JP2000298165A - Pulse modulation signal identifying device and radar signal identifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the small frequency change or amplitude change of a radar signal to identify the radar signal by providing a delay means for delaying a pulse modulation signal, and a multiplying means for multiplying the pulse modulation signal by the delay signal. SOLUTION: An IF signal (a pulse modulation signal) from an LPF 13 of a radar signal receive part is delayed by the specified time by a delay means 20. A mixer 21 is a multiplying means for multiplying the IF signal from the SPF 13 by the delay signal from the delay means 20. The LPF 22 eliminates a high frequency components from the output signal of the mixer 21, and a capacitor 23 eliminates a direct current component from the output of the mixer 21. An identifying means 24 identifies the pulse modulation signal on the basis of the output signal of the capacitor 23 and outputs it as an identification signal. In the case of inputting a signal with micro change in frequency and its delay signal into the mixer 21, a beat signal, that is, a signal corresponding to the frequency difference of both signals, appears. This signal component is extracted by the LPF and capacitor to detect the micro change of frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse modulation signal discrimination device and a radar signal discrimination device.
A pulse modulation signal identification device that extracts the characteristics of the pulse modulation signal to identify the pulse modulation signal, and a radar reverse search device (ESM :) that extracts the characteristics of the received radar signal and identifies the transmitter that is the transmission source of the signal. Electric Support Measure)
And the like.

[0002]

2. Description of the Related Art Usually, a radar transmitter operates at 9 to 10 MHz.
A pulse-shaped radar signal is transmitted by performing pulse modulation for intermittently outputting a radio signal of a degree. FIG. 6 is a diagram schematically showing such a radar signal.

If the type of the radar signal to be transmitted differs for each radar transmitter, the radar transmitter can be identified by extracting the characteristics of the radar signal. For example, a frequency F constituting a pulse of a radar signal, a pulse interval PRI (Pulse Repetition Interval), a pulse width P
By extracting W (Pulse Width), the radar transmitter can be identified relatively easily. However, the frequency and the like of the radar signal are common to many radar transmitters, and in many cases, the radar transmitter cannot be specified only by these features.

Therefore, it is conceivable to extract a frequency change in a pulse of a radar signal and identify a radar transmitter based on the extraction result. FIG. 7 is a block diagram showing the configuration of such a conventional radar signal identification device.
In the figure, 14 is a high-speed switch device which repeats ON / OFF at regular time intervals and divides a continuous signal into a plurality of pulse signals, and 15 is an IFM (Instan
taneous Frequency Measurement) circuit.

[0005] A radio frequency signal (RF signal) received by the antenna 10 is mixed with a local signal generated by a local oscillator 11 in a mixer 12, and is mixed in a low-pass filter 13.
At which the high frequency component is removed, and the intermediate frequency signal (I
F signal). The IF signal is cut by the high-speed switch device 14 at a time interval shorter than the pulse width PW, and the IFM circuit 15 detects the frequency of each cut waveform.

That is, one pulse is divided on the time axis, and a frequency change in the pulse is detected by obtaining each frequency. Therefore, in the case of a radar signal whose frequency changes within a pulse, it is possible to specify the radar transmitter that transmits the radar signal.

However, the detection accuracy of the IMF circuit is several M
Hz, and a radar signal having a large frequency change in a pulse, for example, in the case of a chirp signal having a frequency change of 10 MHz or more, a radar transmitter can be specified using this radar signal identification device. A frequency change of less than several MHz could not be detected.

In a relatively inexpensive radar transmitter, frequency modulation or the like is not performed in a pulse of a radar signal, and the frequency in the pulse is almost constant. For this reason, the radar transmitter could not be specified using the conventional radar signal identification device.

[0009]

However, it is known that even a radar signal transmitted from an inexpensive radar transmitter contains an unintended frequency or amplitude fluctuation in the pulse of the radar signal. ing. Such a frequency,
The fluctuation of the amplitude is caused by the characteristics of the radar transmitter, and has a characteristic for each radar transmitter. For this reason,
By analyzing the wobble characteristic, the name of the radar transmitter can be specified only by analyzing "one pulse".

