Noise Performance of a Cross-Product AFC with Decision Feedback for DPSK Signals

This paper presents a derivation of the noise performance of the cross-product AFC with decision feedback (CPAFCDF). This is an AFC loop configured for use with differentially phase-shift-keyed (DPSK) signals and gives excellent performance in noise.     

Nearly Shot-Noise-Limited Performance of Dual-Channel Linear Optical Sampling for Ultrafast DPSK Signals

This paper describes a newly developed dual-channel linear optical sampling technique for observing ultrafast optical differential phase-shift keying (DPSK) signals. As the proposed measurement scheme offsets two parallel interferometers by a relative delay corresponding to 1-symbol length of the DPSK signal, the measured phase distribution reflects the signal quality which is determined by the phase difference between adjacent symbols. This technique, based on interferometric optical gating by local short-pulses, also offers ultrafast measurement at symbol rates of greater than 100 Gsymbol/s. Moreover, its detection sensitivity can reach the shot noise limit. The waveform degradation caused by the coherence of the light source and the pattern effect of the phase modulator is successfully observed in continuous waves and 10-Gsymbol/s nonreturn-to-zero DPSK signals, and the constellation measurement is demonstrated for a 160-Gsymbol/s return-to-zero DPSK signal. Measurement system noise is also discussed for characterizing the detection sensitivity, and the nearly shot-noise-limited performance is experimentally verified.      

基于积分二次相位函数的多分量LFM信号分析

基于二次相位函数的调频率估计算法用于多分量LFM信号时,信号间互扰严重并且会产生伪峰。针对这一问题,该文采用积分二次相位函数,提出了一种改进的多分量LFM信号分析方法,仿真实验表明：该方法相比于原方法能够有效抑制伪峰和信号间互扰,同时要求的信噪比门限低,估计均方误差更接近CRLB。     

未知相位信道下 Turbo码编码DPSK信号的联合迭代解调解码

本文提出了未知相位信道下Turbo码编码DPSK信号的联合迭代解调解码算法 .推导了未知相位信道的最大后验概率 (MAP)算法 ,推导表明该MAP算法同样可用前向、后向递推方程来有效实现 .其次 ,采用等效信道的方法将未知相位信道的Turbo码解码问题化为AWGN信道下Turbo码的解码问题 .最后 ,引进了联合迭代解调解码算法 ,可用于Turbo码的解调解码 .模拟表明本文算法可有效用于未知相位信道Turbo码的解码     

Phase Noise Pre-correction Scheme for SC-FDMA Signals in LTE-Uplink

This paper proposes a novel carrier Phase noise (PN) pre-correction scheme with an adaptive PN prediction algorithm for Single-carrier Frequency-division multiple-access (SC-FDMA) systems to alleviate degrada-tion due to the PN. Our proposed PN prediction algorithm is a modified polynomial fitting algorithm which is based on receding horizon principle. The parameters of the pre-diction model are optimized by using the algorithm on PN samples of the local oscillator signal in a training window. By using the optimized prediction model parameters and the latest PN samples, we can predict future PN samples. Then these predicted PN samples are put into our pro-posed PN pre-correction scheme and the SC-FDMA sym-bols at the transmitter are pre-compensated. Due to the absence of the radio frequency delay device, the proposed scheme has a low hardware complexity. Simulation results show that our proposed scheme can greatly reduce the ef-fect of the PN on the transmitted SC-FDMA signal.     

Measured Noise Performance for Heterodyne Detection of 10-Gb/s OOK and DPSK

Heterodyne detection of 10-Gb/s nonreturn-to-zero (NRZ) on-off keying and NRZ differential phase-shift keying is demonstrated. The noise performance of the heterodyne receiver with and without the use of an optical preamplifier is experimentally investigated     

小型低相噪恒温晶体振荡器设计

根据用户需要,该文设计了一种小体积低相噪40 MHz恒温晶体振荡器。该振荡器采用低噪声线性稳压器(LDO)作为电源、SC-切晶体谐振器及B模抑制网络等设计,在减小体积的同时提高了产品的相位噪声。温控系统采用直放式加热电路,比例积分的算法,有源负载作为加热元件,提高产品的控温精度,降低环境温度变化对振荡器带来的影响。该振荡器工作稳定可靠,工作电压仅为5 V。其温度-频率特性绝对值不大于0.02×10~(-6)(-30～+70℃),相位噪声不大于-160 dBc/Hz@1 kHz的指标。功耗仅为0.9 W,体积仅为20 mm×12 mm×10 mm。     

Phase-Regenerative Wavelength Conversion for BPSK and DPSK Signals

Phase-regenerative wavelength conversion is demonstrated experimentally. The simultaneous combination of two nonlinear optical processes, phase conjugation and frequency conversion (Bragg scattering), produces phase-sensitive gain at two new idler wavelengths in addition to the original signal wavelength. This single-stage approach does not require phase-locking of the tunable pump. At maximum pump depletion, amplitude and phase regeneration occur simultaneously.     

Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed.     

Performance limits of multilevel DPSK

Recently introduced differential phase-shift keying (DPSK) extensions, collectively referred to here as multilevel differential phase (MDP) formats, explore an increase in data throughput for a given bandwidth by effectively multiplexing differential phase encoding and amplitude modulation onto the same fiber link. In this letter, we derive and present analytic models for the quantum limits of bit-error rate for leading MDP modulation formats (binary phase differential phase amplitude-shift keying (DPASK), quaternary phase DPASK), comparing their performance to that of conventional systems.     

一种新型频率合成器的实现

小数分频技术解决了锁相环频率合成器中的频率分辨率和转换时间的矛盾，但是却引入了严重的相位噪声，传统的相位补偿方法由于对A／D等数字器件的要求很高并具有滞后性实现难度较大。△∑调制器对噪声具有整形的功能，因而将多阶的△∑调制器用于小数分频合成器中可以很好地解决他的相位噪声的问题，大大促进了小数分频技术的发展和应用。文章最后给出了在GHz量级上实现的这种新型小数分频合成器的应用电路，并测得良好的相噪性能。     

瑞利衰落信道MDPSK相位比较解调性能

本文提出一种适合于瑞利衰落信道多进制差分相移键控系统相位比较解调的性能分析方法，推导出符号错误率解析表示式，考虑了瑞利衰落、时间选择性衰落和高斯白噪声对体制性能的影响，并针对衰落功率谱为高斯型和矩形分别对二进制、四进制和八进制情形进行了数值计算。     

Simplified Soft-Output Detection of CPM Signals Over Coherent and Phase Noise Channels

We consider continuous phase modulations (CPMs) in iteratively decoded serially concatenated schemes. Although the overall receiver complexity mainly depends on that of the CPM detector, almost all papers in the literature consider the optimal maximum a posteriori (MAP) symbol detection algorithm and only a few attempts have been made to design low-complexity suboptimal schemes. This problem is faced in this paper by first considering the case of an ideal coherent detection, then extending it to the more interesting case of a transmission over a typical satellite channel affected by phase noise. In both cases, we adopt a simplified representation of an M-ary CPM signal based on the principal pulses of its Laurent decomposition. Since it is not possible to derive the exact detection rule by means of a probabilistic reasoning, the framework of factor graphs (FGs) and the sum-product algorithm (SPA) is used. In the case of channels affected by phase noise, continuous random variables representing the phase samples are explicitly introduced in the FG. By pursuing the principal approach to manage continuous random variables in a FG, i.e., the canonical distribution approach, two algorithms are derived which do not require the presence of known (pilot) symbols, thanks to the intrinsic differential encoder embedded in the CPM modulator.     

基于信噪歪度比的二次相位耦合信号增强新算法

提出了信噪歪度比分析法,在这个分析法中用三阶累积量切片首次定义了信噪歪度比的概念,导出了其理论计算公式。从理论分析可知：当背景噪声为对称分布噪声时,信噪歪度比为无限值;当背景噪声为非对称分布噪声时,在一定条件下,其大于等于输入信噪比。理论分析和仿真结果表明：用三阶累积量切片从非高斯非对称分布的噪声中提取二次相位(动态)耦合信号是有效的,且无需对背景噪声的分布作任何假定。这在工程实践中是非常有意义的。     

A Fiber-Based All-Optical 3R Regenerator for DPSK Signals

Analysis of an all-optical 3R regenerator for differential phase-shift keying (DPSK) signals is presented. Incoming DPSK signals impaired by noise are first demodulated to on-off keying (OOK) signals by a delay interferometer. The amplitude of the OOK signals is then stabilized by a fiber-based all-optical 2R regenerator. In a subsequent nonlinear fiber, locally generated optical clock pulses are phase-modulated by the stabilized OOK pulses and are output as regenerated signals. It is shown that significant phase-noise suppression is achieved by strong amplitude regeneration     

