Estimation algorithm of maneuvering target acceleration based on optical fiber delay loop in single echo
阅读说明：本技术 单回波内基于光纤延迟环的机动目标加速度的估计算法 (Estimation algorithm of maneuvering target acceleration based on optical fiber delay loop in single echo ) 是由 贾舒宜 王海鹏 唐田田 谭顺成 郭强 刘传辉 于 2019-07-23 设计创作，主要内容包括：本发明涉及一种单回波内基于光纤延迟环的机动目标加速度的估计算法,其属于雷达信号处理技术领域。估算方法如下：利用环形波导对一个脉冲信号进行复制再生,得到不同延时后的信号波形,将信号波形与发射信号相乘处理得到至少一个相参回波,可等效延长回波脉冲的观测时间,通过新的回波脉冲序列估算出机动目标加速度。该算法能长时间地观测解读出目标信号的一切脉内特征,对于雷达接收到的单个回波脉冲,能使其在特定传输线中长时间传播并被采样,等效延长了回波脉冲的观测时间,消除了脉冲相参积累导致的脉内特征丢失问题,并且在估计目标径向加速度方面的实时性明显增强,提高目标参数的估计效率。(The invention relates to an estimation algorithm of maneuvering target acceleration based on an optical fiber delay loop in a single echo, and belongs to the technical field of radar signal processing. The estimation method is as follows: the annular waveguide is used for copying and regenerating a pulse signal to obtain signal waveforms after different delays, the signal waveforms are multiplied by the transmitting signal to obtain at least one coherent echo, the observation time of the echo pulse can be equivalently prolonged, and the maneuvering target acceleration is estimated through a new echo pulse sequence. The algorithm can observe and interpret all intra-pulse characteristics of a target signal for a long time, for a single echo pulse received by the radar, the single echo pulse can be transmitted in a specific transmission line for a long time and sampled, the observation time of the echo pulse is equivalently prolonged, the intra-pulse characteristic loss problem caused by pulse coherent accumulation is solved, the real-time performance in the aspect of estimating the radial acceleration of the target is obviously enhanced, and the estimation efficiency of target parameters is improved.)
1. An estimation algorithm of the acceleration of a maneuvering target based on a fiber delay loop in a single echo is characterized in that the estimation method comprises the following steps:
the method comprises the steps that a pulse signal is copied and regenerated by utilizing an annular waveguide to obtain signal waveforms after different delays, the signal waveforms are multiplied by a transmitting signal to obtain at least one coherent echo, the observation time of an echo pulse can be equivalently prolonged by the algorithm, and the acceleration of a maneuvering target is estimated through a new echo pulse sequence;
the specific calculation steps are as follows:
when the radar transmits a constant carrier frequency signal and the influence of range migration is not considered, a maneuvering target radio frequency echo signal received by the radar antenna is output as a linear frequency modulation signal s after the first matching filtering processing1(t) is represented by
Wherein t is more than or equal to 0 and less than or equal to tau, f0Is the center frequency of the frequency band, and is,is the initial phase of the echo signal; w is a1(t) is white Gaussian noise, mean E (w)1(t)) -0, variance σ (w)1(t))＝σ1，Is the frequency of the doppler frequency and is,for the Doppler slope of the signal, v0A is the initial velocity of the acceleration target andacceleration, c is the speed of light;
inputting the echo signal into the annular waveguide, so that the echo signal circularly propagates in the annular waveguide, and extracting s1A Doppler frequency in (t); the extraction method comprises the following steps: when the radius of the annular waveguide is R, the time required by one turn of electromagnetic wave is T ═ l/c, namely the delay time of one turn of the optical fiber delay ring, wherein l ═ 2 pi R is the length of the waveguide, T ≧ tau, namely R ≧ tau c/(2 pi), s1(t) coupling the ring waveguide through the inlet port to couple out the delayed echo signal s1(t + nT) is output from an output port, wherein N is more than or equal to 0 and less than or equal to N-1, and N is the observation frequency;
s2(t) as a backup for the transmitted signal, s2(t) is the same as the frequency of the transmitted signal, s2(t) is represented by
s2(t)＝cos(2πf0t+φ0)+w2(t) (2)
Wherein t is more than or equal to 0 and less than or equal to tau, phi0For the initial phase of the signal, w2(t) is white Gaussian noise, mean E (w)2(t)) -0, variance σ (w)2(t))＝σ2；
