JPH05281344A - Unnecessary signal suppressing radar equipment - Google Patents

Abstract

PURPOSE:To enable the title radar equipment to change its transmaitting frequency without losing its moving target detecting function by vibrating local signals from which transmitting signals are generated in an appropriate cycle after modulation the signals by using a modulate signal and averaging received signals after demodulation. CONSTITUTION:Local signals from a local transmitter 23 are supplied to a local signal modulator 27 at which the signals are modulated by using a modulate signal from a modulate signal generator 28. The modulated local signals are supplied to an amplitude modulator 29 at which they are subjected to amplitude modulation by means of local signals from another local transmitter 21 and radiated through a transmission- reception antenna 12 as transmitting RF signals after they are subjected to pulse modulation 25. The reflected waves of the RF signals from a fixed or moving target are received by the antenna 12 and sent to a receiving section 3. The received RF signals are subjected to phase detection at a phase detector 34 by using the local signals after they are subjected to frequency conversion by the local signals and amplitude detection at an amplitude demodulator 36. Video signals containing interference components are averaged by means of an unnecessary-signal suppresser 37 which averages the signals by integrating the signals with respect to time and displayed on a moving target display device 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of rapidly changing the transmission frequency without losing the function of the moving target display device and suppressing unnecessary signals having a function of removing unnecessary signals due to reflection from a stationary target. The present invention relates to a radar device.

[0002]

2. Description of the Related Art As is well known, as shown in FIG. 5, an unnecessary signal suppressing radar device comprises an antenna unit 1, a transmitting unit 2, a receiving unit 3 and a moving target display device 4.

First, in the transmitter 2, the second local signal (frequency f0) generated by the second local oscillator 21 is mixed with the first local signal (frequency fx) generated by the first local oscillator 23 in the mixer 22. Then, the frequency is converted, and unnecessary frequency components are removed by the frequency filter 24 to form a transmission RF signal. The transmission RF signal is pulsed by the pulse modulator 25, amplified by the high power amplifier 26, and sent to the antenna unit 1.

In the antenna section 1, a transmission RF signal from the transmission section 2 is transmitted via the transmission / reception switch 11 to the transmission / reception antenna 1
2 and is radiated as a transmitted wave. When the transmitted wave is reflected by various fixed or moving targets, the reflected wave is received by the transmission / reception antenna 12 and is sent to the receiving unit 3 via the transmission / reception switch 11 as a received RF signal.

In the receiving section 3, the RF signal received from the antenna section 1 is amplified by the low noise amplifier 31, and then the mixer 32 produces a first local signal (frequency) coherent with the transmission system generated by the first local oscillator 23. fx),
It is converted to an intermediate frequency and becomes a reception IF signal. The received IF signal is amplified by the intermediate frequency amplifier 33 and then amplified by the second local oscillator 21 to generate a second coherent signal with the transmission system.
Phase detection is performed based on the local signal. This phase detection signal is converted into a digital signal by an A / D (analog / digital) converter 35 and sent to the moving target display device 4.

In the moving target display device 4, the digital signal from the receiver 3 is input, and the signal component whose phase changes with time is extracted by digital signal processing. This component is the Doppler frequency component due to the moving target.
Then, the position of the moving target is appropriately displayed together with other radar information.

As described above, in the conventional unnecessary signal suppressing radar device, the frequency shift component changed by the moving target is extracted for each transmission pulse on the basis of the transmission frequency. That is, in order to detect a moving target, the moving target display device 4 detects the Doppler frequency based on the transmission frequency, and therefore the frequency of the transmission signal is constant.

However, when the transmission signal has a constant frequency, it is easy to detect the radar radio wave, and the radio wave is easily disturbed particularly in the electronic warfare. Therefore, it is strongly desired to be able to change the transmission frequency at high speed in response to radio wave interference and the like.

[0009]

As described above, in the conventional unnecessary signal suppression radar device, if the transmission frequency is changed in response to the radio wave interference or the like, the Doppler frequency corresponding to the moving target cannot be detected, There is a problem that the moving target cannot be detected and displayed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an unnecessary signal suppressing radar device capable of changing the transmission frequency at high speed without losing the function of detecting a moving target.

