KR101323681B1 - Apparatus and method for velocity estimation in ofdm radar system - Google Patents

Abstract

The present invention relates to a speed estimating apparatus and a speed estimating method for estimating the speed of a target in an OFDM radar system, the sequence signal generating unit for generating an arbitrary sequence signal; A phase shift modulator for performing phase shift keying on the sequence signal generated by the sequence signal generator; A serial-to-parallel converter for converting the phase-shifted signal in parallel in the phase shifter; An IFFT processor for performing an inverse fast fourier transform (IFFT) process on the signals converted in parallel in the serial-parallel converter; A first signal synthesizing unit configured to transmit a transmission signal obtained by synthesizing the IFFT-processed signal from the IFFT processor and the local oscillation signal generated by the local oscillator through an antenna; A second signal synthesizing unit reflecting the transmission signal to a target to synthesize a reception signal received through the antenna and a local oscillation signal generated by the local oscillator; A pulse compression unit which pulse-compresses the signal synthesized by the second signal synthesis unit; An FFT processor which performs an FFT (Fast Fourier Transform) process on the signal compressed by the pulse compression unit; A parallel-serial converter for serially converting the signal FFT processed by the FFT processor; And a speed estimator for estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the serial-converted signal in the parallel-serial converter and the sequence signal included in the transmission signal. It is composed.

Description

A speed estimating device and a method for estimating the speed of an off-grid radar system {APPARATUS AND METHOD FOR VELOCITY ESTIMATION IN OFDM RADAR SYSTEM}

The present invention relates to a speed estimating apparatus and a speed estimating method of a radar system for obtaining the moving speed information of a target, and in particular, a speed estimating apparatus and a speed estimating method for estimating a moving speed of a target in an OFDM radar system using multiple carriers. It is about.

In general, the greatest purpose of military radar systems is to protect the allies from enemy danger by tracking the most dangerous targets by grasping the location and speed information of the targets. In order to achieve the objective of protecting allies, speed information must be accurately estimated as quickly as possible using the Doppler effect between the transmitted and received signals. In addition, the bio radar system accurately detects Doppler information in order to measure the heartbeat or other movement of the human body and then detects the movement of the object. In order to obtain the speed information of the target in the radar system, the speed information of the target is obtained by estimating the frequency difference between the transmission signal and the reception signal using the Doppler effect generated by the movement of the target.

On the other hand, unlike the Doppler estimation method of general radar, the method of estimating the velocity of a target in an Orthogonal Frequency Division Multiplexing (OFDM) radar system is estimated by estimating Doppler information using individual symbols carried on a subcarrier. Estimated. This is because a change in the frequency domain due to the Doppler effect in the OFDM signal results in rotating the phase of the time domain symbol.

More specifically, FIG. 1 is a diagram illustrating an OFDM signal arrangement for each frequency with respect to a time axis in an OFDM radar system according to the prior art, and includes a target of a target in a pulse burst PB composed of X OFDM signals having Ns subcarriers. When the Doppler effect occurs due to speed, the phase of the symbol on all subcarriers of the OFDM signal is rotated. Here, the pulse burst means that a plurality of radar signals are gathered to form a group. Doppler information was estimated by calculating the average value of phase shifts of all kth subcarriers in the X OFDM signals by the number of subcarriers Ns and re-averaging them.

However, since the technique of estimating velocity using phase change is very vulnerable to phase noise, background noise, clutter, etc., it is often difficult to obtain accurate Doppler information. Occurred.

[references]

G. Lellouch, P. Tran, R. Pribic, P. van Genderen, "OFDM waveforms for frequency agility and opportunities for Doppler processing in radar", in Proc. Radar Conf., May 2008, pp. 1-6.

In order to solve the above problems, there is provided a speed estimating apparatus and a speed estimating method of the OFDM radar system capable of accurate speed estimation by extracting the Doppler information more accurately using the autocorrelation and phase change between the transmission signal and the received signal. The purpose is.

