JP2002122660A - Pulse radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse radar device needing only short signal transmission time for one composite band processing even when a relative distance R between the pulse radar device and a target is long. SOLUTION: This pulse radar device is provided with a fixed initial phase frequency synthesizer generating a locally oscillating signal for transmission of a predetermined frequency and an initial phase per pulse repetition period of a positive integral multiple of an inverse number of a predetermined step frequency interval, a frequency calculator determining frequency information of a reception wave using predetermined relative distance information with the target, and a fixed initial phase frequency synthesizer generating a locally oscillating signal for transmission of a frequency corresponding to a frequency of the reception wave in a predetermined phase by using the frequency information of the reception wave determined by the frequency calculator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse radar device for improving a distance resolution by a synthetic band process.

[0002]

The pulse radar apparatus utilizing the Related Art Synthetic band processing, at the time of transmission, as shown in FIG. 5, the frequency step for N pulses, the transmission frequency from f ₀ for each pulse to f _N-1 The transmission is performed by changing the interval Δf. The transmission signal S _n (t) at that time is expressed by Equation 1. However, here, each signal is represented by a complex signal in order to simplify the expression by mathematical expressions.

[0003]

(Equation 1)

[0004] Here, A is the amplitude of the transmission signal, φ _n is the initial phase of each transmission frequency, T _p is the pulse width, and T _pri is the pulse repetition period. When this transmission signal is reflected by a target located at a distance R away from the pulse radar device and received by the pulse radar device, the received signal becomes _Un (t):
It is represented by Equation 2.

[0005]

(Equation 2)

Here, A 'represents the amplitude of the received signal, and c represents the speed of light. When the received signal is subjected to frequency conversion using the reference signal V _n (t) having the same initial phase as that of the transmission signal as shown in Equation 3, the signal W after the frequency conversion is obtained.
_n (t) is expressed by Equation 4.

[0007]

(Equation 3)

[0008]

(Equation 4)

When the inverse Fourier transform is performed using the signal of the pulse-modulated portion of W _n (t) expressed by the equation (4), the signal P (k) after the inverse Fourier transform is expressed by the equation (5). You.

[0010]

(Equation 5)

When linear detection is used as the method of envelope detection, the signal | P (k) |
The absolute value of (k) is represented by Equation 6.

[0012]

(Equation 6)

From equation (6), it can be seen that | P (k) | becomes a peak value when k becomes equal to 2RNΔf / c.
When │P (k) │ is a k to be the peak value and k _p, as shown in Equation 7 from k _p, it is possible to determine the relative distance R between the pulse radar apparatus and the target.

[0014]

(Equation 7)

The distance resolution ΔR is expressed by the following equation (8).

[0016]

(Equation 8)

From equation (8), it can be seen that the distance resolution ΔR can be improved by increasing NΔf.

FIG. R. Wehner
Written, "High-Resolution Rada
r ", Arttech House, pp. 197-23.
7, 1995, by improving the range resolution ΔR and obtaining a range resolution ΔR equal to or smaller than the target size,
It is a conventional pulse radar apparatus for obtaining a target range profile as shown in FIG. In FIG. 6, 1 is a timing generator, 2 is a fixed initial phase frequency synthesizer,
3a and 3b are distributors, 4 is a reference intermediate frequency signal generator,
5a and 5b are frequency converters, 6 is a pulse modulator, 7 is a power amplifier, 8 is a duplexer, 9 is an antenna, 10 is a target, 11 is an intermediate frequency amplifier, 12 is a 90-degree hybrid device, and 13a and 13b are A phase detector, 14a and 14b are A / D converters, 15 is a synthesis band, 16 is an envelope detector, and 17 is a display.

The operation of the above-described conventional pulse radar device will be described with reference to FIG. The timing generator 1 outputs the frequency switching signal to the fixed initial phase frequency synthesizer 2, the pulse modulation signal to the pulse modulator 6, and the transmission / reception switching signal to the transmission / reception switch 8 at intervals of the pulse repetition period _Tpri . In the fixed initial phase frequency synthesizer 2, one type of signal among N types of signals whose frequency and initial phase is determined in advance is determined in advance by a frequency switching signal from the timing generator 1, for example,
It is generated for each pulse repetition period _{Tpri in} order from the lowest frequency and output to the distributor 3a.

