JP2013167580A - Target speed measuring device, signal processing apparatus, radar device, target speed measuring method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement accuracy of the Doppler velocity of a target.SOLUTION: A target speed measuring device 100 calculates the Doppler velocity of a target on the basis of a complex received signal in which a transmission signal transmitted at a predetermined repetition period via a radar antenna 30 is reflected on the target and received. The target speed measuring device 100 calculates the Doppler velocity of the target by performing the extended discrete Fourier transform (DFT) to the complex received signal in a range including an area where velocity return based on the predetermined repetition period occurs.

Description

  The present invention relates to a technique for measuring a Doppler velocity of a target by a radar.

  Conventionally, a radar measures the approach speed (hereinafter referred to as “Doppler speed”) of a target with respect to its own ship based on the phase change amount of a received echo signal between transmission cycles.

  In the measurement of the Doppler speed, when the Doppler speed is high, so-called speed folding occurs. Speed folding is a phenomenon in which when the Doppler frequency of the received signal exceeds the sampling frequency according to the sampling theorem (hereinafter also referred to as the Nyquist velocity), a velocity value different from the actual approaching velocity of the target is observed. .

FIG. 8 is a diagram illustrating the relationship between the measured Doppler speed and the true Doppler speed when the speed turnaround occurs. Measurement is possible when the Doppler frequency of the received signal (that is, the measured Doppler speed) exceeds 1/2 the pulse repetition frequency (hereinafter referred to as PRF (pulse repetition frequency)) of the radar transmission signal, which is the sampling frequency. The maximum speed ± V _N is exceeded (dotted line in FIG. 8). As a result, a speed value different from the actual approach speed is measured, for example, a Doppler speed with a reversed sign is detected.

  When the speed turn-back occurs, the operator erroneously recognizes the approach speed between the ship and the other ship, which hinders the safety of navigation. As a method for expanding the speed measurement range, a double PRF method in which two types of PRF are switched and the Doppler speed in each case is measured may be used (for example, see Non-Patent Documents 1 to 3).

Fukao, Hamazu, “Radar Remote Sensing of Weather and Atmosphere”, Kyoto University Academic Press, 2005, p.491 Baba, et al. "Meteorological Doppler Radar" Japan Radio Technical Bulletin No.48, 2005, p.12-34 Adachi, Sato "Doppler weather radar" Toshiba review Vol.55 No.5, 2000, p.27-30

  In particular, navigation radar generally uses a process that changes the repetition period for each transmission signal (Pulse to pulse stagger) in order to reduce the influence of mutual interference with transmission signals from other radar devices. It is done. Here, the repetition period is represented by the reciprocal of PRF. In this processing (hereinafter referred to as stagger processing), the PRF also changes. Therefore, for example, when the above-described double PRF method is applied, the speed measurement error increases. Therefore, inconveniences such as inability to appropriately determine the number of times of speed return occur.

  An object of the present invention is to improve the measurement accuracy of the Doppler velocity of a target.

  According to one aspect of the present invention, an object that calculates a Doppler velocity of a target based on a complex reception signal that is received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna. A target speed measuring device that calculates a Doppler speed of a target by performing an extended DFT, which is a discrete Fourier transform on a complex received signal, in a range including a region where a speed return based on a predetermined repetition period occurs. A velocity measuring device is provided.

  According to another aspect of the present invention, an object that calculates a Doppler velocity of a target based on a complex received signal that is received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna. A standard velocity measuring device, which performs an extended DFT, which is a discrete Fourier transform on a complex received signal, in a range including a region where a folding speed based on a predetermined repetition period does not occur and a region outside the region where a folding speed occurs. To calculate the Doppler velocity of the target.

  According to still another aspect of the present invention, the target velocity measuring device, an A / D converter that converts a complex reception signal from an analog value to a digital value, and quadrature detection of the complex reception signal converted to a digital value. A signal processing apparatus including an orthogonal detection unit is provided.

  According to still another aspect of the present invention, a transmission signal is transmitted, a radar antenna that receives a complex reception signal by reflection, a transmission signal transmitted by the radar antenna is generated, and a frequency conversion between the transmission signal and the complex reception signal is performed. There is provided a radar apparatus comprising: a transmission / reception unit that performs the above-described signal processing device that calculates a Doppler velocity based on a complex reception signal acquired from the transmission / reception unit.

