JP2010197147A - Radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand a maximum search range and a maximum measurement doppler velocity without increasing a peak transmission power or a transmission pulse width, in a linear FM modulation pulse compression radar system. <P>SOLUTION: In a pulse compression radar system, a modulated pulse with a linear FM modulation in a pulse width is emitted into a space with a frequency sweep direction inverted per transmission repetition cycle period. Concurrently, a non-modulated pulse having a carrier frequency different from that of the modulated pulse is emitted into the space at a period shorter than the transmission repetition cycle period of the modulated pulse. A first pulse compression processing part which pulse-compresses a reflected wave from a target with a compression coefficient in the frequency sweep direction same with that of the modulated pulse and a second pulse compression processing part which pulse-compresses with a compression coefficient in the reverted direction are provided. A primary and a secondary echos are classified using the pulse compression processing, i.e. signal selectivity in matched filter processing, and the latter is connected to an end of the former to obtain a reflected signal of which the maximum search range is expanded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a linear FM modulation system that obtains high resolution by emitting a modulation pulse subjected to linear frequency modulation (linear FM modulation) within a pulse width to a space and subjecting a reflected wave from a target to pulse compression processing. The present invention relates to a pulse compression radar apparatus.

In order to expand the target detection range in the radar apparatus, it is necessary to increase the peak transmission power or pulse width of pulses emitted into the space to increase the average transmission power. However, if the peak transmission power cannot be increased due to hardware restrictions, a wide modulated pulse with a special modulation in the pulse is emitted, and the reflected wave from the target is subjected to pulse compression processing by reception processing. To obtain a reflected wave from the target with an equivalently high peak transmission power and a narrow pulse. A radar apparatus that detects a target using this method is called a pulse compression radar apparatus (Non-patent Document 1).

In order to perform this pulse compression processing, the modulation applied to the transmission pulse is linearly frequency modulation method (linear FM modulation method), non-linear frequency modulation method (nonlinear FM modulation method), code modulation method using pseudo-random code ( Phase modulation method) is used.

The pulse compression process is a so-called matched filter process, which is a correlation process in the time domain by a transversal filter using the same waveform as the modulation pulse as a filter coefficient regardless of the modulation method.

The radar device uses a transmission repetition period (PRI).
Interval) intermittently emits a pulse wave into the space and measures the target distance by the time delay of the reflected wave. Therefore, the maximum detection range distance of the radar apparatus is determined as shown in (Equation 1) by PRI and the speed of light.
(Expression 1) Maximum detection distance = (PRI × speed of light) / 2

When there is a target having a large reflection cross section beyond the maximum detection distance determined by the equation (1), it seems as if the target exists at a short distance in the received signal obtained by this transmission. A false image appears. This false image is called a secondary echo, and a received signal other than the false image is called a primary echo (Non-Patent Document 2).

Since the secondary echo is a reflected wave with a time delay exceeding the PRI, the primary echo and the secondary echo are separated, and the secondary echo is connected to the end of the primary echo, so that the maximum target detection range of the radar device is obtained. It can be enlarged up to twice.

In the conventional method, in order to separate the primary echo and the secondary echo, the initial phase of the pulse is randomly changed for each PRI, modulated, emitted into space, and the primary echo and the secondary echo are separated in the received signal processing. (For example, nonpatent literature 3).

On the other hand, from the phase change amount of the target reflected wave between the PRIs, the maximum measured Doppler speed when measuring the target moving speed, that is, the Doppler speed, depends on the carrier wavelength of the pulse wave emitted to the PRI and the space (Equation 2) It is determined as follows.

(Equation 2) Maximum measured Doppler velocity = carrier wavelength / (4 × PRI)

  When there is a target having a Doppler speed larger than the maximum measured Doppler speed determined by the formula (2), the Doppler speed detected by the radar apparatus is observed with the sign reversed, so-called speed folding occurs ( Non-patent document 4).

  In the conventional method, a method called a continuous method is used in which continuity in the distance and azimuth direction of the Doppler velocity is assumed on the basis of one point having a target reflected wave, and the folding of the Doppler velocity is corrected ( For example, Non-Patent Document 5).