In order to achieve the above object, a speed estimating apparatus for estimating the speed of a target in an OFDM radar system according to the present invention comprises: a sequence signal generator for generating an arbitrary sequence signal; A phase shift modulator for performing phase shift keying on the sequence signal generated by the sequence signal generator; A serial-to-parallel converter for converting the phase shift modulated signal in parallel in the phase shift modulator; An IFFT processor for performing an inverse fast fourier transform (IFFT) process on the signals converted in parallel in the serial-parallel converter; A first signal synthesizing unit configured to transmit a transmission signal obtained by synthesizing the IFFT-processed signal from the IFFT processor and the local oscillation signal generated by the local oscillator through an antenna; A second signal synthesizing unit reflecting the transmission signal to a target to synthesize a reception signal received through the antenna and a local oscillation signal generated by the local oscillator; A pulse compression unit which pulse-compresses the signal synthesized by the second signal synthesis unit; An FFT processor which performs an FFT (Fast Fourier Transform) process on the signal compressed by the pulse compression unit; A parallel-serial converter for serially converting the signal FFT processed by the FFT processor; And a speed estimator for estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the serial-converted signal in the parallel-serial converter and the sequence signal included in the transmission signal. It is composed.

Here, the serial-parallel converter converts the phase shift-modulated signal in parallel within the same bandwidth, and converts the N-subcarrier of Ns and the sub-carrier of Ns / 2 in parallel at a predetermined time interval. .

The sequence signal generation unit may generate two sequence signals having the same length set at a predetermined time interval, and generate a sequence signal such that one sequence signal is disposed between the other sequence signals. More preferably, when the target is approaching, when the one sequence signal is disposed between the remaining sequence signals, a sequence signal is generated such that the sequence is arranged to be rearranged so as to be allocated to subcarriers of lower frequencies within the entire bandwidth, and the target moves away. In this case, when the one sequence signal is disposed between the other sequence signals, it is preferable to generate the sequence signal so that the sequence is arranged in the front portion so as to be allocated to a subcarrier of a higher frequency within the entire bandwidth.

In addition, the sequence signal generated by the sequence signal generator is a sequence signal having autocorrelation characteristics or cross-correlation characteristics, and includes an m-sequence signal, a gold sequence signal, a Kasami sequence signal, a Z4 sequence signal, and a polyphase sequence signal. It is preferable that any one of a sequencer signal, a barker sequence signal, a low correlation zone (LCZ) sequence signal, and a zero correlation zone (ZCZ) sequence signal.

On the other hand, in order to achieve the above object in the OFDM radar system according to the present invention, a speed estimation method for estimating the speed of the target, (a) generating an arbitrary sequence signal; (b) phase shift keying the generated sequence signal; (c) serial-to-parallel conversion of the phase shift signal; (d) performing an Inverse Fast Fourier Transform (IFFT) process on the serial-parallel converted signal; (e) transmitting a transmission signal obtained by combining the IFFT processed signal and the local oscillation signal through an antenna; (f) synthesizing the local oscillation signal with the reception signal received through the antenna by reflecting the transmission signal to a target; (g) pulse-compressing the signal synthesized in step (f); (h) performing a Fast Fourier Transform (FFT) process on the pulse compressed signal; (i) parallel-to-serial converting the FFT processed signal; And (j) estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the parallel-serial converted signal and the sequence signal included in the transmission signal.

In the step (c), the phase shift-modulated signal is converted in parallel within the same bandwidth, and the N-subcarriers of Ns and Ns / 2 sub-carriers are converted in parallel in alternating time. do.

In the step (a), two sequence signals having the same length are set at a predetermined time interval, and the sequence signals are generated such that one sequence signal is disposed between the other sequence signals. More preferably, when the target is approaching, when the one sequence signal is disposed between the remaining sequence signals, a sequence signal is generated such that the sequence is arranged to be rearranged so as to be allocated to subcarriers of lower frequencies within the entire bandwidth, and the target moves away. In this case, when the one sequence signal is disposed between the other sequence signals, the sequence signal is generated so as to be disposed in the front portion so as to be allocated to a subcarrier of a higher frequency within the entire bandwidth.

In addition, the sequence signal generated in step (a) is a sequence signal having autocorrelation characteristics or cross-correlation characteristics, and includes an m-sequence signal, a gold sequence signal, a Kasami sequence signal, a Z4 sequence signal, and a polyphase sequence signal. It is preferable that any one of a sequencer signal, a barker sequence signal, a low correlation zone (LCZ) sequence signal, and a zero correlation zone (ZCZ) sequence signal.