According to another aspect of the present invention, an object that calculates a Doppler velocity of a target based on a complex received signal that is received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna. A target speed measurement method, comprising a Doppler speed estimation step and a Doppler speed correction step, is provided. In the Doppler velocity estimation step, the Doppler velocity V _d of the target is calculated in a region where velocity folding based on a predetermined repetition period does not occur. In the Doppler velocity correction step, a Doppler velocity estimation step is performed using an extended DFT, which is a discrete Fourier transform in which the velocity range for measuring the Doppler velocity V _{d of the} target is expanded to a region where velocity folding based on a predetermined repetition period occurs. The Doppler velocity V _r of the target is calculated by correcting the Doppler velocity V _d calculated in step (1).

  According to still another aspect of the present invention, a computer program for causing a computer to execute the target velocity measuring method is provided.

  According to the present invention, the measurement accuracy of the Doppler speed of a target can be increased.

1 is a schematic configuration diagram of a radar device according to a first embodiment. Schematic block diagram of the configuration of the signal processing apparatus according to the embodiment The figure for demonstrating the ship speed correction process by the embodiment A diagram for explaining the Doppler speed corrected for speed folding Comparison diagram of Doppler spectra respectively calculated by the general DFT and the DFT according to the embodiment The flowchart which shows the process by the signal processing apparatus by the same embodiment Schematic block diagram of the configuration of the signal processing device according to the second embodiment Diagram showing the relationship between the measured Doppler speed and the true Doppler speed when speed wrapping occurs

<1 First Embodiment>
Hereinafter, a radar apparatus according to an embodiment of the present invention will be described with reference to the drawings.
<1-1 Radar device configuration>
FIG. 1 is a diagram illustrating a schematic configuration of a radar apparatus according to the present embodiment. A radar apparatus 1 shown in FIG. 1 is a ship radar apparatus that is provided, for example, in a ship or the like and detects a target such as another ship on the sea, a buoy, or land. As shown in FIG. 1, the radar device 1 includes an antenna 30, a transmission / reception unit 20, a signal processing unit 10, and an input / output device 40. Hereafter, each element which comprises the radar apparatus 1 is demonstrated in detail.

Although a marine radar device will be described here as an example of a radar device, the present invention can be applied to other radar devices, for example, a radar device for other uses such as a weather radar and a port monitoring radar. Can also be applied. Such a radar apparatus includes not only a solid-state radar apparatus using a semiconductor amplifier as a transmitter but also a magnetron radar apparatus.
<1-1-1 Antenna 30>
In the radar device 1, the antenna 30 transmits a pulsed radio wave beam having a sharp directivity and receives a reflected wave from a target around the antenna 30. The beam width is set to 2 degrees, for example. The antenna 30 repeats the above transmission and reception while rotating in a horizontal plane. The number of rotations is, for example, 24 rpm. A unit of processing performed while the antenna 30 rotates once is called one scan. In addition, transmission and reception operations in a period from when a transmission signal is transmitted to immediately before the next transmission signal is transmitted are called sweeps. The time for one sweep, that is, the transmission cycle is, for example, 1 ms. The number of received data per sweep is called the number of sample points.

  The antenna 30 receives a complex reception signal including a reflected wave from a target by concentrating and emitting transmission signals in a certain direction. In addition to the target signal component, the complex received signal may include components such as radio wave interference waves and receiver noise from clutter and other radar devices.

The distance from the antenna 30 to the target is obtained from the time difference between the reception time of the reception signal including the target signal and the transmission time of the transmission signal corresponding to the reception signal. Further, the direction of the target is obtained from the direction of the antenna 30 when transmitting the corresponding transmission signal.
<1-1-2 Transceiver 20>
The transmission / reception unit 20 generates a transmission signal and sends it to the antenna 30. Further, the transmission / reception unit 20 takes in the received signal from the antenna 30 and converts the frequency of the received signal. Therefore, in this embodiment, the transmission / reception unit 20 includes a transmission signal generator 21, a frequency converter 22, a local oscillator 23, a transmission / reception switch 24, and a frequency converter 25.

