoidal pulse with a constant attenuation slope, and this control signal Ee is converted into a control signal Ee which is a trapezoidal pulse whose falling edge is a trapezoidal pulse having a constant attenuation slope. It is applied to the gate end of the field effect transistor Tr of the Takagi wave generator shown in FIG. Therefore, at the rising edge of the control signal Ee, the cutoff frequency of the Takagi reactor is controlled to be
The constant attenuation gradient is gradually changed to (《÷) at the falling edge, and an improvement in the S/N ratio is achieved in the range where the sea surface reflection disturbance component does not exist. In this case, a sufficiently high S/C ratio can be obtained.

As shown in FIG. 4f, the output signal of the radar receiving apparatus of the present invention obtained in this manner is such that the interference component due to sea surface reflection is reliably removed, and the S of the target object reflection component in the area without sea surface reflection is The N/N ratio is also intact. FIG. 4 is a block diagram showing another embodiment of the radar reception log according to the present invention.

In FIG. 4, parts that perform the same functions as those in FIG. 1 are denoted by the same reference numerals, and the explanation thereof will be omitted.
In this embodiment, by providing a gate circuit 13 that applies the transmission pulse output from the transmitter 1 as a gate signal to the controller 6, the controller 6 controls the timing at which the cutoff frequency of the Takagi wave generator 5 is changed. That's what I do. This gate circuit 13 outputs a gate signal Eg in synchronization with the transmission pulse Ea input from the transmitter turtle, and only during a time width equal to or wider than the area where sea surface reflection exists, that is, the period of the gate width. This limits the output timing of the determination signal Ed from the controller 6 to the Takagi wave generator 5. For example, if the radar device is a fixed radar station installed near the coastline, the gate period is appropriately set in accordance with the predicted range of sea surface reflection interference. FIG. 5 is a block diagram of the controller 6 controlled by the gate circuit 13. In addition, the fifth
In the figure, parts that perform the same functions as those in FIG. 3 are designated by the same reference numerals, and their explanation will be omitted. This controller 6
The reception signal Ed detected by the logarithmic intensifier 4 is applied to the input terminal 101, and the gate signal Eg is also applied from the gate circuit 13.Therefore, the determiner 1W and the low frequency amplifier When the gate signal Eg is applied, the judgment signal Ed, which is the comparison result between the output signal Ec extracted by the gate signal Ec and a predetermined threshold value, is output to the waveform shaping circuit 15. In this way, the circuit configuration is as follows. FIG. 7 shows the signal waveforms Ea to Ee of each part of the controller 6 and the output signal waveform of the radar receiver 3 shown in FIG. 5.

In Fig. 7, a is the transmitted pulse Ea, and b is the received signal Eb.
, c is the output signal Ec of the low-frequency wave generator, and d is the judgment output signal E
d and e represent the control signal Ee corresponding to FIG. 6, f represents the output signal Ef of the radar receiver 3 of FIG. 5, and g represents the gate output signal Eg of the gate circuit member 3.

Here, the operation of the controller 6 shown in FIG. 6 will be explained using the signal waveform shown in FIG. The received signal Eb in FIG. 7b includes an interference signal component due to reflection from the sea surface in the range indicated by time tc, and a reflected signal component from the target superimposed thereon, and this is repeated with the transmission period of the transmission pulse Ea. This received signal Ed is passed through the low-frequency wave generator 2 to remove the reflected signal from the target object and extract only the low-frequency component of interference caused by sea surface reflection, and is output as the output signal Ec of the low-frequency wave generator 2. The decision unit 14 has a discrimination reference value S as a function value, compares it with the gate output signal Ec, and determines that the gate output signal Ec exceeding the threshold value S becomes a rectangular pulse. The determination output signal Ed is output in synchronization with the rising edge of the transmission pulse Ea, and the gate output signal Eg is applied to the determiner 14 during a gate period equal to or wider than the period in which the sea surface reflection disturbance exists. When the waveform shaping circuit 1
Output to 5. This discrimination output signal Ed is the waveform shaping circuit 1
5, its falling edge is converted into a control signal Ee that is a trapezoidal pulse with a constant attenuation slope, and this control signal Ee is
The voltage is applied to the gate end of the field effect transistor Tr of the Takagi furnace wave generator 6 shown in the figure, that is, the high area furnace wave generator shown in FIG. Therefore, at the rising edge of the control signal Ee, the cutoff frequency of the blast reactor waver is controlled to M, (ra32; mu), and at the falling edge of the constant attenuation slope, it is gradually changed to (mo《÷), Improvement of the S/N ratio is achieved in the range where no reflection interference components exist,
In addition, a sufficiently high S/C ratio can be obtained in a region where sea surface reflection disturbance components exist.

As shown in FIG. 7, the output signal of the radar receiving apparatus of the present invention obtained in this manner is shown in FIG. /N ratio is not impaired. In the above embodiment, the cutoff frequency fo of the Takagi reactor wave generator 5 was continuously variably controlled by the control signal of the controller 6, but as shown in FIG. From the conditions of equations {1' and (2) above, the different cutoff frequencies fo., fo2, f used in the high area reactor wave generator 5 are determined.
o3 things...fon resistor R,? R2, R3,...
, Rn and the time constant of the capacitor Co,
The cutoff frequency of the region receiving sea surface reflection and the region not receiving it may be controlled by selectively switching the switch S using a control signal from the controller 6.