According to the present invention as described above, the Doppler information is extracted more accurately by using the autocorrelation and phase change between the transmission signal and the reception signal, so that even in an environment with a lot of external disturbances such as noise, background noise, clutter, etc. Accurate speed estimation is possible.

1 is a view showing the frequency-specific OFDM signal arrangement on the time axis in the OFDM radar system according to the prior art.
2 is a block diagram showing a speed estimating apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating frequency-specific OFDM signal placement on a time axis in an OFDM radar system according to an embodiment of the present invention. FIG.
4 is a diagram illustrating a structure of an OFDM signal carrying an m-sequence on a subcarrier according to an embodiment of the present invention.
5 is a constellation diagram showing a change between a transmission signal and a reception signal in an OFDM radar system.
6 is a graph showing the change of the OFDM signal due to the Doppler effect in the frequency domain.
7 is a conceptual diagram illustrating a process of calculating an average value of ε _f in a pulse burst according to an embodiment of the present invention.
8 is a graph showing a performance comparison of the prior art and the present invention.
9 is a flow chart showing a speed estimation method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a block diagram showing a speed estimating apparatus according to an embodiment of the present invention, the speed estimating apparatus for estimating the speed of the target in the OFDM radar system according to the present invention, generating a sequence signal generating an arbitrary sequence signal Part 10; A phase shift modulator 20 performing phase shift keying on the sequence signal generated by the sequence signal generator 10; A series-parallel converter 30 for converting the phase-shifted signal in parallel in the phase shift modulator 20; An IFFT processor 40 which performs IFFT (Inverse Fast Fourier Transform) processing on the signal converted in parallel by the serial-parallel converter 30; A first signal synthesizer 50 which transmits a transmission signal obtained by synthesizing the IFFT-processed signal from the IFFT processor 40 and the local oscillation signal generated by the local oscillator 55 through the antenna 130; A second signal synthesizing unit 60 reflecting the transmission signal to a target to synthesize a reception signal received through the antenna 130 and a local oscillation signal generated by the local oscillator 55; A pulse compression unit 70 which pulse-compresses the signal synthesized by the second signal synthesis unit 60; An FFT processor 80 which performs an FFT (Fast Fourier Transform) process on the signal compressed by the pulse compression unit 70; A parallel-serial converter 90 for serially converting the FFT-processed signal by the FFT processor 80; And a speed estimation unit for estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the serial-converted signal in the parallel-serial conversion unit 90 and the sequence signal included in the transmission signal. It comprises 100. For reference, in FIG. 2, the duplexer 150 is used to use one antenna 130 for transmission and reception.

Here, the serial-to-parallel converter 30 converts the phase shift-modulated signal in parallel within the same bandwidth, but performs parallel conversion alternately between subcarriers of Ns and subcarriers of Ns / 2, which are set at regular time intervals. It features.

In addition, the sequence signal generator 10 generates two sequence signals having the same length at a predetermined time interval, and generates a sequence signal such that one sequence signal is disposed between the other sequence signals. More preferably, when the target approaches, a lower frequency (eg, lowest frequency (Hz) to lowest frequency + (full bandwidth) / 2 within the entire bandwidth when the one sequence signal is disposed between the other sequence signals) (Hz) generates a sequence signal to be disposed later to be assigned to a subcarrier, and when the target is far away, when one sequence signal is disposed between the other sequence signals, an upper frequency (eg, lowest) within the entire bandwidth is generated. It is desirable to generate a sequence signal so that it is placed in front of it so that it is allocated to a subcarrier of frequency + (full bandwidth) / 2 (Hz) to highest frequency (Hz).

The sequence signal generated by the sequence signal generator 10 is a sequence signal having good autocorrelation characteristics or cross-correlation characteristics, and includes an m-sequence signal, a gold sequence signal, a Kasami sequence signal, a Z4 sequence signal, and a polyphase ( It is preferable that the sequence signal is any one of a polyphase sequence signal, a Barker sequence signal, a low correlation zone (LCZ) sequence signal, and a zero correlation zone (ZCZ) sequence signal.

