Showing papers on "Continuous phase modulation published in 2022"

Modular Arithmetic CPM for SDR Platforms

Abstract: This brief presents a new Continuous Phase Modulation (CPM) module for multi- $h$ transmission based on modular arithmetic processing. It is well known that CPM systems are sensitive to changes in the modulation index, which is implied when fixed-point format is used in the hardware implementation. In this scenario, modular arithmetic allows a more accurate signal processing regarding SQNR performance. This proposal has been shown to improve performance compared to other state-of-the-art methods, even when the modulation indices do not have an exact representation in a given fixed-point format. Due to its highly reconfigurable architecture, this hardware block is suitable for Software Defined Radio (SDR) platforms. A complete digital architecture is also provided. Implementation results show that the new proposal have clear advantages in terms of hardware resources and operating frequency against other CPM transmitters in open-literature.

Application of Continuous Wavelet Transform and Artificial Naural Network for Automatic Radar Signal Recognition

Abstract: This article aims to propose an algorithm for the automatic recognition of selected radar signals. The algorithm can find application in areas such as Electronic Warfare (EW), where automatic recognition of the type of intra-pulse modulation or the type of emitter operation mode can aid the decision-making process. The simulations carried out included the analysis of the classification possibilities of linear frequency modulated pulsed waveform (LFMPW), stepped frequency modulated pulsed waveform (SFMPW), phase coded pulsed waveform (PCPW), rectangular pulsed waveforms (RPW), frequency modulated continuous wave (FMCW), continuous wave (CW), Stepped Frequency Continuous Wave SFCW) and Phase Coded Continuous Waveform (PCCW). The algorithm proposed in this paper is based on the use of continuous wavelet transform (CWT) coefficients and higher-order statistics (HOS) in the feature determination of selected signals. The Principal Component Analysis (PCA) method was used for dimensionality reduction. An artificial neural network was then used as a classifier. Simulation studies took into account the presence of noise interference with signal-to-noise ratio (SNR) in the range from −5 to 10 dB. Finally, the obtained classification efficiency is presented in the form of a confusion matrix. The simulation results show a high recognition test accuracy, above 99% with a signal-to-noise ratio greater than 0 dB. The article also deals with the selection of the type and parameters of the wavelet. The authors also point to the problems encountered during the research and examples of how to solve them.

1.8 m/0.5 s Resolution Coherent Doppler Wind Lidar Using Continuous Phase Modulation

Abstract: A high-spatial-resolution coherent Doppler wind lidar (CDWL) with high modulation efficiency is reported. The pseudo-random phase coding (PRPC) links the spatial resolution to the modulation rate but suffers from the non-rectangular transition caused by the limited bandwidth. With the help of continuous phase modulation (CPM), the abrupt phase switching between successive bit intervals is avoided, thus significantly reducing the bandwidth requirement. By mapping the binary sequence into different transition states rather than phase levels, a 10-fold modulation efficiency improvement is realized. In experiments, the performance of the proposed lidar is compared with lidars in the PRPC method and conventional non-coding method. Continuous radial wind profile measurement of 800 m is demonstrated with spatial and temporal resolution of 1.8 m and 0.5 s, which is the highest spatial resolution realized by a pulsed CDWL to our best knowledge.

Performance evaluation during extraction technique in modified rotating disc column: Experimental and mathematical modeling

Abstract: In this survey, the reactive mass transfer data are determined for extraction technique in the modified rotating disc column. Mathematical models are investigated to compute the mass transfer coefficients of the dispersed phase. An increase in the dispersed phase holdup from 0.85 to 0.12 and a decrease in droplet diameter from 2.24 to 0.74 mm are observed with increasing rotation speed from 170 to 410 rpm in the optimized system. The experiments showed that the optimum transport efficiency in rotor speed of 410 rpm in this column is equal to 98.85% and 99.45% for extraction and stripping stages, respectively. The model's achievement is compared with the solvent extraction data and a significant validity is obtained by coupling the forward mixing approach (average absolute relative error lower than 13%). The mathematical modeling expresses that the axial dispersion and backflow coefficients based on the continuous phase increase by an increase in the rotor speed and inlet continuous phase rate. In contrast, these coefficients reduce at a higher inlet dispersed phase rate. High mass transfer coefficients were obtained in the stripping stage compared to the extraction stage. This report's study provides beneficial information to design solvent extraction equipment.

