JP2002372579A - Fm pulse radar device group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interference suppressing technique in the case where a conventional technique is unadoptable, as an interference suppressing technique between a plurality of FM pulse radar devices. SOLUTION: This FM pulse radar device group is provided with a pulse width regulator 20 capable of variably setting pulse width, and a waveform memory 21 outputting FM pulses without changing the lower limit frequency, upper limit frequency and frequency change pattern of transmit FM pulses even when the pulse width changes. The readout signal is converted into an analog signal by a digital-to-analog converter 22 and sent to a transmitter 11 after eliminating unwanted signals across the pulse width by a waveform shaper 7, and the compression characteristic of a compressor 25 on the receiving side is conformed to the compression of an FM pulse signal of pulse width set by the pulse width regulator 20, to suppress the input signals of the other pulse width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of interference cancellation technology in an FM pulse radar device.

[0002]

2. Description of the Related Art Conventionally, when interference is considered to occur between FM pulse radar devices, techniques for preventing or suppressing the interference include changing a frequency band to be used.
If the frequency modulation is linear modulation, the modulation is different from increasing modulation to decreasing modulation. If the frequency modulation is different from linear modulation to non-linear modulation, if the non-linear modulations are different, the non-linear aspect (pattern) is different. , Combining phase modulation with frequency modulation, and so on.

[0003]

However, although it is technically possible to change the frequency band, the frequency bandwidth allocated to this type of radar apparatus is narrow, and in practice, frequency modulation is not performed. The lower limit frequency and the upper limit frequency are determined, and it is impossible to change them.

[0004] The technique of performing the increase modulation and the decrease modulation when the frequency modulation is linear modulation is effective when only two radar devices interfere with each other. It will not cut.

[0005] Regarding the technique of performing linear modulation and non-linear modulation, the time side lobe level is -13 dB in linear modulation, but can be further reduced in non-linear modulation. There is a case where the user specifies the use of the non-linear modulation and the linear modulation cannot be used because the visibility is improved.

With respect to the technique of differentiating the non-linear aspect (pattern) between the non-linear modulations, a user requests a time side lobe level from the viewpoint of the visibility of a radar image, and the technique is used to provide a difference. In some cases, the width becomes narrow and the effect of interference suppression cannot be sufficiently obtained.

[0007] The technique of performing phase modulation in addition to the frequency modulation has a drawback that a moving target is likely to appear large or misaligned due to the influence of the Doppler effect.

As described above, the conventional interference suppression technology has problems associated with the technology itself, such as restrictions due to frequency allocation and user demands, and problems with respect to moving targets. In some cases, any of the technologies can be adopted. There is a problem that there may be no case.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide three interference devices without changing a frequency band, satisfying a user's demand for radar image visibility, and performing no phase modulation. Even with the above, an object of the present invention is to provide a technique capable of suppressing interference.

[0010]

Means of the present invention for achieving the above object are as follows. That is,
When a plurality of frequency-modulated (FM) pulse radar devices are unilaterally or mutually present in a region where the transmission radio wave of another FM pulse radar device is received at an intensity equal to or higher than the minimum reception level, the plurality of FM pulse radars are provided. This is a group of FM pulse radar devices characterized in that interference in a radar output caused by reception of a transmission radio wave of another FM pulse radar device is suppressed by different transmission / reception pulse widths between the devices.

[0011]

According to the present invention, the lower limit frequency f _L and the upper limit frequency f _H of the frequency modulation cannot be changed, and even when the conventional interference prevention technique cannot be applied, it is possible to suppress and reduce the interference in the radar output. That is. The principle is the lower limit frequency f _L of the frequency modulation in the transmission pulse width, even impossible made different upper limit frequency f _H and aspects of the frequency change (pattern), a transmission pulse width as shown in FIG. 3 and tau ₁ tau Due to the difference as in _2, the rate of change of the frequency within the pulse width with respect to time is different.When the receiving device compresses the received pulse with the compressor, the frequency change of the target reflected signal of the transmission wave of the own device is obtained. Since the rate matches the characteristics of the compressor, it is output at a regular output level.However, when a transmission wave from another device with a different pulse width is input, the time change rate of the frequency is Since the characteristics do not match, the signals are suppressed and output. For this reason, an interference suppression effect can be obtained.