  The transmission signal generator 21 generates a transmission signal having an intermediate frequency according to a command from the stagger setting unit 18 of the signal processing unit 10 described later, and outputs the transmission signal to the frequency converter 22. In this embodiment, the transmission signal generated by the transmission signal generator 21 is a signal that changes a repetition cycle (or transmission timing), that is, a signal that is subjected to stagger processing. Here, changing the repetition period (or transmission timing) includes not only the repetition period (or transmission timing) being different for each transmission, but also the case where the same repetition period (or transmission timing) is partially continuous.

  The frequency converter 22 mixes the output signal of the transmission signal generator 21 with the local signal output from the local oscillator 23, converts the frequency of the output signal of the transmission signal generator 21, and outputs it to the transmission / reception switch 24. The frequency band of the output signal of the frequency converter 22 is, for example, a 3 GHz band or a 9 GHz band.

  The transmission / reception switch 24 is configured to be connectable to the antenna 30. The transmission / reception switch 24 switches signals between the antenna 30 and the transmission / reception unit 20. That is, the transmission / reception switch 24 prevents the transmission signal from entering the reception circuit (ie, the frequency converter 25) during transmission, and prevents the reception signal from entering the transmission circuit (ie, the frequency converter 22) during reception. To do. As the transmission / reception switching device 24, for example, an electronic component such as a circulator is used.

  The frequency converter 25 takes in a reception signal output from the antenna 30 via the transmission / reception switch 24. Then, the frequency converter 25 mixes the received signal with the local signal output from the local oscillator 23, converts the output signal of the transmission / reception switch 24 into an intermediate frequency, and outputs it to the signal processing unit 10 described later.

In the transmission / reception unit 20 of FIG. 1, illustration of an amplifier and a filter is omitted.
<1-1-3 Signal Processing Unit 10>
The signal processing unit 10 performs signal processing by converting the complex reception signal into a digital signal. The signal processing unit 10 is, for example, a device or an integrated circuit including a processor and a memory, and processes reception data output from an A / D conversion unit 11 described later to generate a video signal. The signal processing device 10 is realized by, for example, a general-purpose DSP or FPGA that executes a program stored in a memory. The signal processing unit 10 can also be realized by a digital circuit such as an ASIC (Application Specific Integrated Circuit).

The detailed configuration and operation of the signal processing unit 10 will be described later.
<1-1-4 I / O device 40>
The input / output device 40 is a device including a processor, a memory, and the like (not shown). The input / output device 40 includes a display unit such as an LCD (Liquid Crystal Display) and an input unit such as buttons and a keyboard that can be operated by an operator. The input / output device 40 stores the received data obtained in each sweep in a memory for image display, reads the stored data from the memory in a predetermined order, and displays it as a video on the display unit. Usually, a radar image displays a target in a 360-degree azimuth centering on the position of the radar device (antenna). The origin of the display corresponds to the position of the radar device. The operator of the radar apparatus 1 can recognize the azimuth and distance of the target from the amplitude of the reflected wave from the target, that is, the position where the received signal is displayed on the radar image.
<1-2 Configuration of Signal Processing Unit 10>
FIG. 2 schematically shows the configuration of the signal processing unit 10 (an example of a signal processing device) according to the present embodiment. The signal processing unit 10 includes an A / D conversion unit 11, a quadrature detection unit 12, a pulse compression unit 13, a Doppler velocity measurement unit 100 (an example of a target velocity measurement device), and a stagger setting unit 18. Further, the Doppler speed measurement unit 100 includes a Doppler speed estimation unit 14, a folding determination unit 15, a Doppler speed correction unit 16, and a ship speed correction unit 17. In addition, the Doppler speed estimation unit 14, the folding determination unit 15, and the Doppler speed correction unit 16 constitute a Doppler speed calculation unit 19.

  The A / D converter 11 converts an analog intermediate frequency signal output from the frequency converter 25 of the transceiver 20 into a digital signal.

The quadrature detection unit 12 performs quadrature detection on the digital intermediate frequency signal output from the A / D conversion unit 11. Specifically, the quadrature detection unit 12 generates an I (In-Phase) signal and a Q (Quadrature) signal having a phase different from that by π / 2 from the output signal of the A / D conversion unit 11. Here, the I signal and the Q signal (hereinafter abbreviated as “I” and “Q” as appropriate) are a real part and an imaginary part of the complex reception signal of the radar, respectively. The amplitude of the complex received signal is represented by (I ² + Q ² ) ^1/2 and the phase is represented by tan ⁻¹ (Q / I). Hereinafter, the complex reception signal may be simply referred to as reception data. The number of transmissions / receptions per scan (= number of sweeps) is K, and the number of received data per sweep is N. The received data S sampled n-th (0 ≦ n ≦ N−1) in the k-th (0 ≦ k ≦ K−1) sweep is represented by S [k, n]. k corresponds to the azimuth of the antenna 30, and n corresponds to the distance. Further, k is an azimuth number and n is a distance number. Further, the antenna direction at the first sweep (k = 0) is set as the bow direction. Further, a set (k, n) of these numbers is used as data coordinates.

  The pulse compression unit 13 includes, for example, a Fourier transform unit, a matched filter, and an inverse Fourier transform unit, and performs pulse compression on the modulated pulse signal from the quadrature detection unit 12 by a known method, and outputs a pulse-compressed signal.

The Doppler velocity estimation unit 14 uses the pulse pair method for the received data S [k, n] (0 ≦ k ≦ K−1, 0 ≦ n ≦ N−1) output from the pulse compression unit 13 to each coordinate (k , N), the Doppler velocity is calculated. Hereinafter, this Doppler velocity is represented by V _d [k, n] (0 ≦ k ≦ K−1, 0 ≦ n ≦ N−1). In general, there are two types of methods for measuring the Doppler velocity: a pulse pair method and a DFT (Discrete Fourier Transform). In this embodiment, the pulse pair method has higher velocity measurement accuracy than DFT. Is used. The pulse pair method fires two consecutive transmission pulses and calculates the complex autocorrelation coefficient of the received signal reflected from the same distance. Based on this result (the phase difference of the received signal), the Doppler speed of the other ship is calculated.

The aliasing determination unit 15 applies an extended DFT described later to the reception data S [k, n] (0 ≦ k ≦ K−1, 0 ≦ n ≦ N−1) output from the pulse compression unit 13, A Nyquist number N _num that is the number of times of speed folding at the coordinates (k, n) is calculated.

Based on the Nyquist number N _num calculated by the turn-back determination unit 15 and the maximum speed ± V _N of the Doppler speed V _d in a speed region in which speed turn-back does not occur, which will be described later, the Doppler speed correction unit 16 The output Doppler velocity V _d [k, n] is corrected, and the actual Doppler velocity V _r which is the true Doppler velocity or its approximate value is calculated.

The ship speed correction unit 17 calculates the approach speed (absolute speed) of the other ship by subtracting the speed of the ship from the Doppler speed V _r (relative speed) output from the Doppler speed correction unit 16, and inputs and outputs Output to the device 40. FIG. 3 is a diagram for explaining the ship speed correction processing by the ship speed correcting unit 17, and the ship speed correction in a situation where the own ship is traveling straight at the ship speed V ₀ and the other ship is _traveling at the ship speed V _t. Represents processing. At this time, the approach speed V _a of the other ship is expressed by the following equation.

V _a = V _r −V ₀ · cos θ _t
However,
θ _t : angle between own ship's traveling direction and current antenna direction (direction of other ship) V _a : own ship's speed vector V _t : other ship's speed vector V _r : speed measured by pulse pair method (relative speed)
V _a : Approach speed of other ship (= radial component of speed vector of other ship)
And

The stagger setting unit 18 generates a setting signal having a predetermined stagger pattern from the maximum stagger rate, PRF, pulse width, and the like, and outputs the setting signal to the transmission signal generator 21.
<1-3 Operation of Signal Processing Unit 10>
<Outline of measurement of 1-3-1 Doppler velocity>
As described, the maximum value f _dmax of the Doppler frequency that can be measured is obtained by the following equation using the sampling theorem.

Further, the relative velocity of the target, that is, the measured Doppler velocity V _d is obtained by the following equation.

From the above equations (1) and (2), the maximum velocity V _{N at} which velocity folding does not occur is obtained by the following equation.

Including the case where the Doppler speed of the target exceeds the Nyquist speed, the Doppler speed of the target, that is, the actual Doppler speed V _r is obtained by the following equation.

Here, N _num indicates the number of times of speed folding.
<1-3-2 Determination of speed return>
FIG. 4 is a diagram illustrating a relationship between values obtained by the above formulas (2) to (4).

In the present embodiment, the number of times N _{num of} speed folding is calculated using a method applying DFT, which has been used for measuring the Doppler velocity V _d of a conventional target. Specifically, it is as follows.

  When the number of DFT points is M, the absolute value of the Doppler spectrum indicates the amplitude of the received signal component included in the subband (channel) obtained by dividing the band of the width PRF into M pieces. That is, the DFT process is equivalent to an output from a filter bank composed of M filters.

When the range of the velocity v of the target to be observed is −A · V _N ≦ v ≦ A · V _N (A is a natural number), the output X [k _d ] of each filter bank is calculated by the following equation: The

Here, M = 0,..., M..., M-1 (where M is an even number). S _m is a stagger rate, which is a ratio of the amount of time shift accompanying stagger processing to the average transmission period.

  In addition, A can be set based on the maximum speed estimated according to the kind (ship etc.) of a target, for example.

  The above DFT processing (hereinafter referred to as “extended DFT”) expands the velocity range of the target to be observed to the velocity region where velocity folding occurs, and the Doppler frequency measurement range (range of k) is larger than that of the conventional DFT. It differs from the conventional DFT in that it is A times and the phase error corresponding to the time shift associated with the stagger processing of the transmission signal is corrected.

  Next, a specific example will be described.

If the target velocity range to be observed is -3V _N ≤ v ≤ 3V _N , the target Doppler velocity is 2.5 x V _N , the number of DFT points is M = 16, and stagger processing is used, FIG. 5 shows Doppler spectra calculated in each of the extended DFTs of the embodiment. FIG. 5A is a Doppler spectrum calculated by a conventional DFT, and FIG. 5B is a Doppler spectrum calculated by the extended DFT (equation (5)).

In FIG. 5A, the measurement range of the Doppler velocity is −V _N ≦ v ≦ V _N , and the Doppler spectrum exceeding this velocity range is obtained by sampling the Doppler spectrum in the velocity range of −V _N ≦ v ≦ V _N. The spectrum is repeated every 2V _N which is the speed corresponding to (PRF). Accordingly, the level difference between the Doppler spectrum corresponding to the actual target speed and the Doppler spectrum corresponding to the false target speed appearing due to the alias becomes equal. For this reason, it cannot be determined which is the correct measurement result. On the other hand, in FIG. 5B, the phase error corresponding to the time shift associated with the stagger processing is corrected using S _m . As a result, for the Doppler spectrum corresponding to the actual target velocity, the phase error is appropriately corrected, and a spectrum level equivalent to that when no stagger processing is performed is maintained. On the other hand, for the Doppler spectrum corresponding to the false target velocity, the phase error is not appropriately corrected, and the spectrum level is lowered. Since the level of the Doppler spectrum corresponding to the actual target velocity is the highest, the number of velocity folding times, that is, N _num can be obtained by selecting this bank.

That is, in the above example, since the speed folding occurs once, N _num = 1. By substituting this into the above equation (4), the actual Doppler velocity V _r is measured.
<1-3-3 Doppler velocity measurement process>
FIG. 6 is a flowchart of the measurement processing of the Doppler speed of the target by the signal processing device 10 according to the present embodiment.

  Step S101: The intermediate frequency signal output from the frequency converter 25 of the transmission / reception unit 200 is converted into a digital signal by the A / D converter 11.

  Step S102: The digital signal output from the A / D converter 11 is subjected to quadrature detection by the quadrature detection unit 12, and the I signal and the Q signal are output as described above.

  Step S103: The I signal and the Q signal output from the quadrature detection unit 12 are pulse-compressed by the pulse compression unit 13, and a pulse compression signal is output.

Step S104: The Doppler velocity estimation unit 14 applies the pulse pair method to the pulse compression signal output from the pulse compression unit 13, and the Doppler velocity V _d [k, n] (0 ≦ k ≦ K−1, 0 ≦). n ≦ N−1) is calculated. On the other hand, the folding determination unit 15 applies the above-described extended DFT method to the pulse compression signal output from the pulse compression unit 13, and calculates the number N _num of speed foldings at each coordinate (k, n). The

Step S105: The Doppler speed V _d [k, n] calculated by the Doppler speed estimation unit 14 is corrected by the Doppler speed correction unit 16 using the above equation (4). The Doppler speed V _d is corrected when the number of speed folding N _num ≠ 0. When the number of speed folding N _num = 0, the Doppler speed V _d is output without correction. It will be.

Step S106: The ship speed correcting unit 17 performs ship speed correction processing on the Doppler speed V _r output from the Doppler speed correcting unit 16.

  Step S107: The output from the ship speed correction unit 17 is output as the Doppler speed of the other ship and displayed on the display unit of the input / output device 40.

In addition, the execution order of the processing method in the said embodiment is not necessarily restrict | limited to description of the said embodiment, The execution order can be changed in the range which does not deviate from the summary of invention.
<1-4 Features of this Embodiment>
According to the signal processing unit 10 of the radar device 1 according to the embodiment, the Doppler spectrum can be calculated in the entire Doppler frequency range corresponding to the actual velocity range of the target by using the above-described extended DFT. . Thereby, the measurement accuracy of the Doppler speed can be increased.

The extended DFT is applied to the calculation of the number of times of speed folding N _num , and the Doppler velocity V _d is calculated by using the pulse pair method having higher measurement accuracy than the normal DFT, thereby further increasing the Doppler velocity measurement accuracy. Can do.
<2 Second Embodiment>
FIG. 7 schematically shows a configuration of a signal processing unit 210 (an example of a signal processing device) according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the part which has the structure and function similar to the said 1st Embodiment.

  The signal processing unit 210 includes an A / D conversion unit 11, a quadrature detection unit 12, a pulse compression unit 13, a Doppler velocity measurement unit 200 (an example of a target velocity measurement device), and a stagger setting unit 18. Further, the Doppler speed measurement unit 200 includes a Doppler speed calculation unit 219 and a ship speed correction unit 17. In the signal processing unit 210 according to the present embodiment, the Doppler speed measurement unit 200 does not include the Doppler speed estimation unit 14, the folding determination unit 15, and the Doppler speed correction unit 16, but instead includes only the Doppler speed calculation unit 219. This is different from the first embodiment. About others, since a structure, a function, and operation | movement are the same as that of the said 1st Embodiment, detailed description is abbreviate | omitted.

  The Doppler velocity calculation unit 219 uses the extended DFT for the reception data S [k, n] (0 ≦ k ≦ K−1, 0 ≦ n ≦ N−1) output from the pulse compression unit 13. The Doppler velocity at the coordinates (k, n) is calculated. Specifically, the actual Doppler velocity is calculated by converting the received signal calculated by the following equation (5) into the frequency domain and detecting the maximum value of the Doppler spectrum shown in FIG.

Here, M = 0,..., M..., M-1 (where M is an even number). S _m is a stagger rate, which is a ratio of the amount of time shift accompanying stagger processing to the average transmission period.

  In addition, A can be set based on the maximum speed estimated according to the kind (ship etc.) of a target, for example.

In this embodiment, unlike the first embodiment, it is not necessary to count the number of times of speed folding, and an extended DFT in which the range for measuring the Doppler speed V _{d of the} target is extended to the speed region where the speed folding occurs is directly used. Thus, the Doppler velocity V _d is calculated. Therefore, although the measurement accuracy may be lower than that in the first embodiment, the measurement accuracy of the Doppler velocity can be increased as compared with the conventional case even if the speed is turned back.
<3 Other Embodiments>
<3-1>
Although the signal processing unit 10 of the radar device 1 according to the above embodiment includes the pulse compression unit 13, it is not limited to this. Even if there is no pulse compression part, the effect by the said embodiment can be acquired.
<3-2>
Although the signal processing unit 10 (or 210) of the radar device 1 according to the above-described embodiment includes the boat speed correction unit 17, it is not limited to this. Relative speed data output from the Doppler speed correction unit 16 (or Doppler speed calculation unit 219) may be output to the input / output device 40 without the ship speed correction unit.
<3-3>
In the signal processing unit 10 of the radar device 1 according to the above embodiment, the Doppler velocity estimation unit 14 calculates the Doppler velocity using the pulse pair method, but instead of this, a normal DFT may be used. In the case of DFT, DFT processing is applied to the received signal to convert it to the frequency domain (speed domain), and a Doppler spectrum is calculated. The Doppler velocity is measured by reading the maximum value of the Doppler spectrum. The pulse pair method has an advantage that the Doppler velocity can be measured more accurately than the DFT, but the DFT can measure the velocity of only the signal by separating the signal, clutter and noise on the Doppler spectrum.
<3-4>
In the above embodiment, the signal processing apparatus 10 has been described as an apparatus or an integrated circuit, but the present invention can also be realized as a target speed measurement method or a computer program.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 10 Signal processing apparatus 11 A / D conversion part 12 Quadrature detection part 13 Pulse compression part 14 Doppler speed estimation part 15 Turn-back determination part 16 Doppler speed correction part 17 Ship speed correction part 18 Stagger setting part 19 Doppler speed calculation part 20 Transmission / reception unit 21 Transmission signal generator 22 Frequency converter 23 Local transmitter 24 Transmission / reception switch 25 Frequency converter 30 Antenna 40 Input / output device 100 Doppler velocity measurement unit 200 Doppler velocity measurement unit 210 Signal processing device 219 Doppler velocity calculation unit

Claims (14)

A target speed measurement device that calculates a Doppler speed of a target based on a complex reception signal that is received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna.
Calculating the Doppler velocity of the target by performing an extended DFT which is a discrete Fourier transform on the complex received signal in a range including a region where velocity folding based on the predetermined repetition period occurs.
Target speed measuring device. The transmission signal is a signal whose repetition period changes.
The target velocity measuring apparatus according to claim 1. The extended DFT corrects a phase error according to a time shift associated with a change in the repetition period of the transmission signal.
The target velocity measuring apparatus according to claim 2. A Doppler velocity estimation unit that calculates a Doppler velocity V _d of the target in a region where velocity folding based on the predetermined repetition period does not occur, and a Doppler velocity calculated by the Doppler velocity estimation unit using the extended DFT A Doppler speed correction unit that calculates a Doppler speed V _r of the target by correcting V _d ;
The target velocity measuring device according to claim 1, comprising: A folding determination unit that determines the number of times N _{num of the} speed folding by the extended DFT;
The Doppler speed correction unit corrects the Doppler speed V _d calculated by the Doppler speed estimation unit based on the number of times N _{num of} speed wrapping.
The target velocity measuring apparatus according to claim 4. The folding determination unit
The expanded DFT calculates the Doppler spectrum level corresponding to the direction θ where the target exists,
Determining the number of speed wraps N _num by identifying a speed region with the highest level of the Doppler spectrum;
The target velocity measuring device according to claim 5. The Doppler velocity estimation unit calculates the Doppler velocity V _d of the target using a pulse pair method.
The target velocity measuring apparatus according to claim 4. The Doppler velocity correction unit calculates the Doppler velocity V _r of the target according to the following equation:
The target velocity measuring apparatus according to claim 4.

However, V _N is the maximum speed in a region where the speed folding does not occur. A target speed measurement device that calculates a Doppler speed of a target based on a complex reception signal that is received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna.
By performing an extended DFT, which is a discrete Fourier transform on the complex received signal, in a range including a region where a folding speed based on the predetermined repetition period does not occur and a region outside the region where the folding speed occurs. To calculate the Doppler speed of
Target speed measuring device. The target velocity measuring device according to claim 1 or 9,
A signal processing apparatus comprising: an A / D conversion unit that converts the complex reception signal from an analog value into a digital value; and an orthogonal detection unit that performs quadrature detection on the complex reception signal converted into a digital value. Further, a stagger setting unit that generates a signal for changing the repetition period of the transmission signal,
Comprising
The signal processing device according to claim 10. A radar antenna that transmits the transmission signal and receives the complex reception signal by reflection;
The transmission signal transmitted from the radar antenna is generated, a transmission / reception unit that converts the frequency of the transmission signal and the complex reception signal, and the Doppler velocity is calculated based on the complex reception signal acquired from the transmission / reception unit. The signal processing device according to claim 10,
A radar device comprising: A target velocity measurement method for calculating a Doppler velocity of a target based on a complex reception signal received by reflecting a transmission signal transmitted at a predetermined repetition period via a radar antenna.
In the region where the speed folding based on the predetermined repetition period does not occur, the product Doppler velocity estimation step of calculating a Doppler velocity V _d of the target, and the speed range for measuring the Doppler velocity V _d of the target object, the predetermined The Doppler velocity V _{r of the} target is corrected by correcting the Doppler velocity V _d calculated in the Doppler velocity estimation step using an extended DFT that is a discrete Fourier transform extended to a region where velocity folding based on the repetition period occurs. Doppler speed correction step for calculating
A method for measuring a target speed.   A computer program for causing a computer to execute the target velocity measuring method according to claim 13.

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