JP2566090B2 - MTI radar device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MTI radar device capable of changing the transmission frequency at high speed without losing the function of a moving target display device and having a function of removing an unnecessary signal due to reflection from a stationary target. Regarding

[0002]

2. Description of the Related Art As is well known, an MTI radar device, as shown in FIG. 13, has an antenna section 1, a transmitting section 2 and a receiving section 3.
And a moving target display device 4.

First, in a transmitter 2, a second local signal (frequency f0) generated by a second local oscillator 21 is mixed with a first local signal (frequency fx) generated by a first local oscillator 23 by a mixer 22. Then, the frequency is converted, and unnecessary frequency components are further removed by the frequency filter 24 to be 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 unit 1, the transmission RF signal from the transmission unit 2 is transmitted via a transmission / reception switch 11 to the transmission / reception antenna 1.
2 and radiated as a transmission 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 sent as a received RF signal to the receiver 3 via the transmission / reception switch 11.

[0005] In the receiving unit 3, the RF signal received from the antenna unit 1 is amplified by a low noise amplifier 31, and then a first local signal (frequency) coherent with a transmission system generated by a first local oscillator 23 by a mixer 32. fx)
The signal is converted into an intermediate frequency and becomes a reception IF signal. The received IF signal is amplified by the intermediate frequency amplifier 33, and then coherently transmitted to the transmission system generated by the second local oscillator 21.
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.

[0006] The moving target display device 4 receives a digital signal from the receiving section 3 and extracts a signal component whose phase changes with time by digital signal processing. This component is a Doppler frequency component due to the moving target.
In this example, the position of the moving target is displayed as appropriate in combination with other radar information.

As described above, in the conventional MTI radar device, the frequency shift component changed by the moving target is extracted for each transmission pulse with reference to the transmission frequency. That is, in order to detect the moving target, the moving target display device 4
Since the Doppler frequency is detected based on the transmission frequency by, 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 jammed, especially during the electronic warfare. Therefore, it is strongly desired that the transmission frequency can be changed at a high speed in response to radio wave interference or the like.

[0009]

As described above, in the conventional MTI radar device, if the transmission frequency is changed in response to radio wave interference or the like, the Doppler frequency corresponding to the moving target cannot be detected, and the moving object is not detected. There was a problem that the mark could not 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 MTI radar device capable of changing the transmission frequency at high speed without losing the function of detecting a moving target.

[0011]

MTI radar device according to the present invention in order to achieve the above object In order to achieve the above, are each coherency <br/> rent sine wave, a first different frequencies, a second local signal Occurs and either one of the local
Signal frequency is fixed and the frequency of the other local signal is
Within the transmission repetition period, local signal generating means for changing the unit of the transmission repetition period and the second local signal are distributed to a plurality of systems and given different modulation function characteristics .
To generate a sub-pulse signal train by time-division output to
A blanking pulse signal train generating means, Sa output from the unit
Sub amplitude modulating means, the output signal of the amplitude modulating means for amplitude modulating said first local signal in blanking pulse signal train
It is pulsed for each pulse and repeatedly transmitted at the transmission repetition cycle.
The transmitting means for receiving and the pulse signal transmitted by this means
The reflected signal is based on the local signal whose frequency is changed.
A receiving means for receiving have, given by distributing the received signal obtained by the receiving means into a plurality of systems at the time of transmission to each signal
Weighted addition means for removing a reflection signal component from a stationary target by demodulating by giving characteristics opposite to the obtained modulation function characteristics , and delaying and adding at the same timing, and Amplitude the signal obtained by means
After demodulation, phase detection is performed with the frequency fixed local signal.
By doing so, the shift component detection means for detecting the frequency component shifted by the moving target due to the frequency-fixed local signal, and the moving target is displayed based on the detection output of this means. That the display means for
It is a feature of. In addition, with each coherent sine wave
Yes, first and second local signals of different frequencies
Generate and fix the frequency of either local signal
And the frequency of the other local signal
Local signal generating means for changing in units, and the second
Local signal is distributed to multiple systems and within the transmission repetition cycle
To generate a sub-pulse signal train by time-division output to
B pulse signal train generation means and the server output from this means.
Amplitude-modulate the first local signal with a pulse train
The amplitude modulation means and the output signal of this amplitude modulation means
After pulsing every pulse, make different polarization
Transmitting means for repeatedly transmitting at the transmission repetition period, and
The reflected signal of the pulse signal transmitted by
Receiving based on a local signal whose frequency is changed
And a receiving means within the transmission repetition cycle.
The timing of each received signal obtained in
Fixed so that it does not move by delaying and adding
Weighted addition means for removing the reflection signal component from the target
After amplitude demodulating the signal obtained by this means,
By performing phase detection with a local signal with a fixed wave number,
Deviation due to moving target due to local signal with fixed wave number
A deviation component detecting means for detecting the frequency component
Display means for displaying a moving target based on the detection output of the means
The second feature is that the structure is provided with.