However, while the frequency detection accuracy of the IMF circuit is about several MHz, unintended fluctuations in frequency and amplitude are subtle changes of 1 KHz or less. For this reason, it was not possible to detect the fluctuation of the frequency using the conventional pulse identification device. Also, there is no pulse identification device for detecting fluctuations in amplitude.

The present invention has been made in view of the above circumstances, and has as its object to detect a small frequency change or amplitude change in a pulse of a pulse modulation signal and identify the pulse modulation signal. It is another object of the present invention to detect a small frequency change or amplitude change of a radar signal transmitted by a radar transmitter and identify the radar signal.

[0012]

A pulse modulation signal discriminating apparatus according to the present invention comprises: a delay means for delaying a pulse modulation signal; a multiplication means to which the pulse modulation signal and an output signal of the delay means are input; And a signal identification unit for identifying a pulse modulation signal based on an output signal of the band limitation unit. By band limiting after multiplication with the delay signal, only the frequency change component can be detected. Therefore, the pulse modulation signal can be identified based on the frequency change in the pulse.

Further, the pulse modulation signal discriminating apparatus according to the present invention is provided with DC cutoff means for removing a DC component from an envelope detection signal of the pulse modulation signal, and an output signal from the DC cutoff means is provided with a delay means and a multiplier. Input to the means.
After removing the DC component of the envelope detection signal, the frequency band is limited after multiplication with the delay signal, so that only the frequency change component can be detected. Therefore, the pulse modulation signal can be identified based on the amplitude change in the pulse.

Further, the pulse modulation signal discriminating apparatus according to the present invention comprises a first DC cutoff means for removing a DC component from an envelope detection signal of the pulse modulation signal, and a second DC signal for removing a DC component from the output of the delay means. It is provided with direct current cutoff means. Therefore, the envelope detection signal from which the DC component has been removed and the delay signal thereof are input to the multiplication means.

In the pulse modulation signal identification device according to the present invention, the signal identification means compares the output signal of the band limiting means with a predetermined threshold, and a series of comparison results output from the threshold comparison means. Is compared with pattern data stored in advance. Therefore, the pulse signal can be identified based on the pattern comparison.

Further, a radar signal identification device according to the present invention includes an antenna for receiving a radar signal, a delay circuit for delaying a received signal, a mixer to which a detection signal and an output signal of a delay unit are input, and a mixer generated by the mixer. And a signal identification unit for identifying a radar signal based on the output signal of the filter. For this reason, the radar transmitter can be identified based on the frequency change of the radar signal.

Further, the radar signal discriminating apparatus according to the present invention includes a detection circuit for detecting the envelope of the received signal, and a capacitor for removing a DC component from the detected signal, and an output signal of the capacitor is input to the delay circuit and the mixer. You. Therefore, the radar transmitter can be identified based on the change in the amplitude of the radar signal.

Further, the radar signal discriminating apparatus according to the present invention comprises a first capacitor for removing a DC component from a detection signal, and a second capacitor for removing a DC component from an output signal of the delay circuit. A signal is input to the delay circuit, and output signals of the first capacitor and the second capacitor are input to the mixer. Therefore, the detection signal from which the DC component has been removed and the delay signal thereof are input to the mixer.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing an example of a radar signal identification device according to the present invention. The radar signal identification device 1A includes a radar receiving unit 10A.
To 13 and a pulse identification unit 2A.
Is a delay means 20, a mixer 21, a low-pass filter (L
It comprises a PF (Low Pass Filter) 22, a capacitor 23 and an identification means 24. The components corresponding to those of the conventional radar signal identification device are denoted by the same reference numerals, and description thereof is omitted.