Multi-User Reconfigurable Intelligent Surface-Aided Communications Under Discrete Phase Shifts

Abstract: This paper focuses on studying orthogonal and non-orthogonal multiple access in intelligent reflecting surface (IRS)-aided systems. Unlike most prior works assuming continuous phase shifts, we employ the practical setup where only a finite number of discrete phase shifts are available. To maximize the sum rate, active beamforming and discrete reflection need to be jointly optimized. We therefore propose an alternative optimization method to get the optimal continuous phase shifts iteratively, and then quantize each phase shift to its nearest discrete value. The sum-rate maximization of different schemes is theoretically analyzed and numerically evaluated with different numbers of phase-control bits.

Variable removal function in atmospheric pressure plasma processing for fabrication of continuous phase plate with small spatial period

Abstract: Spatial period is an important characteristic parameter in the design and fabrication of continuous phase plate (CPP). The smaller the minimum spatial period, the more freedom of CPP design and the more difficult of CPP manufacture. The minimum spatial period of continuous phase plate determines removal function size of tool in high-precision machining of continuous phase plate. Based on chemical reaction, atmospheric pressure plasma processing (APPP) is a non-contact and high efficiency material removal method. The removal function of APPP is nonlinear with dwell time because of chemical reaction rate affected by temperature. The dwell-time algorithm of variable removal function was proposed in order to solve the nonlinear removal function. APPP for fabrication of continuous phase plate with small spatial period is introduced in this paper. Finally, APPP with variable removal function dwell time algorithm was used to fabrication a continuous phase plate with spatial period of 8mm, surface peak-valley (PV) more than 790nm, wavefront gradient root-mean-square (RMS) of 1.07um/cm. The results show that residual surface error between designed surface and measured surface root-mean-square (RMS) is down to 50 nm. The variable removal function in APPP for fabrication of continuous phase plate with small spatial period is validated.

Investigation of Minimizing the Probability of Errors Arising in the Demodulation of Signals with Multiple Phase Modulation

Abstract: The main attention in the article is paid to the conversion of a digital signal into a continuous one, which corresponds to the conversions carried out in the modulator and demodulator at the reception. Due to distortions in the communication channel caused by interference, it is necessary to minimize the probability of errors that appear after demodulation. Currently, a number of discrete modulation methods are known, and here it is also important to establish a theoretically optimal (good) method for comparing the digital signal with the values of the modulated signal. So, for example, two specific methods of on-off quadruple discrete modulation were investigated: on-off discrete amplitude-phase modulation and on-off discrete relative-phase modulation. The article also explores the method of multiple discrete modulation. The article considered general approaches to solving this problem and obtained specific estimates for a number of discrete modulation methods.

Prefiltered Single-Carrier Frequency-Domain Equalization for Binary CPM over Shallow Water Acoustic Channel

Abstract: The continuous phase modulation (CPM) technique is an excellent solution for underwater acoustic (UWA) channels with limited bandwidth and high propagation attenuation. However, the severe intersymbol interference is a big problem for the algorithm applying in shallow water. To solve this problem, an algorithm for prefiltered single-carrier frequency-domain equalization (PF-SCFDE) is presented in this paper. The regular whitening filter is replaced by a prefilter in the proposed algorithm. The output information sequence of this prefilter contains the forward information. To improve the performance, the output of the equalizer, combined with the forward information, is used to make the maximum likelihood estimation. The simulation results with minimum-shift keying and Gaussian-filtered minimum-shift keying signals over shallow water acoustic channels with low root mean square delay spread demonstrate that PF-SCFDE outperformed the traditional single-carrier frequency-domain equalization (SCFDE) by approximately 1 dB under a bit error rate (BER) of 10−4. A shallow sea trial has demonstrated the effectiveness of PF-SCFDE; PF-SCFDE had a reduction in BER of 18.35% as compared to the traditional SCFDE.

A Comprehensive Study of CPM Trellis Initialization Methods

Abstract: Short burst CPM transmission is of practical relevance in e.g. sensor or tactical networks. When an optimal symbol wise detection shall be carried out, the BCJR algorithm is deployed whose recursion must be initialized in one way or other to avoid performance impacts. While carrying out a fair and comprehensive comparison of several CPM schemes and trellis initialization methods, this paper also introduces the novel, yet simple method of terminating the trellis in a correlation zero state. Theoretical metrics as the channel symbol information as well as practical relevant error rates and computational complexities are examined. The novel method will show to be the best compromise between error rate and complexity and thus is regarded as the appropriate choice for most use cases.

Fluid Dynamics in a Continuous Pump-Mixer

Abstract: The fluid dynamic (flow rates) and hydrodynamic behavior (local droplet size distributions and local holdup) of a continuous DN300 pump-mixer were investigated using water as the continuous phase and paraffin oil as the dispersed phase. The influence of the impeller speed (N = 375 to 425 rpm), the feed phase ratio (φF = 10 to 30 vol.-%), and the flow rate (V˙tot ≈ 0.5 to 2.3 L/min) were investigated by measuring the pumping height, local holdup of the disperse phase, and the droplet size distribution (DSD). The latter one was measured at three different vessel positions using an image-based telecentric shadowgraphic technique. The droplet diameters were extracted from the acquired images using a neural network. The Sauter mean diameters were calculated from the DSD and correlated with an extended model based on Doulah (1975), considering the impeller speed, the feed phase ratio, and additionally the flow rate. The new correlation can describe an extensive database containing 155 experiments of the fluid and hydrodynamic within a 15% error range.

Noise Immunity of Dual Modulation Signals

Abstract: In the class of emissions with continuous phase modulation (Continuous Phase Modulation – CPM), the properties of Dual Phase Modulation (DPM) signals are not fully understood. It is necessary to develop an analytical model for calculating the bit error probability of DPM signals in order to assess their noise immunity in a channel with additive Gaussian noise. The choice of the forming phase function for DPM signals in the form of a low-frequency phase-shift keyed oscillation is substantiated. It is proposed to use DPM signals in radio communication systems operating in a limited frequency band.

Robust Automatic Modulation Classification Using Convolutional Deep Neural Network Based on Scalogram Information

Abstract: This study proposed a two-stage method, which combines a convolutional neural network (CNN) with the continuous wavelet transform (CWT) for multiclass modulation classification. The modulation signals’ time-frequency information was first extracted using CWT as a data source. The convolutional neural network was fed input from 2D pictures. The second step included feeding the proposed algorithm the 2D time-frequency information it had obtained in order to classify the different kinds of modulations. Six different types of modulations, including amplitude-shift keying (ASK), phase-shift keying (PSK), frequency-shift keying (FSK), quadrature amplitude-shift keying (QASK), quadrature phase-shift keying (QPSK), and quadrature frequency-shift keying (QFSK), are automatically recognized using a new digital modulation classification model between 0 and 25 dB SNRs. Modulation types are used in satellite communication, underwater communication, and military communication. In comparison with earlier research, the recommended convolutional neural network learning model performs better in the presence of varying noise levels.

Multi-user detection for CPM spread system with turbo in VDES

Abstract: The multi-user detection technology uses the spread sequence, delay, amplitude and phase information of each user to jointly detect users, which can effectively suppress multiple access interference, It is one of the key technologies in satellite communication system to make full use of uplink spectrum resources and improve system performance and capacity. Continuous phase modulation spread signal can adapt to multi-user communication due to the random variation of spread sequence, which is gradually applied to satellite communication. QPSK-CPM spread modulation scheme is adopted in the random access channel of VHF data exchange system. Aiming at the multi-user detection problem of QPSK-CPM spread system, proposing a multi-user detection algorithm based on interference elimination joint Turbo iterative detection based on the characteristics of CPM spread sequence. Compared with the traditional serial interference cancellation algorithm, the algorithm can effectively eliminate the multiple access interference problem caused by user aliasing by using the characteristics of Turbo codes. The theoretical simulation shows that the algorithm has a good detection effect on multi-user aliased signals.