[0012]

The MTI radar according to the first characteristic construction
In the equipment, one frequency is fixed and the other frequency is fixed.
Generate first and second local signals whose wave numbers are changed,
Within the transmission repetition period, the second local signal
Generate a sub-pulse signal train with the modulation function characteristics
Amplitude modulation of the first local signal with the sub-pulse signal train of
Then pulsed and sent repeatedly
The local signal whose frequency is changed from the reflected signal of the pulse signal
Signal, and distribute it to multiple systems for each signal.
The characteristics opposite to the modulation function characteristics given at the time of transmission are given.
Demodulate and delay so that the timing is the same.
Reflection signal from fixed target that does not move by adding
After removing the components and demodulating the amplitude further, the fixed frequency
By detecting the phase with the local signal,
Frequency shifted by the moving target due to the local signal
Detects components and displays moving target based on the detection results
I am trying to do it. In addition, the second characteristic configuration
In the MTI radar device according to
First and second rows that are fixed and whose other frequency is changed
Cull signal is generated and each second
Generate a sub-pulse signal train from local signals and
Amplitude-modulates the first local signal with a pulse train,
And transmit repeatedly with different polarization for each subpulse.
The reflected signal of the transmitted pulse signal for each polarization.
Each received based on a local signal whose frequency is changed
Add the received signals with delay so that they have the same timing
Reflected signal component from a fixed target that does not move by moving
After removing the
The frequency fixed local signal can be detected by performing phase detection on the local signal.
Frequency component shifted by moving target caused by mobile signal
Detected and display the moving target based on the detection result
Like that.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the basic configuration of the MTI radar device according to the present invention, which includes the antenna section 1, the transmitting section 2,
In addition to the receiving unit 3 and the moving target display device 4, a control unit 5 is further provided.

First, in the transmitter 2, the second local signal (frequency f0) generated by the second local oscillator 21 is supplied to the sub-pulse former 27. The sub-pulse shaper 27 distributes the input second local signal to a plurality of systems and linearly frequency-modulates it with different modulation functions such as up-chirp and down-chirp to form a plurality of pulse signal trains. After giving a predetermined delay time so as to have the same phase, the signals are time-division output. The pulse signal train generated by the sub-pulse generator 27 is the amplitude modulator 2
8 is supplied.

The amplitude modulator 28 includes a first local oscillator 23.
The first local signal (frequency fx) generated in 1 is input as a carrier wave, and the carrier wave is amplitude-modulated by the pulse signal train from the sub-pulse former 27 to generate 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 unit 1, the transmission RF signal from the transmission unit 2 is transmitted to the transmission / reception antenna 1 via the transmission / reception switch 11.
2 and radiated as a transmission 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 sent as a received RF signal to the receiver 3 via the transmission / reception switch 11.

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) coherent with the transmission system generated by the first local oscillator 23 by the mixer 32. fx),
The signal is converted into an intermediate frequency and becomes a reception IF signal. The received IF signal is amplified by the intermediate frequency amplifier 33 and then MTI.
It is supplied to the processor 36.