The delay means 20 includes a delay line or a SAW (Surf)
ACE Acoustic Wave) element, and outputs a delayed signal obtained by delaying the IF signal from the low-pass filter 13 by a predetermined time. The mixer 21 is a multiplication unit that multiplies the IF signal from the low-pass filter 13 by the delay signal from the delay unit 20.

The LPF 22 removes high frequency components from the output signal of the mixer 21, and the capacitor 23 removes DC components from the output signal of the mixer 21. That is, this LPF2
The band-limiting means (band-pass filter) is formed by the capacitor 2 and the capacitor 23. The high-frequency component and the DC component generated by the mixer are removed, and only the low-frequency component excluding the DC component is extracted. The identification unit 24 identifies the pulse modulation signal based on the output signal of the capacitor 23, and outputs the identification result as an identification signal.

When a signal having a small change in frequency and its delay signal are input to a mixer, a signal component corresponding to the frequency difference between the two signals, called a beat signal, appears. L
By extracting this signal component using a PF and a capacitor, a minute change in frequency, that is, a fluctuation of a frequency of about several KHz included in the radar signal can be detected.

When the antenna 10 receives a radar signal having a frequency fluctuation in a pulse, the IF signal output from the LPF 13 also has a frequency fluctuation in the pulse.
If the frequency within the pulse of this IF signal is ω / 2π and the frequency of the fluctuation is △ ω (t) / 2π, the IF signal S ₁
(T) is represented by equation (1). S ₁ (t) = sin {ω ・ t + △ ω (t)} (1)

Assuming that the delay time in the delay means 20 is ΔT, the delay signal S ₂ (t) output from the delay means is expressed by equation (2). S ₂ (t) = sin {ω ・ (t- △ T) + △ ω (t- △ T)} (2)

The output signal S ₃ (t) of the mixer 21 is the result of multiplication of the equations (1) and (2) and is expressed by the equation (3). S ₃ (t) = sin {ω ・ t + △ ω (t)} ・ sin {ω ・ (t- △ T) + △ ω (t- △ T)} = 1/2 ・ cos {ω ・ △ T + △ ω (t)-△ ω (t- △ T)} -1/2 ・ cos {ω ・ (2t- △ T) + △ ω (t) + △ ω (t- △ T)} (3)

Here, since the fluctuation frequency △ ω is sufficiently smaller than the pulse frequency ω, if △ ω is ignored, the frequency of the second term of the equation (3) becomes 2ω / 2π,
The frequency of the first term is zero. That is, the mixer 21 generates a harmonic component having a frequency approximately twice that of the IF signal and a low frequency component having a frequency sufficiently lower than the IF signal.

The LPF 22 removes harmonic components from the output signal of the mixer 21 and passes only low harmonic components. Therefore, the output signal S ₄ (t) of the LPF 22 is represented by the first term of Expression (3), that is, Expression (4). S ₃ (t) = 1/2 ・ cos {ω ・ △ T + △ ω (t)-△ ω (t- △ T)} (4)

In formula (4), △ ω △ (t)-△ ω ・ (t- △ T) is a fluctuation component in the period △ T, and ω · △ T is a constant. Accordingly, the LPF 22 has a fluctuation frequency △ ω (t)
It is sufficient that the cutoff frequency has a cutoff frequency higher than that of the IF signal and lower than twice the frequency (ω / π) of the IF signal.

The capacitor 23 removes the DC component from the output signal of the LPF, and passes only the AC component that changes with time. If there is no fluctuation in the frequency of the IF signal.
ω (t) is fixed to zero, the frequency of the output signal of the LPF 22 becomes zero, and the capacitor 23 does not output a signal. On the other hand, when there is fluctuation, a signal is output from the capacitor 23.

In other words, if the frequency deviation of the IF signal changes for each ΔT period, a signal is output from the capacitor 23. If the frequency deviation of the IF signal for each ΔT period is constant, the capacitor 23 Does not output a signal.