Implementation of Variable Rate CPM Modulator

Abstract: Spectrum is a non-renewable resource, and the spectrum resources of telemetry system are increasingly scarce. However, the demand for high bit-rate transmission is increasing. Continuous phase modulation (CPM), an efficient bandwidth modulation method, can alleviate this contradiction. This paper focuses on the implementation of CPM modulation with variable rate sampling technology based on Farrow structure, and proposes a variable rate sampling method for shaped offset quadrature phase-shift keying signal(SOQPSK). When the phase correlation length is greater than 1, it is called SOQPSK- TG. SOQPSK-TG has better power spectrum characteristics. According to the SOQPSK-TG signal model, the integer rate sampling is realized by interpolating baseband and interpolating phase. Combined with the analysis of demodulation results, it is concluded that the interpolating phase has the advantages of lower demodulation error rate and less hardware implementation.

A High-Performance Multistep Phase-Shifting Interferometric Fiber Optic Sensing Method With Modulation Error Correction Capability

Abstract: Modulation error is a main error source of phase-shifting technique in the field of interferometric fiber optic sensing. To solve this problem, a multistep phase-shifting method with modulation error correction capability using rectangular-pulse binary phase modulation is proposed in this paper. In this method, a pair of three-step interference signals are obtained with the $\pi $ /2 phase modulation to generate multistep phase-shifting interference signals. The cross-correlation operation of the two signals with the same phase shift is calculated. Then, precise control of $\pi $ /2 modulation can be realized using simulated annealing algorithm to correct the modulation error. In addition, compared with the three-step phase-shifting algorithm, the extracted five-step phase-shifting algorithm itself has a higher ability to suppress the modulation error. Simulation and experimental results demonstrate that this method can be used to demodulate the phase result with high effectiveness and stability, improve the time domain signal and reduce the total harmonic distortion (THD), which provides a novel perspective for high-performance fiber-optic sensing and phase-shifting technique. In the actual experiment, after the calibration of modulation error, THD is effectively reduced from 7.5% to 4.5%. In addition, the method is verified by the demodulation of 200 Hz and 1000 Hz signals. The method also shows excellent repeatability and linearity in demodulation of sensing signals.

Recognition of Continuous Phase Modulation Signals Based on Synchrosqueezing Wavelet Transform

Abstract: We present a new algorithm that can solve the problem of recognition of continuous phase modulation (CPM) signals to phase shift keying (PSK) signals. The algorithm uses synchrosqueezing wavelet transform (SWT) to extract the instantaneous frequency (IF) of the signal. On this basis, a recognition characteristic parameter is proposed. This paper verifies the parameter is suitable for PSK and CPM signals with different modulation parameters. Finally, the simulation shows that the algorithm can fully recognize CPM signals to BPSK and QPSK signals when signal-to-noise ratio (snr) is above 6dB. Compared with the existing algorithms, the algorithm proposed in this paper has a higher recognition rate in the low snr environment.

Evolutionary Optimization of CPM Schemes over a Range of Spectral Efficiencies

Abstract: We consider the optimization of coded continuous phase modulation (CPM) systems operating at the spectral efficiencies 0.5bps/Hz, 1.0bps/Hz, 1.5bps/Hz and 2.0bps/Hz. Due to the difficulty of defining an analytic fitness function and the discreteness of the CPM parameters, we opt for an evolutionary optimization, which easily deals with such limitations. We apply a bi-objective instance of the non-dominated sorting genetic algorithm II (NSGA-II) where the mutual information between the transmit bits and soft bits at the output of the CPM detector as well as the complexity are taken as objective functions. This enables us to quantify the trade-off between complexity and performance. The results show that for all considered spectral efficiencies, the best schemes are usually quaternary or octal with a frequency pulse length not exceeding 2 symbol durations and a code rate ranging between 0.7−0.8.

Single Sideband Modulation Based Phase-coded Continuous Wave Inverse Synthetic Aperture Ladar Demonstration and Outdoor Experiment

Abstract: Inverse synthetic aperture LADAR(ISAL) is a coherent imaging technology whose resolution is independent of the target distance. Compared with traditional linear frequency modulation scheme, phase-coded ISAL can refer to the methods in communication to reduce noise interference or compensate the carrier phase error. In this paper, a novel single sideband modulation based phased coded continuous-wave ISAL system is proposed and experimentally demonstrated. The spectral efficiency of the new system is twice that of the traditional system, resulting in twice the utilization of echo energy. In addition, the use of continuous wave modulation improves anti-noise capability and imaging quality. Imaging results with azimuth resolution of 1.51cm are obtained by two 4cm aperture diameter telescopes at the distance of 7km, achieved about twenty times higher than conventional real aperture imaging system.

Using Dual Approximation for Best Linear Unbiased Estimators in Continuous Time, with Application to Continuous-Time Phase Estimation

Abstract: Best linear unbiased estimator (BLUE) theory is well established for discrete, finite-dimensional vectors, where methods of vector gradients can be used on a constrained optimization problem. However, when the observation is infinite-dimensional (e.g., continuous-time functions), the gradient-based approach can be problematic. We pose the BLUE problem as an instance of a dual approximation problem, which recasts the problem into finite dimensional space employing the principle of orthogonality, requiring no gradients for solution. To demonstrate the ideas, they are first developed on a finite-dimensional problem, then extended to infinite dimensional problems. We present an example application of phase estimation from continuous-time observations.

Simple phase unwrapping method with continuous convex minimization.

Abstract: Phase unwrapping is a problem to reconstruct true phase values from modulo 2π phase values measured using various phase imaging techniques. This procedure is essentially formulated as a discrete optimization problem. However, most energy minimization methods using continuous optimization techniques have ignored the discrete nature and solved it as a continuous minimization problem directly, leading to losing exactness of the algorithms. We propose a new minimum norm method that can yield the optimal solution of the discrete problem by minimizing a continuous energy function. In contrast to the graph-cuts method, which is state of the art in this field, the proposed method requires much less memory space and a very simple implementation. Therefore, it can be simply extended to 3D or 4D phase unwrapping problems.

Two-Time Procedure for Calculation of Carrier Frequency of Phasomodulated in Communication Systems

Abstract: The use in radio communication systems of phase modulation of a signal intended for the transmission of useful information in a continuous mode creates the problem of frequency uncertainty of the received signal by frequency.In practice, it is not possible to implement frequency estimation in the conditions of chat uncertainty of the signal in the channel with low energy of the signal received in the continuous mode. Therefore, the estimation of the carrier frequency offset of the signal received relative to the nominal value is carried out before other synchronization procedures are included, namely: phase synchronization and clock synchronization. The paper generalizes the procedure and forms a two-step procedure for calculating the carrier frequency of the phase-modulated signal of a radio communication system for data transmission in a continuous mode, taking into account the condition of uncertainty of all signal parameters. Achieving the minimum observation interval in the given order of calculation of the carrier frequency is ensured by the use of the fast Fourier transform function. In order to analyze the effectiveness of this procedure, the process of estimating the carrier frequency of the phase-modulated signal of the radio communication system during data transmission in continuous mode and functional dependences of the maximum frequency in the signal spectrum and the minimum variance of carrier frequency estimation. This procedure allows a two-stage assessment of the carrier frequency according to the rule of maximum likelihood, taking into account the condition of uncertainty of all parameters of the signal received by the satellite communication system in a continuous mode with a minimum observation interval. Achieving the minimum observation interval in the given order of carrier frequency estimation is ensured by using the fast Fourier transform function and two estimation steps. The analysis of the efficiency of the estimation of the specified order was carried out on the basis of comparison of a ratio of the received minimum variance of an estimation of a carrier frequency and theoretically possible border of the minimum variance.

Delay Optimization of Conventional Non-Coherent Differential CPM Detection

Abstract: The conventional non-coherent differential detection of continuous phase modulation (CPM) is quite robust to channel impairments such as phase and Doppler shifts. Its implementation is on top of that simple. It consists in multiplying the received baseband signal by its conjugate and delayed version of one symbol period. However it suffers from a signal-to-noise ratio gap compared to the optimum coherent detection. In this paper, we improve the error rate performance of the conventional differential detection by using a delay higher than one symbol period. We derive the trellis description as well as the branch and cumulative metric that take into account a delay of $K$ symbol periods. We then derive an optimization criterion of $K$ based on the minimum Euclidean distance between two differential signals. We finally determine optimized delays for some popular CPM formats whose values are confirmed by error rate simulations.