This MTI processor 36 receives the received reception IF
The signal is separated for each received signal corresponding to each transmission pulse that is time-divided at the time of transmission, and the time-divided signal is subjected to subtraction processing according to the same time. The output of the MTI processor 36 is supplied to the amplitude demodulator 37 for amplitude detection and then phase detected by the phase detector 34 by the second local signal (frequency f0) coherent with the transmission system. This phase detection signal is converted into a digital signal by the A / D converter 35,
It 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 a Doppler frequency component due to the moving target.
Then, the position of the moving target is appropriately displayed together with other radar information.

First when changing the frequency of the transmitter 2
The frequency control of the local oscillator 21, the delay time control of the sub pulse former 27, the pulse timing control of the pulse modulator 25, and the delay time control of the MTI processor 36 of the receiving unit 3 are
It is performed by the control unit 5.

2 and 3 show specific configurations of the sub-pulse former 27 and the MTI processor 36, which are essential parts of the present invention, respectively.

That is, in the sub pulse former 27, as shown in FIG. 2, the second local signal from the second local oscillator 21 is divided into n systems by the signal divider 271. The n-system second local signals are supplied to frequency modulators 2721 to 272n having different modulation functions, and are linearly frequency-modulated. The modulated signals of each system are given a predetermined delay time by delay elements 2731 to 273n to have their phases aligned, and are sequentially switched out by a signal switch 274 to be a time division pulse signal train.

The above-mentioned modulation function is arbitrary, and examples thereof include up-chirp (linear frequency modulation pulse whose frequency increases with time) and down-chirp (linear frequency modulation pulse whose frequency decreases with time). The frequency vs. time characteristics of each chirp are shown in FIGS. In this case, two lines are enough. The delay time of each of the delay elements 2731 to 273n and the signal switching timing of the signal switch 274 are controlled for each transmission pulse repetition period (PRI).

Further, in the MTI processor 36, as shown in FIG. 3, the reception IF signal from the intermediate frequency amplifier 33 is distributed to the n systems by the signal distributor 361. The received IF signals of the n systems are respectively frequency demodulators 3621 to 362.
n. These demodulators 3621 to 362n are distributed delay lines having demodulation functions corresponding to the modulation functions of the frequency modulators 2721 to 272n of the transmission system, and pulse-compress the input reception IF signal. When the modulation function of the transmission system is up-chirp or down-chirp having the characteristics shown in FIGS. 4 and 5, the demodulation function of the reception system is shown in FIGS.
The characteristics are shown in.

The compressed pulse signals obtained by the demodulators 3621 to 362n are delayed by delay elements 3631 to 363n, and the weights W1 to
Wn is multiplied and addition processing is performed by the adder 365.

The first local oscillator 23 is specifically constructed as shown in FIG. That is, the oscillator 23 includes a plurality of (here, m) local oscillator signal generation circuits 2311 to 231m, and each of the circuits 2311 to 23m.
To generate signals of different frequencies, and the signal switch 2
By appropriately controlling switching of 32 according to a control signal from the control unit 5 and selectively outputting an arbitrary frequency signal, the first local signal whose frequency is arbitrarily changed is obtained.

The operation of the above configuration will be described below.

First, as shown in FIG. 9, the transmission signal radiates n pulse trains at the same frequency and at equal intervals within a repetition period. The second local signal component (modulation signal component of frequency f0) for each pulse train within the repetition period is controlled to have the same phase. That is, the modulation signal component of the amplitude-modulated transmission signal is controlled so as to have the same phase within the pulse of each pulse train. Further, the carrier frequency and the time interval of the pulse train are switched for each repetition period. FIG.
, Fx1 and fx2 are different, and dt1 and dt2 are different.

Here, an example will be described in which up-chirp and down-chirp are used for the modulation function and two transmission pulse signals are radiated within the repetition period.