Supervised by Takashi Yoshida “Revised Radar Technology” The Institute of Electrical Communication, Japan 25 May 1999 First edition, 3rd edition issued p275-280 Edited by Masahito Ishihara "Meteorological Research Note No.200" Japan Meteorological Society December 26, 2001 First edition issued p15-17 Edited by Masahito Ishihara "Meteorological Research Note No.200" Japan Meteorological Society December 26, 2001 First edition issued p27-30 Edited by Masahito Ishihara "Meteorological Research Note No.200" Japan Meteorological Society December 26, 2001 First edition issued p15 Edited by Masahito Ishihara "Meteorological Research Note No.200" Japan Meteorological Society December 26, 2001 First edition issued p32-34

From equation (1), it is necessary to increase the PRI in order to increase the maximum detection distance of the radar apparatus. On the other hand, from the formula (2), in order to increase the maximum measured Doppler speed, it is necessary to shorten the PRI. Therefore, the maximum detection distance of the radar device and the maximum measured Doppler velocity are in a contradictory relationship, and it is difficult to expand both at the same time.

In order to expand the maximum detection distance in the above-described problem, the present invention uses a signal compression in a pulse compression process, that is, a matched filter process, in a linear FM modulation type pulse compression radar apparatus. Distinguish from echo.

The linear FM modulation type pulse compression radar apparatus according to the present invention emits a wide modulation pulse, which has been subjected to linear frequency modulation (linear FM modulation) in a pulse, to the space in the first PRI period, and reflects from the target. A pulse compression process is performed in the wave reception process to obtain a reflected wave from the target with an equivalently high peak transmission power and a narrow pulse.

In the present invention, the modulation pulse subjected to the linear FM modulation is emitted in space with the frequency sweep direction reversed for each PRI. Thereby, the frequency sweep direction on which the primary echo depends depends on the current transmission. On the other hand, since the secondary echo is a reflected wave with a time delay exceeding the PRI, the frequency sweep direction in which the echo is dependent is the previous transmission, that is, the frequency sweep direction in which the primary echo is dependent is inverted.

When the reflected wave from the target is subjected to pulse compression processing, a pulse compression processing unit that performs pulse compression processing of the reflected wave from the target with a compression coefficient in the same frequency sweep direction as the modulation pulse, and a frequency inverted with respect to the modulation pulse A pulse compression processing unit that performs pulse compression processing with a compression coefficient in the sweep direction is provided. For convenience, the former is referred to as a first pulse compression processing unit, and the latter is referred to as a second pulse compression processing unit.

In the first pulse compression processing unit, the correlation of the primary echo is concentrated to form a significant echo, but the secondary echo is diffused and cannot form a significant echo. On the other hand, in the second pulse compression processing unit, the primary echo is diffused and does not form a significant echo, but the correlation of the secondary echo is concentrated and a significant echo is formed.

Thus, in order to solve the above problems, the present invention
In linear FM modulation type pulse compression radar,
A modulation pulse waveform signal is stored in the modulation pulse waveform storage memory unit, and the address counter unit realizes pulse transmission by designating an address value of the modulation pulse waveform storage memory unit,
When the first address transition is that the address value is in the increasing direction from the head address of the storage pulse and the second address transition is that the address value is in the decreasing direction from the last address of the storage pulse,
An address counter unit that operates so that the waveform on the time axis of the modulation pulse is reversed horizontally for each transmission repetition period by repeating the first transition and the second transition for each transmission repetition period;
A first pulse compression processing unit for pulse-compressing the reflected wave of the modulated pulse according to the first transition by subjecting the reflected wave from the target to pulse compression with a compression coefficient in the same frequency sweep direction as the modulated pulse;
A second pulse compression processing unit for pulse-compressing the reflected wave of the modulated pulse according to the second transition by subjecting the reflected wave from the target to pulse compression processing with a compression coefficient in the frequency sweep direction inverted with respect to the modulated pulse. When,
A pulse compression signal for discriminating the reflected wave of the pulse transmission at the current time and the reflected wave of the pulse transmission of one repetition period before the output of the first pulse compression processor and the output of the second pulse compression processor A selection section;
The reflected wave of the pulse transmission at the current time output from the pulse compression signal selection unit is the first reflected wave, and the reflected wave of the pulse transmission one repetition period before the pulse transmission at the current time is the second reflected wave. In this case, a pulse compression signal synthesizer for connecting the reflected wave of the pulse transmission one repetition period before the second reflected wave is coupled to the end of the first reflected wave;
A modulated pulse Doppler velocity calculation unit for calculating a target Doppler velocity from the signal output by the pulse compression signal synthesizer;
A radar device characterized by comprising

According to the present invention, the maximum target detection range of the radar apparatus is obtained by separating the primary echo and the secondary echo and connecting the secondary echo to the end of the primary echo without increasing the transmission peak power or the transmission pulse width. Can be expanded up to twice. The reflected wave obtained through this process is called the first reflected wave, and the Doppler velocity is also called the first Doppler velocity.

  Since the maximum measured Doppler velocity of the first Doppler velocity is determined by the equation (2), if there is a target having a Doppler velocity exceeding the maximum measured Doppler velocity in the first reflected wave observation range, A so-called speed turn-back in which the sign of the Doppler speed is reversed at the target point occurs.