In the distributor 3a, the input signal from the fixed initial phase frequency synthesizer 2 is divided into two, and one of them is used as a local oscillation signal (transmission local oscillation signal) of the transmission signal generation frequency converter 5a. The other is output as a local oscillation signal (reception local oscillation signal) of the frequency converter 5b for generating an intermediate frequency signal to 5a. The frequency converter 5a generates a transmission carrier signal having the sum of the frequency of the local oscillation signal for transmission from the distributor 3a and the frequency of the reference intermediate frequency signal generated by the reference intermediate frequency signal generator 4, and generates a pulse. Output to the modulator 6.

In the pulse modulator 6, a pulse modulation signal from the timing generator 1 is applied to the input signal from the frequency converter 5 a at every pulse repetition period _Tpri .
Performs pulse modulation of a predetermined pulse width T _p. The output signal of the pulse modulator 6 is input to the power amplifier 7,
The power is amplified and output to the transmission / reception switch 8. The transmission / reception switch 8 outputs an input signal from the power amplifier 7 to the antenna 9 at a predetermined time interval at every pulse repetition period _Tpri according to the transmission / reception switching signal from the timing generator 1.

The antenna 9 radiates an input signal from the transmission / reception switch 8 into space as a transmission signal. The transmission signal is reflected by the target 10 and the background, becomes a reflection signal, is received by the antenna 9, and is output to the transmission / reception switch 8. The transmission / reception switch 8 outputs an input signal from the antenna 9 at a predetermined time interval to the frequency converter 5b at every pulse repetition period _Tpri according to the transmission / reception switching signal from the timing generator 1. Further, a local oscillation signal for reception is also input to the frequency converter 5b from the distributor 3a.

The frequency converter 5b generates an intermediate frequency signal having the difference between the frequency of the received signal and the frequency of the local oscillation signal for reception, and outputs it to the intermediate frequency amplifier 11. The intermediate frequency amplifier 11 amplifies the power of the intermediate frequency signal,
The result is output to the distributor 3b. The splitter 3b divides the input signal from the intermediate frequency amplifier 11 into two, and outputs each to the phase detectors 13a and 13b. On the other hand, the reference intermediate frequency signal generated by the reference intermediate frequency signal generator 4 is
90 degree phase difference with 90 degree hybrid device 12
The signals are separated into two signals and output to the phase detectors 13a and 13b.

The phase detectors 13a and 13b have a frequency difference between the frequency of the intermediate frequency signal and the frequency of the reference intermediate frequency signal from the input signal from the distributor 3b and the input signal from the 90-degree hybrid device 12, An I component and a Q component video signals having a phase difference of 90 degrees are generated. The generated I, Q video signal, the sampling frequency is input 1 / T _p of the A / D converter 14a, a 14b, a digital I for each range bin of the same interval as the pulse width T _p, is converted to a Q video signal , To the synthesis band unit 15.

In the synthesis bander 15, digital I and Q video signals in the same range bin for N transmission pulses having different transmission frequencies are subjected to inverse Fourier transform,
A synthesis band process for obtaining a distance resolution ΔR equal to or less than the pulse width T _p is performed, and the result is output to the envelope detector 16. The envelope detector 16 obtains the amplitude values of all the complex signals input from the synthesis band unit 15 and outputs the result to the display 17. The display 17 displays the input signal from the envelope detector 16.

[0026]

In the combined band processing, in order to obtain the phase information corresponding to the relative distance R from the target at all frequencies of the transmission signal, the following equations (1) to (4) are used.
As shown in, it is necessary to use a reference signal having the same initial phase as the initial phase of the transmission signal of the corresponding frequency for the reception signal of each frequency.

However, in practice, as shown in the conventional pulse radar apparatus using the synthetic band processing in FIG. 6, a transmission signal is generated using a reference intermediate frequency signal and a transmission local oscillation signal, and is used as a reference signal. Uses a local oscillation signal for reception and a reference intermediate frequency signal. Reference intermediate frequency signal frequency, and while the initial phase is not always changed, transmission local oscillation signal is the pulse repetition period T _pri frequency for each,
And the initial phase changes. Therefore, for the reception signal of each frequency, the initial phase φ _Ln of the local oscillation signal for transmission used when generating the transmission signal of the corresponding frequency,
By using the receiving local oscillation signal having the same initial phase, it is possible to obtain phase information corresponding to a relative distance R from a target required for the synthesis band processing.