First, in the transmission system, one transmission pulse signal is an up-chirp having the characteristic shown in FIG. 4, and the other transmission pulse signal is a down-chirp having the characteristic shown in FIG.
Send in time division within the repetition period.

In this case, in the receiving system, the received signal is first set to 2
To divide. Each divided reception signal is a composite signal of a reflection signal component corresponding to the up-chirp transmission pulse signal and a reflection signal component corresponding to the down-chirp transmission pulse signal. Then, by demodulating one of the received signals with the characteristic shown in FIG. 6, a compressed pulse of only the reflected signal component corresponding to the up-chirp transmission pulse signal is formed, and the other received signal is shown in FIG. By performing the demodulation processing with the above characteristic, the compressed pulse of only the reflected signal component corresponding to the down-chirp transmission pulse signal is formed. This separates the two signal components.

Specifically, the transmission wave in the transmission system is (1)
It is shown like the formula. Tx (t) = A (t) ・ cos (2πf0 ・ t) ・ exp (j2πfx ・ t) + A (t-dt) ・ cos {2πf0 ・ (t-dt)} ・ exp (j2πfx ・ t)… ( 1) where Tx (t) is the transmission signal, A (t) is the pulse modulation function, dt is the pulse delay time, fx is the frequency of the first local signal, and f0 is the frequency of the second local signal.

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 wave at this time is shown in Eqs. (2) to (6). Rx (t) = Rx1 (t) + Rx2 (t)… (2) Rx1 (t) = A (t-ta) ・ Pa ・ cos {2πf0 ・ (t-ta) + f0a ・ t} ・ exp [j2π {fx ・ (t-ta) + fxa ・ t}] + A (t-tb) ・ Pb ・ cos {2πf0 ・ (t-tb)} ・ exp {j2πfx ・ (t-tb)… (3) Rx2 ( t) = A (t-dt-ta ') ・ Pa ・ cos {2πf0 ・ (t-dt-ta') + f0a ・ (t-dt)} ・ exp [j2π {fx ・ (t-dt-ta ' ) + fxa ・ (t-dt)}] + A (t-dt-tb) ・ Pb ・ cos {2πf0 ・ (t-dt-tb)} ・ exp {j2πfx ・ (t-dt-tb)… (4 ) ta = 2Ra / c, ta '= 2 (Ra-v ・ dt) / c, tb = 2Rb / c… (5) f0a = (2v / c) ・ f0, fxa = (2v / c) ・ fx… (6) where Rx (t); received signal, Rx1 (t); received signal corresponding to the first pulse signal, Rx2 (t); received signal corresponding to the second pulse signal, Pa, Pb; target A And the reception intensity of the reflected signal of the target B, fxa; the Doppler frequency at the frequency fx, f0a; the Doppler frequency at the frequency f0, ta; the signal delay time of the first pulse of the target A, ta '; the target of the second pulse Signal delay time due to A, tb; first and second pulsed objects Signal delay time by B, c; is the speed of light.

