匹配滤波器的多相实现

本文介绍了匹配滤波器在直接序列扩频通信系统的同步捕获中的应用，研究了数字匹配滤波器的实现方法，提出了基于多相分解的实现结构。与传统的直接实现形式和折叠滤波器等改进形式相比，多相形式具有占用资源少的优点。     

Optimized weighted averaging of peak matched multiple windowspectrum estimators

Periodogram averaging with multiple windows can be used in spectrum analysis of nonstationary data. Usually, however, the windows for the subspectra are equally weighted in the estimate. In this correspondence, a criterion for the optimization of weighting factors is formulated as the average of normalized bias, variance, or mean square error in a certain frequency interval around a predefined peaked spectrum. The weighting factors are optimized using the peak matched multiple windows, the sinusoid multiple windows, and the discrete prolate spheroidal sequences     

Speech enhancement with adaptive spectral estimators

Common statistical estimators for speech enhancement rely on several assumptions about statistical properties of speech and noise processes. In real applications, these assumptions may not be always satisfied due to the effects of a nonstationary environment. In this work, we propose new robust spectral estimators for speech enhancement by incorporation of calculation of rank-order statistics to existing speech enhancement estimators. The proposed estimators are better adapted to nonstationary characteristics of speech signals and noise processes in real environments. By means of computer simulations, we show that the proposed estimators outperform the known estimators in terms of objective criteria of quality.     

On the Cramer-Rao bound of finite-length cepstrum spectral estimators

Spectral estimators based on finite-length cepstrum modelling are useful in several applications. The Cramer-Rao lower bound of the asymptotic variance of their logarithmic spectral estimates can be obtained in explicit form. This does not depend on the specific underlying spectrum.<>     

State-space FDTD implementation of anisotropic perfectly matched layer

New formulations based on the state-space approach are presented for implementing the anisotropic perfectly matched layer into the finite difference time domain (FDTD) algorithm. The formulations are simple and independent from the material properties of the FDTD computational domain. Numerical tests are included to validate the proposed formulations.     

Efficient estimators for the land mobile satellite channel

A novel class of adpative Kalman channel estimators (AKCEs) for low-data-rate signalling via the land mobile satellite (LMS) channel is presented in this paper. The proposed technique is based on a scheme known as the ‘parallel processing algorithm’ and assumes a discrete Gauss–Markov extension of the LMS channel model. Three different approaches compared against the non-adaptive filter show an improved estimation error variance under various environmental conditions. Trading off computational complexity and performance, the derived maximum a posteriori (MAP) approach has been found to be best applicable. © 1998 John Wiley & Sons, Ltd.     

Tunable line spectral estimators based on state-covariance subspace analysis

Subspace methods for spectral analysis can be adapted to the case where state covariance of a linear filter replaces the traditional Toeplitz matrix formed out of a partial autocorrelation sequence of a time series. This observation forms the basis of a new framework for spectral analysis. The goal of this paper is to quantify potential advantages in working with state-covariance data instead of the autocorrelation sequence. To this end, we identify tradeoffs between resolution and robustness in spectral estimates and how these are affected by the filter dynamics. The approach leads to a novel tunable high-resolution frequency estimator.     

Efficient implementation of all-digital interpolation

B-splines are commonly used for continuous representation of discrete time signals. This kind of representation proves to be very useful in applications such as image interpolation, rotation and edge detection. In all these applications, the first step is to compute the B-spline coefficients of the signal, and this involves the use of an IIR noncausal filter called the direct B-spline filter. The signal reconstruction is achieved using the indirect B-spline filter, which in many applications operates at a higher rate. We introduce a simplified implementation of the signal reconstruction part that will significantly reduce the overall complexity. We also show that the direct B-spline filter can safely be replaced with a short FIR filter, without compromising the performance of the traditional method. Numerous examples show both visually and numerically that the differences between this method and the traditional one are indeed very small. Finally, we report the performance of these newly proposed methods in other image processing applications such as edge detection and least squares approximation.     

