JP2001183446A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device for preventing target distance from generating ambiguity, even if the pulse repetition time is not more that the time required for a transmit signal to go and back a target maximum distance. SOLUTION: This device comprises a transmission frequency control device for producing a reference frequency different for each pulse repetition time, a phase detector for simultaneously detecting a phase with a plurality of different reference frequencies, and a distance converter for rearranging outputs from the phase detector by distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device for detecting a target such as a ship or an aircraft.

[0002]

2. Description of the Related Art FIG. 9 is an operation diagram of a conventional radar device. 1 is a radar device, 2 is a target, and the radar device 1 radiates a transmission pulse 3 in an arbitrary direction and receives a reflected echo 4 from the target 2. The position of the target 2 can be known by measuring the time from when the transmission pulse 3 is emitted to when the reflected echo 4 is received. Usually, the received signal includes a reflected echo 4 from the target 2.
In addition, unnecessary signals such as a reflection echo 6 (hereinafter, referred to as clutter) from the mountain 5 are also included.

FIG. 10 is a configuration diagram of a conventional radar device. 7 is a coherent oscillator that generates a reference signal, 8 is a transmitter that generates a transmission pulse signal, 9 is an antenna that radiates the transmission pulse signal into space and receives a reflected echo, 1
0 is a transmission / reception switch that outputs the transmission pulse signal to the antenna 9 at the time of transmission, and outputs the reflected echo to the receiver at the time of reception, and 11 performs filtering, amplification, frequency conversion, and the like on the output of the transmission / reception switch 10. Receiver to perform, 12
A converts the output of the receiver 11 into a digital signal.
A / D converter 13 is a phase detector for detecting the output of the A / D converter 12 with the output signal of the coherent oscillator 7, and 14 is a target information detector.

[0004] The conventional radar device is configured as described above, and the transmitter 8 generates a high-frequency pulse based on the reference signal output from the coherent oscillator 7. This high-frequency pulse is sent to the antenna 9 via the transmission / reception switch 10. The antenna 9 radiates this pulse signal into space and receives a reflected echo from a target or the like. The reflected echo is sent to the receiver 11 via the transmission / reception switch 10, and is output to the A / D converter 12 after processing such as filtering, amplification, and frequency conversion. The A / D converter 12 converts the input analog signal into a digital signal and outputs the digital signal to the phase detector 13. The phase detector 13 detects the phase of the output signal of the A / D converter 12 based on the reference signal output from the coherent oscillator 7. The output of the phase detector 13 is sent to the target information detector 14, and the target information such as the target position is detected by the target information detector 14.

[0005]

In the conventional radar device as described above, if the next transmission pulse is transmitted before the transmission pulse is reflected back to the target, the distance to the target is reduced. There was a problem of ambiguity. For this reason, when it is desired to know the target distance, it is necessary to limit the transmission pulse transmission interval (hereinafter, referred to as a pulse repetition time) to the time required for the transmission pulse to reciprocate over the target maximum distance. On the other hand, in order to improve the target noise power in the received signal, it is effective to shorten the pulse repetition time, which contradicts the above-mentioned limitation.

The present invention has been made to solve such a problem. Even if the pulse repetition time is set to be equal to or less than the time required for the transmission signal to reciprocate over the target maximum distance, the ambiguity in the target distance is obtained. The present invention is to provide a radar apparatus that does not cause the problem.

[0007]

According to a first aspect of the present invention, there is provided a radar apparatus for controlling a transmission frequency for each transmission pulse, and an oscillator for generating a transmission signal in accordance with a control signal generated by the transmission frequency controller. A transmitter that generates a transmission pulse signal based on the output signal of the oscillator, an antenna that radiates the transmission pulse signal into space and receives a reflected echo from a target, and filters and amplifies a reception signal of the antenna. And a delay unit for delaying a control signal generated by the transmission frequency controller, and a phase detector for detecting the output of the receiver by an output signal of the delay unit (where N is 2 or more). An integer) number of phase detectors, a distance converter for rearranging the outputs of the N phase detectors in order of distance for each transmission pulse, and a target related to the output from the distance converter. It is provided with a the target information detector to extract information.

A radar apparatus according to a second aspect of the present invention is a high resolution radar which combines the outputs of the N phase detectors as a distance converter in the order of distance, and performs an inverse discrete Fourier transform of the signals rearranged in the order of distance for each distance. This uses a distance converter.