9 is a flowchart illustrating a speed estimating method according to an embodiment of the present invention. As shown in FIG. 9, a speed estimating method for estimating a speed of a target in an OFDM radar system according to the present invention includes ( a) generating any sequence signal; (b) phase shift keying the generated sequence signal; (c) serial-to-parallel conversion of the phase shift signal; (d) performing an Inverse Fast Fourier Transform (IFFT) process on the serial-parallel converted signal; (e) transmitting a transmission signal obtained by combining the IFFT processed signal and the local oscillation signal through an antenna; (f) synthesizing the local oscillation signal with the reception signal received through the antenna by reflecting the transmission signal to a target; (g) pulse-compressing the signal synthesized in step (f); (h) performing a Fast Fourier Transform (FFT) process on the pulse compressed signal; (i) parallel-to-serial converting the FFT processed signal; And (j) estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the parallel-serial converted signal and the sequence signal included in the transmission signal.

In the step (c), the phase shift-modulated signal is converted in parallel within the same bandwidth, and the N-subcarriers of Ns and Ns / 2 sub-carriers are converted in parallel in alternating time. do.

In the step (a), two sequence signals having the same length are set at a predetermined time interval, and the sequence signals are generated such that one sequence signal is disposed between the other sequence signals. More preferably, when the target is approaching, when the one sequence signal is disposed between the remaining sequence signals, a sequence signal is generated such that the sequence is arranged to be rearranged so as to be allocated to subcarriers of lower frequencies within the entire bandwidth, and the target moves away. In this case, when the one sequence signal is disposed between the other sequence signals, the sequence signal is generated so as to be disposed in the front portion so as to be allocated to a subcarrier of a higher frequency within the entire bandwidth.

In addition, the sequence signal generated in step (a) is a sequence signal having autocorrelation characteristics or cross-correlation characteristics, and includes an m-sequence signal, a gold sequence signal, a Kasami sequence signal, a Z4 sequence signal, and a polyphase sequence signal. It is preferable that any one of a sequencer signal, a barker sequence signal, a low correlation zone (LCZ) sequence signal, and a zero correlation zone (ZCZ) sequence signal.

In order to extract Doppler information more accurately in a situation where there are a lot of external disturbances such as phase noise, background noise, and clutter, the core of the present invention is a two-step using a sequence having good correlation characteristics such as m-sequence to subcarriers of an OFDM signal. The Doppler estimation technique estimates the speed of the target. That is, in the present invention, when extracting Doppler information of a received signal according to a moving speed of a target, the received signal may be processed in two steps to achieve accurate estimation and complexity reduction of the Doppler information. Specifically, a wide range of Doppler information is extracted by using autocorrelation performance such as m-sequence that is carried on a subcarrier of an OFDM signal in a first step, and a sequence signal (eg, m) carried on a subcarrier in a second step. -PSK extracts a narrow range of Doppler information using phase rotation due to the Doppler effect. By using the Doppler information extracted through the two steps, the speed of the target is finally estimated.

In the OFDM radar system according to the present invention, the speed estimator 100 of the speed estimating apparatus estimates the speed through the following process.

1. Due to the Doppler effect OFDM  Change of signal

First, an equation for an individual OFDM radar signal, that is, a transmission signal s (t) in a pulse burst may be defined as in Equation 1.

Here, f _sub and N _s represent the subcarrier bandwidth and the number of subcarriers, respectively, and it is assumed that f _sub * N _s , which is the total bandwidth (BW) occupied by the OFDM signal, is always constant. That is, as N _s increases, f _sub decreases to BW / N _s . In the above equation, x (k) means a sequence signal (eg, m-PSK signal) carried on the k-th subcarrier in OFDM. Meanwhile, the present invention is described using an m-sequence converted into an m-PSK signal by x (k), but a Gold sequence signal, a Kasami sequence signal, a Z4 sequence signal, a polyphase sequence signal, and a barker sequence Various sequences having good autocorrelation or crosscorrelation characteristics such as signals, low correlation zone (LCZ) sequence signals, and zero correlation zone (ZCZ) sequence signals may be used.

As shown in FIG. 1 by using the OFDM signal of Equation 1, when a general pulse burst is configured, ICI (inter) is performed under a specific condition due to the Doppler effect in the process of fast Fourier transform (FFT) processing of the received OFDM signal. carrier interference occurs. When ICI occurs, the m-sequence for Doppler estimation is not properly decoded, resulting in performance degradation.

In contrast, in the present invention, as shown in FIG. 3, the pulse burst of the OFDM signal has the same total bandwidth (BW), but the number of subcarriers is arranged differently. That is, the serial-to-parallel converter 20 converts the phase shift modulated signal outputted through the phase shift modulator 20 in parallel within the same bandwidth, but has a number of 512 subcarriers set to a predetermined time interval T _r . Pulse bursts are arranged by alternately converting the number to 256 subcarriers in parallel.