The identification means 24 identifies a pulse signal by identifying a change pattern of a series of output signals output from the capacitor 23. FIG. 2 is a diagram showing an example of the configuration of the identification unit 24, which includes a threshold value comparison unit 240, a pattern comparison unit 241, and a pattern generation unit 242.

The threshold comparing section 240 compares the output signal from the capacitor 23 with a predetermined threshold and outputs the comparison result. For this reason, data consisting of “0” or “1” is output from the threshold comparing unit 240 in chronological order.

When the radar signal discriminating unit 2A receives a radar signal, the pattern generating unit 242 controls the threshold value comparing unit 24.
This is storage means for storing a time-series pattern output from a plurality of radar signals, and stores patterns of at least one pulse for a plurality of radar signals, and reproduces and outputs these patterns. The pattern comparing section 241 compares the pattern from the threshold comparing section 240 with each pattern output from the pattern generating section 242 to identify a pulse signal. This identification result is output as an identification signal.

As described above, by detecting the output pattern based on the frequency change in the pulse of the radar signal,
A small frequency change included in the pulse can be analyzed for each pulse in real time, and the radar transmitter that transmits the radar signal can be specified.

Further, the device can be constituted by simple hardware comprising a combination of inexpensive general-purpose components such as a delay line, an LPF and a capacitor. Further, the configuration can be made without performing the processing by software. Therefore, it is possible to provide an inexpensive radio wave searching device that detects the fluctuation of the frequency of the received radio wave in real time.

Embodiment 2 FIG. 3 is a block diagram showing an example of a radar signal identification device according to the present invention. In this radar signal identification device, the pulse signal identification unit 2B includes the envelope detector 25 and the capacitor 26. Note that the same components as those of the radar signal identification device 1A shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The envelope detector 25 performs envelope detection on the IF signal output from the LPF 13 and converts it into a detection signal (video signal). The capacitor 26 cuts off the DC component of the detection signal, passes only the AC component, and outputs the signal to the delay means 20 and the mixer 21.

FIG. 4 is a diagram showing an example of a detection signal of the envelope detector 25. In this figure, a detection signal for one pulse is shown. An ideal detection waveform (video waveform) has a rectangular pulse waveform, and the upper part of the pulse portion is flat. However, since the actual radar signal fluctuates in amplitude due to the characteristics of the radar transmitter, the upper part of the pulse portion (that is, the amplitude of the pulse portion) is not constant but has a wavy shape.

This wavy shape is not regular, and the wave itself changes with time. By detecting the time change of the wave, the radar signal can be identified, and the radar transmitter can be specified. That is, assuming that the average amplitude of the pulse portion is S ₀ and the fluctuation of the amplitude is △ ω (t), the waveform S _{5 of the} pulse portion is expressed by Expression (5). S ₅ (t) = S ₀ + sin △ ω (t) (5)

Since S _{0 in} equation (5) is a DC component, it is removed by the capacitor 26. Therefore, the mixer 21
Is represented by equation (6). S ₃ (t) = sin △ ω (t) ・ sin △ ω (t- △ T) = 1/2 ・ cos {△ ω (t)-△ ω (t- △ T)} -1/2 ・ cos {△ ω (t) + △ ω (t- △ T)} (6)

The frequency of the first term in the equation (6) is given by △ ω (t) /
The difference between 2π and △ ω (t- △ T) / 2π, and the frequency of the second term is the sum of these. That is, in the mixer 21, a harmonic component having a frequency approximately twice as high as the output signal of the capacitor 26 (the frequency is △ ω (t) / 2π),
, A low-frequency component having a frequency sufficiently lower than that of the output signal is generated.