A radar apparatus according to a third aspect of the present invention uses a non-constant transmission pulse interval as a distance converter and combines the outputs of the N phase detectors so as not to generate a blind distance. It uses a converter.

A radar apparatus according to a fourth aspect of the present invention is provided with a clutter suppressor for suppressing clutter in an output signal of the distance converter.

According to a fifth aspect of the present invention, the transmission frequency controller has means for generating a different transmission frequency for each transmission pulse.

In a sixth aspect of the present invention, the transmission frequency controller has means for generating different transmission frequencies for each transmission pulse at the same interval.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.
Reference numerals 9, 10, 11, 12, and 14 are the same as those of the conventional device. 15 is a transmission frequency controller, 16 is an oscillator, 1
7a to 17d are phase detectors, and 18 is a distance converter.
19 is a data rate converter, 20a to 20c are delay units, 21 is a combiner, and 27a to 27c are delay units.

The operation of the present invention will be described below. First, the transmission frequency controller 15 generates a different frequency for each pulse repetition time. The type of frequency is equal to or more than the number N of the phase detectors, and the same frequency is not generated within the N pulse repetition time. For example, for each pulse repetition time, the frequencies A1, A2, A3, A4, A1,
A2 ... are generated. The oscillator 16 has a frequency A according to the frequency generated by the transmission frequency controller 15.
1, A2, A3, A4, A1, A2,. The transmitter 8 generates a transmission pulse based on an output signal of the oscillator 16. The transmission pulse is sent to the antenna 9 via the transmission / reception switch 10. The antenna 9 radiates this transmission pulse into space,
Receives reflected echoes from a target or the like. The reflected echo is sent to the receiver 11 via the transmission / reception switch 10, and after processing such as filtering, amplification, and frequency conversion, the A / A
It is output to the D converter 12.

The A / D converter 12 converts the input analog signal into a digital signal and outputs the digital signal to the phase detector 17a.
To 17d simultaneously. The delay unit 27a delays the frequency generated by the transmission frequency controller 15 by one pulse repetition time and outputs it to the phase detector 17b. The delay unit 27b delays the output of the delay unit 27a by one pulse repetition time. Output to the phase detector 17c, the delay unit 27c delays the output of the delay unit 27b by one pulse repetition time, and outputs it to the phase detector 17d. For example, assuming that a transmission pulse generated based on a sine wave of frequency A4 is transmitted and a reflected echo is received, the phase detector 17a uses the sine wave of frequency A4 as a reference signal to perform the A / D conversion. The output signal of the detector 12 is subjected to phase detection. Similarly, the phase detector 17b uses a sine wave of frequency A3 as a reference signal, the phase detector 17c uses a sine wave of frequency A2 as a reference signal, and the phase detector 17d uses a frequency A
The output signal of the A / D converter 12 is phase-detected using the sine wave of 1 as a reference signal.

The distance converter 18 is connected to the phase detector 17
The output signals a to 17d are rearranged in order of distance and combined into one. The output signal of the phase detector 17b is a reflection echo from a transmission pulse transmitted one pulse repetition time ago, and the output signal of the phase detector 17c is a reflection echo from a transmission pulse transmitted two pulse repetition times ago. The output signal of the phase detector 17d is a reflected echo from a transmission pulse transmitted three pulse repetition times before. Therefore, the data rate converter 19 increases the data rate of the output signals of the phase detectors 1a, 17b, 17c, 17d by four times, and
1. The signals are sent to the delay units 20a, 20b, and 20c, the delay units 20a, 20b, and 20c each delay 1 to 3 pulse repetition times, and the combiner 21 is connected to the data rate converter 19, the delay units 20a, and 20c. By combining the outputs of 20b and 20c, a reflected echo at a distance corresponding to the 4-pulse repetition time is obtained for each transmission pulse.

FIG. 2 is a processing time chart of the distance converter 18, wherein B1 is a transmission pulse generated based on a sine wave of frequency A1, and B2 is generated based on a sine wave of frequency A2. Transmission pulse, similarly B3, B4, B
5, B6 are transmission pulses generated based on sine waves of frequencies A3, A4, A1, A2, C1 is an output signal of the distance converter 18 with respect to a signal received at the time of transmitting the transmission pulse B1, and C2 is a transmission pulse. The output signal of the distance converter 18 with respect to the signal received at the time of transmitting B2,
C4 and C5 are output signals of the distance converter 18 with respect to signals received when the transmission pulses B3, B4 and B5 are transmitted. The output of the distance converter 18 is sent to the target information detector 14, and the target information detector 14 detects target information such as a target distance. Therefore, the maximum target distance that can be measured without ambiguity is the distance that the transmission pulse reciprocates during the four-pulse repetition time.