In order to correct the rate wrapping, i.e. to increase the maximum measured Doppler velocity, the present invention emits unmodulated pulses that differ in the carrier frequency and the modulated pulse. The unmodulated pulse is launched into space with a PRI shorter than the first PRI. The short PRI is referred to as a second PRI.

  When the reflected wave from the target by the non-modulated pulse is the second reflected wave and the Doppler velocity is the second Doppler velocity, for example, if the second PRI is selected to be 10 times the first PRI, the second reflected wave The maximum wave detection distance is 1/20 of the first reflected wave, but the maximum measured Doppler velocity is 10 times. Therefore, with respect to the first Doppler speed, the maximum Doppler speed of the first Doppler speed is obtained by correcting the speed folding using the continuous method shown in Non-Patent Document 5 with the second Doppler speed as a reference. It can be enlarged up to 10 times.

Thus, in order to solve the above problems, the present invention
In linear FM modulation type pulse compression radar,
An unmodulated pulse waveform storage memory unit stores an unmodulated pulse waveform signal having a center frequency different from that of the first modulated pulse and the second modulated pulse, and the unmodulated pulse address counter unit stores the unmodulated pulse waveform. Realizing pulse transmission by specifying the address value of the waveform storage memory part,
An unmodulated pulse quadrature detection unit that generates the unmodulated pulse by the second PRI and quadrature-detects the reflected wave from the target when the transmission repetition period shorter than the first PRI is the second PRI. When,
An unmodulated pulse Doppler velocity calculator for calculating a target Doppler velocity from the quadrature signal obtained by the unmodulated pulse quadrature detector;
A radar device characterized by comprising:

By connecting the secondary echo separated by the pulse compression signal selector to the end of the primary echo by the pulse compression signal synthesizer, the peak transmission power and transmission pulse width can be reduced in the linear FM modulation type pulse compression radar device. Without increasing, the maximum target detection range can be expanded up to twice.

  In addition, speed folding correction is performed by a continuous method using the Doppler speed output from the modulated pulse Doppler speed calculation unit and the Doppler speed output from the unmodulated pulse Doppler speed calculation unit. With this correction, the maximum measured Doppler velocity of the Doppler velocity output from the modulated pulse Doppler velocity calculator can be expanded by the maximum ratio of the first PRI to the second PRI.

  As described above, the maximum detection distance and the maximum measured Doppler speed of the radar apparatus are simultaneously expanded.

The block diagram which shows the structure of the radar apparatus concerning this invention. Relationship between the frequency sweep direction in which the transmitted pulse and the primary and secondary echo depend. Relationship between modulated pulse PRI and unmodulated pulse PRI. Relationship between modulated pulse spectrum and unmodulated pulse spectrum. Echo output by each part. Observed Doppler velocity with modulated pulse and Observed Doppler velocity with unmodulated pulse Doppler speed folding correction by continuous method

The most preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a linear FM modulation type pulse compression radar apparatus of the present invention.

A modulation pulse waveform storage memory unit 1 in FIG. 1 stores a digital waveform of a modulation pulse subjected to linear FM modulation.

The modulation pulse transmission timing measurement instructing unit 2 in FIG. 1 measures the PRI of the modulation pulse and generates a modulation pulse transmission trigger that indicates the timing of emitting the modulation pulse to space.

The modulation pulse transmission trigger count instructing unit 3 in FIG. 1 counts the number of modulation pulse transmission triggers generated by the modulation pulse transmission timing timing instructing unit 2, and instructs the odd / even.

The modulation pulse address counter unit 4 in FIG. 1 issues an address for sequentially reading the digital waveform of the modulation pulse subjected to linear FM modulation stored in the modulation pulse waveform storage memory unit 1. The headquarters uses the modulation pulse transmission trigger generated by the modulation pulse transmission timing timing instruction unit 2 as the address scanning start timing, and the even number of the modulation pulse transmission trigger generation number indicated by the modulation pulse transmission trigger count instruction unit 3 as the scanning direction. Issue.

For example, when the modulation pulse transmission trigger occurrence number is an even number, the modulation pulse digital waveform stored in the modulation pulse waveform storage memory unit 1 is addressed from the start address of the modulation pulse digital waveform toward the end address. Address scanning from the head address to the head address. As a result, the frequency sweep direction of the modulation pulse subjected to linear FM modulation for each PRI is reversed.