基于积分二次相位函数和分数阶Fourier变换的多分量LFM信号参数估计

针对高斯白噪声中多分量线性调频信号参数估计问题,提出了一种基于积分二次相位函数（IQPF）和分数阶Fourier变换的新方法。分析了IQPF估计线性调频信号调频率的原理,指出IQPF有压制弱信号的缺点。为解决强度相差较大的多分量线性调频信号中弱分量信号的参数估计问题,提出利用分数阶Fourier变换域的信号分离技术,逐次估计强信号分量的参数并将其消去,来提高多分量信号参数估计的可靠性。最后通过计算机仿真,验证了该方法的有效性。这种方法与Radon-Winger变换法、Radon-Ambiguity变换法和单纯的分数阶Fourier变换法相比,极大的简化了计算。因此,该方法非常适合于多分量LFM信号的快速参数估计。      

广义多径信道MDPSK相位比较解调性能

本文提出了一种适合于广义多径信道多进制差分相移键控信号相位比较解调的性能分析方法，推导出符合平均错误率积分表达式。该表达式考虑了信号幅度衰落，时间选择性衰落和高斯白噪声对体制性能的影响。并针对几种形式的衰落功率谱分别对二进制，四进制和八进制的符号平均错误率进行了数值计算，讨论了衰落功率谱的形式对ＭＤＰＳＫ信号性能的影响，并给出了ＭＤＰＳＫ信号的“不可克服符号错误率”与衰落功率谱归一化带宽的关系曲线     

基于基带噪声互相关法的同源多路信号相位差测量

根据同一激励源信号通过功分器得到的同源多路信号间表现为纯时延的特性,本测量方法对仅存在时延差异的同源多路噪声调频信号进行自相关运算和互相关运算,再根据相关运算得到的不同谱峰位置计算出信号间的相对时延,也就是信号间的相位差。信号间相位差的计算精度与采样频率、采样时间、调频指数有关。随着上述3个参数值的增大,相位差的测量精度增加。     

SSB Phase Noise Evaluation of Analog/IF Signals on Standard Digital ATE

This paper presents a low-cost solution for the evaluation of frequency-domain phase noise characteristics for analog/IF signals. The technique is based on 1-bit signal acquisition with a standard digital channel of an Automated Test Equipment (ATE) and a dedicated post-processing algorithm that permits to reconstruct the time-domain phase fluctuations of the analog/RF signal from the captured binary vector. Single SideBand (SSB) phase noise is then obtained based on FFT applied on the reconstructed phase fluctuations. Simulation results demonstrate a very good agreement between SSB phase noise obtained using the proposed digital method and the conventional analog method on a large range of measurement frequency offset. The digital method also permits spur detection and exhibits similar performance than the conventional method in terms of measurement variability. The technique is also validated through hardware measurements on a practical case study, i.e. SSB phase noise evaluation on the 1.3125 MHz sinusoidal signal delivered by the transceiver of a JN5168 wireless microcontroller.     

Performance Evaluation of Silence-Feature Normalization Model using Cepstrum Features of Noise Signals

Speech enhancement algorithms play an important role in speech signal processing. Over the past several decades, many algorithms have been studied for speech enhancement. A speech enhancement algorithm uses a noise removal method and a statistical model filter to analyze the speech signal in the frequency domain. Spectral subtraction and Wiener filters have been used as representative algorithms. These algorithms have excellent speech enhancement performance, but suffer from deterioration in performance due to specific noise or low signal-to-noise ratio (SNR) environments. In addition, according to estimations of erroneous noise, a noise existing in a voice signal is maintained so that a spectrum corresponding to a voice signal is distorted, or a frame corresponding to a voice signal cannot be retrieved, and voice recognition performance deteriorates. The problem of deterioration in speech recognition performance arises from the difference between speech recognition and training model. We use silence-feature normalization model as a methodology to improve the recognition rate resulting from the difference in the noisy environments. Conventional silence-feature normalization has a problem in that the silent part of the energy increases, which affects recognition performance due to unclear boundaries categorizing the voice. In this study, we use the cepstrum feature of the noise signals in the silence-feature normalization model to improve the performance of silence-feature normalization in a signal with a low SNR by setting a reference value for voiced and unvoiced classification. As a result of recognition rate confirmation, the recognition rates improve in performance, compared with other methods.