를 부반송파의 대역폭 f_sub으로 나눈 몫 이상이면 된다. 다시 말하면, 최대 도플러 주파수 값보다 큰 주파수를 포함하는 길이면 된다. 마찬가지로, 부반송파가 256개인 경우는 m-sequence의 길이가 127인 m-sequence를 이용하여 생성하면 된다. 이 때, m-sequence를 상하에 배치하는 이유는 도플러 정보 추정 과정에서 수신된 m-sequence의 자기 상관 성능이 순환 콘볼루션 해야 얻을 수 있으므로 이를 구현하기 위함이다. 도 4에서 BW는 레이더 신호 즉 OFDM 신호의 대역폭을 의미하며, T_pulse는 레이더 신호의 시간 폭을 나타낸다. In addition, the m-sequences carried on the subcarriers of the OFDM signal in the pulse burst of FIG. 3 are generated by, for example, the following method. In FIG. 3, the first OFDM signal having 512 subcarriers generates two identical m-sequences of length 255, one of which is disposed in the middle and the other of which is located in the middle of the upper and lower portions of the subcarriers. Place each to be assigned to the part. Here, the length of the sequence on the upper and lower parts of the subcarrier is the maximum value of the Doppler frequency proportional to the maximum speed of the target that we want to estimate.

Is equal to or greater than the quotient of the subcarrier bandwidth f _sub . In other words, the length may include a frequency greater than the maximum Doppler frequency value. Similarly, in the case of 256 subcarriers, m-sequences having a length of 127 may be generated using m-sequences. In this case, the reason for arranging the m-sequences up and down is to implement the autocorrelation performance of the m-sequence received during the Doppler information estimation process since it can be obtained by circular convolution. In FIG. 4, BW denotes a bandwidth of a radar signal, that is, an OFDM signal, and T _pulse denotes a time width of the radar signal.

Subsequently, when the transmission signal of Equation 1 is transmitted and reflected on the moving target, the Doppler effect is generated according to the speed of the target to receive the following reception signal r (t-τ).

Where s (t) is an OFDM transmission signal and α represents a variable related to the attenuation of the signal. w (t) means background noise. In addition, τ means a delay time of propagation according to the position of the target. In addition, f _D means a Doppler frequency corresponding to the moving speed of the target and is calculated as in Equation 3.

Where v _r represents the speed of the target, f _c represents the carrier frequency, and c represents the speed of propagation. Also, θ represents the angle at which the target approaches the radar. For example, θ when the target approaches the radar front is 0 degrees.

Subsequently, after receiving an OFDM signal as shown in Equation 2, performing a pulse compression process, the distance information about the target, that is, the propagation delay time information τ is obtained, and the received signal r (t) FFT processing is performed as in Equation 4.

는 다양한 노이즈에 의하여 손상된 k번째 m-sequence를 담은 m-PSK 심볼을 나타낸다. 그리고 Ns는 FFT의 크기와 부반송파의 수를 의미한다. 또한, ε은 정규화된 계수로서 f_D/f_sub 를 나타낸다. f_D는 목표물의 속도에 해당하는 도플러 주파수를 나타내고, f_sub는 부반송파의 대역폭을 의미한다. 특히, ε은 f_sub의 크기와 목표물의 속도에 따라 가변적으로 변하게 되며 정수 부분인 ε_i와 소수 부분인 ε_f로 구성된다.here,

Denotes an m-PSK symbol containing the k-th m-sequence damaged by various noises. And Ns means the size of the FFT and the number of subcarriers. Ε denotes f _D / f _sub as a normalized coefficient. f _D denotes the Doppler frequency corresponding to the velocity of the target, and f _sub denotes the bandwidth of the subcarrier. In particular, ε varies variably depending on the size of f _sub and the speed of the target, and is composed of an integer part ε _i and a fractional part ε _f .