When the received signal is mixed with the first local signal and converted into the intermediate frequency, the equations (7) to (9) are obtained. IF (t) = Rx1 (t) ・ exp (-j2πfx ・ t) + Rx2 (t) ・ exp {-j2πfx ・ (t-dt)} = IF1 (t) + IF2 (t)… (7) IF1 ( t) = A (t-ta) ・ Pa ・ cos {2πf0 ・ (t-ta) + f0a ・ t} ・ exp {j2π (fxa ・ t-fx ・ ta} + A (t-tb) ・ Pb ・ cos {2πf0 ・ (t-tb)} ・ exp (-j2πfx ・ tb)… (8) IF2 (t) = A (t-dt-ta ') ・ Pa ・ cos {2πf0 ・ (t-dt-ta') + f0a ・ (t-dt)} ・ exp [j2π {fxa ・ (t-dt) -fx ・ ta '}] + A (t-dt-tb) ・ Pb ・ cos {2πf0 ・ (t-dt-tb )} ・ Exp (-j2πfx · tb) (9) This received IF signal is separated into the first received IF signal corresponding to the first pulse signal and the second received IF signal corresponding to the second pulse signal by the method described above. Then, the delay time dt is given to the first reception IF signal, and the difference S (t) from the second reception IF signal is obtained as shown in equation (10): S (t) = IF1 (t-dt )-IF2 (t) = A (t-dt-ta) ・ Pa ・ cos {2πf0 ・ (t-dt-ta) + f0a ・ (t-dt)} ・ (exp [j2π {fxa ・ (t-dt ) -fx ・ ta}] -exp [j2π {fxa (t-dt) -fx ・ ta '}]) (10) However, the frequency f0 of the second local signal is the first low. Since the frequency is very small compared with the frequency fx of the cull signal and the signal delay time difference between the first pulse signal and the second pulse signal of the target A is small, the approximate expression of the equation (11) can be used. = f0 · ta '(11) From equation (10), the received signal component (clutter component) of the fixed target B is removed, and the frequency f of the first local signal is
When x is changed, the difference signal component fluctuates, but also in this case, the clutter component can be removed, as is apparent from the equation (10).

Next, when the difference signal is amplitude-detected and time-corrected, it becomes as shown in equation (12).

X (t) = | S (t + dt) | ² = A (t-ta) ² · Pa ² · cos ² {2πf0 · (t-ta) + f0a · t} · [Real (t) ² + Imag (t) ² ] = 4 ・ A (t-ta) ²・ Pa ²・ cos ² {2πf0 ・ (t-ta) + f0a ・ t} ・ sin ² {2πfx (ta'-ta)} = 4 ・ A (t-ta) ²・ Pa ²・ cos ² {2πf0 ・ (t-ta) + f0a ・ t} ・ sin ² {4πfx ・ v ・ dt ・ fx / c) = 2 ・ cons ・ cos ² { 2πf0 ・ (t-ta) + f0a ・ t} = const ・ [1 + cos {4πf0 ・ (t-ta) + f0a ・ t}]… (12) Real (t) = cos {2π (fxa ・ t- fx ・ ta)}-cos {2π (fxa ・ t-fx ・ ta ')} = -2sin [2π {fxa ・ 2t-fx (ta + ta')}] ・ sin {2πfx (ta'-ta)} (13) Imag (t) = sin {2π (fxa ・ t-fx ・ ta)}-sin {2π (fxa ・ t-fx ・ ta ')} = 2 cos [2π {fxa ・ 2t-fx (ta + ta ')}] ・ sin {2πfx (ta'-ta)}… (14) const = 2 ・ A (t-ta) ²・ Pa ²・ sin ² (4πfx ・ v ・ dt / c)… (15 ) Here, assuming that the speed of the target A is constant, if dt and fx are constant, then the const shown in equation (15) becomes constant,
The amplitude detection output is a signal output that does not depend on the frequency fx of the first local signal.

As is clear from the above relational expression, since the frequency shift component due to the moving target that does not depend on the first local signal can be obtained, the first local oscillator 2 can cope with the radio interference.
Even if the oscillation frequency of No. 3 is changed for each transmission pulse, the movement target indicating device 4 can be made to function. Also, (1
As is clear from the equation (2), the phase detection using the second local signal makes it possible to detect the Doppler frequency component corresponding to f0.

Therefore, the MTI radar device having the above-described structure can change the transmission frequency at high speed without losing the function of detecting the moving target, changes the transmission frequency in response to radio wave interference, etc. The moving target can be detected and displayed by detecting the Doppler frequency corresponding to.

By the way, in the above-mentioned embodiment, the method of using different modulation functions is explained as the means for separating the pulse signal train, but there is another method of switching the polarization. The structure is shown in FIG. However, in FIG.
The same parts as those in FIG. 1 are designated by the same reference numerals, and different parts will be described here.