FIG. 7 shows the relationship among a transmission pulse, a reception pulse, a local oscillation signal for transmission, and a local oscillation signal for reception of a pulse radar apparatus utilizing the conventional synthetic band processing. In the figure, St indicates a transmission pulse, Sr indicates a reception pulse, Lt indicates a local oscillation signal for transmission, and Lr indicates a local oscillation signal for reception. However, to keep things simple,
The number of pulses N used for the synthesis band processing is set to 3.

As shown in FIG. 7, in a conventional pulse radar apparatus using the synthetic band processing, a signal generated by one frequency synthesizer is used for a transmission local oscillation signal Lt and a reception local oscillation signal Lr by a distributor. Since the two phases are used, the initial phases of the two are always the same at all the frequencies, and the synthesis band processing can be realized.

However, since a signal generated by one fixed initial phase frequency synthesizer is used for the local oscillation signal Lt for transmission and the local oscillation signal Lr for reception, the following process is performed until a reflected signal from a target for a certain transmission pulse is received. Cannot be transmitted. That is, it can be used only when the relative distance R between the pulse radar device and the target and the pulse repetition period _Tpri have the relationship of _Expression 9.

[0031]

(Equation 9)

Therefore, when the relative distance R between the pulse radar device and the target is long, a long pulse repetition period T
_pri is required. As described above, in the synthesis band processing, digital I and Q video signals generated from reception pulses for N transmission pulses having different transmission frequencies are subjected to inverse Fourier transform, so that transmission signals of N pulses are required. It is. Therefore, a signal transmission time of N times the pulse repetition period _Tpri is required to obtain the result of one combined band process. Therefore, in the conventional pulse radar device using the synthetic band processing, there is a problem that the signal transmission time for obtaining one result is long because the pulse repetition period T _pri is long.

The present invention has been made to solve such a problem. In a pulse radar apparatus which improves the distance resolution ΔR by combining band processing, a relative distance R between the pulse radar apparatus and a target and a pulse repetition cycle are provided. T
_The synthesis band processing can be performed even when _pri is in the relation of several tens, and the relative distance R between the pulse radar device and the target can be calculated.
It is an object of the present invention to obtain a pulse radar device in which the signal transmission time required for one combined band process is short even when the signal is long.

[0034]

(Equation 10)

[0035]

According to a first aspect of the present invention, there is provided a pulse radar apparatus which transmits a predetermined frequency and an initial phase for each pulse repetition cycle of a positive integer multiple of a reciprocal of a predetermined step frequency interval. A fixed initial phase frequency synthesizer that generates an oscillation signal, and using the local oscillation signal for transmission generated by the fixed initial phase frequency synthesizer, a pulse repetition cycle of a positive integer multiple of the reciprocal of a predetermined step frequency interval, and A transmitter that generates a transmission signal that is pulse-modulated with a pulse width, and a transmission / reception switch that switches a transmission / reception signal at a timing of a pulse repetition cycle of the transmission signal, radiates a transmission wave to a target including a background, a target, An antenna for receiving the transmission wave reflected by the background as a reception wave, and an antenna determined in advance. A frequency calculator for determining the frequency information of the received wave using relative distance information of the received wave, and a receiving local unit of a frequency corresponding to the frequency of the received wave using the frequency information of the received wave obtained by the frequency calculator A fixed initial phase frequency synthesizer that generates an oscillation signal at a predetermined initial phase, a receiver that generates digital I and Q video signals from the received wave using the local oscillation signal for reception, and a receiver that generates the video signal. The digital I and Q video signals are provided with a synthesis band-pass filter for performing an inverse Fourier transform.

Further, the pulse radar apparatus according to the second aspect of the present invention is the pulse radar apparatus according to the first aspect of the present invention, while maintaining the relationship that the pulse repetition period is a positive integer multiple of the reciprocal of the predetermined step frequency interval. It is characterized in that the interval of the pulse repetition period is changed every time a transmission pulse is generated in a random or predetermined order.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram of a pulse radar device according to Embodiment 1 of the present invention.
In FIG. 1, 2 to 17 are as described above with reference to FIG. Reference numeral 18 denotes a step frequency synchronization type timing generator, and 19 denotes a frequency calculator.

This operation is performed in the same manner as the conventional pulse radar device.
Until the intermediate frequency amplifier 11 which works differently, using FIG.
Will be explained. Step frequency synchronization type timing generator 1
8, p is an arbitrary positive integer, and the pulse repetition cycle
Period T_priSatisfies the relationship of step 11 with the step frequency interval Δf.
Set the pulse repetition period T _pri
At the interval of the fixed initial phase frequency synth
Pulse modulator sends pulse modulated signals to sizers 2a and 2b
6 and outputs a transmission / reception switching signal to the transmission / reception switch 8.

[0039]

[Equation 11]

In the fixed initial phase frequency synthesizer 2a, one of N types of signals whose frequency and initial phase are determined in advance is determined by a frequency switching signal from the step frequency synchronization type timing generator 18 in a predetermined order. For example, it is generated for each pulse repetition period _{Tpri in} order from a low frequency, and as a local oscillation signal for transmission,
Output to the frequency converter 5a.

The frequency converter 5a transmits the sum of the frequency of the local oscillation signal for transmission generated by the fixed initial phase frequency synthesizer 2a and the frequency of the reference intermediate frequency signal generated by the reference intermediate frequency signal generator 4. A carrier signal is generated and output to the pulse modulator 6. In the pulse modulator 6, the input signal from the frequency converter 5a is
By the pulse modulation signal from the step frequency synchronization type timing generator 18, every pulse repetition period _Tpri ,
Performs pulse modulation of a predetermined pulse width T _p. The output signal of the pulse modulator 6 is input to the power amplifier 7,
The power is amplified and output to the transmission / reception switch 8.

The transmission / reception switch 8 outputs an input signal from the power amplifier 7 to the antenna 9 at a predetermined time interval for each pulse repetition period T _{pri in accordance with} a transmission / reception switching signal from the step frequency synchronization type timing generator 18. I do. In the antenna 9, the input signal from the transmission / reception switch 8 is
It radiates into space as a transmission signal. The transmission signal is target 10,
The light is reflected by the background, becomes a reflected signal, is received by the antenna 9, and is output to the transmission / reception switch 8. The transmission / reception switch 8 outputs an input signal from the antenna 9 at a predetermined time interval to the frequency converter 5b at every pulse repetition period T _pri according to a transmission / reception switching signal from the step frequency synchronization type timing generator 18.

On the other hand, in the frequency calculator 19, the target 10 obtained in advance by the distance measurement processing or the distance tracking processing is obtained.
By using the relative distance information R ′, the number of the received signals is the reflected signal from the target 10 with respect to the transmission pulse of the previous pulse repetition cycle, that is, the transmission pulse is reflected on the target 10 by the equation (12). The number m of the pulse repetition period T _pri within the time required for reception is obtained, the frequency of the received signal is obtained from m and the transmission frequency at that time, and the information on the obtained frequency of the received signal is sent to the fixed initial phase frequency synthesizer 2b. Output.

However, the difference between the relative distance information R ′ to the target 10 and the true relative distance R to the target 10 is m obtained by the equation (12) and m obtained when R ′ is R in the equation (12). It does not differ.

[0045]

(Equation 12)

In the fixed initial phase frequency synthesizer 2b, a local oscillation signal for reception having a frequency corresponding to the frequency is generated at a predetermined initial phase from the information on the frequency of the received signal input from the frequency calculator 19, Output to the frequency converter 5b. In the frequency converter 5b, the frequency of the received signal and the fixed initial phase frequency synthesizer 2b
An intermediate frequency signal having a frequency corresponding to the difference between the frequencies of the local oscillation signals for reception generated in step (1) is generated and output to the intermediate frequency amplifier 11. The processing after the intermediate frequency amplifier 11 is the same as the operation of the conventional pulse radar device.

FIG. 2 shows a relationship among a transmission pulse, a reception pulse, a transmission local oscillation signal, and a reception local oscillation signal in the pulse radar device according to the first embodiment of the present invention. In the figure, St, Sr, Lt, Lr are as described above with reference to FIG. Also, as in FIG. 7, in order to simplify the story, the number of pulses N
Is set to 3, and the number m of the pulse repetition period T _pri within the time required for the transmission pulse obtained by Expression 11 to be reflected on the target 10 and received is set to 1. The initial phase of the local oscillation signal for transmission Lt generated by the fixed initial phase frequency synthesizer 2a and the initial phase of the local oscillation signal for reception Lr generated by the fixed initial phase frequency synthesizer 2b are 0 degrees at all frequencies.