Thereby, the frequency sweep direction on which the primary echo depends depends on the current transmission. On the other hand, since the secondary echo is a reflected wave with a time delay exceeding the PRI, the frequency sweep direction in which the echo is dependent is the previous transmission, that is, the frequency sweep direction in which the primary echo is dependent is inverted. FIG. 2 shows the relationship between the modulation pulse and the frequency sweep direction in which the primary and secondary echoes depend when the frequency sweep direction of the modulation pulse is inverted for each PRI.

In FIG. 2, a modulation pulse transmission trigger 25 is a signal for instructing the modulation pulse emission timing, which is created by the modulation pulse transmission timing timing instructing unit 3 in FIG. The modulation pulse transmission trigger count instructing unit count value 26 counts the number of occurrences of the modulation pulse transmission trigger 25 and indicates its evenness. The modulation pulse 27 is read from the modulation pulse waveform storage memory unit 1 in FIG. 1 using the modulation pulse transmission trigger 25 as transmission timing, and represents the modulation pulse in FIG.

The frequency sweep direction 28 represents the frequency sweep direction of the transmission modulation pulse 25 determined by the even / odd number of the modulation pulse transmission trigger count instruction unit count value 26. In the example of FIG. 2, the frequency is swept from low to high when the modulation pulse transmission trigger count instruction unit count value 26 is an even number, and the frequency is swept from high to low when it is an odd number. In the frequency sweep direction 29 in which the primary echo is dependent, the transmission modulation pulse 27 is emitted from the antenna unit 11 into space, and the reflection from the target whose distance from the antenna unit 11 is within the maximum detection distance determined by (Equation 1). It represents the frequency sweep direction in which the wave and the reflected wave depend.

In the frequency sweep direction 30 in which the secondary echo is dependent, the modulated pulse 27 is emitted from the antenna unit 11 in FIG. 1 into the space, and the distance from the antenna unit 11 is beyond the maximum detection distance determined by (Equation 1). And the frequency sweep direction in which the reflected wave depends. Since the secondary echo is a reflected wave with a time delay exceeding the PRI, the frequency sweep direction to which the echo depends is the previous transmission, that is, the frequency sweep direction 25 to which the primary echo depends is inverted.

The unmodulated pulse waveform storage memory unit 5 in FIG. 1 stores a digital waveform of an unmodulated pulse having a center frequency different from that of the modulated pulse.

The unmodulated pulse transmission timing timing instructing unit 6 in FIG. 1 measures the PRI of the unmodulated pulse, and generates an unmodulated pulse transmission trigger that instructs the timing of emitting the unmodulated pulse into space.
The PRI of the unmodulated pulse is selected to be shorter than the PRI of the modulated pulse.

FIG. 3 shows the relationship between the PRI of the modulated pulse and the PRI of the non-modulated pulse. In FIG. 3, the modulation pulse PRI 31 indicates the timing at which the modulation pulse measured by the modulation pulse transmission timing counter 2 in FIG. 1 is emitted into space. The modulation pulse 32 indicates a modulation pulse emitted according to the PRI 31 of the modulation pulse. The unmodulated pulse PRI 33 indicates the timing at which the unmodulated pulse timed by the unmodulated pulse transmission timing timing instructing unit 6 in FIG. The unmodulated pulse 34 indicates an unmodulated pulse emitted in accordance with the PRI 33 of the unmodulated pulse.

The unmodulated pulse address counter unit 7 in FIG. 1 issues an address for sequentially reading the digital waveforms of the unmodulated pulses stored in the unmodulated pulse waveform storage memory unit 5. The head office issues the address using the non-modulated pulse transmission trigger generated by the non-modulated pulse transmission timing measuring instruction section 6 as the address scanning start timing.

  The pulse synthesizer 8 in FIG. 1 synthesizes the modulated pulse waveform and the non-modulated pulse waveform, and generates a pulse waveform in which both are frequency-multiplexed.

  FIG. 4 shows the positional relationship between the modulated pulse and the non-modulated pulse on the frequency axis. In FIG. 4, the modulation pulse spectrum 35 is stored in the modulation pulse waveform storage memory unit 1 of FIG. 1, and the modulation pulse spectrum generated by the modulation pulse transmission trigger indicated by the modulation pulse transmission timing measuring instruction unit 2 is converted into the modulation pulse spectrum. The center frequency 36 represents the center frequency of the modulation pulse spectrum 35. Similarly, in FIG. 4, an unmodulated pulse spectrum 37 is stored in the unmodulated pulse waveform storage memory unit 5 of FIG. The unmodulated pulse center frequency 38 represents the center frequency of the unmodulated pulse spectrum 37. At the time of implementation, as long as both spectra do not overlap, the distance between the modulation pulse center frequency 36 and the non-modulation pulse center frequency 37 may be reversed or the left and right on the frequency axis may be reversed.