On the other hand, when the change in the frequency domain of the OFDM signal due to the Doppler effect, as shown in Equation (4), the OFDM signal is moved left and right in the frequency domain as shown in FIG. In addition, the m-PSK signal carried on the subcarrier of the OFDM signal undergoes a change caused by ε. When such a change is expressed by dividing ε _i and ε _{f, it} is shown in FIG. 5. Referring to FIG. 5, after the m-PSK signal carried on the k-th subcarrier on the constellation diagram is rotated by the size of the integer ε _i (which corresponds to the shift of ε _i subcarriers), it is confirmed that the phase shift occurs by ε _f . Can be.

2. Proposal of two-stage velocity estimation technique using Doppler effect

The change in the OFDM signal due to the Doppler effect has been described above. A method for obtaining velocity information of a target in an OFDM radar system is to estimate a change in the Doppler effect occurring between a transmission signal and a reception signal.

In order to estimate the change of the Doppler effect in the OFDM radar, the velocity estimation method of the target according to the present invention is to obtain the value of ε consisting of ε _i and ε _f in two steps. It is as follows.

(1) ε _i First Steps to Estimate: Using Autocorrelation

는 송신 OFDM 신호의 x(k)와 비교하여 도플러 효과로 인해 위상 회전을 겪게 된다. 송신 신호 x(k)에 비하여 수신 신호

가 몇 바퀴를 회전했는지(즉, ε_i 값)에 대한 정보를 사전에 부반송파에 실은 m-sequence를 통해 얻을 수 있다. 수신 신호에 실린 m-sequence와 송신 신호에 실린 m-sequence간의 자기 상관(Autocorrelation)을 통하여 얼마만큼 회전했는지에 대한 ε_i 를 구하는 것이 1단계에서 이뤄진다. 다시 말해, OFDM 신호가 주파수 영역에서 도플러 효과에 의하여 천이된 부분ε 중 정수에 해당하는 ε_i 부분을 구하는 것이다. In the received OFDM signal

Is subjected to phase rotation due to the Doppler effect compared to x (k) of the transmitted OFDM signal. Received signal compared to transmit signal x (k)

Information about the number of revolutions (ie, the value of ε _i ) can be obtained from the m-sequence loaded on the subcarrier in advance. Ε _i for how much it has rotated through autocorrelation between the m-sequence in the received signal and the m-sequence in the transmitted signal Finding is done in step 1. In other words, the portion ε where the OFDM signal is shifted by the Doppler effect in the frequency domain Find the part of ε _i that corresponds to the integer.

In other words, referring to FIG. 6, which shows the frequency domain of individual OFDM signals in a pulse burst, the OFDM radar signal is shifted by f _D to the right due to the Doppler effect. from the value obtained by dividing the f _D f in the _sub will ε _i and ε of ε _{f i} that corresponds to the integer part and the fractional part is obtained through the Doppler estimation method of the Step 1.

)과 짝수 번째 OFDM 신호 부분에서 구한 값(

)들의 평균값을 이용하여 최종적으로 ε_f를 구하게 된다.In addition, in order to increase the accuracy of ε, the value obtained in the OFDM signal portion of the odd position as shown in FIG.

) And the value obtained from the part of the even-numbered OFDM signal (

Finally, ε _f is obtained by using the average value of).

However, when ε _f is close to 0.5 when FFTs the received OFDM radar signal, ICI occurs because it corresponds to 1/2 symbol transition in m-sequence. When ICI occurs, most of the m-PSK signals on subcarriers are damaged beyond repair. In this case, since the proposed one-step method becomes meaningless, it can be solved by using a pulse burst having different subcarriers as shown in FIG. 3. Detailed description is as follows.

(2) ε _f Second step to estimate the phase: using phase change

가 최종적으로 천이된 위상으로써, 도 5의 성좌도와 같이 나타나게 된다. 그것에 비례하는 ε_f값을 추정하면 된다. 정확도를 높이기 위하여 펄스 버스트(pulse burst)에서 OFDM 신호의 각 부반송파에 해당하는 값들의 평균을 이용하여 수학식 5와 같은 방법으로 추정한다.The fractional part ε _f excluding the integer part of ε is the received signal from the transmitted signal x (k)

Is the finally shifted phase, as shown in the constellation diagram of FIG. It is sufficient to estimate the value of ε _f proportional to it. In order to increase the accuracy, an average of values corresponding to each subcarrier of the OFDM signal in a pulse burst is estimated using Equation 5 below.