As can be seen from FIG. 2, by separately providing a frequency synthesizer for generating the local oscillation signal for transmission Lt and the local oscillation signal for reception Lr, the local oscillation signal for transmission Lt and the local oscillation signal for reception having different frequencies are provided. Signal Lr
Can be generated within the same pulse repetition period T _pri , so that the pulse of the next frequency does not need to circulate until the reflected signal from the target for a certain transmission pulse is received. Relative distance R
Is shorter, a shorter pulse repetition period T _pri can be used.

Further, by setting the pulse repetition period _Tpri to the relationship shown in Expression 11 with the frequency step interval Δf, the pulse repetition period Tt and the local oscillation signal Lr for all frequencies are transmitted.
_The amount of phase changing within the time interval of _pri is an integral multiple of 2π. That is, as shown in FIG. 2, if the initial phase φ _Ln when generating the local oscillation signal for transmission Lt of the same frequency and the initial phase θ _Ln when generating the local oscillation signal for reception Lr are the same, The amount of change in the phase of the local oscillation signal for reception Lr, which changes during the time difference between the generation of the local oscillation signal for transmission Lt and the local oscillation signal for reception Lr, is an integral multiple of 2π at all frequencies.

Therefore, the initial phase φ _{Ln of the} transmission local oscillation signal Lt and the initial phase θ _Ln of the reception local oscillation signal Lr are
The initial phase θ ′ _Ln converted to the time when the transmission local oscillation signal Lt of the same frequency is generated becomes the same, and the transmission signal used when the transmission signal of the corresponding frequency is generated for the reception signal of each frequency. Initial phase φ _Ln of local oscillation signal
Is equivalent to using the local oscillation signal for reception having the same initial phase.

Accordingly, it is possible to obtain phase information corresponding to the relative distance R from the target required for the synthesis band processing. As a result, even when the relative distance R between the pulse radar device and the target and the pulse repetition period _Tpri have a relationship of several tens, the synthesis band processing can be performed, and the relative distance R between the pulse radar device and the target is long. Even in such a case, the signal transmission time required for one combined band process can be shortened.

Embodiment 2 FIG. 3 is a block diagram of a pulse radar device showing a second embodiment of the present invention. In FIG. 3, 2 to 17 and 19 are as described above with reference to FIGS. Reference numeral 20 denotes a step frequency synchronous random timing generator.

This operation will be described with reference to FIG. 3 up to the intermediate frequency amplifier 11 which operates differently from the conventional pulse radar device. In the step frequency synchronous random timing generator 20, h is a pulse repetition period counter,
Assuming that q (h) is random for each pulse repetition cycle counter h or a positive integer that changes in a predetermined order, a pulse repetition cycle T _pri (h) having a different interval for each pulse repetition cycle counter h is defined as a step frequency interval. The frequency switching signal is set to satisfy the relationship of Δf and Expression 13 and the frequency switching signal is transmitted to the fixed initial phase frequency synthesizers 2a and 2b at intervals of the set pulse repetition period _Tpri .
It outputs the pulse modulation signal to the pulse modulator 6 and the transmission / reception switching signal to the transmission / reception switch 8.

[0054]

(Equation 13)

In the fixed initial phase frequency synthesizer 2a, a step frequency synchronous random timing generator 20
From the N types of signals whose frequency and initial phase have been determined in advance, for each pulse repetition period _Tpri in a predetermined order, for example, in order from the lowest frequency, and transmit them. The signal is output to the frequency converter 5a as a credit local oscillation signal.

The frequency converter 5a transmits the sum of the frequency of the transmission local oscillation signal generated by the fixed initial phase frequency synthesizer 2a and the frequency of the reference intermediate frequency signal generated by the reference intermediate frequency signal generator 4. A carrier signal is generated and output to the pulse modulator 6. In the pulse modulator 6, the input signal from the frequency converter 5a is
The pulse repetition period T _{pri is controlled} by the pulse modulation signal from the step frequency synchronous random timing generator 20.
Each, performs pulse modulation of the pulse width T _p a predetermined.

The output signal of the pulse modulator 6 is a power amplifier
7, the power is amplified, and output to the duplexer 8.
Is forced. In the transmission / reception switch 8, a step frequency synchronous type
The transmission / reception switching signal from the random timing generator 20
And the pulse repetition period T _priPredetermined for each
Input signal from power amplifier 7 at time interval to antenna 9
Output.

The antenna 9 radiates an input signal from the transmission / reception switch 8 to space as a transmission signal. The transmission signal is reflected by the target 10 and the background, becomes a reflection signal, is received by the antenna 9, and is output to the transmission / reception switch 8. The transmission / reception switch 8 outputs an input signal from the antenna 9 at a predetermined time interval to the frequency converter 5b at every pulse repetition period _Tpri according to a transmission / reception switching signal from the step frequency synchronous random timing generator 20. .

On the other hand, in the frequency calculator 19, the target 10 previously obtained by the distance measurement processing and the distance tracking processing is obtained.
By using the relative distance information R ′, the number of the received signals is the reflected signal from the target 10 with respect to the transmission pulse of the previous pulse repetition cycle, that is, the transmission pulse is reflected on the target 10 by the equation (12). The number m of the pulse repetition period T _pri within the time required for reception is obtained, the frequency of the received signal is obtained from m and the transmission frequency at that time, and the information on the obtained frequency of the received signal is sent to the fixed initial phase frequency synthesizer 2b. Output.

However, the difference between the relative distance information R ′ to the target 10 and the true relative distance R to the target 10 is m obtained by Expression 12 and m obtained when R ′ is R in Expression 12. It does not differ. The fixed initial phase frequency synthesizer 2b generates a local oscillation signal for reception of a frequency corresponding to the received frequency from the information on the frequency of the received signal input from the frequency calculator 19 with a predetermined initial phase. 5b.

The frequency converter 5b generates an intermediate frequency signal having a frequency equal to the difference between the frequency of the received signal and the frequency of the local oscillation signal for reception generated by the fixed initial phase frequency synthesizer 2b, and outputs the intermediate frequency signal to the intermediate frequency amplifier 11. The processing after the intermediate frequency amplifier 11 is the same as the operation of the conventional pulse radar device.

FIG. 4 shows the relationship among a transmission pulse, a reception pulse, a transmission local oscillation signal, and a reception local oscillation signal in the pulse radar device according to the second embodiment of the present invention. In the figure, St, Sr, Lt, Lr are as described above with reference to FIG. Also, as in FIG. 7, in order to simplify the story, the number of pulses N
Is set to 3, and the number m of the pulse repetition period T _pri within the time required for the transmission pulse obtained by Expression 11 to be reflected on the target 10 and received is set to 1. The initial phase of the local oscillation signal for transmission Lt generated by the fixed initial phase frequency synthesizer 2a and the initial phase of the local oscillation signal for reception Lr generated by the fixed initial phase frequency synthesizer 2b are 0 degrees at all frequencies.

As can be seen from FIG.
A frequency system for generating the signal Lt and the local oscillation signal Lr for reception.
By providing separate synthesizers,
Transmission local oscillation signal Lt and reception local oscillation signal Lr
With the same pulse repetition period T _priCan be generated within
The reflected signal from the target for a given transmit pulse
The next frequency pulse must wait for transmission until the
The relative distance R between the pulse radar device and the target
Is short, the short pulse repetition period T _priFor
Can be.

Further, by setting the pulse repetition period T _pri (h) and the frequency step interval Δf to the relationship shown in Expression 13, the transmission local oscillation signals L for all frequencies are set.
In the reception local oscillation signal Lr and t, the pulse repetition period T _pri (h) even when different for each pulse repetition period counter h, the pulse repetition period T _pri (h)
Is an integer multiple of 2π.

That is, as shown in FIG. 4, the initial phase φ _Ln when the transmission local oscillation signal Lt of the same frequency is generated.
And initial phase θ _Ln when generating local oscillation signal Lr for reception
Is the same, the amount of change in the phase of the receiving local oscillation signal Lr that changes during the time difference between the generation of the transmitting local oscillation signal Lt and the receiving local oscillation signal Lr is an integer multiple of 2π at all frequencies. Becomes

Accordingly, the initial phase φ _{Ln of the} transmission local oscillation signal Lt and the initial phase θ _Ln of the reception local oscillation signal Lr are
The initial phase θ ′ _Ln converted to the time when the transmission local oscillation signal Lt of the same frequency is generated becomes the same, and the transmission signal used when the transmission signal of the corresponding frequency is generated for the reception signal of each frequency. Initial phase φ _Ln of local oscillation signal
Is equivalent to using the local oscillation signal for reception having the same initial phase.