The D / A converter 9 in FIG. 1 performs analog conversion on a pulse waveform obtained by frequency multiplexing the modulated pulse and the non-modulated pulse output from the pulse synthesizer 8.

The transmission unit 10 in FIG. 1 performs frequency conversion and power amplification up to a frequency at which a pulse obtained by frequency-multiplexing the modulated pulse and the non-modulated pulse analog-converted by the D / A conversion unit 9 is emitted into space.

The antenna unit 11 in FIG. 1 emits a pulse whose frequency has been converted and amplified by the transmitter 10 into space, and receives a reflected wave from the target.

The receiving unit 12 in FIG. 1 performs frequency conversion and power amplification of the reflected wave from the target received by the antenna unit 11 to an intermediate frequency.

The A / D converter 13 in FIG. 1 samples / quantizes the reflected wave from the target converted to the intermediate frequency by the receiver 12.

  The modulation pulse digital filter unit 14 in FIG. 1 is a digital filter having a band through which a non-modulation pulse can be blocked and a modulation pulse can pass. At the headquarters, the reflected wave due to the modulation pulse is classified from the reflected waves from the target sampled / quantized by the A / D converter 13.

The modulation pulse digital quadrature detection unit 15 in FIG. 1 performs quadrature detection of the reflected wave from the target by the modulation pulse output from the modulation pulse digital filter unit 14.

The first pulse compression processing unit 16 of FIG. 1 has a waveform when the digital waveform of the modulation pulse stored in the modulation pulse waveform storage memory unit 1 is read from the start address to the end address, that is, the frequency sweep direction is low to high. It is a transversal filter having a digital waveform of a modulation pulse as a compression coefficient. The head unit performs pulse compression processing on the reflected wave from the target detected by the modulated pulse digital quadrature detection unit 15 using the compression coefficient.

The second pulse compression processing unit 17 in FIG. 1 has a waveform when the digital waveform of the modulation pulse stored in the modulation pulse waveform storage memory unit 1 is read from the terminal address to the head address, that is, the frequency sweep direction is low to high. It is a transversal filter having a digital waveform of a modulation pulse as a compression coefficient. The headquarter performs pulse compression processing on the reflected wave from the target detected by the digital quadrature detection unit 15 using the compression coefficient.

For example, when the modulation pulse transmission trigger generation number is an even number, the modulation pulse digital waveform stored in the modulation pulse waveform storage memory unit 1 starts from the start address of the modulation pulse digital waveform toward the end address. Address scanning is performed toward the head address. As a result, the frequency sweep direction of the modulation pulse subjected to linear FM modulation for each PRI is reversed.

When the frequency sweep direction of the modulation pulse subjected to linear FM modulation in this order is controlled, when the number of modulation pulse transmission trigger generations indicated by the modulation pulse transmission trigger count instruction unit 3 is an even number, the first pulse compression processing unit 16 performs pulse compression processing of the reflected wave from the target with a compression coefficient in the same frequency sweep direction as the modulation pulse. That is, in the first pulse compression processing unit 16, the reflected wave (primary echo) from the target by the current transmission pulse is concentrated in correlation and forms a significant echo, but the reflected wave (secondary wave) from the target by the previous transmission pulse is formed. Echo) diffuses and does not form a significant echo, so the headquarters outputs a primary echo.

On the other hand, the second pulse compression processing unit 17 performs pulse compression processing with a compression coefficient in the frequency sweep direction inverted with respect to the modulation pulse. That is, the primary echo diffuses and does not form a significant echo, but the correlation of the secondary echo concentrates to form a significant echo, so a secondary echo is output.

Similarly, when the number of transmission trigger occurrences indicated by the modulation pulse transmission trigger count instructing unit 3 is an odd number, the above relationship is inverted between the first pulse compression processing unit 16 and the second pulse compression processing unit 17. .

As described above, the pulse compression signal selection unit 18 of FIG. 1 outputs the output signal of the first pulse compression processing unit 16 according to the even / odd number of modulation pulse transmission trigger generations indicated by the modulation pulse transmission trigger count instruction unit 3. And the output signal of the second pulse compression processing unit 17 is classified into a primary echo and a secondary echo.

The pulse compressed signal synthesizer 19 in FIG. 1 connects the secondary echo output from the pulse compressed signal selector 18 to the end of the primary echo output from the pulse compressed signal selector 18. FIG. 5 shows the relationship between the count value of the modulation pulse transmission trigger count instruction unit 3 and the echoes output from the pulse compression signal selection unit 18 and the pulse compression signal synthesis unit 19.

In FIG. 5, a modulation pulse transmission trigger 39 is a signal for instructing the modulation pulse emission timing, which is created by the modulation pulse transmission timing timing instruction unit 2 of FIG. The modulation pulse transmission trigger count instructing unit count value 40 counts the number of occurrences of the modulation pulse transmission trigger 39 and indicates its evenness.

The primary echo 41 output from the pulse compression signal selection unit represents the primary echo sorted by the pulse compression signal selection unit 18 in FIG. 1 according to the even / odd number of the modulation pulse transmission trigger count instruction unit count value 40. In FIG. 5, when the modulation pulse transmission trigger count instructing unit count value 40 is an even number, the output signal of the first pulse compression processing unit 16 is used as the primary echo when it is an odd number, and when it is an odd number, the output signal of the second pulse compression processing unit 17 is used as the primary echo. Sort.

The secondary echo 42 output from the pulse compression signal selection unit represents a secondary echo that is sorted by the pulse compression signal selection unit 18 according to the even / odd number of the modulation pulse transmission trigger count instruction unit count value 40. In FIG. 5, when the modulation pulse transmission trigger count instructing unit count value 40 is an even number, the output signal of the second pulse compression processing unit 17 is the secondary echo, and when it is an odd number, the output signal of the first pulse compression processing unit 16 is the secondary echo. Sort as

The echoes 43 to 45 output from the pulse compression signal synthesis unit represent the result of connecting the secondary echo to the end of the primary echo by the pulse compression signal synthesis unit 19 of FIG. In the echo 43 output from the pulse compression signal synthesis unit, the modulation pulse transmission trigger count instruction unit count value 40 is an even number. Therefore, the output signal of the first pulse compression processing unit 16 is set as the primary echo, and the second echo is output at the end. The output signal of the pulse compression processing unit 17, that is, the secondary echo is connected.

In the echo 44 output by the pulse compressed signal synthesizer after 1 PRI has elapsed from the echo 43 output by the pulse compressed signal synthesizer, the relationship between the primary echo and the secondary echo is reversed, and the output of the second pulse compression processor 17 The signal is the primary echo, and the output signal of the first pulse compression processing unit 16, that is, the secondary echo is connected to the end of the signal. Further, in the echo 45 output from the pulse compression signal synthesizer after 1 PRI has elapsed, the output signal of the first pulse compression processing unit 16 is set as the primary echo, and the output signal of the second pulse compression processing unit 17 is provided at the end thereof, that is, Secondary echoes are connected.

By the operations such as 0029 to 0063, it is possible to expand the maximum target detection range up to twice without increasing the peak transmission power and the transmission pulse width in the linear FM modulation type pulse compression radar apparatus.

The pulse compression signal Doppler velocity calculation unit 20 in FIG. 1 calculates the Doppler velocity of the pulse compression signal obtained by expanding the maximum target detection range output from the pulse compression signal synthesis unit 19 up to twice. For convenience, this Doppler speed is referred to as a first Doppler speed signal.

  The unmodulated pulse digital filter unit 21 in FIG. 1 is a digital filter having a band that blocks a modulated pulse and allows the unmodulated pulse to pass through. At the headquarters, the reflected wave due to the non-modulated pulse is separated from the reflected wave from the target sampled / quantized by the A / D converter 13.

  The unmodulated pulse digital quadrature detection unit 22 in FIG. 1 performs quadrature detection of the reflected wave from the target by the unmodulated pulse output from the unmodulated pulse digital filter unit 21.

The unmodulated pulse signal Doppler velocity calculation unit 23 of FIG. 1 calculates the Doppler velocity of the unmodulated pulse orthogonal detection signal output from the unmodulated pulse digital quadrature detection unit 22. For convenience, this signal is referred to as a second Doppler velocity signal.

The unmodulated pulse signal Doppler velocity calculation unit 23 of FIG. 1 calculates the Doppler velocity of the unmodulated pulse orthogonal detection signal output from the unmodulated pulse digital quadrature detection unit 22. For convenience, this signal is referred to as a second Doppler velocity signal.

6, when the same target is observed with different PRIs, the Doppler velocity aliasing generated in the first Doppler velocity signal observed with the modulated pulse and the second Doppler velocity signal observed with the unmodulated pulse is calculated. explain.

  The true Doppler speed 46 in FIG. 6 indicates the Doppler speed of the target existing in the space. In the example of FIG. 6, the true Doppler velocity 46 is a value that is greater than or equal to the maximum measured Doppler velocity that can be observed with the PRI of the modulated pulse determined by the equation (2) and less than the maximum measured Doppler velocity that can be observed with the PRI of the unmodulated pulse. And distributed from outside the observation range of the unmodulated pulse determined by the equation (1). In FIG. 6, the PRI of the non-modulation pulse is set to a half period of the PRI of the modulation pulse.

  A first Doppler velocity signal 47 in FIG. 6 indicates a Doppler velocity signal obtained when the modulation pulse is observed for the true Doppler velocity 46. Since the true Doppler velocity 46 is equal to or higher than the maximum measured Doppler velocity that can be observed by the PRI of the modulation pulse, velocity folding occurs at a point where the target exists.

  The second Doppler velocity signal 48 in FIG. 6 represents a Doppler velocity signal obtained when the true Doppler velocity 46 is observed by an unmodulated pulse. Since the true Doppler velocity 46 is less than the maximum measured Doppler velocity that can be observed by the PRI of the unmodulated pulse, no speed wrapping occurs at the point where the same target of the unmodulated pulse exists within the observation range of the unmodulated pulse. . However, since it exists from outside the unmodulated pulse observation range defined by the equation (1), it cannot provide the Doppler velocity over the entire range where the true Doppler velocity 46 exists.

  The Doppler speed folding correction unit 24 of FIG. 1 uses the continuous method shown in Non-Patent Document 5 with the second Doppler speed signal as a reference, and performs the first Doppler speed folding including the Doppler speed folding shown in FIG. Correct wrapping.

The operation of the Doppler velocity folding correction unit 24 in FIG. 1 will be described with reference to FIG.

  In FIG. 7, the first Doppler velocity signal 49 is output by the pulse compression signal Doppler velocity calculator 20 of FIG. 1, and within the observation range, the Doppler as indicated by the first Doppler velocity signal 47 of FIG. Indicates a signal that includes a turnback of speed. 7, the second Doppler velocity signal 50 is output from the unmodulated pulse Doppler velocity calculator 23 in FIG. 1, and as shown in the second Doppler velocity signal 48 in FIG. 6 within the observation range. This indicates a signal that does not cause Doppler speed folding but cannot provide Doppler speed over the entire range where the target exists. Similarly, in FIG. 7, a Doppler speed folding correction signal 51 indicates a signal output by the Doppler speed folding correction unit 24 in FIG.

  In FIG. 7, in the reference range 52 where both the first Doppler velocity signal 49 and the second Doppler velocity signal 50 exist, the Doppler velocity folding correction unit 24 of FIG. 1 outputs the second Doppler velocity signal 50. For convenience, the end range bin output by the Doppler velocity folding correction unit 24 in the reference range 52 is referred to as a first Doppler velocity folding correction signal.

On the other hand, at the head of the correction range 53 where only the first Doppler velocity signal 49 exists, the first Doppler velocity folding correction signal and the first range bin in the correction range 53 of the first Doppler velocity signal 49 ( A difference is obtained from a value obtained by adding / subtracting an even multiple of the maximum measured Doppler speed (expressed as Vnyq in FIG. 7 for convenience) determined by the equation (2). Of the difference results, the value that minimizes the residual is output as the first range bin of the correction range 53 of the Doppler velocity folding correction unit 24. For convenience, the range bin is referred to as a second range bin.

  Subsequently, in the second range bin of the correction range 53, an even multiple of the maximum measured Doppler speed determined by the equation (2) is added to or subtracted from the second range bin of the second range bin and the first Doppler speed signal in the correction range 53. Take the difference from the value. Of the difference results, the value that minimizes the residual is output as the second range bin of the correction range 53 of the Doppler velocity folding correction unit 24.

  By repeating the difference in the direction in which the distance from the radar apparatus increases, the Doppler velocity folding included in the first Doppler velocity signal 49 is corrected.

As described above, the loopback correction of the Doppler speed signal is performed.

With the above operation, both the maximum detection distance and the maximum measured Doppler velocity of the radar apparatus are expanded simultaneously.

1 ... Modulation pulse waveform storage memory unit,
2 ... Modulation pulse transmission timing timing indicator,
3 ... Modulation pulse transmission trigger count instruction section,
4 ... modulation pulse address counter section,
5 ... Unmodulated pulse waveform storage memory section,
6 ... Unmodulated pulse transmission timing timing indicator,
7: Unmodulated pulse address counter section,
8: Pulse synthesis unit,
9: D / A converter,
10: Transmitter,
11 ... Aerial line part,
12 ... receiving part,
13 ... A / D conversion section,
14 ... modulation pulse digital filter section,
15: Modulation pulse digital quadrature detection unit,
16: Pulse compression processing unit 1,
17... Pulse compression processing unit 1
18 ... pulse compression signal selection unit,
19 ... pulse compression signal synthesis unit,
20: Pulse compression signal Doppler velocity calculation unit,
21: Unmodulated pulse digital filter section,
22: Unmodulated pulse digital quadrature detector,
23: Unmodulated pulse signal Doppler velocity calculation unit,
24 ... Doppler speed folding correction unit,
25. Modulation pulse transmission trigger,
26: Modulation pulse transmission trigger count instruction unit count value,
27. Modulation pulse,
28: Frequency sweep direction,
29 ... Frequency sweep direction in which the primary echo depends,
30 ... frequency sweep direction in which secondary echo depends,
31 ... Modulation pulse transmission trigger,
32. Modulation pulse,
33: Unmodulated pulse transmission trigger,
34: Unmodulated pulse,
35 ... modulation pulse spectrum,
36 ... modulation pulse center frequency,
37 ... Unmodulated pulse spectrum,
38 ... unmodulated pulse center frequency,
39: Modulation pulse transmission trigger,
40: Modulation pulse transmission trigger count instruction unit count value,
41 ... Primary echo output by the pulse compression signal selection unit,
42 ... Secondary echo output by the pulse compression signal selector,
43 to 45: echoes output from the pulse compression signal synthesizer,
46 ... True Doppler speed,
47. First Doppler speed signal,
48 ... second Doppler velocity signal,
49. First Doppler speed signal,
50 ... second Doppler velocity signal,
51 ... Doppler speed folding correction signal,
52 ... Reference range,
53 ... Correction range

Claims (3)

In linear FM modulation type pulse compression radar,
A modulation pulse waveform signal is stored in the modulation pulse waveform storage memory unit, and the address counter unit realizes pulse transmission by designating an address value of the modulation pulse waveform storage memory unit,
When the first address transition is that the address value is in the increasing direction from the head address of the storage modulation pulse, and the second address transition is that the address value is in the decreasing direction from the last address of the storage modulation pulse. ,
An address counter unit that operates so that the waveform on the time axis of the modulation pulse is reversed horizontally for each transmission repetition period by repeating the first transition and the second transition for each transmission repetition period;
A modulation pulse quadrature detection unit for quadrature detection of a reflected wave from a target, wherein the modulation pulse generated by the first transition is a first modulation pulse, the modulation pulse generated by the second transition is a second modulation pulse; ,
A first pulse compression processing unit for pulse-compressing a reflected wave by the first modulation pulse by performing a pulse compression process with a compression coefficient in the same frequency sweep direction as the first modulation pulse;
A second pulse compression processing unit for pulse-compressing the reflected wave of the second modulated pulse by subjecting the reflected wave from the target to pulse compression with a compression coefficient in the frequency sweep direction that is inverted with respect to the first modulated pulse. When,
A pulse compression signal for discriminating the reflected wave of the pulse transmission at the current time and the reflected wave of the pulse transmission of one repetition period before the output of the first pulse compression processor and the output of the second pulse compression processor A selection section;
The reflected wave of the pulse transmission at the current time output from the pulse compression signal selection unit is the first reflected wave, and the reflected wave of the pulse transmission one repetition period before the pulse transmission at the current time is the second reflected wave. A pulse compression signal synthesizer that outputs a first reflected wave obtained by connecting a reflected wave of a pulse transmission one repetition period before the second reflected wave is coupled to the end of the first reflected wave;
A modulated pulse Doppler velocity calculator for calculating a target Doppler velocity from the signal output by the pulse compression signal synthesizer and outputting a first Doppler velocity signal;
A radar device characterized by comprising: The radar apparatus according to claim 1, wherein
The unmodulated pulse waveform storage memory unit stores an unmodulated pulse waveform signal having a center frequency different from that of the first modulated pulse and the second modulated pulse, and the unmodulated pulse address counter unit stores the non-modulated pulse address counter unit. Realizing pulse transmission by specifying the address value of the modulation pulse waveform storage memory unit,
When the transmission repetition period is a first transmission repetition period and a transmission repetition period higher than the first transmission repetition period is a second transmission repetition period, the non-modulated pulse in the second transmission repetition period An unmodulated pulse quadrature detection unit that quadrature-detects the reflected wave from the target,
A non-modulated pulse Doppler velocity calculation unit for calculating a target Doppler velocity from the quadrature phase signal obtained by the non-modulated pulse quadrature detection unit and outputting a second Doppler velocity signal;
A radar device characterized by comprising: The radar apparatus according to claim 2, wherein
Doppler speed correction that corrects the Doppler speed folding included in the first Doppler speed signal by assuming continuity in the distance and azimuth direction of the Doppler speed on the basis of an arbitrary point of the second Doppler speed signal. And
A radar device characterized by comprising: