Chaos Controlled ZCDPLL for Carrier Recovery in Noisy Channels

The objective of this work is to analyze the performance of the chaos controlled first order Zero Crossing Digital Phase Locked Loop (ZCDPLL) in the presence of Additive White Gaussian Noise (AWGN). The nonlinear behaviour of ZCDPLL shows a period doubling to its route to chaos. The amount of ZCDPLL divergency is measured and fed-back in a form of linear stabilization. The introduction of the chaos control widens the lock range of a ZCDPLL and improves the loop’s operation in the presence of AWGN.     

Jitter performance of a baseband sampled code tracking loop

The purpose of this paper is to investigate the steady-state tracking performance of a digital baseband noncoherent code tracking loop in the presence of additive white Gaussian noise (AWGN). The delay-locked loop (DLL) structure is evaluated. Particular areas of concern are the effect of carrier frequency uncertainty, branch filter bandwidth and loop filter bandwidth. For a fixed data rate, code chip rate and signal-to-noise ratio there is an optimum length for the digital branch filters which minimizes the tracking jitter     

Design and Application of Amplitude-Locked Loop Separation System Based on SignalWAVe

In this paper, we adopt concepts from the SignalWAVe development platform for the multi-speech signal separation system of a frequency modulation system. The signal separation system is formed using a phase-locked loop in combination with an amplitude-locked loop (ALL) and is modeled using a digital finite-impulse response (FIR) filtering algorithm. Therein, the objective is to improve the signal distortion of co-channel interferences and additive white Gaussian noise (AWGN). In comparison to a traditional separation system, the ALL is achieved in the monitored system and in signal interception applications with a characteristic analysis based on the power spectrum density. The field programmable gate array (FPGA) design platform has the advantages of flow simplicity, easy reconfiguration, and high compatibility for verification. The design system is operated in real time and is implemented in the system model using various chip designs. The FPGA is implemented system as a system on a chip for high efficiency. According to the simulated performances under an applied AWGN channel, the ALL system in combination with a digital FIR filter achieves prefect performance. The SignalWAVe verification system was also implemented on the chip by building, verifying programs, and implemented communication functions for practical application in the industry.     

Design of transmit FIR filters for FDM data transmission systems

The design of transmit finite-impulse response (FIR) filters with few coefficients in frequency division multiplexing data transmission systems is considered. In these systems, quality objectives are imposed for transmission over channels affected by additive white Gaussian noise (AWGN) and over channels affected by AWGN plus adjacent channel interference (ACI). The goal of this letter is: given that an adaptive receive filter, possibly cooperating with an adaptive decision feedback equalizer, is used for the AWGN channel and for the AWGN plus ACI channel, what is the best fixed FIR transmit filter to use for both channel cases? This goal is achieved by optimizing the compromise between the performance of the system on the two mentioned channels. Also, the advantages of the proposed design over a rival method based on a fixed receive filter are demonstrated.     

QAM全数字接收机载波相位恢复环路

本文着重研究全数字QAM接收机中载波恢复环路的设计，采用快慢两个数字环路来进行载波恢复，慢环路由锁频器（Frequency Detector)，锁频锁相器（Phase and Frequency Detector)等组成，快环路由相痊解旋器和锁相器（Phase Detector)组成，仿真结果表明，在AWGN条件下，两个环路的环路参数设置存在一个最佳点，当两个环路工作在这个最佳点附近时接收机能够很好的进行载波频率，相位的恢复，相位噪声对接收机性能的影响最小，最后，给出了在不同信噪比下的最佳环路参数表。     

Performance study of high-speed asymmetric digital subscriber linestechnology

Computer simulation results are presented for the loop range coverage of an asymmetric digital subscriber lines (ADSL) system that uses the quadrature amplitude modulation (QAM) signaling scheme, ADSL performance is evaluated in the presence of background additive white Gaussian noise (AWGN), and crosstalk noise from existing services in the local telephone loop plant. It is shown that coverage of the extreme carrier serving area (CSA) is possible at transmission rates that are well above the existing T1 rate     

低信噪比下SMCC+系统精确大频偏估计方案

该文基于由电子科技大学提出的作为中国地面数字多媒体电视广播传输标准候选方案之一的SMCC+系统和OFDM系统,提出了一种在低信噪比下利用特殊构造的短PN序列进行快速精确的大范围频率同步的方法。经仿真证明,信噪比在-20 dB范围以上时,该法在AWGN,单抽头瑞利衰落信道和等值双径瑞利衰落信道环境纠正大范围频偏的性能比Tufvesson等人(1999)同类常规算法性能更优,从理论上而言,该算法可以估计1/2带宽范围内的频率偏移,显然,该算法优于常规同类算法。     