Therefore, it is possible to obtain the phase information corresponding to the relative distance R from the target required for the synthesis band processing. As a result, even when the relative distance R between the pulse radar device and the target and the pulse repetition period _Tpri have a relationship of several tens, the synthesis band processing can be performed, and the relative distance R between the pulse radar device and the target is long. Even in such a case, the signal transmission time required for one combined band process can be reduced.

Further, according to the first embodiment, the pulse repetition period is constant, whereas according to the second embodiment, the pulse repetition period is randomly determined for each pulse repetition period counter by a predetermined interval. The order can be changed in order, and the confidentiality of the radar can be improved.

[0069]

According to the first aspect of the present invention, even when the relative distance R between the pulse radar device and the target and the pulse repetition period _Tpri have a relationship of several tens, the composite band processing can be performed. Even when the relative distance R between the device and the target is long, the signal transmission time required for one combined band processing can be shortened.

According to the second invention, the relative distance R between the pulse radar device and the target and the pulse repetition period T _pri
Can be performed even in the case of the relation of several tens, and even when the relative distance R between the pulse radar device and the target is long, the signal transmission time required for one synthesis band processing can be shortened. Can be. Further, the confidentiality of the radar is improved as compared with the first aspect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing Embodiment 1 of a pulse radar device according to the present invention.

FIG. 2 is a diagram showing a relationship among a transmission pulse, a reception pulse, a local oscillation signal for transmission, and a local oscillation signal for reception in the first embodiment of the pulse radar apparatus according to the present invention;

FIG. 3 is a configuration diagram showing a second embodiment of the pulse radar device according to the present invention;

FIG. 4 is a diagram showing a relationship among a transmission pulse, a reception pulse, a local oscillation signal for transmission, and a local oscillation signal for reception in Embodiment 2 of the pulse radar device according to the present invention.

FIG. 5 is a diagram showing a transmission pulse waveform in the synthesis band processing.

FIG. 6 is a configuration diagram showing a conventional pulse radar device.

FIG. 7 is a diagram showing a relationship among a transmission pulse, a reception pulse, a local oscillation signal for transmission, and a local oscillation signal for reception in a conventional pulse radar device.

FIG. 8 is a view showing a target range profile.

[Explanation of symbols]

Reference Signs List 1 timing generator, 2 fixed initial phase frequency synthesizer, 3 distributor, 4 reference intermediate frequency signal generator, 5 frequency converter, 6 pulse modulator, 7 power amplifier, 8 duplexer, 9 antenna, 10 target, 11
Intermediate frequency amplifier, 12 90 degree hybrid, 1
3 phase detector, 14 A / D converter, 15 synthetic band detector, 16 envelope detector, 17 display, 18 step frequency synchronous timing generator, 19 frequency calculator, 20 step frequency synchronous random timing generator .

Claims (2)

[Claims] A fixed initial phase frequency synthesizer for generating a transmission local oscillation signal having a predetermined frequency and an initial phase for each pulse repetition cycle of a positive integer multiple of a reciprocal of a predetermined step frequency interval; Using the transmission local oscillation signal generated by the initial phase frequency synthesizer, a transmitter that generates a pulse repetition cycle of a positive integer multiple of the reciprocal of a predetermined step frequency interval, and a pulse-modulated transmission signal with a pulse width. Via the transmission / reception switch that switches the transmission signal between transmission and reception signals at the timing of a pulse repetition cycle, radiates a transmission wave to a target including a background, and receives the transmission wave reflected by the target and the background as a reception wave. Antenna and
A frequency calculator for obtaining frequency information of the received wave using relative distance information with a target obtained in advance, and a frequency corresponding to the frequency of the received wave using frequency information of the received wave obtained by the frequency calculator A fixed initial phase frequency synthesizer that generates a local oscillation signal for reception at a predetermined initial phase, a receiver that generates digital I and Q video signals from the received wave using the local oscillation signal for reception, The digital I and Q generated by the machine
A pulse radar device comprising: a synthesis bander for performing an inverse Fourier transform on a video signal. 2. The pulse repetition period is changed at random or in a predetermined order every time a transmission pulse is generated, while maintaining the relationship that the pulse repetition period is a positive integer multiple of the reciprocal of a predetermined step frequency interval. The pulse radar device according to claim 1, wherein: