Discrete Phase Shifts Control and Beam Selection in RIS-Aided MISO System via Deep Reinforcement Learning

Reconfigurable intelligent surface(RIS)for wireless networks have drawn lots of attention in both academic and industry communities.RIS can dynamically control the phases of the reflection elements to send the signal in the desired direction,thus it provides supplementary links for wireless networks.Most of prior works on RIS-aided wireless communication systems consider continuous phase shifts,but phase shifts of RIS are discrete in practical hardware.Thus we focus on the actual discrete phase shifts on RIS in this paper.Using the advanced deep reinforcement learning(DRL),we jointly optimize the transmit beamforming matrix from the discrete Fourier transform(DFT)codebook at the base station(BS)and the discrete phase shifts at the RIS to maximize the received signal-to-interference plus noise ratio(SINR).Unlike the traditional schemes usually using alternate optimization methods to solve the transmit beamforming and phase shifts,the DRL algorithm proposed in the paper can jointly design the transmit beamforming and phase shifts as the output of the DRL neural network.Numerical results indicate that the DRL proposed can dispose the complicated optimization problem with low computational complexity.

Shaped Offset Quadrature Phase Shift Keying Based Waveform for Fifth Generation Communication

Fifth generation(5G)wireless networks must meet the needs of emerging technologies like the Internet of Things(IoT),Vehicle-to-everything(V2X),Video on Demand(VoD)services,Device to Device communication(D2D)and many other bandwidth-hungry multimedia applications that connect a huge number of devices.5G wireless networks demand better bandwidth efficiency,high data rates,low latency,and reduced spectral leakage.To meet these requirements,a suitable 5G waveform must be designed.In this work,a waveform namely Shaped Offset Quadrature Phase Shift Keying based Orthogonal Frequency Division Multiplexing(SOQPSK-OFDM)is proposed for 5G to provide bandwidth efficiency,reduced spectral leakage,and Bit Error Rate(BER).The proposed work is evaluated using a real-time Software Defined Radio(SDR)testbed-Wireless open Access Research Platform(WARP).Experimental and simulation results show that the proposed 5G waveform exhibits better BER performance and reduced Out of Band(OOB)radia-tion when compared with other waveforms like Offset Quadrature Phase Shift Key-ing(OQPSK)and Quadrature Phase Shift Keying(QPSK)based OFDM and a 5G waveform candidate Generalized Frequency Division Multiplexing(GFDM).BER analysis shows that the proposed SOQPSK-OFDM waveform attains a Signal to Noise Ratio(SNR)gain of 7.2 dB at a BER of 10�3,when compared with GFDM in a real-time indoor environment.An SNR gain of 8 and 6 dB is achieved by the proposed work for a BER of 10�4 when compared with QPSK-OFDM and OQPSK-OFDM signals,respectively.A significant reduction in OOB of nearly 15 dB is achieved by the proposed work SOQPSK-OFDM when compared to 16 Quadrature Amplitude Modulation(QAM)mapped OFDM.

An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance

In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform.We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.

Comparative analysis of phase extraction methods based on phase-stepping and shifting curve in grating interferometry

Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam.In this paper,the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.

Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

Digital structured light(SL) profilometry is increasingly used in three-dimensional(3D) measurement technology.However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector–camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.

Multiple-image encryption by two-step phase-shifting interferometry and spatial multiplexing of smooth compressed signal

A multiple-image encryption method based on two-step phase-shifting interferometry(PSI) and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing(CS)and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme,only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.

New representation of the multimode phase shifting operator and its application

Based on the rotation transformation in phase space and the technique of integration within an ordered product of operators, the coherent state representation of the multimode phase shifting operator and one of its new applications in quantum mechanics are given. It is proved that the coherent state is a natural language for describing the phase shifting operator or multimode phase shifting operator. The multimode phase shifting operator is also a useful tool to solve the dynamic problems of the multimode coordinate-momentum coupled harmonic oscillators. The exact energy spectra and eigenstates of such multimode coupled harmonic oscillators can be easily obtained by using the multimode phase shifting operator.

Single-shot phase-shifting digital holography with a photon-sieve-filtering telescope

A method of single-shot phase-shifting digital holography with a photon-sieve-filtering telescope is proposed.Three copy images with different phases are first generated by use of a monofocal photon-sieve filter in Kepler telescope,and then interfere with the reference plane wave by a beam combiner.The hologram is captured by a charge-coupled device(CCD)in one single exposure.The complex-valued amplitude of the test object can be reconstructed by three-step phase-shifting interferometry through three frames of extracted sub-interferograms from the single-exposure hologram.The principle and simulation experiments are carried out and verified the validity of our proposed method.This method can be applied for snapshot imaging and three-dimensional object construction.

Phase-shifting digital holography in image reconstruction

A phase-shifting digital holography scheme developed to investigate internal defects in artworks is described. Phase-shifting is utilized to obtain a clear reconstructed object wave from a rough surface texture. A reverse-transform algorithm is employed to reconstruct the object wave on its original position of unknown distance or the imaging position from the object wave information on the holographic plane. To get the clearest reconstruction the exact registration of the unknown distance is determined by applying the intensity sum as the auto-focusing function. The spatial resolution of the reconstruction image is also investigated for a variety of affecting factors. Laboratory results of reconstruction images under deformation are presented.

2D PHASE SHIFTING AND LOGICAL MOIRE USED IN FRINGES ANALYSIS

Phase Shifting And Logical Moire (PSALM) is a kind of computer imageprocessing method which can be used in phase measurement and to obtain the shape,deformation and strain distribution of an object.This paper presents the structure andworking procedure of a 2D phase measurement PSALM2D program and its application.When analyzing moire interferometric fringes,we can obtain 2D distribution ofdisplacement and strain.When it is used in reflection moire we can measure the slopeof a specimen.Satisfactory visualization and quantitative results are given byPSALM2D.

Phase-Shift Extraction and Wavefront Reconstruction in Generalized Phase-Shifting Interferometry with a Standard Phase Object

A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase shifts.It is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.

Three-step self-calibrating generalized phase-shifting interferometry

An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry(SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normalization and noise suppressing, then the unknown phase shift between the two difference phase-shifting signals is estimated quickly through searching the minimum coefficient of variation of the modulation amplitude, a limited number of pixels are selected to participate in the search process to further save time, and finally the phase is reconstructed through the searched phase shift. Through the reconstruction of phase map by the simulation and experiment, and the comparison with several mature algorithms, the good performance of the proposed algorithm is proved, and it eliminates the limitation of requiring more than three phase-shifting interferograms for high-precision SGPSI. We expect this method to be widely used in the future.

Opto-Mechanical Properties of PTFE Fibres Using Phase Shifting Interferometry

Polytetrafluoroethylene (PTFE) is one of a class of polymer that has many unique properties, which make it valuable in scores of applications. Here, the molecular alignment effect in fibre drawing and its relation with nonlinear optical properties of the PTFE fibres were studied by means of interferometry. For this propose, the phase shifting Mach-Zehnder interferometer was utilized. The fibre drawing device was attached to the interferometer for measuring the opto-mechanical properties of PTFE fibres. From the recorded interferomgrams the wrapped phase map and its contour line were determined using the phase shifting interferometry (PSI) method. From the contour lines the refractive index, refractive index profile, birefringence, polaryzability and orientation function of the investigated sample were determined at different draw ratios. The PSI method showed good results for enhancing the noisy fringe pattern and for obtaining contour line microinterferograms. This study offers the correlation between the mechanical properties and the structure properties of fibres. Thus, a better structure-property correlation can improve the technical and industry performance of the fibres.

Photoelastic Stress Analysis by Use of Hybrid Technique and Fringe Phase Shifting Method

Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured data away from the edge of a geometric discontinuity. Photoelastic data are hybridized with complex variable/mapping techniques to calculate photoelastic stress-field around a circular hole or an elliptical hole in plates under uniaxial tensile loading. This method determines full-field stresses in perforated finite tensile plates containing either a circular or an elliptical hole. The second one is a fringe phase shift method to separate isochromatics and isoclinics from photoelastic fringes of a circular disk under diametric compression by use of phase shift method. Digitally determined isochromatics and isoclinics are agreed well with those of manual measurements.

A NEW ALGORITHM FOR ELIMINATING PHASE-SHIFT ERROR IN PHASE SHIFTING INTERFEROMETRY

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鱼糜pH-shifting工艺及其胶凝机制研究综述及展望

鱼糜是我国低值淡水鱼深加工的主要研究方向之一,但由于低值淡水鱼个体小、刺多,现有工艺得率低,而pH-shifting技术能显著提高低值鱼鱼糜得率,且凝胶强度更好或相当。因此,该技术被认为是很有工业化前景的鱼糜加工新技术。本文综述了近年来的研究进展,包括pH-shifting工艺对鱼糜蛋白组成、鱼糜蛋白质分子结构、鱼糜胶凝特性、蛋白降解、蛋白交联及鱼糜凝胶微结构的影响。并提出以下观点:可采用蛋白质组学方法研究pH-shifting工艺对鱼糜蛋白质组成的影响,解析各蛋白组分在胶凝过程中的作用;pH-shifting鱼糜凝胶是蛋白聚集体与未变性蛋白的混合凝胶,可从共混胶凝、微相分离的角度研究pH-shifting鱼糜凝胶微结构形成机制。

An improved frequency shift method for ATI-SAR flat earth phase removal

An improved frequency shift method is proposed to remove the flat earth phase in ATI-SAR ocean surface motion detection in this study. First, two conventional flat earth effect removal methods(i.e., the frequency shift method and the orbital parameter method) are introduced and compared. Then, two improvements to frequency shift method are suggested. In the first improvement, the phase diagram is divided into several sub-blocks to calculate the phase fringe frequency. In the second improvement, a function between the phase of land regions and position is fitted to correct the residual flat earth phase based on the phase of the land regions that tend toward zero in an along-track interferogram. It is found that the improved frequency shift method is greatly improved;and it agrees well with the orbital parameter method, and achieves similar accuracy.

Intelligent System for Mask Phase-Shifter Design

讨论了一个用于相移掩模智能设计的专家系统。这个系统包括输入输出系统，仿真系统，知识库系统，人—机接口，黑板系统。它有一个包括图形获取、预处理、模式抽取、搜索与解释、图形复合与输出等环节的工作过程。系统的软件实现运用了面向对象的表示方法。

Applications of Wavelet Analysis in Differential Propagation Phase Shift Data De-noising

Using numerical simulation data of the forward differential propagation shift(ΦDP) of polarimetric radar, the principle and performing steps of noise reduction by wavelet analysis are introduced in detail. Profiting from the multiscale analysis, various types of noises can be identified according to their characteristics in different scales, and suppressed in different resolutions by a penalty threshold strategy through which a fixed threshold value is applied, a default threshold strategy through which the threshold value is determined by the noise intensity, or a ΦDPpenalty threshold strategy through which a special value is designed for ΦDPde-noising. Then, a hard- or soft-threshold function, depending on the de-noising purpose, is selected to reconstruct the signal. Combining the three noise suppression strategies and the two signal reconstruction functions, and without loss of generality, two schemes are presented to verify the de-noising effect by dbN wavelets:(1) the penalty threshold strategy with the soft threshold function scheme(PSS);(2) the ΦDPpenalty threshold strategy with the soft threshold function scheme(PPSS). Furthermore, the wavelet de-noising is compared with the mean, median, Kalman, and finite impulse response(FIR) methods with simulation data and two actual cases. The results suggest that both of the two schemes perform well, especially when ΦDPdata are simultaneously polluted by various scales and types of noises. A slight difference is that the PSS method can retain more detail, and the PPSS can smooth the signal more successfully.

Adaptive compensating method for Doppler frequency shift using LMS and phase estimation

The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier.In this way, the phase offsets due to frequency shift are linear.Based on this premise,the compensation processes are:firstly, the phase offsets between the baseband neighbor-symbols after clock recovery is unbiasedly estimated among the reference symbols;then,the receiving signals symbols are adjusted by the phase estimation value;finally,the phase offsets after adjusting are compensated by the least mean squares(LMS) algorithm.In order to express the compensation processes and ability clearly,the quadrature phase shift keying(QPSK) modulation signals are regarded as examples for Matlab simulation.BER simulations are carried out using the Monte-Carlo method.The learning curves are obtained to study the algorithm's convergence ability.The constellation figures are also simulated to observe the compensation results directly.