位置敏感探测器的信号噪声自适应抑制方法

针对位置敏感探测器噪声来源及特点,提出了一种基于自适应FIR维纳滤波器的自适应抑制方法。该方法以维纳滤波器为数字滤波器,自适应地调整传输特性,提高PSD的信噪比,从而大幅提高了PSD应用系统的测量精度。     

Modified FIR filter with phase compensation technique tofeedforward active noise controller design

In this paper, a finite-impulse response (FIR) filter with phase compensation is proposed to design the digital controller for active noise cancellation in ducts. This method can overcome the influence of delay effects, which arise from the analog devices, and then help to improve the ability of noise reduction. Moreover, all the control algorithms are implemented in a fixed-point-type digital signal processor that produces an antinoise signal to cancel noise in the authors' experiments. Experiments are demonstrated in a polyvinyl chloride material circular duct. It is proved that, by using the FIR filter with phase compensation, the reduction of broadband noise is about 20 dB, and about 50 dB of narrowband noise. The system also provides the ability to cancel the noise with two harmonic components, like automobile noise     

Bit-error probability for an adaptive diversity receiver in aRayleigh-fading channel

The bit-error probability is determined for a binary antipodal diversity system with an adaptive receiver using decision-directed channel estimation. The diversity channels are assumed to be nonselective Rayleigh-fading channels with additive white Gaussian noise (AWGN). The analysis is valid for all linear estimators which use a finite-impulse-response (FIR)-type estimation filter. Numerical results are presented for a minimum mean-square error (MMSE) filter and a moving average (MA) filter     

一种模／数混合型FIR噪声滤波器设计

：针对现有数字FIR噪声滤除技术的噪声放大问题,结合模拟电路的方法,提出一种新的混合型FIR噪声滤波技术。该方法采用电荷泵将锁相环中数字控制的相位误差转换为模拟域电荷,调制器的输出经过一个寄存器链实现一个或数个时钟周期的延时,从中选出若干抽头分别去控制对应的分频器或相位选择器,从而量化所产生的经过各支路鉴相器的瞬时相位误差,在一个多输入电荷泵中合成为模拟域误差电荷,通过提供恒定单位直流增益,解决现有数字FIR噪声滤除技术的噪声放大问题。这种新型的滤渡器具有如下特点：离散时间域工作,模拟失配不敏感,有助于提高线性度,额外硬件开销小。     

Performance Optimization of High Order QAM in Presence of Phase Noise and AWGN: Application to a Decision Directed Frequency Synchronization System

The paper presents an analysis of the impact of Local Oscillators (LO) phase noise on the performance of digital transmission systems. Using an efficient phase noise model, we study degradations induced by phase noise and Additive White Gaussian Noise (AWGN) on a carrier recovery system combined to high order Quadrature Amplitude Modulations (QAM). Simulation results show that an optimum trade-off between AWGN and phase noise robustness for the loop bandwidth can be determined. In order to compare simulated and analytical performance, a new general expression of the bit error probability is developped for square QAM in the presence of phase noise over Gaussian channel. Furthermore, novel decision areas related to Quadrature Amplitude Modulations are determined in order to improve the performance of the carrier recovery algorithm in the presence of phase noise and frequency offset.     

Performance Evalution of 2B1Q Data Echo Canceller in Digital Subscriber Access Networks

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Chaos and bifurcation in a third-order digital phase-locked loop

Nonlinear dynamics of a third-order zero crossing digital phase locked loop (ZCDPLL) has been investigated. It has been observed that, while first and second-order ZCDPLLs show period doubling route to chaos, a third-order ZCDPLL manifests a disjoint periodic attractor in its route to chaos. Also, the complexity and predictability of the system dynamics have been characterized by using nonlinear dynamical measures such as Lyapunov exponent, Kaplan–York dimension, correlation dimension and Kolmogorov entropy. All the results show that the chaos in a third-order ZCDPLL is low dimensional.     

Particle Filter-Based Synchronization of Chaotic Colpitts Circuits Combating AWGN Channel Distortion

In this paper, synchronization of chaotic Colpitts circuits using a particle filter (PF) to combat the additive white Gaussian noise (AWGN) channel effect is studied by numeric simulations. A novel PF algorithm suitable for chaos synchronization is proposed. With this algorithm, chaos synchronization of Colpitts circuits can be achieved and maintained in AWGN channels. Parameters in the proposed PF algorithm are studied to understand their effects on synchronization performance. The synchronization performance using the proposed PF algorithm is compared with those using other digital filters, such as the extended Kalman filter and the generic PF. It is found that the proposed PF algorithm performs better than the other digital filters. Simulation results also show that the particle number is not very critical to the synchronization performance when this PF algorithm is used.     