[0011]

In order to achieve the above object, the present invention is a coherent sine wave signal, and local signal generating means for generating first and second local signals having different frequencies, and A local signal modulating means for generating a modulation signal having a frequency different from that of the first and second local signals, and modulating one of the first and second local signals by using this signal, and the modulation means. The transmitted signal modulating means for modulating one side with the other by using the generated local signal and the unmodulated local signal, the transmitting / receiving means for repeatedly transmitting the output signal of the modulating means, and the reflected signal, and the transmitting / receiving means. The demodulation means for performing demodulation corresponding to the modulation system of the transmission signal modulation means on the obtained reception signal, and the reception signal passed through the demodulation means are time-integrated and averaged. Unnecessary signal suppressing means for suppressing an unnecessary signal by means of, a shift component detecting means for detecting a frequency component shifted by the moving target from the signal obtained by this means, and a moving target based on the detection output of this means. And a display means for displaying.

[0012]

In the radar apparatus for suppressing unnecessary signals having the above structure,
A local signal that is generating a transmission signal is modulated with a modulation signal to vibrate at an appropriate period, a reception signal is demodulated, a video signal containing an interference wave component is taken out, and time-integrated to perform averaging processing. Thereby weakens the interference wave component with respect to the signal component and obtains the frequency component of the moving target that does not depend on the local signal.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. However, in FIG. 1, the same parts as those in FIG. 5 are denoted by the same reference numerals.

FIG. 1 shows the structure of an unnecessary signal suppressing radar device according to the present invention. First, in the transmission unit 2, the first local signal generated by the first local oscillator 23 is supplied to the local signal modulator 27, and is modulated (for example, a sine wave) by the modulation signal generated by the modulation signal generator 28 (for example, sine wave). Phase modulation). The first local signal modulated here is supplied to the amplitude modulator 29, amplitude-modulated by the second local signal generated by the second local oscillator 21, and becomes a transmission RF signal. The transmission RF signal is supplied to the pulse modulator 25, pulsed, amplified by the high-power amplifier 26, and sent to the antenna unit 1.

In the antenna section 1, the transmission RF signal from the transmission section 2 is transmitted via the transmission / reception switch 11 to the transmission / reception antenna 1
2 and is radiated as a transmitted wave. When the transmitted wave is reflected by various fixed or moving targets, the reflected wave is received by the transmission / reception antenna 12 and is sent to the receiving unit 3 via the transmission / reception switch 11 as a received RF signal.

In the receiving section 3, the RF signal received from the antenna section 1 is amplified by the low noise amplifier 31, and then the first local signal (frequency) which is coherent with the transmission system generated by the first local oscillator 23 by the mixer 32. fx),
It is converted to an intermediate frequency and becomes a reception IF signal. The received IF signal is amplified by the intermediate frequency amplifier 33 and then supplied to the amplitude demodulator 36 for amplitude detection.

This amplitude detection output is the second local signal (frequency f0) coherent with the transmission system in the phase detector 34.
The phase is detected by. This phase detection signal is converted into a digital signal by the A / D converter 35, and the unnecessary signal suppressor 37
Is supplied to. The unnecessary signal suppressor 37 is a kind of transversal filter, and is specifically configured as shown in FIG.

That is, the unnecessary signal suppressor 37 is
The phase detection signal digitized by the / D converter 35 is sequentially passed through the delay elements 3711 to 371n-1 and delayed within a time shorter than the transmission pulse width. Then, each delay element 3
The outputs of 711 to 371n-1 are multiplied by the multipliers 3721 to 372.
Then, the weights W1 to Wn are multiplied and added by the adder 373. In other words, the input phase detection signal is subjected to data sampling within a time shorter than the transmission pulse width, given a delay time, multiplied by a weight, and then added together to perform an averaging process. The output is sent to the moving target display device 4.

In the moving target display device 4, the digital signal from the receiver 3 is input and the signal component whose phase is temporally changed is extracted by digital signal processing. This component is the Doppler frequency component due to the moving target.
Then, the position of the moving target is appropriately displayed together with other radar information.

The first local oscillator 23 is specifically constructed as shown in FIG. That is, the oscillator 23 includes a plurality of (here, m) local signal generating circuits 2311 to 231m, and each of the circuits 2311 to 231m.
Signals of mutually different frequencies are generated at 31 m, the signal switch 232 is appropriately switched and controlled, and an arbitrary frequency signal is selectively output to obtain the first local signal whose frequency is arbitrarily changed. The operation of the above configuration will be described below.

First, in the transmission system, the amplitude modulator 29 transmits the first local signal as a carrier wave and the second local signal as a modulated wave. The transmitted wave at this time is expressed by Eq. (1).