Signal s output from ring waveguide1(t + nT) and s2(t) multiplying to obtain:
wherein t is more than or equal to 0 and less than or equal to tau, w3(t)＝w1(t)s2(t)+w2(t)s1(t)+w1(t)w2(t) is noise;
when w is1(t)、w2(t) is independent, and w3(t) is white Gaussian noise, mean value E [ w ]3(t)]Variance D [ w ]3(t)]Is shown as
E[w3(t)]＝0 (4)
Signal s3(t) passing throughAfter low-pass filtering, s is obtained4(t)
Wherein t is more than or equal to 0 and less than or equal to tau, fd＝2v0K 2a/λ, λ is radar wavelength, λ c/f0；
In storing signals and sampling in the waveguide ring, when the first sampling is at t0At the time of the day, the sampled value is
The time for one circle of rotation in the annular storage waveguide is T, and the original time is T after the nth cycle0S of the corresponding point of time4(n) is
Wherein N is more than or equal to 0 and less than or equal to N-1, and N is the cycle number;
sampling each pulse once, and taking t in formula (8)0When s is equal to 04(n) is represented by
2. The method according to claim 1, characterized in that after the radar signal is delayed by the annular waveguide, the signal with duration τ is prolonged to Nτ, and a linear frequency modulation signal parameter estimation method based on fractional Fourier transform is adopted to estimate quadratic coefficients of time, so as to estimate acceleration; the specific estimation algorithm is as follows:
the fractional Fourier transform (FRFT) is defined as:
wherein α ═ p π/2, p ∈ [0,4 ]](ii) a Fractional Fourier transform is carried out on the observation signal (9) formula to form a two-dimensional plane of (alpha, u), and the estimated value of the radial acceleration can be obtained by carrying out two-dimensional search of a peak point on the planeWhen in useThe radial acceleration estimate is calculated for the peak point coordinate value using the following equation
fsIs the signal sampling frequency. According to the sampling theorem, 1/T is more than or equal to 2fdThereby obtaining a T range
When estimating the acceleration, at leastThe inequality holds true, i.e.
Technical Field
The invention relates to an estimation algorithm of maneuvering target acceleration based on an optical fiber delay loop in a single echo, and belongs to the technical field of radar signal processing.
Background
For a Pulse Doppler (PD) radar, parameter estimation on a target in an extremely short pulse duration is very difficult, so that the system radar adopts a signal form of a coherent carrier, links data of a plurality of pulses by using the signal phase correlation characteristic, equivalently extends the observation time of the signals and further obtains higher parameter estimation precision; however, because the intrinsic characteristics of radar targets vary with time of observation and angle of view, each rf pulse from a target contains different target information, which, if a plurality of pulse signals are coherently accumulated according to conventional radar, results in the loss of some intrinsic characteristics of the target in subsequent processing.
Because radar echo pulse transmitted in a medium can be used for reading all intra-pulse characteristics of a target signal as long as the radar echo pulse can be observed for a long time no matter how short the echo pulse time is, for a single echo pulse received by a radar, the single echo pulse can be supposed to be transmitted and sampled in a specific transmission line for a long time, so that the observation time of the echo pulse is equivalently prolonged, the problem of intra-pulse characteristic loss of the target signal caused by coherent accumulation can be solved, and the estimation efficiency of target parameters is improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides an estimation algorithm of the maneuvering target acceleration based on the optical fiber delay loop in the single echo, so that the long-time observation of the single pulse echo signal is realized, the problem of intra-pulse feature loss caused by pulse coherent accumulation of the existing PD radar is solved, and the observation time required by target acceleration estimation is shortened.
The technical scheme for solving the technical problems is as follows:
an estimation algorithm of the acceleration of a maneuvering target based on a fiber delay loop in a single echo comprises the following steps:
the method comprises the steps that a pulse signal is copied and regenerated by utilizing an annular waveguide to obtain signal waveforms after different delays, the signal waveforms are multiplied by a transmitting signal to obtain at least one coherent echo, the observation time of an echo pulse can be equivalently prolonged by the algorithm, and the acceleration of a maneuvering target is estimated through a new echo pulse sequence;
the specific calculation steps are as follows:
optical fiber delay technique
When the radar transmits a constant carrier frequency signal and the influence of range migration is not considered, a maneuvering target radio frequency echo signal received by the radar antenna is output as a linear frequency modulation signal s after the first matching filtering processing1(t) is represented by
Wherein t is more than or equal to 0 and less than or equal to tau, f0Is the center frequency of the frequency band, and is,is the initial phase of the echo signal; w is a1(t) is white Gaussian noise, mean E (w)1(t)) -0, variance σ (w)1(t))＝σ1，Is the frequency of the doppler frequency and is,for the Doppler slope of the signal, v0A is the initial speed and the acceleration of the acceleration target respectively, and c is the light speed;
inputting the echo signal into the annular waveguide, so that the echo signal circularly propagates in the annular waveguide, and extracting s1A Doppler frequency in (t); the extraction method comprises the following steps: when the radius of the annular waveguide is R, the time required by one turn of electromagnetic wave is T ═ l/c, namely the delay time of one turn of the optical fiber delay ring, wherein l ═ 2 pi R is the length of the waveguide, T ≧ tau, namely R ≧ tau c/(2 pi), s1(t) inserting the ring through the introduction portA waveguide for coupling out delayed echo signal s1(t + nT) is output from an output port, wherein N is more than or equal to 0 and less than or equal to N-1, and N is the observation frequency;
s2(t) as a backup for the transmitted signal, s2(t) is the same as the frequency of the transmitted signal, s2(t) is represented by
s2(t)＝cos(2πf0t+φ0)+w2(t) (2)
Wherein t is more than or equal to 0 and less than or equal to tau, phi0For the initial phase of the signal, w2(t) is white Gaussian noise, mean E (w)2(t)) -0, variance σ (w)2(t))＝σ2；
Signal s output from ring waveguide1(t + nT) and s2(t) multiplying to obtain:
wherein t is more than or equal to 0 and less than or equal to tau, w3(t)＝w1(t)s2(t)+w2(t)s1(t)+w1(t)w2(t) is noise;
when w is1(t)、w2(t) is independent, and w3(t) is white Gaussian noise, mean value E [ w ]3(t)]Variance D [ w ]3(t)]Is shown as
E[w3(t)]＝0 (4)
Signal s3(t) obtaining s after low-pass filtering4(t)
Wherein t is more than or equal to 0 and less than or equal to tau, fd＝2v0K 2a/λ, λ is radar wavelength, λ c/f0；
In storing signals and sampling in the waveguide ring, when the first sampling is at t0At the moment of time, samplingHas a value of
The time for one circle of rotation in the annular storage waveguide is T, and the original time is T after the nth cycle0S of the corresponding point of time4(n) is
Wherein N is more than or equal to 0 and less than or equal to N-1, and N is the cycle number;
sampling each pulse once, and taking t in formula (8)0When s is equal to 04(n) is represented by
After the radar signals are delayed through the annular waveguide, the signals with duration time tau are prolonged to Ntau, a quadratic coefficient of time is estimated by adopting a linear frequency modulation signal parameter estimation method based on fractional Fourier transform, and then acceleration is estimated; the specific estimation algorithm is as follows:
the fractional Fourier transform (FRFT) is defined as:
wherein α ═ p π/2, p ∈ [0,4 ]](ii) a Fractional Fourier transform is carried out on the observation signal (9) formula to form a two-dimensional plane of (alpha, u), and the estimated value of the radial acceleration can be obtained by carrying out two-dimensional search of a peak point on the planeWhen in useThe radial acceleration estimate is calculated for the peak point coordinate value using the following equation
fsIs the signal sampling frequency. According to the sampling theorem, 1/T is more than or equal to 2fdThereby obtaining a T range
When estimating the acceleration, at leastThe inequality holds true, i.e.
Compared with the prior art, the invention has the beneficial effects that: for a single echo pulse received by the radar, the single echo pulse can be transmitted in a specific transmission line for a long time and sampled, the observation time of the echo pulse is equivalently prolonged, the intra-pulse feature loss problem caused by pulse coherent accumulation is solved, the instantaneity in the aspect of estimating the radial acceleration of a target is obviously enhanced, and the estimation efficiency of target parameters is improved.
Drawings
Figure 1 is a fiber delay loop technique of the present invention.
Fig. 2 is a waveform of a delayed copy sequence of the present invention.
Fig. 3 is a time-delayed replica sequence spectrum of the present invention.
Fig. 4 is a waveform of a replica sequence at a time delay of 0dB in SNR according to the present invention.
Fig. 5 shows the spectrum of the replica sequence at 0dB delay with SNR according to the invention.
Fig. 6 is a FRFT transform angle peak distribution of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
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