一种用于DS-CDMA基站的全数字非相干延迟锁相环

本文根据直接序列扩频码分多址(DS-CDMA)系统上行链路伪随机码跟踪的特点,给出并分析一种全数字非相干延迟锁相环 (DLL),该DLL采用了二元鉴相和数字序贯滤波的实现结构。文中推导了多用户环境下环路的数学模型及鉴相误差统计特性,给出了跟踪性能的计算机仿真结果。研究结果表明,本文给出的DLL能以小的复杂度实现良好的跟踪性能,具有较高的应用价值。     

A CMOS oversampling D/A converter with a current-mode semidigitalreconstruction filter

Oversampling digital-to-analog (D/A) converters employing sigma-delta modulation noise shaping and single-bit quantization are attractive for use in digital audio applications because of their relaxed reconstruction filtering requirements and their tolerance of component mismatch. However, the use of a two-level D/A interface results in a large amount of out-of-band quantization noise that typically must be attenuated by a carefully designed analog reconstruction filter. This paper introduces a means of simplifying the reconstruction filter design through the use of a semidigital finite-impulse-response (FIR) filter. In particular, it describes an oversampling D/A converter wherein a current-mode semidigital reconstruction filter is used to implement a multilevel D/A interface that attenuates the out-of-band quantization noise without requiring precise component matching. An experimental implementation of the converter achieves a dynamic range of 94 dB and 72 dB attenuation of out-of-band quantization noise for a baseband of 20 kHz. The prototype converter, which consists of a linear interpolator, a second-order noise shaper, and a 128-tap semidigital FIR filter, dissipates 59 mW from a 5-V supply and occupies an active area of 3 mm² when integrated in a 1.2-μm digital CMOS technology     

Application of Adaptive Filtering to Direct-Sequence Spread-Spectrum Code Acquisition

A novel hybrid scheme utilizing an adaptive FIR filter is proposed for acquisition of DS-SS signals. Timing information on the delay offset between the incoming DS-SS signal and the locally generated replica of the spreading code is extracted from the tap-weight vector of the acquisition adaptive filter. Expressions for the mean acquisition time, detection, and false alarm probabilities for a coherent, chip synchronous DS-SS system in AWGN are derived. The improvement in acquisition performance over serial search techniques is twice the length of the adaptive filter. This is similar to that gained by other hybrid schemes that search the same number of cells at a time. However, a significant reduction in hardware complexity is obtained. The proposed system is also compared to a system utilizing a partial matched filter structure. Moreover, the same hardware could be used for code tracking and, hence, eliminating the need for a separate tracking loop.     

基于可调谐真相移的可调谐光电振荡器

提出一种基于真相移(TPS)实现可调谐光电振荡器( OEO)的方案。只需通过调谐Mach-Zehnder 调制器(MZM)的偏置电压,就可以实现可谐滤波器的频谱响应的改变,即可实现TPS滤波器。 其中,两个抽头的可调谐滤波器是由双光源、双调制器以及叠印光栅来实现。OEO的输出频 率由二抽头可调 谐滤波器的峰值频率决定,而滤波器可调谐,这样就可以实现输出OEO的输出频率可调。 仿真结果表明,输出频率可以实现5～10GHz宽带宽可调谐。     

1D and 2D economical FIR filters generated by Chebyshev polynomials of the first kind

Christoffel–Darboux formula for Chebyshev continual orthogonal polynomials of the first kind is proposed to find a mathematical solution of approximation problem of a one-dimensional (1D) filter function in the z domain. Such an approach allows for the generation of a linear phase selective 1D low-pass digital finite impulse response (FIR) filter function in compact explicit form by using an analytical method. A new difference equation and structure of corresponding linear phase 1D low-pass digital FIR filter are given here. As an example, one extremely economic 1D FIR filter (with four adders and without multipliers) is designed by the proposed technique and its characteristics are presented. Global Christoffel–Darboux formula for orthonormal Chebyshev polynomials of the first kind and for two independent variables for generating linear phase symmetric two-dimensional (2D) FIR digital filter functions in a compact explicit representative form, by using an analytical method, is proposed in this paper. The formula can be most directly applied for mathematically solving the approximation problem of a filter function of even and odd order. Examples of a new class of extremely economic linear phase symmetric selective 2D FIR digital filters obtained by the proposed approximation technique are presented.