Therefore, the LPF 22 has the function of {△ ω (t)-△ ω (t- △
T)} / 2π and a cutoff frequency smaller than △ ω (t) / π, only low frequency components can be passed. At this time, the output signal S ₄ (t) of the LPF 22 is
It is represented by the first term of equation (6), that is, equation (7). S ₄ (t) = 1/2 · cos {△ ω (t)-△ ω (t- △ T)} (7)

The capacitor 23 removes the DC component from the output signal of the LPF 22, and passes only the AC component that changes with time. That is, if there is no fluctuation in the amplitude of the IF signal, Δω (t) −Δω (t−ΔT) becomes zero, and the capacitor 23 does not output a signal. On the other hand, when there is fluctuation, a signal is output from the capacitor 23.

In other words, if the amplitude deviation of the IF signal changes every ΔT period, a signal is output from the capacitor 23. If the amplitude deviation of the IF signal changes every ΔT period, the capacitor 23 Does not output a signal.

As in the first embodiment, the identification means 24 identifies a pulse signal by identifying a change pattern of a series of output signals output from the capacitor 23.

In this way, by detecting an output pattern based on the amplitude change in the pulse of the radar signal, a small amplitude change included in the pulse can be analyzed in real time for each pulse, and the radar signal is transmitted. The radar transmitter can be specified.

Further, the device can be constituted by simple hardware consisting of a combination of inexpensive general-purpose components such as a delay line, an LPF and a capacitor. Further, the configuration can be made without performing the processing by software. Therefore, it is possible to provide an inexpensive radio wave searching device that detects fluctuations in the amplitude of a received radio wave in real time.

Embodiment 3 FIG. 5 is a block diagram showing an example of a radar signal identification device according to the present invention. The radar signal identification device 1C further includes a pulse signal identification unit 2C having a capacitor 27. The delay means 20 delays the detection signal of the envelope detector 25, and thereafter, the capacitor 27 removes a DC component from the delay signal.

Therefore, as in the case of the second embodiment, the envelope detection signal whose DC component is cut off and its delay signal are input to the mixer 21. Therefore, the identification unit 24 can identify the pulse signal and output the identification signal in the same manner as in the second embodiment.

In the first to third embodiments, the delay time in the delay means 20 needs to be determined based on the change in the frequency of the IF signal. For example, when the frequency change in the pulse occurs only at intervals of 1 μsec or more,
If the delay time is 1 μsec or less, a frequency change cannot be detected. For this reason, it is desirable that the delay means 20 be configured by means capable of changing the delay time, for example, a delay line whose length can be changed. In this case, the operator adjusts the delay time so that the frequency change can be easily detected, so that the pulse discrimination ability can be improved.

The cut-off frequency of the LPF 22 is also
It must be determined based on the frequency change of the IF signal. That is, it is necessary to determine the cutoff frequency so as to separate the high frequency component and the low frequency component. Therefore, the LPF 22
Is desirably constituted by means capable of changing the cutoff frequency. In this case, the operator can adjust the cutoff frequency and pass only the low frequency components, thereby improving the pulse discrimination ability.

In particular, the delay time in the delay means 20;
By making it possible to change both the cutoff frequency and the cutoff frequency of the LPF 22, the pulse discrimination ability can be improved.

In the first to third embodiments, the input signals to the pulse discriminating sections 2A, 2B, and 2C are IF signals, but the RF signal is inputted to the pulse discriminating sections 2A, 2B, and 2C. Is also good. That is, the output signal of the antenna 10 can be input to the pulse signal identification units 2A, 2B, and 2C without passing through the mixer 12 and the LPF 13.

[0054]

The pulse modulation signal discriminating apparatus according to the present invention comprises:
By multiplying the pulse modulation signal and its delay signal to remove the high-frequency component and the DC component, it is possible to detect a frequency change in the pulse. Therefore, the pulse modulation signal can be identified based on the frequency change in the pulse.
Further, the pulse modulation signal identification device according to the present invention multiplies the pulse modulation signal and its delay signal after removing the DC component,
By removing the high-frequency component and the DC component, it is possible to detect a change in amplitude in the pulse. Therefore, the pulse modulation signal can be identified based on the amplitude change in the pulse. In addition, the radar signal identification device according to the present invention,
A radar signal is identified based on a frequency change or an amplitude change of the radar signal received by the antenna. Therefore, the transmitter of the radar signal can be identified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a radar signal identification device according to the present invention (Embodiment 1).