는 홀수 번째 OFDM 신호의 k번째 부반송파에 의해 수신된 m-sequence를 담은 m-PSK 심볼이고,

는 홀수 번째 부반송파에 의해 송신된 m-sequence를 담은 m-PSK 심볼이다. 그리고 E[]는 평균을 의미한다.

는 홀수 번째 OFDM 신호들의 k번째 부반송파들로부터 얻은 평균값이다. 위와 같은 방법으로 부반송파의 수에 해당하는 만큼 위 수학식 5을 반복하여 그것의 평균값을 구하게 되면 홀수 번째 OFDM 신호들에 의하여 얻어진

가 된다. 수학식 5의 경우는 pulse burst 상에서 홀수 위치에 해당하는 OFDM 레이더 신호의

를 구하기 위하여 사용되지만 짝수 위치에 해당하는 OFDM 레이더 신호도 수학식 6을 통하여 동일한 방법으로 구하면 된다. Here, 1 ≦ k ≦ N _s , where N _b is the total number of OFDM signals in a pulse burst,

Is an m-PSK symbol containing the m-sequence received by the k-th subcarrier of the odd-numbered OFDM signal,

Is an m-PSK symbol containing the m-sequence transmitted by the odd subcarrier. And E [] means mean.

Is the average value obtained from the kth subcarriers of the odd numbered OFDM signals. By repeating Equation 5 above to find the average value of the subcarriers in the same way as above, the odd number of OFDM signals are obtained.

. In the case of Equation 5, the OFDM radar signal corresponding to the odd position on the pulse burst

Although used to obtain the OFDM radar signal corresponding to the even position can also be obtained in the same manner through the equation (6).

와

의 평균값이 ε_f가 된다. 다시 말해, 도 7과 같이, 펄스 버스트에서 각 부반송파의 위상 변화에 대한 평균값으로 ε_f를 구한다.So obtained

Wow

The average value of becomes ε _f . In other words, as shown in FIG. 7, ε _f is obtained as an average value of the phase change of each subcarrier in a pulse burst.

Thus, the estimated integer ε _i and the fractional estimated value obtained Through ε _f , the velocity v _e of the target is estimated as shown in equation (7).

으로 계산되었다. 여기에서 v_r은 목표물의 실제 속도이고,

은 종래 기술과 본 발명에 따라 얻어진 목표물의 추정 속도이다. 도 8에서 보이듯이 본 발명의 2단계 도플러 추정 기법을 이용하였을 경우 기존 도플러 추정 기법을 이용한 경우보다 도플러 모호성이 없이 좋은 성능을 보인다는 것을 확인할 수 있다.8 is a graph showing the performance comparison between the prior art and the present invention, and the performance comparison with the prior art uses a root mean square error (RMS).

Respectively. Where v _r is the actual velocity of the target,

Is the estimated speed of the target obtained according to the prior art and the present invention. As shown in FIG. 8, it can be seen that when the two-step Doppler estimation technique of the present invention is used, better performance is achieved without Doppler ambiguity than when using the conventional Doppler estimation technique.

According to the present invention as described above, the Doppler information is extracted more accurately by using the autocorrelation and phase change between the transmission signal and the reception signal, so that even in an environment with a lot of external disturbances such as noise, background noise, clutter, etc. Accurate speed estimation is possible.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. Therefore, the scope of the patent right of the present invention is not limited to the embodiments described in the present invention, and the embodiments within the scope of the equivalents which do not depart from the technical idea and scope of the present invention are within the scope of the patent right of the present invention .

10: sequence signal generator 20: phase shift modulator
30: serial-parallel conversion unit 40: IFFT processing unit
50: first signal synthesizer 55: local oscillator
60: second signal synthesis unit
70: pulse compression unit 80: FFT processing unit
90: parallel-serial converter 100: speed estimation
130: Antenna
150: duplexer

Claims (10)

