Pseudo-random Code Phase Research Articles

Highly accurate absolute optical transfer delay measurement over a long distance assisted by the pulse time signal

In this paper, an absolute optical transfer delay measurement method based on pulse time signal, pseudo-random code phase, and microwave phase is proposed. By employing two-stage integer ambiguity resolution, not only can a measurement range of several hundred kilometers be achieved, but sub-picosecond level measurement accuracy can also be attained. A test system was built in the laboratory and experimentally verified on a fiber optic link. The experimental results verify an accuracy of ±0.1 ps in measuring an ultrahigh-accuracy optical delay line. In addition, long fiber is also tested, which proves that a measurement range of at least 100 km can be achieved. The refresh rate of the measurement results can reach 100 ms each time.

Research on a Wind Lidar Without Blind Zone Based on the Technologies of Pseudo Random Code Phase Modulation and Heterodyne Detection

In this measurement method, a wind lidar system with no blind zone based on the technologies of heterodyne detection and pseudorandom code phase modulation is proposed. The simulation results show the feasibility of the method. 15m range resolution and 7.75cm/s line of sight (LOS) wind velocity resolution can be achieved from 0 m to 300m, when the laser transmitted power is 2mW, the transmitted pulse length is 100us, the receiving telescope aperture is 2cm, and an accumulation times of 10. The simulation results also show the positive effect of the transmitted pulse length.

Optimization of Orthogonal MSK Waveforms for Active Sonar Using Genetic Algorithm

In order to solve the high peak to average power ratio (PAPR) problem of pseudo random code phase modulation (PRCPM) signals, minimum shift keying (MSK) modulation waveforms with constant envelope were introduced into underwater detection. Genetic algorithm (GA) was proposed to optimize pseudo random binary codes used for MSK waveforms, in order to design sonar waveforms with various performances. After MSK complex envelope signal was obtained by theoretical analysis, the optimizing objective functions for a single waveform and a group of waveforms were presented. The optimized single waveform with low autocorrelation sidelobe values can reduce false alarm number and the difficulty of target decision. When multiple sonar systems work as a team, the optimized group of orthogonal waveforms with low autocorrelation sidelobe values and cross-correlation values can alleviate interferences between each other. In the simulation, the correlation performances of a single waveform and a group of orthogonal waveforms were presented, and ambiguity function showed that the designed waveforms had good velocity and distance resolution, which means that the optimized MSK waveforms are suitable for underwater detection.

基于伪随机码相位调制和相干探测的激光测距技术研究

基于伪随机码相位调制和相干探测的激光测距技术研究

Combined Eigenvector Analysis and Independent Component Analysis For Multi-Component Periodic Interferences Suppression In PRCPM-PD Detection System

Interference suppression and information extraction in pseudorandom code phase modulated pulse Doppler detection system is a practical and challenging problem. In order to extract useful range and velocity in the presence of single-channel multi-component periodic interferences, this paper presents an interference suppression method based on eigenvector analysis and independent component analysis (ICA) by leveraging the characteristic of generalized periodicity of received signal. Using the generalized period of the transmitted signal, we divide the observed received signal into different segments and derive the sample covariance matrix. By computing the eigenvalue decomposition of the sample covariance matrix, we obtain all the eigenvectors and find the corresponding eigenvector with the maximum eigenvalue, which is the sum of the basic waveform components with the same generalized period. Then multi-dimensional matrix can be structured by changing the length of observed signal. The multi-dimensional matrix is used to accomplish ICA so as to separate all the components. Finally, the useful echo signal can be reconstructed; the range and velocity information can be obtained. Simulation results show that the proposed method is effective to excise multi-component periodic interferences and obtain the range and velocity information accurately at high signal to interference ratio (SIR). At low SIR, recursive separation is required. Compared with the existing methods, the proposed method has better performance.

Optical security verification by synthesizing thin films with unique polarimetric signatures.

This Letter reports the production and optical polarimetric verification of codes based on thin-film technology for security applications. Because thin-film structures display distinctive polarization signatures, this data is used to authenticate the message encoded. Samples are analyzed using an imaging ellipsometer able to measure the 16 components of the Mueller matrix. As a result, the behavior of the thin film under polarized light becomes completely characterized. This information is utilized to distinguish among true and false codes by means of correlation. Without the imaging optics the components of the Mueller matrix become noise-like distributions and, consequently, the message encoded is no longer available. Then, a set of Stokes vectors are generated numerically for any polarization state of the illuminating beam and thus, machine learning techniques can be used to perform classification. We show that successful authentication is possible using the k-nearest neighbors algorithm in thin-films codes that have been anisotropically phase-encoded with pseudorandom phase code.

Single channel source separation and parameter estimation of multi-component PRBCPM-SFM signal based on generalized period

This paper proposes an approach of single channel source separation and parameter estimation of multi-component PRBCPM-SFM (pseudo-random binary code phase modulated sinusoidal frequency modulation) signal. By transforming all components to SFM signals through square calculation, we may then apply singular value decomposition to determine the generalized period and the modulation frequency of the SFM signal. The modulation index and carrier frequency are determined by searching for discrete points and optimizing calculations. The initial phase can be determined by calculating the inner product. Finally, given that the pseudo-random binary code is a real signal, the PN (Pseudo-noise) sequence and the amplitude can be estimated. Our proposed method can estimate the SNR by using the method of subspace-based decomposition, and the estimated SNR can be used to adaptively stop separation. Experimental results demonstrate the algorithm's performance.

Research on Multi-Fuze Co-Channel Interference Suppression Based on Pseudorandom Code Phase Modulation

This paper introduces the working principle of the pseudorandom code phase modulation pulse, analyzes the theoretical foundation of multi-fuze co-channel interference suppression achieved by phase modulation of the signals through pseudorandom coding, and through the calculation and analysis of simulation, verifies the feasibility of the multi-fuze co-channel interference suppression based on pseudorandom code phase modulation.

Anti-Jamming Performance Simulation of PN-LFM Combined Ranging System

The pseudo-random binary-phase code phase modulation and linear frequency modulation (PN-LFM) combined ranging system is a new detection system, which has proven to be powerful capacity in range resolution, velocity resolution and maximum range measurable without ambiguity. In this paper, we study the anti-jamming performance of the new ranging system, especially in the fractal stochastic noise environments. We analyze the impact mechanism of fractal noise on the PN-LFM detection system, and simulate the output of correlating detection. The cross correlation function, power spectrum function and average power of pseudo random signal and fractal noise are deduced, compared with the impact of white noise on the pseudo code detection system. Simulation shows that PN-LFM combined ranging system possess powerful anti-jamming capacity, and performs better in the fractal noise environment than Pseudo random code phase modulation system.

Performance Research on Anti-Noise AM Spot Jamming of PRBC-SFM Combined Fuze

This paper gives the research on the anti-noise AM spot jamming performance of pseudo-random binary code phase modulation and sine FM combined fuze based on the criterion of signal to jamming ratio gain. First, the overall signal to jamming ratio gain of its receiver is reduced in detail under the noise AM spot jamming, then, the factors affecting anti-jamming performance are analyzed. The results show that the PRBC-SFM combined fuze has stronger performance of anti-noise AM spot jamming, and its anti-jamming performance can be improved effectively by choosing the parameters of the n-th order Bessel function, and along with decreasing periods and narrowing code width, Doppler frequencys influence on the anti-noise AM spot jamming performance of the PRBC-SFM combined fuze is debased.

Performance Analysis Concerning Anti-noise for Pseudo-random Code Phase Modulation and Pulse Amplitude Modulation Combined Fuze Based on Doppler Effect

Performance Analysis Concerning Anti-noise for Pseudo-random Code Phase Modulation and Pulse Amplitude Modulation Combined Fuze Based on Doppler Effect

Spatial-phase code-division multiple-access system with multiplexed Fourier holography switching for reconfigurable optical interconnection

A new, to our knowledge, space-variant optical interconnection system based on a spatial-phase code-division multiple-access technique with multiplexed Fourier holography is described. In this technique a signal beam is spread over wide spatial frequencies by an M-sequence pseudorandom phase code. At a receiver side a selected signal beam is properly decoded, and at the same time its spatial pattern is shaped with a Fourier hologram, which is recorded by light that is encoded with the same M-sequence phase mask as the desired signal beam and by light whose spatial beam pattern is shaped to a signal routing pattern. Using the multiplexed holography, we can simultaneously route multisignal flows into individually specified receiver elements. The routing pattern can also be varied by means of switching the encoding phase code or replacing the hologram. We demonstrated a proof-of-principle experiment with a doubly multiplexed hologram that enables simultaneous routing of two signal beams. Using a numerical model, we showed that the proposed scheme can manage more than 250 routing patterns for one signal flow with one multiplexed hologram at a signal-to-noise ratio of ~5.

Phase-Error Considerations for the Practical Phase Code Multiplexed Holographic Memory

For analysis of an effective phase code multiplexing in a holographic memory system, the Hadamard matrix (HAM) and the pseudorandom phase code (PRC) are generated and used as a reference beam. In computer simulations, the size of the address beam is fixed to 32×32 pixels, and 0%, 5%, 10%, 15%, 20%, or 25% phase error rate in a pixel is purposely added to the real phase values in order to consider the nonlinear phase modulation characteristics of the practical spatial-light modulator (SLM). Crosstalks and signal-to-noise ratios (SNRs) are comparatively analyzed for these two phase codes by calculating the auto- and cross-correlation. The cross-correlation mean values of the PRC and the HAM are 0.067 and 0.139, respectively, which means that the SNR of the PRC is higher than the HAM.