Tx (t) = A (t) ・ cos (2πf0 ・ t) ・ exp {(j2πfx ・ φ (t)} (1) where Tx (t); transmission signal, A (t); pulse Modulation function, fx: frequency of first local signal (carrier wave), f0: frequency of second local signal (modulation wave), φ (t); local signal phase modulation function.

With respect to this transmission wave, a reflection signal reflected by a fixed or moving target is received as a reception RF signal. The received RF signal is composed of signal components of reflected waves from each target and interference wave components due to mutual interference of these reflected waves. These signal components and interference wave components depend on the transmission frequency. The received wave at this time is shown in Eq. (2). Rx (t) = A (t-ta) ・ Pa ・ cos {2πf0 ・ (t-ta)} ・ exp [j {2π {fx ・ (t-ta) + φ (t-ta)}] + A ( t-tb) ・ Pb ・ cos {2πf0 ・ (t-tb)} ・ exp [j {2π {fx ・ (t-tb) + φ (t-tb)}]… (2) However, Rx (t) Received signal, Pa, Pb; received intensity of reflected signal of target A, target B, ta: signal delay time for target A, tb: signal delay time for target B,

In the receiving system, the received RF signal is frequency-converted by the first local signal that is coherent with the transmitting system, amplitude detected by the amplitude demodulator 36, and then phase detected by the second local signal by the phase detector 34. The video signal components at this time are as shown in Eqs. (3) and (4). S (t) = | Rx (t) ・ exp {j (-2πfx ・ t)} ｜ ² ・ [Exp {j (-2πf0 ・ t)}] ² = [A (t-ta) ・ Pa ・ cos (-2πf0 ・ ta)] ² + [A (t-tb) ・ Pb ・ cos (-2πf0 ・ tb)] ² + C (t, fx) (3) where C (t, fx) = A (t-ta) ・ A (t-tb) ・ Pa ・ Pb ・ cos {2πf0 ・ ta)} ・ cos {2πf0・ Tb)} ・ cos {2πfx ・ (tb-ta) + φ (t-ta) -φ (t-tb)} (4) where S (t); video signal, C (t, fx); The interference wave components of the target A and the target B are:

The first term and the second term of the equation (3) are signal components relating to the target A and the target B, respectively, and the third term is the interference wave component. The first and second terms are not related to the frequency fx of the first local signal, and the frequency shift effect on fx itself is removed. However, the video signal has an interference wave component depending on fx, as shown in equation (4).

Therefore, the frequency component of the first local signal is not completely erased as it is, and when the frequency of the first local signal is changed for each pulse, the interference wave component fluctuates and the video signal also fluctuates. To do. Therefore,
Even if this signal is input to the moving target display device 4, the target cannot be detected sufficiently.

By the way, it can be approximated that the signal delay times ta and tb are constant in a very short time interval (within one pulse). Therefore, in Eq. (4), only the cosine function term cos {2πfx ・ (tb-ta) + φ (t-ta) -φ (t-tb)} including the local signal phase modulation function φ changes with time within ± 1. To do.

Therefore, in the transmission system, for example, the modulation method of the local signal modulator 27 is phase modulation, and the first local signal is vibrated at an appropriate cycle with the modulation function φ as a vibration function such as a sine wave. As a result, in Eq. (4), the cosine function term oscillates.

Then, in the receiving system, the video signal containing the interference wave component is input to the unnecessary signal suppressor 37, and averaged within the pulse (time integration by giving delay time and adding). As a result, the interference wave component represented by equation (4) is weakened with respect to the signal components of the first and second terms of equation (3).

Therefore, according to the above configuration, since the frequency component due to the moving target that does not depend on the first local signal is obtained, the oscillation frequency of the first local oscillator 23 is changed for each transmission pulse in response to the radio interference. Even in this case, the movement target indicating device 4 can be made to function accurately.

FIG. 4 shows another embodiment according to the present invention. In the transmitter 2, the second local signal generated by the second local oscillator 21 is supplied to the local signal modulator 27 to generate a modulated signal. The modulation signal (eg, sine wave) generated by the modulator 28 is modulated (eg, phase modulated), and the amplitude modulator 29 amplitude-modulates the first local signal generated by the first local oscillator 23. To do.

That is, in this embodiment, as is apparent from comparison with FIG. 1, the second local signal is vibrated instead of the first local signal, and its operation and effect are as shown in FIG. This is exactly the same as the example.