A speed estimator for estimating the speed of a target in an OFDM radar system,
A sequence signal generator for generating an arbitrary sequence signal;
A phase shift modulator for performing phase shift keying on the sequence signal generated by the sequence signal generator;
A serial-to-parallel converter for converting the phase shift modulated signal in parallel in the phase shift modulator;
An IFFT processor for performing an inverse fast fourier transform (IFFT) process on the signals converted in parallel in the serial-parallel converter;
A first signal synthesizing unit configured to transmit a transmission signal obtained by synthesizing the IFFT-processed signal from the IFFT processor and the local oscillation signal generated by the local oscillator through an antenna;
A second signal synthesizing unit reflecting the transmission signal to a target to synthesize a reception signal received through the antenna and a local oscillation signal generated by the local oscillator;
A pulse compression unit which pulse-compresses the signal synthesized by the second signal synthesis unit;
An FFT processing unit which performs an FFT (Fast Fourier Transform) process on the signal compressed by the pulse compression unit;
A parallel-serial converter for serially converting the signal FFT processed by the FFT processor;
A speed estimating unit estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the serial-converted signal in the parallel-serial conversion unit and the sequence signal included in the transmission signal;
Speed estimating apparatus comprising a. The method of claim 1,
The serial-parallel converter converts the phase shift-modulated signal in parallel within the same bandwidth, and performs parallel estimation by alternately converting the subcarriers of Ns and the subcarriers of Ns / 2, which are set at regular time intervals. Device. 3. The method of claim 2,
The sequence signal generator,
And generating two sequence signals having a predetermined length at a predetermined time interval, wherein the sequence signals are generated such that one sequence signal is disposed between the other sequence signals. The method of claim 3, wherein
The sequence signal generator,
When the target is approaching, when the one sequence signal is disposed between the remaining sequence signals, the sequence signal is generated so that the sequence is arranged in the rear part so as to be allocated to subcarriers of lower frequencies within the entire bandwidth.
And when the target is far from the target sequence, when the one sequence signal is disposed between the other sequence signals, the sequence signal is generated such that the sequence signal is arranged in a forward portion so as to be allocated to a subcarrier of a higher frequency within the entire bandwidth. The method of claim 3, wherein
The sequence signal generated by the sequence signal generator is
As a sequence signal having autocorrelation characteristics or cross-correlation characteristics, m-sequence signal, Gold sequence signal, Kasami sequence signal, Z4 sequence signal, polyphase sequence signal, barker sequence signal, low correlation zone (LCZ) A speed estimating apparatus, characterized in that the sequence signal, any one of the sequence sequence signal ZCZ (zero correlation zone) sequence signal. As a speed estimation method for estimating the speed of a target in an OFDM radar system,
(a) generating any sequence signal;
(b) phase shift keying the generated sequence signal;
(c) serial-to-parallel conversion of the phase shift signal;
(d) performing an Inverse Fast Fourier Transform (IFFT) process on the serial-parallel converted signal;
(e) transmitting a transmission signal obtained by combining the IFFT processed signal and the local oscillation signal through an antenna;
(f) synthesizing the local oscillation signal with the reception signal received through the antenna by reflecting the transmission signal to a target;
(g) pulse-compressing the signal synthesized in step (f);
(h) performing a Fast Fourier Transform (FFT) process on the pulse compressed signal;
(i) parallel-to-serial converting the FFT processed signal;
(j) estimating the speed of the target by using autocorrelation and phase change of the sequence signal included in the parallel-serial converted signal and the sequence signal included in the transmission signal;
Speed estimation method comprising a. The method according to claim 6,
The step (c)
And converting the phase shift-modulated signal in parallel within the same bandwidth, and performing parallel conversion alternately between subcarriers of Ns and subcarriers of Ns / 2, which are numbers set at regular time intervals. The method of claim 7, wherein
The step (a)
And generating two sequence signals having a predetermined length at a predetermined time interval, wherein the sequence signals are generated such that one sequence signal is disposed between the other sequence signals. The method of claim 8,
The step (a)
When the target is approaching, when the one sequence signal is disposed between the remaining sequence signals, the sequence signal is generated so that the sequence is arranged in the rear part so as to be allocated to subcarriers of lower frequencies within the entire bandwidth.
And when the target is far from the target sequence, generating the sequence signal so that the sequence is arranged in the forward portion so as to be allocated to a subcarrier of a higher frequency within the entire bandwidth when the one sequence signal is disposed between the other sequence signals. The method of claim 8,
The sequence signal generated in the step (a),
As a sequence signal having autocorrelation characteristics or cross-correlation characteristics, m-sequence signal, Gold sequence signal, Kasami sequence signal, Z4 sequence signal, polyphase sequence signal, barker sequence signal, low correlation zone (LCZ) A sequence estimating method comprising any one of a sequence signal and a zero correlation zone (ZCZ) sequence signal.

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