Phase Synchronization Scheme Research Articles

An Advanced Approach to Improve Synchronization Phase Accuracy with Compressive Sensing for LT-1 Bistatic Spaceborne SAR

In the bistatic synthetic aperture radar (BiSAR) system, the unavoidable frequency deviation between the oscillators (USOs) will result in additional phase modulation in the demodulated radar signal, which significantly degrades the quality of the SAR image and digital elevation model (DEM) product. The innovative L-band spaceborne BiSAR system LuTan-1 (LT-1) employs a non-interrupted synchronization scheme to acquire the synchronization phase error. This advanced phase synchronization scheme avoids interrupting the normal BiSAR data acquisition and further increases the synchronization frequency. However, some non-ideal factors in the transmission link like attenuation, multipath effect, interference, etc., may cause the synchronization phase to be polluted by noise. A phase denoising approach based on compressive sensing (CS) is proposed to improve the accuracy of synchronization phase. The imaging phase with high signal-to-noise ratio (SNR) is input into the K-SVD algorithm to learn the prior information, and then the noise of the synchronization compensation phase is eliminated by maximum a posteriori (MAP) estimation. The data acquired from the ground validation system of the LT-1 synchronization module are adopted for the validation experiment. The proposed phase denoising method achieves higher phase synchronization accuracy compared with traditional ones. The processing results verify the effectiveness of the proposed method and demonstrate its potential for future on-orbit applications of the LT-1 mission.

Simulation of the influence of negative internal factors on performance indicators of the synchronization system of a coherent demodulator of satellite telecommunications in permanent and transient modes of carrier frequency estimation

The subject of study in the article is the system of phase synchronization of radio technical devices of communication technology. The purpose of the article is theoretical research in the direction of development, analysis and improvement of known and synthesis of new phase synchronization schemes, which are characterized by high interference resistance, accuracy and speed of operation with a simple design. The problem to be solved is to investigate the possibilities of closed and combined synchronization systems in terms of operation in conditions of internal noise and disturbances against the background of external additive Gaussian noise and Doppler frequency shift. The article presents a model that allows you to investigate the influence of negative internal factors on the performance indicators of the synchronization system of the coherent demodulator of satellite telecommunications in stable and transient modes of carrier frequency estimation. With its help, the article analyzes closed-type synchronization systems when operating under the influence of negative internal factors and shows its inconsistency in minimizing the dispersion of the phase error and increasing the dynamics during tracking of the carrier frequency. The process of synthesis of open communication in the combined synchronization system has been clarified and analytical dependencies have been proposed, which allow to clarify the methodology of synthesis of open communication for the combined synchronization system, taking into account the influence of internal negative factors. It was established that under the influence of negative internal factors for the combined synchronization system, by selecting the parameters of the proportionalintegrating filter, it is possible to achieve an expansion of the noise bandwidth of the input signal and thereby ensure the necessary dynamics of the system and achieve the preservation of the optimal value of the dispersion of the phase error in it.

Absolutely Consistent Fiber-Optic Phase Synchronization Based On Fixed-Phase-Reference Optical Active Compensation

An absolutely consistent fiber-optic phase synchronization scheme based on fixed-phase-reference optical active compensation is proposed. By measuring the time interval of time pulse and the phase difference of frequency signal, and then using the optical delay line to compensate the phase change in real time according to a fixed phase reference, the phase period ambiguity and the phase-lock control initial randomness are eliminated, realizing a stable and repeatable fixed phase difference between different sites. Then the phase synchronization performances of stability and absolute consistence have been demonstrated through experiments in different scenarios. The phase difference fluctuation within 10000 s is only ±0.0006 rad, showing an ultra-high stability. Under the total of 5 different operations, including the signal source restart, system restart, adding 20 m additional fiber, adding 1 km additional fiber, and adding 2 km additional fiber, the maximum inconsistency of the mean phase difference is about 1% of one full cycle. The proposed and verified absolutely consistent phase synchronization method can well maintain the coherence in transferring frequency signal, having important application prospects in radar network and other time-frequency-phase synchronization-based coherent detection.

An Advanced Phase Synchronization Scheme Based on Coherent Integration and Waveform Diversity for Bistatic SAR

In the bistatic synthetic aperture radar (BiSAR) system, the deviation between two oscillators in different platforms will cause an additional modulation of BiSAR echoes. Therefore, phase synchronization is one of the key issues that must be addressed for the BiSAR system. The oscillator phase error model and the principle of phase synchronization are firstly described. The waveform diversity technology has been widely used in many fields, for example, the hearing aids device and the recognition of auditory input source in cocktail party problem. Inspired by this, an advanced phase synchronization scheme based on coherent integration and waveform diversity is proposed. The synchronization signal and radar signal are orthogonal signals which can be separated by using waveform diversity technique. After extracting the synchronization signal, the phase synchronization accuracy can be further improved by coherent integration. The transmission of synchronization signals between two synchronization antennas is analyzed, followed by the theoretical error analysis. Then, the processing of separating the echo signal and synchronization signal is described in detail. The simulation experiments are performed. The accuracy of phase synchronization can reach 1 degree, which verifies the effectiveness of the proposed synchronization scheme.

The Processing Framework and Experimental Verification for the Noninterrupted Synchronization Scheme of LuTan-1

The bistatic synthetic aperture radar (BiSAR) plays an important role in remote sensing. However, the deviation between the two oscillators in BiSAR systems will cause a residual modulation of the echo signal. Therefore, the phase synchronization is an important issue that must be addressed in the BiSAR system. An advanced noninterrupted phase synchronization scheme is used for LuTan-1. The synchronization pulses are exchanged immediately after the ending time of the radar echo receiving window and before the starting time of the next pulse repetition interval, which will not interrupt the normal SAR operation. In order to evaluate the accuracy of the phase synchronization scheme, the model of phase synchronization is introduced at first. The hardware design and processing flow of LuTan-1 are introduced in detail. An innovative internal calibration strategy is also described. Then, the test data acquired by the ground validation system are analyzed to verify the effectiveness of the phase synchronization scheme. The signal-to-noise ratio (SNR) and the synchronization rate are the two most important factors to influence the accuracy in phase synchronization. The conclusions have guiding significance for the synchronization module design of LuTan-1 and the future BiSAR system.

Implementation of a Phase Synchronization Scheme Based on Pulsed Signal at Carrier Frequency for Bistatic SAR.

Phase synchronization is one of the key technical challenges and prerequisites for the bistatic synthetic aperture radar (SAR) system, which can form a single-pass interferometry system to perform topographic mapping. In this paper, an advanced phase synchronization scheme based on a pulsed signal at carrier frequency is proposed for a bistatic SAR system and it is verified by a ground validation system. In the proposed phase synchronization scheme, the pulsed signal at carrier frequency is used for phase synchronization link, and it is exchanged by virtue of a time slot between radar signals. The feasibility of the scheme is proven by theoretical analysis of various factors affecting the performance of phase synchronization, and the reliability of the scheme is verified by the test results of the ground validation system.

The Synchronization Transceiver Design and Experimental Verification for the LuTan-1 SAR Satellite

The deviation between the two oscillators in BiSAR systems will cause a residual modulation of echo signal. Therefore, the phase synchronization is an important issue that must be addressed for BiSAR systems. An advanced non-interrupted phase synchronization scheme is used for the LuTan-1 SAR satellite. The synchronization transceiver (STR) is designed for transmitting and receiving synchronization signals. In addition, STR mainly consists of master and auxiliary transceivers and switch module. Furthermore, the function and working principle of STR are introduced, and the detailed design of each part is described. The measured results are also evaluated to prove the performance of the STR. In addition, the phase synchronization accuracy is also demonstrated to verify the effectiveness of the non-interrupted synchronization scheme. The standard deviation (STD) of the residual phase is less than 0.3 degrees. The results have guiding significance for the synchronization unit design of LuTan-1 and the future BiSAR system.