FIG. 2 is a block diagram showing an example of a configuration of an identification unit 24 shown in FIG.

FIG. 3 is a block diagram showing an example of a radar signal identification device according to the present invention (Embodiment 2).

FIG. 4 is a diagram illustrating an example of a detection signal of the envelope detector 25 illustrated in FIG. 2;

FIG. 5 is a block diagram illustrating an example of a radar signal identification device according to the present invention (Embodiment 3).

FIG. 6 is a diagram schematically showing a pulse-modulated radar signal (prior art).

FIG. 7 is a block diagram showing a configuration of a conventional radar signal identification device.

Claims (7)

[Claims] A delay means for delaying a pulse modulated signal;
Multiplying means to which the pulse modulation signal and the output signal of the delay means are input; band limiting means for removing high-frequency components and DC components generated by the multiplying means from the output signal of the multiplying means; A pulse modulation signal identification device comprising: a signal identification unit that identifies a pulse modulation signal. 2. A DC cutoff means for removing a DC component from an envelope detection signal of a pulse modulation signal, a delay means for delaying an output signal of the DC cutoff means, an output signal of the DC cutoff means and an output signal of the delay means. Input multiplying means, band limiting means for removing high frequency components and DC components generated by the multiplying means from the output signal of the multiplying means, and signal identifying means for identifying a pulse modulation signal based on the output signal of the band limiting means A pulse modulation signal identification device comprising: 3. A delay means for delaying an envelope detection signal of a pulse modulation signal, a first DC cutoff means for removing a DC component from an envelope detection signal of the pulse modulation signal, and a DC component from an output of the delay means. A second DC cutoff unit to be removed, a multiplication unit to which an output signal of the first DC cutoff unit and an output signal of the second DC cutoff unit are input, and a multiplication of a high frequency component and a DC component generated by the multiplication unit A pulse modulation signal identification device comprising: band limiting means for removing from an output signal of the means; and signal identification means for identifying a pulse modulation signal based on an output signal of the band limiting means. 4. The apparatus according to claim 1, wherein said signal discriminating means includes a threshold comparing means for comparing an output signal of said band limiting means with a predetermined threshold value, and a series of comparison results outputted from said threshold comparing means with pattern data stored in advance. 4. The pulse modulation signal identification circuit according to claim 1, further comprising a pattern comparison unit for comparing. 5. An antenna for receiving a radar signal, a delay circuit for delaying a received signal, a mixer to which a detection signal and an output signal of the delay circuit are input, and a high-frequency component and a DC component generated by the mixer. A radar signal identification device comprising: a filter for removing from an output signal; and signal identification means for identifying a radar signal based on an output signal of the filter. 6. An antenna for receiving a radar signal, a detection circuit for detecting an envelope of the received signal, a capacitor for removing a DC component from the detection signal, a delay circuit for delaying an output signal of the capacitor, and an output signal of the capacitor. A mixer to which the output signal of the delay circuit is input, a filter that removes a high-frequency component and a DC component generated in the mixer from the output signal of the mixer, and a signal identification unit that identifies a radar signal based on the output signal of the filter. Radar signal identification device provided. 7. An antenna for receiving a radar signal, a detection circuit for detecting an envelope of the received signal, a delay circuit for delaying the detection signal, a first capacitor for removing a DC component from the detection signal, and a delay circuit. A second capacitor for removing a DC component from the output signal, a mixer to which an output signal of the first capacitor and an output signal of the second capacitor are input, and a high-frequency component and a DC component generated in the mixer, which are output from the mixer. A radar signal identification device, comprising: a filter to remove from a signal; and signal identification means for identifying a radar signal based on an output signal of the filter.