Parallelization of Microfluidic Droplet Junctions for Ultraviscous Fluids.

Abstract: The parallelization of multiple microfluidic droplet junctions has been successfully achieved so that the production throughput of the uniform microemulsions/particles has witnessed considerable progress. However, these advancements have been observed only in the case of a low viscous fluid (viscosity of 10-2 -10-3 Pa s). This study designs and fabricates a microfluidic device, enabling a uniform micro-emulsification of an ultraviscous fluid (viscosity of 3.5 Pa s) with a throughput of ≈330 000 droplets per hour. Multiple T-junctions of a dispersed oil phase, split from a single inlet, are connected into the single post-crossflow channel of a continuous water phase. In the proposed device, the continuous water phase undergoes a series circuit, wherein the resistances are continuously accumulated. The independent corrugations of the dispersed oil phase channel, under the theoretical guidance, compromise such increased resistances; the ratio of water to oil flow rates at each junction becomes consistent across T-junctions. Owing to the design being based on a fully 2D interconnection, single-step soft lithography is sufficient for developing the full device. This easy-to-craft architecture contrasts with the previous approach, wherein complicated 3D interconnections of the multiple junctions are involved, thereby facilitating the rapid uptake of high throughput droplet microfluidics for experts and newcomers alike.

Modulator vulnerability in continuous-variable quantum key distribution

Abstract: Encoding of key bits in the quadratures of the electromagnetic light field is an essential part of any continuousvariable quantum key distribution system. However, flaws of practical implementation can make such systems susceptible to leakage of secret information. We verify a side channel presence in an optical in-phase and quadrature modulator which is caused by limited suppression of a quantum information-carrying sideband. We investigate various strategies an unauthorized third party can exploit the vulnerability in a proof-of-concept experiment and theoretically assess the modulation leakage effect on a security of the Gaussian coherent-state continuous-variable quantum key distribution protocol and show that the leakage reduces the range of conditions which support secure key generation. Without the control of sideband modulation in practical in-phase and quadrature modulator-based systems the security can be compromised.

A modulation index estimation algorithm for multi-h CPM signals

Abstract: Continuous Phase Modulation (CPM) signal has been widely used in modern satellite, mobile communication and military communication system due to its good spectrum and power utilization and constant envelope characteristics. The premise of demodulation or jamming of CPM signal intercepted in military communication confrontation is the accurate estimation of signal parameters. Aiming at the difficulty and complexity of multi-h CPM signal modulation index estimation, this paper puts forward a kind of blind estimation algorithm of the modulation index based on first order cyclic moment and the second-order cyclic cumulants, using the first and second order cyclic properties in frequency domain on the spectral properties to signal parameter estimation. The estimation algorithm is suitable for both single h CPM signals and multi-h CPM signals, where the multi-h CPM requires the synchronization of the guidance sequence. Simulation results show that the algorithm has better performance under low signal-to-noise ratio with less symbols required. When the number of symbols is 128 and the signal-to-noise ratio is 15 dB, the accurate recognition rate of the multi-index CPM signal can reach 98% and the recognition rate can reach 99% with the allowable error of 1/32.

A CPM-DSSS Based Low Complexity Carrier Phase and Symbol Timing Offset Joint Estimator

Abstract: Continuous Phase Modulation-Direct Sequence Spread Spectrum (CPM-DSSS) is a promising technique with the advantages of constant envelope, high spectral efficiency and anti-jamming. The demodulation of CPM-DSSS requires precise synchronisation of carrier phase and symbol timing offset at the receiver side. However, the existing synchronization methods have the problem of high computational complexity. In this work, a low-complexity joint estimator of carrier phase and symbol timing offset based on CPM-DSSS and PAM decomposition is proposed. By performing PAM decomposition on the CPM-DSSS signal and optimising the estimation algorithm with energy weights of each pulse, the computational complexity is reduced by 90 %. Simulation analysis shows that the proposed estimator can achieve the same estimation performance as the ML algorithm with low operational complexity.