First, in the antenna section 1, the transmission RF signal from the transmission section 2 is supplied to the signal switch 13 and selectively derived to one of the n systems according to the control signal from the control section 5. Transmission / reception switchers 111 to 11n and transmission / reception antennas 121 to 12n are provided in each system. The transmission / reception switchers 111 to 11n are switching-controlled by a control signal from the control unit 5, guide the transmission RF signal from the transmission unit 2 to the antennas 121 to 12n, and the antennas 121 to 12n.
The received RF signal received in step 3 is sent to the receiving section 3. The antennas 121 to 12n have polarization directions different from each other, and for example, vertical polarization and horizontal polarization are used. In this case, two lines are enough.

In the receiving section 3, n from the antenna section 1
The received RF signals of the system are low noise amplifiers 311 to 311 respectively.
1n, mixed with the first local signal from the first local oscillator 23 by the mixers 321 to 32n, converted to an intermediate frequency, further amplified by the intermediate frequency amplifiers 331 to 33n, and supplied to the MTI processor 36. .

The sub-pulse generator 27 of the transmitter 2 and the MTI processor 36 of the receiver 3 are shown in FIG. 11 and FIG. 12, respectively.
It is configured as shown in. That is, as can be seen by comparing with FIG. 2 and FIG. 3, the sub-pulse former 27 in this case is
Directly uses the delay elements 2731 to 2 as the distribution outputs of the signal distributor 271 without using the frequency modulators 2721 to 272n.
73n, and the MTI processor 36 supplies the signal distributor 361.
Also, the reception IF signals of n systems are directly supplied to the delay elements 3631 to 363n without using the frequency demodulators 3621 to 362n.

In the above structure, the characteristic operation, that is, the means for separating the pulse signal train will be described below.

First, in the transmission system, the transmission signal is as shown in FIG.
As shown in, the n pulse trains are radiated at the same frequency and at equal intervals within the repetition period. The second local signal component (modulation signal component of frequency f0) for each pulse train within the repetition period is controlled to have the same phase. That is, the modulation signal components of the amplitude-modulated transmission signal are controlled so as to have the same phase within the pulse of each pulse train. Further, the carrier frequency and the time interval of the pulse train are switched for each repetition period.

Here, the antenna unit 1 is of two systems, and uses vertical polarization and horizontal polarization as polarizations, and 2
A case will be described as an example in which individual transmission pulse signals are radiated.

First, in the transmission system, one transmission pulse signal is a vertically polarized wave and the other transmission pulse signal is a horizontally polarized wave, and the signals are time-divisionally transmitted within a repetition period. Antenna 121
Is for vertical polarization, and the antenna 122 is for horizontal polarization.

A signal transmitted by vertical polarization is reflected from a moving or fixed target. This reflected signal is a combined signal of the vertically polarized component and the horizontally polarized component. However, the amplitude level of the vertically polarized component is considerably larger than that of the horizontally polarized component, and is mainly received by the vertically polarized transmitting / receiving antenna 121.

The signal transmitted in the horizontal polarization is exactly the same as in the case of the vertical polarization, and is reflected from the moving or fixed target. This reflected signal is a composite signal of the vertical polarization component and the horizontal polarization component, but the amplitude level of the horizontal polarization component is considerably larger than that of the vertical polarization component,
It is mainly received by the horizontally polarized transmission / reception antenna 122. Therefore, the two signal components can be separated.

The present invention is not limited to the above-mentioned embodiment, and it is not always necessary to make the time intervals of the pulse trains in the repetition period equal intervals as in the above-mentioned embodiment. That is, it can be applied even when the intervals are not equal.

As a method of separating each pulse train within the repetition period, the case where the modulation function of linear frequency modulation is changed has been described in the above embodiment, but modulation is performed by any of amplitude, phase, frequency or a combination thereof. It can also be applied in cases. It can also be applied to code modulation methods such as coded phase modulation using Barker codes.