Embodiment 2 FIG. FIG. 3 is an overall configuration diagram showing a second embodiment of the present invention.
Reference numerals 0, 11, 12, and 14 are the same as those in the conventional apparatus. 15, 16, 17a-17d, 19, 20a-20
c, 21, 27a to 27c are the same as those in the first embodiment. 22 is a high-resolution distance converter and 23 is an inverse discrete Fourier transformer.

The operation of the present invention will be described below. First, the transmission frequency controller 15 has four kinds of equally spaced frequencies A.
1, A2, A3 and A4 are generated. For example, if A1 is 5
A2 is 60 MHz when the frequency is 0 MHz and the interval is 10 MHz.
z and A3 are 70 MHz, and A4 is 80 MHz. Next, as in the first embodiment, a transmission pulse is generated based on the sine wave, transmission and reception are performed, and the coupler 21 combines the received signals rearranged in the order of distance into one. The inverse discrete Fourier transformer 23 performs an inverse discrete Fourier transform process on the output signal of the combiner 21 for each distance.

FIG. 4 shows a data string to be subjected to the inverse discrete Fourier transform. In FIG. 4, C1, C2, C3, C4
Is the same as FIG. D is the result of the inverse discrete Fourier transform processing. The distance resolution of the inverse discrete Fourier transform processing result D is four times the distance resolution determined by the transmission pulse width. When the size of the target is equal to or smaller than the distance resolution, the target-to-noise power is improved by the integration effect.

Embodiment 3 FIG. 5 is an overall configuration diagram showing a third embodiment of the present invention.
Reference numerals 0, 11, 12, and 14 are the same as those in the conventional apparatus. 15, 16, 17a to 17d, 19, 21, 27a
27c are the same as those in the first embodiment. 24
Is a blind removal type distance converter, and 25a to 25d are timing adjusters.

The operation of the present invention will be described below. As in the first embodiment, the transmission frequency controller 15 generates four types of frequencies, and the oscillator 16 generates a sine wave according to the output frequency of the transmission frequency controller. The transmitter 8 generates transmission pulses at unequal intervals based on the output signal of the oscillator 16.

FIG. 6 shows the generation timing of the transmission pulse. In the figure, B1 to B5 are the same as those in FIG. E1 is the time from transmission of the transmission pulse B1 to transmission of the transmission pulse B2, E2 is the time from transmission of the transmission pulse B2 to transmission of the transmission pulse B3, and E3 is the transmission pulse B3 Is transmitted to transmit the transmission pulse B4, and E4 is the time from transmission of the transmission pulse B4 to transmission of the transmission pulse B5. Here, E1 and E2 are different times. As in the first embodiment, the transmission pulse is transmitted and received, and the blind removal type distance converter 24 is used.
Is input to The blind removal type distance converter 24
Adjusts the delay time of the received signal using the timing adjusters 25a to 25d, thereby rearranging the output signals of the phase detectors 17a to 17d in order of distance and combining them into one.

FIG. 7 shows the blind removing type distance converter 2.
4 shows the output signal. In the figure, E1 to E4 are the same as those in FIG. F1 is the output signal of the blind elimination type distance converter 24 with respect to the signal received at the E1,
F2 is the output signal of the blind elimination type distance converter 24 for the signal received at the E2, and F3 is the blind elimination type distance converter 2 for the signal received at the E3.
The output signal F4 is an output signal of the blind removal type distance converter 24 with respect to the signal received at E4. In F1 to F4, shaded portions are blind distances. As can be seen from the figure, the blind distance can be removed by integrating F1 to F4.

Embodiment 4 FIG. 8 is an overall configuration diagram showing a fourth embodiment of the present invention.
Reference numerals 0, 11, 12, and 14 are the same as those in the conventional apparatus. 15, 16, 17a to 17d, 18, 19, 20a
20c, 21, 27a to 27c are the same as those in the first embodiment. 26 is a clutter suppressor.