In each of the above-described embodiments, the case of the phase modulation system as the local signal modulation system has been described.
The modulation method is not limited to this method, and a modulation method using any of frequency, phase, and amplitude, or a combination thereof can be used, and the modulation method and demodulation method may be appropriately changed.

Further, the amplitude modulation method and the amplitude detection method corresponding thereto have been described as the modulation methods of the transmission wave.
The present invention is not limited to this method, and any one of frequency, phase, amplitude, or a combination thereof, or a modulation method using a function such as up-chirp or down-chirp and a demodulation method corresponding thereto can also be used. It is more effective to change the value as appropriate. At this time, if necessary, the first local oscillator 2 may be used for demodulating the received signal.
The output signal of 3 may be used.

Further, although the case where the unnecessary signal suppressor 37 is formed by digital arithmetic processing is shown, the same arithmetic processing can be performed by an analog signal. Moreover, the CW is not limited to the case where the transmission signal is pulse-modulated and output.
The same can be realized when transmitting with (continuous wave). Needless to say, the present invention can be similarly implemented even if various modifications are made without departing from the scope of the present invention.

[0036]

As described above, according to the present invention, it is possible to provide an unnecessary signal suppressing radar device capable of changing the transmission frequency at high speed without losing the function of detecting a moving target.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an unnecessary signal suppressing radar device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of an unnecessary signal suppressor of the same embodiment.

FIG. 3 is a block diagram showing a specific configuration of a first local oscillator of the same embodiment.

FIG. 4 is a block diagram showing another embodiment according to the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional unnecessary signal suppression radar device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Antenna part, 11 ... Transmission / reception switcher, 12 ... Transmission / reception antenna, 2 ... Transmission part, 21 ... 2nd local oscillator, 22 ... Mixer, 23 ... 1st local oscillator, 2311-231m ... Local signal generation circuit, 232 ... Signal switcher, 24 ... Frequency filter, 25 ... Pulse modulator, 26 ... High output amplifier,
27 ... Local signal modulator, 28 ... Modulation signal generator, 2
9 ... Amplitude modulator, 3 ... Receiver, 31 ... Low noise amplifier, 3
2 ... Mixer, 33 ... Intermediate frequency amplifier, 34 ... Phase detector, 35 ... A / D converter, 36 ... Amplitude demodulator, 37 ... Unwanted signal suppressor, 4 ... Moving target display device.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Seiichi Maeda 1-9-2 Fujimachi, Hoya-shi, Tokyo 203 Heimsquae 203 (72) Inventor Tsutomu Watanabe 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock company Inside the Toshiba Komukai Plant (72) Inventor Mitsuyoshi Shinonaga 1 Komukai Toshiba-cho, Komu-ku, Kawasaki-shi, Kanagawa Stock Company Toshiba Komukai Plant

Claims (6)

[Claims] 1. A local signal generating means which is a coherent sine wave signal and generates first and second local signals having different frequencies, and a modulation signal having a frequency different from those of the first and second local signals. And local signal modulating means for modulating either one of the first and second local signals using this signal, and one using the local signal modulated by this means and the unmodulated local signal. On the other hand, the transmission signal modulating means, the transmitting / receiving means for repeatedly transmitting the output signal of the modulating means and receiving the reflected signal, and the modulation of the transmitting signal modulating means with respect to the received signal obtained by the transmitting / receiving means. Demodulation means for performing demodulation corresponding to the system, and unnecessary signal suppression means for suppressing unnecessary signals by time-integrating and averaging the received signals that have passed through this demodulation means, and Unwanted signal suppression comprising: a shift component detecting means for detecting a frequency component shifted by the moving target from the signal obtained by the means; and a display means for displaying the moving target based on the detection output of the means. Radar equipment. 2. The unnecessary signal suppressing radar apparatus according to claim 1, wherein the local signal modulating means generates a sine wave signal as a modulation signal. 3. The local signal modulating means generates a modulated signal based on a specific function.
The unnecessary signal suppression radar device described. 4. The unnecessary signal suppressing radar device according to claim 1, wherein the local signal modulating means arbitrarily switches a plurality of modulation systems. 5. The local signal generating means comprises frequency changing means for changing the frequency of either one of the first local signal and the second local signal in units of a transmission repetition period. The unnecessary signal suppression radar device according to item 1. 6. The transmission signal modulating means uses a plurality of modulation systems by arbitrarily switching them, and the first demodulating means selects a demodulation system of a reception signal corresponding to the switching of the modulation systems of the transmission signal modulating means. The unwanted signal suppression radar device according to claim 1, wherein the radar device is switched.