Further, as a method of separating each pulse train within the repetition period, the case where the modulation function of the linear frequency modulation is changed is shown in the above embodiment, but it can be applied to the case where right-handed and left-handed circularly polarized waves are used. . Of course, it can be applied to the case where each pulse train is separated by a combination with the case where the modulation function is changed.

Further, in the above embodiment, the case where the pulse signal train within the repetition period is separated by the MTI processor by the analog signal is shown. However, it is digitally converted by the A / D (analog / digital) converter. It can also be applied to a case where signal separation is performed later by a digital signal.

Further, in the above embodiment, the case where the pulse modulator is used to perform the pulse modulation has been described, but the present invention is also applicable to the case where the signal is switched within the repetition period and the signal is transmitted by CW (continuous wave).

In addition to the above, it is needless to say that various modifications can be made without departing from the scope of the present invention.

[0056]

As described above, according to the present invention, it is possible to provide an MTI 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 basic configuration diagram showing an embodiment of an MTI radar device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration of a sub pulse generator of the embodiment.

FIG. 3 is a block diagram showing a specific configuration of the MTI processor of the embodiment.

FIG. 4 is a characteristic diagram showing characteristics of an up-chirp used as a transmission system modulation function in the embodiment.

FIG. 5 is a characteristic diagram showing characteristics of a down chirp used as a transmission system modulation function in the same embodiment.

6 is a characteristic diagram showing characteristics of a demodulation function used in a reception system when the up-chirp of FIG. 4 is used for a modulation function in the embodiment.

7 is a characteristic diagram showing characteristics of a demodulation function used in a reception system when the downchirp of FIG. 5 is used for a modulation function in the embodiment.

FIG. 8 is a block diagram showing a specific configuration of a first local oscillator of the same embodiment.

FIG. 9 is a time chart for explaining a pulse signal time division transmission method of the same embodiment.

FIG. 10 is a block diagram showing a configuration when a method of switching polarization is used as a means for separating a pulse signal train from another embodiment according to the present invention.

FIG. 11 is a block diagram showing a specific configuration of a sub pulse former in the embodiment of FIG.

12 is a block diagram showing a specific configuration of an MTI processor in the embodiment of FIG.

FIG. 13 is a block diagram showing a configuration of a conventional MTI radar device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Antenna part, 11 ... Transmission / reception switcher, 12 ... Transmission / reception antenna, 13 ... Signal switcher, 2 ... Transmission part, 21 ... 2nd local oscillator, 22 ... Mixer, 23 ... 1st local oscillator, 231
1 to 231 m ... Local signal generation circuit, 232 ... Signal switcher, 24 ... Frequency filter, 25 ... Pulse modulator, 26
... High-power amplifier, 27 ... Sub-pulse former, 271 ... Signal distributor, 2721-272n ... Frequency modulator, 273
1-273n ... Delay element, 274 ... Signal switcher, 28 ...
Amplitude modulator, 3 ... Receiving section 31, 31, 311-31n ... Low noise amplifier, 32, 321-32n ... Mixer, 33, 33
1 to 33n ... Intermediate frequency amplifier, 34 ... Phase detector, 35
... A / D converter, 36 ... MTI processor, 361 ... Signal distributor, 3621-362n ... Frequency demodulator, 3631-
363n ... Delay elements, 3164 to 364n ... Multipliers, 3
65 ... Adder, 37 ... Amplitude demodulator, 4 ... Moving target display device, 5 ... Control unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Watanabe 1 Komukai-Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Komukai factory (72) Inventor Mitsuyoshi Shinonaga Komukai-Toshiba, Kawasaki-shi, Kanagawa No. 1 in Toshiba Komukai factory (56) Reference JP-A-49-131393 (JP, A) JP-A-60-24476 (JP, A) JP-A-51-139292 (JP, A) JP-A 61-167891 (JP, A)

Claims (7)