First Demonstration of Multipath Effects on Phase Synchronization Scheme for LT-1

LuTan-1 (LT-1) refers to an innovative mission of spaceborne bistatic synthetic aperture radar (BiSAR) adopting the phase synchronization scheme of pulse exchange, which is scheduled to be launched in 2020. In this mission, the multipath effect caused by the reflection of satellites and Doppler frequency shift resulting from the relative motion between satellites constitute two critically latent factors deteriorating the performance of the phase synchronization scheme. This article details a loss factor to evaluate the fading of synchronization signals under the reflection of smooth and rough surfaces and estimates the influence of Doppler frequency shift on synchronization signals. Furthermore, the multipath channel impulse response is modeled, and the correlation characteristics of multipath channel are described by the coherent bandwidth and coherent time. In addition, two simulation experiments based on the system parameters of LT-1, are implemented to assess the influence of time-invariant and -varying multipath effects on the phase synchronization scheme. A scale experiment is also executed to quantify the influence of multipath effect on phase synchronization, and its result demonstrates that the phase synchronization scheme of LT-1 can not only achieve full coverage of space and backup capability of pulse exchange but also meet the application requirements under multipath effect.

Design and Development of Hybrid Time Synchronization Scheme to Mitigate the Phase and Frequency error for Asynchronous Link in Heterogeneous Network

The arbitrary deployment of HeNodeBs high-lights the importance of interference minimization in order to capture the best. Timing as well as synchronization are equally essential for control of HeNodeBs in 4G LTE devices. So as to sustain HeNodeBs for management, IEEE1588 master slave strategies are being used in order to maintain HeNodeBs for the control purpose. Nonetheless, as a result of poor internet connectivity for a long period HeNodeBs undergoes synchronization problems that leads to clock offset problem. Asymmetric link delays, due to phase and frequency misalignment causes the effects on interference and system QoS. Moreover, to mitigate interference and for QoS synchronization is prerequisite for heterogeneous network. This paper inspects the pros and cons of the IEEE 1588 algorithm and IEEE Precision Timing Protocol (PTP). Therefore, this paper proposed a hybrid phase and frequency synchronization scheme. Comparing to IEEE1588 and PTP, hybrid scheme can improve the clock Phase (offset), and frequency error in two-tier Heterogeneous Network. The proposed scheme is evaluated by Monte Carlo system level simulation, and the results are benchmarked with the existing techniques. The simulation outcome ensures that the hybrid time synchronization strategy is much better in Heterogeneous network with regards to phase (offset) and frequency errors

Collaborative beamforming techniques for data transmission in wireless sensor networks

Collaborative beamforming is a technique for improving energy efficiency of uplink communications in wireless sensor networks. It is done by synchronizing carrier phases of individual sensor nodes precisely enough, so that they jointly form a beampattern with a stable mainlobe. In this paper, we analyze the impact of additive noise in the received signal on the behavior of an iterative phase synchronization scheme. Besides, we analyze the bit error rate performance of such collaborative transmission. In particular, we consider a decentralized antenna array where sensors are allowed to perform distributed carrier synchronization and collaborative data transmission simultaneously. We evaluate the system performance by using numerical simulations and provide a semi-analytical solution for the algorithm convergence characteristics and the overall bit error rate as a function of the algorithm's iteration index.

Feedforward Joint Clock and Phase Estimation Schemes for SOQPSK-Type Signals

Feedforward algorithms are investigated for estimating carrier phase and symbol timing in SOQPSK modulations. We begin showing that an SOQPSK signal with correlated data symbols is equivalent to a conventional CPM signal with independent data. Then, based on maximum likelihood criteria, we derive joint phase and timing synchronization schemes that are suitable for full digital implementation. The performance of the proposed algorithms is investigated by simulation and the results are compared with Cramer-Rao bounds. It turns out that the timing estimation accuracy is very close to the theoretical limits. Also, the proposed estimators largely outperform other synchronizers already known in literature with a comparable complexity.

A Fast-Locking ADPLL With Instantaneous Restart Capability in 28-nm CMOS Technology

This brief presents a bang-bang all-digital phase-locked loop (ADPLL) clock generator for multiprocessor system-on-chip applications in Globalfoundries 28-nm superlow-power CMOS technology. The circuit features a single-shot phase synchronization scheme for instantaneous phase lock after power-up. This feature is used for fast frequency search during lock-in, resulting in less than 1-μs initial lock time and the capability of instantaneous restart. The ADPLL provides a wide range of output clocks from 83 MHz to 2 GHz and exhibits 31-ps accumulated jitter with 3-ps period jitter at 2 GHz. It occupies an area of only 0.00234 mm2 and consumes 0.64 mW from a 1.0-V supply.

Phase and clock synchronization of the Viterbi demodulator of continuous-phase modulation signals

The possibility of constructing the synchronization system of the Viterbi demodulator of continuous-phase modulation (CPM) signals is analyzed. The concept of multiphase trellis is introduced to provide the phase self-synchronization of a demodulator. The results calculated via computer simulation of the phase synchronization scheme that ensures efficient reception of CPM signals with constant and cyclically varying modulation indices are presented. The clock synchronization scheme whose main component is a delay discriminator is proposed and investigated. Its operability is demonstrated with the use of a minimum frequency-shift keying signal.

Nonlinear observer based phase synchronization of chaotic systems

This Letter analyzes the phase synchronization problem of autonomous chaotic systems. Based on the nonlinear state observer algorithm and the pole placement technique, a phase synchronization scheme is designed. The phase synchronization of a new chaotic system is achieved by using this observer controller. Numerical simulations further demonstrate the effectiveness of the proposed phase synchronization scheme.

Phase synchronization of chaotic systems based on nonlinear observers

The phase synchronization problem of autonomous chaotic systems is discussod. Based on the nonlinear state observer algorithm and the pole placement technique, a phase synchronization scheme is designed. The phase synchronization of a new chaotic system is achieved by using this observer controller. Numerical simulations are carried out to verify its effectiveness.

A block turbo phase synchronization scheme

This letter presents an original phase synchronization scheme designed for block turbo coded systems. This is a low-complexity scheme. It copes with low signal-to-noise ratios, taking complete advantage of the turbo coding possibilities. We display various results, showing that the proposed algorithm is able to process blocks of a few hundreds bits and that it tackles the case of large quadrature amplitude modulation constellations very well and with no phase ambiguity.

Reduced-complexity detection and phase synchronization of CPM signals

Based on an extension of Laurent (1986) decomposition of continuous phase modulation (CPM) signals into a sum of linearly modulated components, we derive a class of reduced-complexity maximum-likelihood (ML) coherent detection and closed-loop phase synchronization schemes. The complexity of the resulting detection schemes, expressed in terms of the number of matched filters and states of a Viterbi algorithm, is significantly reduced with respect to that of optimal coherent receivers with negligible performance loss. This result extends a known one valid for the binary case to multilevel CPM. The proposed synchronization schemes do not require an increased number of matched filters, and are perfectly suitable to be used in conjunction with these receivers. Based on the phase-locked loop (PLL) equivalent linear model, a method for optimizing the parameters of digital second-order PLL's is presented. Numerical examples, based on theoretical analysis and computer simulation, are provided for two specific formats in the CPM class: tamed frequency modulation (TFM) and a quaternary raised-cosine (RC) modulation.

A new method for phase synchronization and automatic gain control of linearly modulated signals on frequency-flat fading channels

An optimal phase synchronization and automatic gain control (AGC) scheme for coherent reception of linearly modulated signals on frequency-flat mobile fading channels is presented. The channel model and receiver performance are described. It is shown that using the technique allows the irreducible error floors (due to random FM) known from the noncoherent methods to be practically eliminated. Depending on the fastness of the fading, large power gains over the noncoherent methods are achieved. Unfavorable analog signal processing and/or the high bandwidth inefficiency of the FDM-pilot coherent methods are also avoided.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>