Further, as another circuit example of the controller 6 shown in FIG. 6, the gate output signal of the gate circuit 13 may be applied to a low frequency wave generator or a waveform shaping circuit. Furthermore, since changing the cutoff frequency by the controller used in the radar receiving device of the present invention is nothing but changing the time constant of the Takagi wave generator, it can be easily applied to variable control of the time constant circuit. .

Furthermore, in radar receivers for applications where the sea surface reflected interference reception area (time) is determined individually in advance, for example, the fourth
Since the control signal Ee in Figure e is a constant waveform signal, in such a case, the controller should synthesize a constant waveform cut-off frequency control signal synchronized with the transmitted pulse and apply it to the high-frequency reactor. It is also possible to simplify the cut-off frequency of the Takagi wave generator by changing it at a constant waveform period. As explained above, the radar receiving device of the present invention determines the presence or absence of sea surface reflection interference and varies the cutoff frequency of the Takagi reactor, thereby making it possible to sufficiently detect the S/C ratio in the area where sea surface reflection exists, as well as detecting the presence of sea surface reflection interference. S/ in non-existent area
It has been possible to realize a radar receiving apparatus that can improve the N ratio and provides a received signal output in which detection of a target object is not affected in any way even by interference reflected from the sea surface.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of a radar device having a radar receiving device of the present invention, and FIG. The figure is a circuit block diagram showing an embodiment of the controller in the radar receiving device of the present invention, and FIG. 4 is the controller 6 shown in FIG.
5 is a block diagram showing another embodiment of the radar receiving device according to the present invention, and FIG. 6 is a block diagram of the controller shown in FIG. 5. 7 is a waveform explanation showing an example of the signal waveform of each part of the controller shown in FIG. 6 and the signal output of the radar receiving device, and FIG. 8 is a waveform explanation of the signal waveform of each part of the controller shown in FIG. 6, and FIG. It is a circuit diagram showing another embodiment. 1... Transmitter, 2... Antenna, 3...
...Radar receiving device, 4... Logarithmic intensifier, 5...
・・・Takagi wave generator, 6... Controller, 7, 7', 10, 1
1... Input end, 8, 8', 16... Output end, 9... Related U control signal end, 12... Low range wave generator, 13... ...Gate circuit, 14 ... Discriminator, 15 ... Waveform shaping circuit, Co ... Capacitor, Tr ... Field effect transistor, R, ~Rn.
·····resistance. Figure - Figure 2 Figure 3 Figure 5 Figure 6 Figure 8 Figure 4 Figure 7

Claims (1)

[Scope of Claims] 1. A radar receiving device including a reception amplification circuit formed by vertically connecting a logarithmic amplifier and a high-pass filter whose cut-off frequency can be varied; When the level of the low frequency component corresponding to the reflected disturbance wave is below a predetermined threshold, the cutoff frequency f_0 of the high-pass filter is changed to f_
0≒(1-1.5)/γ (where γ is the pulse width of the transmission pulse), and when the level of the low frequency component exceeds the threshold, the cutoff frequency of the high-pass filter is f_
A radar receiving device comprising: a controller that changes 0 to f_0≪1/γ. 2. The controller includes a low-pass filter that extracts a low-frequency component corresponding to a sea surface reflected interference wave from a received signal, a determiner that provides a threshold output for the interference signal component given from the low-pass filter, and a determiner that provides a threshold output for the interference signal component provided from the low-pass filter. 2. The radar receiving device according to claim 1, further comprising a waveform shaping circuit that applies a threshold output to said high-pass filter as a cut-off frequency control signal. 3. The radar receiving device according to claim 1, wherein the high-pass filter changes the cutoff frequency by changing the conduction resistance of an active element that is bias-controlled by a control signal applied from a controller. . 4. The radar receiving device according to claim 1, wherein the high-pass filter has a plurality of different cut-off frequencies varied by a switch that is selectively switched by a control signal applied from a controller. 5. In a radar receiving device, a reception amplification circuit consisting of a logarithmic amplifier and a high-pass filter whose cut-off frequency can be varied are connected in series, and a reception amplifier circuit that corresponds to sea surface reflected disturbance waves among the input signals to the high-pass filter. When the level of the low frequency component is below a predetermined threshold, the cutoff frequency f_0 of the high-pass filter is changed to f_
0≒(1-1.5)/γ (where γ is the pulse width of the transmission pulse), and when the level of the low frequency component exceeds the threshold, the cutoff frequency of the high-pass filter is f_
0 to f_0≪1/γ, and a gate circuit that applies a signal that changes the cutoff frequency f_0 of the high-pass filter of the controller to the high-pass filter only for a predetermined period. radar receiving device. 6. The radar receiving device according to claim 5, wherein the predetermined period is a time period from the rise of the transmission pulse to a time period during which sea surface reflected interference waves are present. 7. The controller includes a low-pass filter for extracting a low-frequency component corresponding to a sea surface reflected disturbance wave from the received signal, and a threshold value for a disturbance signal component given from the low-pass filter to 6. The radar receiving device according to claim 5, further comprising a waveform shaping circuit that applies a cutoff frequency control signal to the filter. 8. The radar receiving device according to claim 5, wherein the high-pass filter changes the cutoff frequency by changing the conduction resistance of an active element that is bias-controlled by a control signal applied from a controller. . 9. The radar receiving device according to claim 5, wherein the high-pass filter has a plurality of different cut-off frequencies varied by a switch that is selectively switched by a control signal applied from a controller.