(57) [Claims] 1.RespectivelyA coherent sine wave,
Generates first and second local signals with different frequencies
Then, fix the frequency of either one of the local signals,
The frequency of the other local signal in units of transmission repetition period
changeLocal signal generating means, and2The local signal of is distributed to multiple systems, and
Give different modulation function characteristicsWithin the transmission repetition period
Sub output that generates a sub pulse signal train by dividing outputPa
The loose signal sequence generation means and the output from this meanssubIn the pulse signal train, the first1of
Amplitude modulation means for amplitude modulating the local signal and the output signal of this amplitude modulation meansFor each sub-pulsePulsed
do itA transmission means for repeatedly transmitting at the transmission repetition period, The reflected signal of the pulse signal transmitted by this means is
Recipients receiving based on a local signal whose number is changed
Steps and  thisReceiveThe received signal obtained by the meansDistributing to multiple systems
What is the modulation function characteristic given to each signal during transmission?
Demodulate by giving the opposite characteristics, And the same timing
Fixed target that does not move by delaying and adding
A weighted addition means for removing the reflection signal component fromAfter amplitude demodulation,
The frequency is detected by phase detection with a fixed local signal.
Due to fixed local signalDeviated by moving target
Deviation component detecting means for detecting the frequency component, and a display for displaying the moving target based on the detection output of this means
A MTI radar device comprising: 2. The sub-pulse signal train generating means is characterized in that
Distribution means for distributing the second local signal to a plurality of systems,
The second local signals of multiple channels distributed by this means
Frequency modulation means giving different modulation function characteristics
And of the multiple systems given the modulation function characteristics by this means.
Delay means for delaying two local signals at different times
And a plurality of second local signals delayed by this means.
Signals are switched within the transmission repetition period in ascending order of delay time.
To generate a sub-pulse signal train is time-divided by outputting
And a time-division output unit.
The described MTI radar device. 3. The sub-pulse signal train generating means is characterized in that
The delay time of each system of the delay means is calculated by the local signal generator.
Has a delay time change function that changes according to the frequency change of the stage
The MTI radar device according to claim 2, wherein
Place. 4. The MT according to claim 1, wherein the modulation function is up-chirp or down-chirp.
I radar device. 5.RespectivelyA coherent sine wave,
Generates first and second local signals with different frequencies
Then, fix the frequency of either one of the local signals,
The frequency of the other local signal in units of transmission repetition period
changeLocal signal generating means, and2The local signal of is distributed to multiple systems,The transmission
Sub-pulse signal train by time-division output within the repetition period
To generate a subPulse signal train generating means and output from this meanssubIn the pulse signal train, the first1of
Amplitude modulation means for amplitude modulating the local signal and the output signal of this amplitude modulation meansFor each sub-pulsePulsed
After that, change to different polarizationThe transmission repetition period
And a transmission means for repeatedly transmitting with, The reflected signal of the pulse signal transmitted by this means is used as the polarization component.
It is received based on the local signal whose frequency is changed every time.
Receiving means to trust, That obtained by the receiving means within the transmission repetition period
Receiving each Delay the signals so that they have the same timing
Reflection from a stationary target that does not move by adding
Weighted addition means for removing signal components and the signal obtained by this meansAfter amplitude demodulation,
The frequency is detected by phase detection with a fixed local signal.
Due to fixed local signalDeviated by moving target
Deviation component detecting means for detecting the frequency component, and a display for displaying the moving target based on the detection output of this means
A MTI radar device comprising: 6. The sub-pulse signal train generating means is characterized in that
Distribution means for distributing the second local signal to a plurality of systems,
The second local signal of the distributed plurality of systems in this section
The delay means for delaying and the multiple lines delayed by this means
The transmission of the second local signal is repeated in ascending order of delay time.
Time-divided sub pulse by switching output within the cycle
A time-division output means for generating
The means adjusts the delay time of each system to
6. The MTI radar device according to claim 5 , further comprising a phase adjusting function for aligning the phases of the respective slots. 7. The sub-pulse signal train generating means includes:
According to the frequency change of the local signal generating means, the delay
Has a delay time change function to change the delay time of each stage system
MTI radar apparatus according to claim 6, characterized in that the.