As an embodiment of the present invention, the same type of FM
A form in which the transmission pulse width is changed in advance when the pulse radar device is present at a plurality of locations in a region where interference is likely, or when a pulse radar device is newly added to an interference possibility region where one or more devices are already present. In each FM pulse radar device, the pulse width can be changed stepwise or continuously, and the pulse width can be appropriately selected according to the interference situation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example for determining a transmission pulse width of an FM pulse radar device according to the present invention will be described with reference to the drawings. FIG. 1 shows a surface acoustic wave-dispersion type delay line such as a conventional FM pulse radar device.
ve Delay Line: This is an example of a digital processing type FM pulse radar device that generates an FM pulse by a digital method without using SAW-DDL (hereinafter simply referred to as DDL) and digitally compresses the pulse on the receiving side.

The pulse length adjuster 20 is a means for outputting a pulse width signal for determining a transmission pulse width, and can change the pulse width continuously or stepwise. Waveform memory 21
When a pulse width signal is input and a trigger is input from the trigger generator 23, the lower limit frequency (or upper limit frequency) determined at the front end of the pulse width and the upper limit frequency (or lower limit frequency) determined at the rear end of the pulse width are obtained. , And outputs an FM pulse whose frequency changes in a straight line or curve pattern determined in the meantime as a digital signal.

When the pulse width is changed by the pulse length adjuster 20, the lower limit frequency and the upper limit frequency do not change, and the pattern of the change in the middle frequency is a pattern enlarged or reduced in the pulse width direction.

The FM pulse signal thus obtained is D /
After being converted into an analog signal by the A converter 22, the signal is input to the waveform shaper 7, where unnecessary signals appearing before and after the pulse width are cut and shaped by the gate signal from the gate generator 10 and transmitted. Sent to the vessel 11.

The trigger generator 23 generates a trigger at a pulse repetition period determined for the radar device. The width information is sent from the pulse length adjuster 20 to the gate generator 10 so that the width of the output gate coincides with the pulse width set by the pulse length adjuster 20.

The transmission signal sent to the transmitter 11 is converted into a transmission frequency by a signal from the stabilizing oscillator 12, and then radiated from the antenna 14 through the transmission / reception switch 13 into the air. The radio wave that is reflected back from the target is the antenna 14
And input to the receiver 15 via the transmission / reception switch 13. Here, the signal is converted into an intermediate frequency (IF) by a signal from the stabilized oscillator, amplified by the IF amplifier 16, converted into a digital signal by the A / D converter 24, and input to the compressor 25. Performs digital pulse compression.

The compressed signal is supplied to a digital display 1
9 and displayed on the screen. Normally, when a PPI is displayed as in a radar scope, the digital signal of the compressor 25 is converted into an analog signal by a D / A converter and sent to the indicator. In this embodiment, by selecting the pulse width by the pulse length adjuster 20 and changing the characteristics of the compressor 25, the pulse width of the radar device is changed without changing the lower limit frequency, the upper limit frequency, and the pattern of the frequency change. .

FIG. 2 shows an example of an FM pulse radar device using DDL. The frequency of the output of COHO1 (for example, 3
0 MHz) is divided by a frequency divider 2 into a trigger generator 3
, The pulse generator 4 is activated by a trigger from the trigger generator 3, and the generated pulse is sent to the mixer 5.
The signal from COHO1 is input to mixer 5,
This signal is pulse-modulated.

When a pulse-modulated signal is passed through a DDL 6 having a frequency characteristic in a delay time, a pulse width is extended, and a transmission signal with a frequency that changes with time is obtained. This transmission signal is sent to the waveform shaper 7, where the gate signal from the gate generator 10
Unnecessary signals appearing before and after the pulse width are cut and shaped and sent to the transmitter 11.

The gate generator 10 generates a trigger generator 9 based on a signal obtained by dividing the signal of the COHO 1 by the frequency divider 8.
And triggers to generate a gate. The transmission signal transmitted to the transmitter 11 is converted into a transmission frequency by a signal from the stabilizing oscillator 12 and then radiated from the antenna 14 through the transmission / reception switch 13 into the air.

The radio wave reflected back from the target object is received by the antenna 14 and is input to the receiver 15 via the transmission / reception switch 13. Here, the signal is converted into an intermediate frequency (IF) by the signal from the stabilized oscillator 12, amplified by the IF amplifier 16 and input to the DDL 17, and the pulse is compressed to the original pulse width. At the time of frequency conversion, if the transmission wave and the sideband are reversed, the pulse is compressed to the original pulse width even with the same delay line as DDL6. The received signal compressed by the DDL 17 is converted into a video signal by the IF amplification detector 18, input to the display 19, and displayed as an image.

Here, in order to change only the pulse width without changing the lower limit frequency, the upper limit frequency, and the manner of frequency change within the transmission pulse width to suppress interference, DDL6 and DDL17 correspond to the changed pulse width. In addition to the characteristic, the gate width of the gate generator 10 is adjusted to the changed pulse width.

Hereinafter, in a certain frequency band in which the width from the lower limit frequency to the upper limit frequency is 14 MHz, the transmission pulse width is 1
The result of the interference suppression simulation when the interference signal having the same frequency band and the same frequency change pattern and only the pulse width of 90 μs is input to the 00 μs FM pulse radar apparatus is shown.

FIG. 4 is a diagram showing the non-linear chirp of the FM transmission pulse. The horizontal width of -5 to 5 corresponds to a pulse width of 100 μs, and the vertical axis of -7 to 7 corresponds to the lower limit frequency to the upper limit frequency. And its width is 14 MHz. That is, within one transmission pulse width having a width of 100 μs, the frequency changes with time as shown by the curve in FIG.

FIG. 5 is a waveform diagram in the case where compression is performed in conformity with the 100 μs nonlinear chirp of FIG. 4, and corresponds to the waveform observed at the output point of the compressor 25 of FIG. The horizontal axis is
The distance corresponds to 0 to 2 and corresponds to 200 μs. The vertical axis represents the output level in dB.

On the other hand, as a pseudo interference wave, an FM pulse wave obtained by proportionally compressing the non-linear chirp of FIG. 4 to a pulse width of 90 μs is received, and a compressor 25 (adapted to the non-linear chirp of 100 μs is used. FIG. 6 shows a simulated output in the case of compression in FIG. 1).

FIG. 7 shows the output waveform of FIG. 7 superimposed on the output waveform of FIG. 5 and the output waveform of FIG. According to this, the output of the FM pulse wave whose pulse width is compressed to 90 μs is suppressed by about 20 dB in the output level after compression even if the lower limit frequency, the upper limit frequency, and the pattern of the frequency change are the same. It can be said that practically, the function of interference suppression or interference cancellation can be sufficiently achieved.

[0030]

As described above, as described above, F
The M pulse radar device group has different pulse widths in the respective radar devices, so that even if the lower limit frequency, the upper limit frequency, and the frequency change pattern of the transmitted FM pulse are the same, the time change rate of the frequency is different. Even if the transmission wave of the device is received, it does not match the characteristics of the compressor. At the output of the compressor, the degree of suppression is greater than the target reflected signal due to the transmission pulse of the device itself. There is an advantage of having.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an FM pulse radar apparatus to which the present invention can be applied and which has a variable pulse width by digital processing.

FIG. 2 is a block diagram showing a configuration of an FM pulse radar device using DDL to which the present invention can be applied.

FIG. 3 is a diagram illustrating a frequency modulation state when only a pulse width is changed without changing a lower limit frequency, an upper limit frequency, and a frequency change pattern.

FIG. 4 is a graph showing a non-linear chirp of an FM transmission pulse.

FIG. 5 is a waveform diagram when compression is performed in conformity with the non-linear chirp in FIG. 4 and is a waveform diagram observed at an output point of the compressor 25 in FIG. 1;

FIG. 6 shows an output when a non-linear FM pulse in which the pulse width of the non-linear chirp shown in FIG. 4 is proportionally compressed to 90 μs is received and compressed by a compressor 25 (FIG. 1) adapted to the non-linear chirp of 100 μs; FIG. 7 is an output waveform diagram simulating the above.

FIG. 7 shows the waveform diagram of FIG. 5 superimposed on the waveform diagram of FIG. 6,
FIG. 11 is a waveform diagram that makes it easy to understand the suppression degree of a 90 μs FM pulse.

[Explanation of symbols]

 1 COHO 2 Divider 3 Trigger Generator 4 Pulse Generator 5 Mixer 6 DDL 7 Waveform Shaper 8 Divider 9 Trigger Generator 10 Gate Generator 11 Transmitter 12 Stabilized Oscillator 13 Transmission / Reception Switch 14 Antenna 15 Receiver Reference Signs List 16 IF amplifier 17 DDL 18 IF amplification detector 19 Display 20 Pulse length adjuster 21 Waveform memory 22 D / A converter 23 Trigger generator 24 A / D converter 25 Compressor

Claims (1)

[Claims] When a plurality of frequency-modulated (FM) pulse radar devices are unilaterally or mutually present in an area where a transmission radio wave of another FM pulse radar device is received at an intensity higher than a minimum reception level, A group of FM pulse radar devices, characterized in that interference in a radar output caused by receiving a transmission radio wave of another FM pulse radar device is suppressed by a difference in transmission / reception pulse width between a plurality of FM pulse radar devices.