The operation of the present invention will be described below. As in the first embodiment, the oscillator 16 generates a sine wave and sends it to the transmitter 8. The transmitter 8 is connected to the oscillator 1
A transmission pulse is generated based on the output signal of the antenna 6, and the antenna 9 transmits and receives the transmission pulse. The reflected echo is
The signal is sent to the receiver 11 and output to the A / D converter 12 after performing processing such as filtering, amplification, and frequency conversion. The A / D converter 12 converts the input analog signal into a digital signal and outputs the digital signal to the phase detectors 17a to 17d.
Performs phase detection on the output signal of the A / D converter 12. The distance converter 18 sorts the output signals of the phase detectors 17a to 17d in order of distance and combines them. The clutter suppressor 26 extracts an output signal of the distance converter 18 every four transmission pulses and outputs an MTI (Moving Tar).
get Indicator). Since the signal extracted every fourth transmission pulse is a coherent signal, the clutter is suppressed by the clutter suppressor 26.

[0027]

According to the first and fifth aspects of the present invention, N (N is 2
The reflected echo in the distance range corresponding to the pulse repetition time can be measured for each transmission pulse. That is, even if the pulse repetition time is set to the I / N (N is an integer of 2 or more) of the time required for the transmission pulse to reciprocate over the target maximum distance, there is no ambiguity in the target distance.

According to the second and sixth aspects, in addition to the effect of the first aspect, the distance resolution can be improved to N times (N is an integer of 2 or more).

According to the third aspect, in addition to the effect of the first aspect, the blind distance can be eliminated.

According to the fourth aspect, in addition to the effect of the first aspect, clutter can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a radar apparatus according to the present invention.

FIG. 2 is a diagram showing a processing timing chart of a time converter.

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

FIG. 4 is a diagram showing a data sequence for performing an inverse discrete Fourier transform.

FIG. 5 is a diagram showing a third embodiment of the radar device according to the present invention;

FIG. 6 is a diagram showing the generation timing of a transmission pulse.

FIG. 7 is a diagram illustrating an output signal of a blind elimination type distance converter.

FIG. 8 is a diagram showing a fourth embodiment of the radar apparatus according to the present invention;

FIG. 9 is an operation diagram of a conventional radar device.

FIG. 10 is a configuration diagram of a conventional radar device.

[Explanation of symbols]

8 transmitter, 9 antenna, 10 duplexer, 11
Receiver, 12 A / D converter, 13 Phase detector, 14
Target information detector, 15 transmission frequency controller, 16 oscillator, 17 phase detector, 18 distance converter, 19 data rate converter, 20 delay unit, 21 combiner, 22
High-resolution distance converter, 23 inverse discrete Fourier transformer,
24 Blind removal type distance converter, 25 Timing adjuster, 26 Clutter suppressor, 27 Delay unit.

Claims (6)

[Claims] A transmission frequency controller that controls a transmission frequency for each transmission pulse; an oscillator that generates a transmission signal according to a control signal generated by the transmission frequency controller; and a transmission pulse signal based on an output signal of the oscillator. And an antenna that radiates the transmission pulse signal into space and receives a reflected echo from a target, a receiver that performs filtering, amplification, and frequency conversion on the reception signal of the antenna, and the transmission frequency. A delay unit for delaying a control signal generated by a controller, N (N is an integer of 2 or more) phase detectors for detecting the output of the receiver by an output signal of the delay unit, and the N number of phase detectors A distance converter for rearranging the output of the phase detector in order of distance for each transmission pulse, and a target information detector for extracting information about a target from the output of the distance converter. And a radar apparatus characterized by the above. 2. The distance converter according to claim 1, further comprising: an inverse discrete Fourier transformer for performing an inverse discrete Fourier transform on the signals rearranged in order of distance for each distance and outputting the signals to the target information detector. 2. The radar device according to 1. 3. The distance converter has means for removing a blind distance by using the fact that transmission pulse intervals are not constant when rearranging the outputs of the N phase detectors in order of distance for each transmission pulse. The radar device according to claim 1, wherein: 4. The radar apparatus according to claim 1, further comprising a clutter suppressor for removing clutter from an output of the distance converter. 5. The radar apparatus according to claim 1, wherein the transmission frequency controller generates a different transmission frequency for each transmission pulse. 6. The radar apparatus according to claim 2, wherein the transmission frequency controller generates different transmission frequencies at the same interval for each transmission pulse.