JP2006349472A - Radar system and its signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate the Doppler velocity of high reliability even at the time, the deviation of velocity distribution is large or folding of the velocity is occurred. <P>SOLUTION: The Doppler velocity calculation process is constituted such that: the velocity spectrum representing the power intensity distribution of the Doppler velocity value of each power intensity is transformed into the power vector of the polar coordinate system (step S3a); the resultant power vector of the polar coordinate is composited then the power resultant vector is obtained (step S3b); the angle of deviation of the above obtained power resultant vector is calculated (step S3c); and the Doppler velocity is calculated based on the deviation angle of the power resultant vector (step S3d). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radar apparatus used in a Doppler weather radar that captures dynamic conditions of rain and clouds, for example, and a signal processing method thereof.

Conventionally, FFT (Fast Fourier Transform) is used as one of the methods for obtaining the target velocity by Doppler radar. The FFT method has been put to practical use because a high-speed DSP (Digital Signal Processor) has appeared and signal processing can be performed in real time by software. The FFT method is a method of detecting a Doppler velocity by converting a received phase signal into a frequency domain (speed domain) and reading a maximum value of a velocity spectrum (see, for example, Non-Patent Document 1).
Toshiba Review, Volume 55, Issue 5, May 1, 2000, “Doppler Weather Radar”, p. 28-30

  However, when obtaining the Doppler velocity from a target having a large variation in received waves such as weather echoes, in the signal processing method using the conventional FFT method, the size of the variation greatly affects the velocity accuracy. When the target speed is disturbed, such as weather echo, the obtained speed spectrum is also disturbed.For example, normal speed calculation methods such as peak detection and power average have large variations and are near the Nyquist speed. There is a problem that the obtained speed accuracy is deteriorated due to the return of the speed.

  The present invention has been made by paying attention to the above circumstances, and the object of the present invention is to calculate a highly reliable Doppler velocity even when there is a large variation in the velocity distribution of the observation target or when a turnback of the velocity occurs. A radar apparatus and a signal processing method thereof can be provided.

  To achieve the above object, a radar apparatus according to the present invention includes a transmission / reception unit for transmitting radar pulses and receiving radar echoes, and a velocity spectrum indicating power intensity distributions of a plurality of Doppler velocity values from the received signals of the radar echoes. And a signal processing unit that calculates the Doppler velocity of the target based on the velocity spectrum. The signal processing unit converts the power intensity of each of the Doppler velocity values of the velocity spectrum into a power vector of a polar coordinate system, obtains a power synthesis vector by synthesizing the converted power vector, and obtains the power synthesis vector. Based on this, the Doppler speed of the target is calculated.

  The signal processing method according to the present invention is a signal processing method used in a radar apparatus that transmits radar pulses and receives radar echoes, and shows power intensity distributions of a plurality of Doppler velocity values from the received signals of the radar echoes. A signal processing step is provided for obtaining a velocity spectrum and calculating a Doppler velocity of the target based on the velocity spectrum. Then, the signal processing step converts the power intensity of each of the Doppler velocity values of the velocity spectrum into a power vector of a polar coordinate system, obtains a power synthesized vector by synthesizing the converted power vector, and this power synthesized vector Based on the above, the Doppler speed of the target is calculated.

  In the radar apparatus and the signal processing method configured as described above, the Doppler velocity of the target is calculated by converting the velocity spectrum into the power intensity distribution of the polar coordinate system and calculating the weighted average of each power vector. This makes it possible to calculate a highly reliable Doppler velocity even when there is a large variation in velocity distribution or when there is a turnback, compared to conventional peak detection or average power in the velocity spectrum. Become.

  Therefore, according to the present invention, it is possible to provide a radar device and a signal processing method thereof that can calculate a Doppler velocity with high reliability even when the variation in the velocity distribution of the observation target is large or when a return of velocity occurs. .

FIG. 1 is a functional block diagram showing an embodiment of a radar apparatus according to the present invention.
The modulation unit 12 generates a digital value of an intermediate frequency signal of a designated modulation system under the control given from the signal processing unit 11 via the interface (I / F). This digital value is converted into an analog value by the D / A converter 13 to generate a transmission intermediate frequency signal (fi). The generated transmission intermediate frequency signal is up-converted to the transmission frequency of the radar pulse in the transmission / reception unit 14, and after power amplification, is transmitted from the antenna 15 to the space.

  The radar pulse with the frequency f0 transmitted from the antenna 15 is reflected by a target such as raindrops, and the radar echo returns. This radar echo is accompanied by a Doppler frequency (fd) reflecting the moving speed of the target, and the reception frequency is represented as (f0 + fd). The radar echo arrives at the transmitter / receiver 14 via the antenna 15 and is amplified and then down-converted to generate a reception intermediate frequency signal of (fi + fd). This received intermediate frequency signal is converted into a digital value by the A / D converter 16 and then subjected to quadrature detection by the demodulator 17.

  Further, the quadrature-detected signal is demodulated by the demodulation unit 17 by a plurality of modulation methods. The received data of the I component (in-phase component) and Q component (quadrature phase component) obtained in this way is given to the signal processing unit 11 via the interface (I / F). The signal processing unit 11 calculates observation data such as echo reflection intensity, target velocity and velocity width from the received data. In particular, the target Doppler velocity can be calculated from the velocity spectrum obtained by performing the FFT process on the received data.

  FIG. 2 is a flowchart showing a processing procedure of the radar apparatus of FIG. The received signal is A / D converted and then subjected to quadrature detection, and I component (in-phase component) and Q component (quadrature phase component) signals are output. Further, the signal processing unit 11 performs FFT processing on the output I / Q signal. In this FFT processing, the I / Q signal can be converted into the frequency domain to obtain a velocity spectrum. Based on the velocity spectrum thus obtained, the Doppler velocity of the target is detected.

Next, the Doppler speed calculation process performed by the signal processing unit 11 will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart showing the procedure and contents of the Doppler velocity calculation process. FIG. 4 is a conceptual diagram of the Doppler speed calculation process.
First, in step S3a, the power intensity of each of the Doppler velocity values of the velocity spectrum obtained by the FFT process described above is converted into a power vector in the polar coordinate system. This is indicated by P1 to P8 in FIG. Next, in step S3b, the converted polar coordinate system power vectors (P1 to P8) are synthesized to obtain a power synthesis vector (P). In step S3c, the deviation angle of the obtained power combined vector is obtained, and the Doppler velocity is calculated in step S3d based on this deviation angle. With such a procedure, the Doppler speed is obtained as shown in FIG.

A specific processing method will be described below using mathematical expressions.
The Doppler velocity of −Vmax ≦ Vi ≦ Vmax is replaced with an angle of −π ≦ θi ≦ π by the following equation to convert it into a power distribution in the polar coordinate system.
θi = πVi / Vmax (1)
In Equation (1), θi represents the deflection angle [rad] of the power vector, Vi represents the Doppler velocity, and Vmax represents the Nyquist velocity.

  Next, the replaced power vector distribution is vector synthesized by the following equation.

Pv = Preal + jPimage (2)
Preal = Σ (Pi · cosθi) (3)
Pimage = Σ (Pi · sinθi) (4)
Here, Pv is an intensity composite vector of Doppler velocity, Preal is a real part of the power composite vector, and Pimage is an imaginary part of the power composite vector. Pi is the power value for each speed, and θi is the deflection angle [rad] of each power vector.

Then, the deflection angle θavg of the power combined vector can be calculated by the following equation.
θavg = arc tan (Pimage / Preal) (5)
Based on the deviation angle θavg of the power combined vector obtained by the equation (5), the Doppler velocity v is calculated by the following equation.
v = Vmax · θavg / π (6)
As described above, in the above-described embodiment of the present invention, the power intensity of each Doppler velocity value of the velocity spectrum indicating the power intensity distribution is converted into a power vector of the polar coordinate system. Next, the power vector of the converted polar coordinate system is synthesized to obtain a power synthesis vector. Then, the deviation angle of the obtained power combination vector is obtained, and the Doppler velocity is calculated based on the deviation angle of the power combination vector.

  The present invention is particularly effective in the following cases. For example, when the Doppler velocity is obtained by simple peak detection when there is a large variation in the velocity spectrum, the Doppler velocity is detected by the maximum value read regardless of the velocity distribution. On the other hand, in the present invention, since the Doppler velocity is calculated using the power intensity in a wide range of velocity distribution, a highly reliable Doppler velocity value can be obtained.

  It is also effective when speed wrapping occurs in the speed spectrum. FIG. 5 shows a conceptual diagram of the Doppler speed calculation processing of the present invention when the return of speed occurs. When the speed is obtained by simply averaging the power distribution of the speed spectrum as in the prior art, when the Doppler speed of the target increases, the region exceeding the Nyquist speed is folded back, and a correct Doppler speed value cannot be obtained. However, as shown in FIG. 5, the velocity near the turn-back can be accurately obtained by once converting the velocity spectrum into the power vector distribution of the polar coordinate system.

  Therefore, according to the present invention, when compared with the conventional simple peak detection and power average of the speed spectrum, a highly reliable Doppler speed is calculated even when there is a large variation in speed distribution or when there is a return of speed. It becomes possible.

  The present invention is not limited to the above embodiment. For example, in FIG. 1, the functions of the D / A conversion unit 13 and the A / D conversion unit 16 can be combined with other functional blocks. The present invention is not limited to a weather radar but can be applied to other Doppler radars.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The functional block diagram which shows one Embodiment of the radar apparatus concerning this invention. The figure which shows the signal processing procedure of the radar apparatus shown in FIG. The flowchart which shows the procedure of the Doppler speed calculation process of the radar apparatus shown in FIG. 1, and its content. The conceptual diagram which shows the Doppler speed calculation process of the radar apparatus shown in FIG. The conceptual diagram which shows the Doppler speed calculation process of the radar apparatus shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Signal processing part, 12 ... Modulation part, 13 ... D / A conversion part, 14 ... Transmission / reception part, 15 ... Antenna, 16 ... A / D conversion part, 17 ... Demodulation part

Claims (2)

A transmission / reception unit for transmitting radar pulses and receiving radar echoes;
A signal processing unit that obtains a velocity spectrum indicating a power intensity distribution of each of a plurality of Doppler velocity values from the received signal of the radar echo, and calculates a Doppler velocity of a target based on the velocity spectrum;
The signal processing unit
Conversion means for converting the power intensity of each of the Doppler velocity values of the velocity spectrum into a power vector of a polar coordinate system;
Combining means for determining a power combined vector by combining the power vector;
A radar apparatus comprising: a calculating unit that calculates a Doppler velocity of a target based on the power combined vector. In a signal processing method used in a radar apparatus that transmits radar pulses and receives radar echoes,
A signal processing step of obtaining a velocity spectrum indicating a power intensity distribution of each of a plurality of Doppler velocity values from the received signal of the radar echo, and calculating a Doppler velocity of the target based on the velocity spectrum;
The signal processing step includes
Converting the power intensity of each of the Doppler velocity values of the velocity spectrum into a power vector of a polar coordinate system;
A combining step of determining a power combined vector by combining the power vector;
And a calculation step of calculating a target Doppler velocity based on the power combined vector.

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