Asymptotic statistical properties of AR spectral estimators forprocesses with mixed spectra

The influence of a point spectrum on large sample statistics of the autoregressive (AR) spectral estimator is addressed. In particular, the asymptotic distributions of the AR coefficients, the innovations variance, and the spectral density estimator of a finite-order AR(p) model to a mixed spectrum process are presented. Various asymptotic results regarding AR modeling of a regular process with a continuous spectrum are arrived at as special cases of the results for the mixed spectrum setting. Finally, numerical simulations are performed to verify the analytical results     

基于FPGA的匹配滤波接收机实现技术研究

高效数字匹配滤波器设计是数字接收机中提高信噪比改善系统信号处理性能的一项关键技术。数字匹配滤波器在通信和雷达接收机中应用广泛,文中分析了匹配滤波接收机的基本原理,介绍了QPSK信号匹配滤波接收机的FPGA实现过程,并给出了基于Xilinx ISE 8.2i的Test Bench Waveform仿真结果。     

Efficient implementation of error-feedback LSL algorithm

An error feedback LSL algorithm is presented which has a reduced computational complexity and makes use of both a priori and a posteriori prediction errors. A simple numerical convention is proposed to assure numerical stability for poor persistent excitation. Simulation results illustrate that divisions can be implemented with reduced wordlength without leading to a significant decrease in the overall accuracy even in floating-point implementations. This fact allows the use of lookup tables for implementing divisions. Moreover, the proposed algorithm has an inherent parallelism that can be advantageously exploited for fast implementations     

Efficient implementation technique of LDPC decoder

An efficient implementation technique of the low density parity check code decoder is proposed. Using the technique, the decoder can be implemented with additions only and there is considerably lower complexity compared with the standard sum-product decoder     

Efficient implementation of the Volterra filter

An efficient implementation of the Volterra filter is presented which uses a frequency domain representation to reduce the number of computations. The multidimensional convolution of the Volterra filter is transformed to the frequency domain giving a transformed input matrix which is sparse and obtained directly from a one-dimensional Fourier transform, in addition to the sparse nature of the transformed input matrix, symmetries in both the Volterra filter and the frequency domain representation are exploited to increase the efficiency of the algorithm. The computational saving is demonstrated by comparing it with the direct implementation of the time domain representation and another technique which uses a frequency domain representation but does not utilise symmetry     

Efficient FPGA implementation of bit-stream multipliers

A four-input adder structure for the FPGA implementation of a sigma-delta bit-stream multiplier is proposed. Conventional bit-stream multiplier implementations involve two-input adder circuits. It is shown that the four-input adder structure is more resource-efficient (over 40% hardware savings) and faster (over 20% higher clock frequency) when implemented using state-of-the-art FPGA architecture featuring six-input look-up tables     

Efficient implementation of lifting-based discrete wavelettransform

A recursive architecture for implementing the lifting-based discrete wavelet transform is proposed. Processing of the transform stages is interleaved, improving the hardware utilisation and efficiency, by exploiting the wavelet decimation structure     

NONPARAMETRIC SPECTRAL ESTIMATORS FORSECOND-ORDER (ALMOST) CYCLOSTATIONARYCOMPLEX PROCESSES

Second-order almost cycloststionary complex processes are complex random signals with almost periodically time-varying statistics. Smoothed periodograms are proposed for related to cyclic spectral estimation and are shown to be consistent. Asymptotic covariance expressions are derived along with their computable forms.     

Efficient calculation of far-field patterns of waveguidediscontinuities using perfectly matched layers

A new efficient method is outlined for calculating the far-field pattern of waveguide discontinuities. An open configuration is turned into a closed configuration using perfectly matched layers. Using a mode-matching scheme on the resulting configuration, the total field on the discontinuity can be determined. The far-field is calculated by taking the Fourier transform of this field and multiplying it by the Huygens obliquity factor. Results are presented for a GaAs-AlGaAs laser facet and a truncated grounded dielectric slab     

DSP techniques for implementation of perfectly matched layer fortruncating FDTD domains

A new algorithm for implementing the perfectly matched layer (PML) using digital signal processing (DSP) is presented for truncating finite difference time-domain (FDTD) domains. The algorithm is based on incorporating digital filtering techniques into the PML formulation. A simple, unsplit-field and material independent PML formulation is achieved