3带紧支撑的正交小波

本文首先通过Householder矩阵扩充构造了3带紧支撑的正交小波．当尺度函数具有紧支撑对称正交性时,本文通过仿酉矩阵对称扩充构造了3带紧支撑对称的正交小波,并且研究了所构造对称小波的结构．所构造小波函数的支撑不超过尺度函数的支撑,构造方法容易推广到一般d带的情形．另外,本文还给出了容易实施的显式构造算法．最后,给出了构造算例．     

基于多相结构和部分锐化的CIC抽取滤波器

该文将传统的CIC(Cascaded Integrator Comb)滤波器传递函数分解为递归和非递归部分,可独立调整两者的级联因子;对递归部分进行尖锐化处理改善滤波器的通带衰落,利用电路的等价交换性将抽取因子提前使其工作在低采样率;对非递归部分进行多相分解,实现高速滤波。计算机仿真表明:与传统的CIC、锐化CIC滤波器相比,改进的CIC具有好的通阻带特性;并从通带衰落和混叠抑制的角度,分析了递归和非递归部分的级联因子的取值对整个改进的CIC滤波器特性的影响。     

DESIGN OF POLYPHASE WAVE DIGITAL FILTERS WITH APPROXIMATELY LINEAR PHASE

It is well known that IIR digital filters require quite fewer computations,comparedwith FIR filters,in order to meet stringent magnitude specifications when the phase distortioncan be tolerated.An approximately linear phase,however,can be also obtained with the IIRfilter by making use of a technique without increasing the complexity.Based on a certain numberof attenuation zeros in the pass band,a new approach is developed for the design of polyphasewave digital filters with exact magnitude responses and Chebyshev approximation of the desiredphase responses.The minimum number of attenuation zeros is estimated,and some examples areincluded.     

A survey of efficient MDCT implementations in MP3 audio coding standard: Retrospective and state-of-the-art

This tutorial paper describes various efficient implementations (published and new unpublished) of the forward and backward modified discrete cosine transform (MDCT) in the MPEG layer III (MP3) audio coding standard developed in the time period 1990-2010, including the efficient implementation of polyphase filter banks for completeness. The efficient MDCT implementations are discussed in the context of (fast) complete analysis/synthesis MDCT filter banks in the MP3 encoder and decoder. In general, for each efficient forward/backward MDCT block transforms implementation are presented: complete formulas or sparse matrix factorizations of the algorithm, the corresponding signal flow graph for the short audio block and the total arithmetic complexity as well as the useful comments related to improving the arithmetic complexity and a possible structural simplification of the algorithm. Finally, all efficient forward/backward MDCT implementations are compared both in terms of the arithmetic complexity and structural simplicity. It is important to note that almost all presented algorithms can be also used for the 2ⁿ-length data blocks in others MPEG audio coding standards and proprietary audio compression algorithms.     

High-performance active polyphase filter design for digital TV tuner

This paper presents the polyphase filter design for the tuner of DTV front-end system. The polyphase filter is designed with an active circuit to improve the chip performance. Most of passive capacitor and resistor components are replaced with MOS transistors. The proposed method not only can reduce the chip area but also gain the signal level. For the prototyping implementation, the current channel bands in Taiwan are referred, which the frequency range is from 530 to 602 MHz for DTV programs. In experiments, the polyphase filter can achieve 85 dB for the image rejection in the center frequency. The main signal can be gained about 2-5 dB without using extra amplifier. The chip size is about 0.09 mm², and the average power dissipation is about 15 mW, when the chip technology employed TSMC 0.35 μm CMOS process. The proposed chip outperforms with less area and higher gain.     

具有近似线性相位特性的多相波数字滤波器的设计

不考虑相位失真,而要求满足比较苛刻的振幅特性的时候,和FIR滤波器比较起来,采用 IIR 滤波器,计算量要小很多.但对某些IIR滤波器,采取适当的方法,也可以使其相位失真变得很小.本文提出一种新的设计方法,用来设计振幅响应完全满足设计要求,而相位特性用Chebyshev 近似来实现的多相波数字滤波器.这种方法的关键在于确定通带中的若干衰减零点.文中对需要的最小衰减零点数作了估计.实例表明,用这种方法设计的滤波器,时延小,相位特性非常接近线性.     

Design and implementation of an energy efficient power conditioner for fuel cell generation system

The energy use of the world grows continuously and the development of a clean distributed power generation becomes environmentally important. Fuel cells are one such integral part of Renewable Energy Sources based clean energy supply; that they operate with hydrogen as fuel and water with heat as process waste. Due to the electrochemical reaction, fuel cell has the power quality of delivering low voltage with high current capability. Here an attempt is made to develop a power conditioner with a series of conversion to get a 220 V sinusoidal AC, 50 Hz single phase voltage of low distortion and fast dynamic regulation to cater load variations. A novel Polyphase Boost DC-to-DC switching converter based on parallel connection of 8 identical converters with current mode control is devised to have minimum reflected ripple current and voltage injected to fuel cell input. A full bridge converter with high frequency transformer isolation, step-up the DC voltage level from the low voltage fuel cell along with poly phase boost converter, deliver required DC to the PWM inverter, which generate AC utility power output. Recent trend of Ultra-capacitor based transient energy storage and retrieval system, to cater for the sluggish behavior of fuel cell, for load transients is incorporated. DSP and FPGA based digital real time controllers are used to realize the gating of MOSFETs and IGBTs used in the power conditioner. A 1 kW power conditioner is developed for a PAFC fuel cell system with 12 V DC nominal and their performance evaluations are satisfactory.     

基于多相分解滤波器实现的局部频率细化

本文介绍了一种基于多相分解滤波器实现的zoom FFT算法 ,该算法是在复调制zoom FFT算法基础上 ,采用多相分解滤波器方法来实现低通滤波器 ,并利用多抽取频率系统的网络结构等效变换来减少运算量。分析表明 :这种基于多相分解滤波器实现的zoom FFT算法在保留了选带细化的灵活性基础上 ,其运算量仅约为常规复调制zoom FFT算法的 1 N2 (N2 为细化倍数 )。论文首先推导基于多相分解滤波器实现zoom FFT的算法 ,然后讨论该算法的实现方法 ,并与一些常用的zoom FFT算法进行比较 ,最后给出仿真结果。     

A fast parameter estimation algorithm for polyphase coded CW signals

A fast parameter estimation algorithm is discussed for a polyphase coded Continuous Waveform (CW) signal in Additive White Gaussian Noise (AWGN). The proposed estimator is based on the sum of the modulus square of the ambiguity function at the different Doppler shifts. An iterative refinement stage is proposed to avoid the effect of the spurious peaks that arise when the summation length of the estimator exceeds the subcode duration. The theoretical variance of the subcode rate estimate is derived. The Monte-Carlo simulation results show that the proposed estimator is highly accurate and effective at moderate Signal-to-Noise Ratio (SNR).     

Symbol Timing Synchronization Using Interpolation-Based Matched-Filters

This paper presents a symbol timing synchronization method by interpolating the discrete impulse response of matched-filter, in which the group delay of matched-filter is adjusted by different interpolation step to achieve symbol timing synchronization. The proposed method is of much less complexity than the conventional polyphase filterbank method that could be viewed as a special case of interpolated matched-filters. The interpolated matched-filters are used in a loop, and the loop is simulated at 2 samples/symbol, the simulation results show that the proposed method can provide precise symbol timing synchronization with less complexity.