一种类正余弦CIC滤波器

传统CIC滤波器由于其实现不需要乘法器和存储器,因此已在各种变采样率系统中得到了广泛的应用。但是传统CIC滤波器的通带失真较大,阻带衰减较小,而且其积分器工作在高采样率端,这很大程度限制了它在对性能要求较高的变采样率系统中的应用。而后来提出的各种CIC滤波器,如锐化CIC滤波器、ISOP-CIC滤波器和CIC-Cosine滤波器等,或者只改善通带特性,或者只改善阻带特性,或者积分器运行在高采样率端。本文在分析对比了传统的CIC滤波器、锐化CIC滤波器、ISOP-CIC滤波器和CIC-Cosine滤波器的频率特性的基础上,引入一种类余弦预滤波器和一种类正弦预滤波器,再加上多级级联的传统CIC滤波器,构成一种多级结构的类正余弦CIC滤波器。所引入的类正弦预滤波器和类余弦预滤波器分别用于减小CIC滤波器的通带失真和增大其阻带衰减。仿真结果表明,所提出的类正余弦CIC滤波器比传统的CIC滤波器、ISOP-CIC滤波器、CIC-Cosine滤波器都具有更小的通带失真和更大的阻带衰减。同时所引入的两级预滤波器工作在低采样率端,并且通过使用多相分解技术同样可使多级级联的CIC滤波器工作于低采样率端。      

Design of selective CIC filter functions

The aim of this letter is to provide graphs which can be used to design a novel class of selective CIC (Cascaded-Integrator–Comb) filters given insertion loss specification. The goal is to choose the free integer filter parameters such that the filter function yields a desired frequency response. To determine the filter parameters needed to satisfy the desired specifications, one can use the graphs of normalized passband and stopband cut-off frequencies versus filter order N. Two graphs, one for maximum attenuation in the passband and one for minimum attenuation in the stopband, are given here. Achieved improvement of performances of the novel class of CIC filter functions over the classical CIC filters is also given. In case of N = 7, the novel class of CIC filter functions gives improvements of 27.68 dB, 47.29 dB and 66.53 dB for different values 1, 2 and 3 of free parameter L, respectively.     

改进型CIC抽取滤波器的FPGA实现

为了解决以往设计的CIC抽取滤波器存在的数据速率高以及功耗高的问题,研究了改进型CIC抽取滤波器的FPGA实现过程,优化CIC抽取滤波器硬件实现结构,采用FPGA实现抽取滤波器的设计。分析CIC抽取滤波器的硬件实现结构和位宽,通过Hogenauer抽取滤波器结构,得到6级16抽取的CIC硬件实现结构,将该结构变换成4个CIC抽取滤波器的级联式FPGA实现,逐级降低数据速率,提升数据位宽。以FPGA实现CIC抽取滤波器过程中,分析了其运算时寄存器所需的最高位宽,避免产生数据溢出问题。实验结果表明,所设计的改进型CIC抽取滤波器是有效的,可降低数据速率和系统功耗。     

基于CIC滤波的重采样技术

采样率变换是一种改变数字信号处理速率的方法,在通信工程中有着非常重要的作用,当系统中有多种通信速率时,可以通过采样率变换使速率归一化,简化设计.基于CIC滤波器的重采样技术根据输入时钟和输出时钟进行处理,无需输入和输出时钟的最小共倍数时钟,具有明显的工程意义.     

高性能CIC抽取滤波器研究与设计

针对采样率变换系统中CIC抽取滤波器存在通带失真较大和阻带衰减较小的问题,提出一种高性能CIC抽取滤波器的设计方法,该方法采用补偿滤波器技术和非递归并行结构.仿真结果表明,通带失真与阻带衰减特性明显优于传统的CIC,CIC-Cosine,ISOP-CIC等滤波器.因此,适用于对幅频特性要求较高的采样率变换系统.     

基于DSP Builder的CIC梳状滤波器的设计

CIC梳状滤波器具有结构简单、规整,占用存储量小,不需要乘法器,实现简单且速度高等特点,在高速抽取或插值系统应用广泛。采用DSPBuilder软件工具,在Simulink平台上构建了一级4阶CIC梳状滤波器仿真模型,通过多种EDA工具仿真与分析,最终在EP2C35F484C8型FPGA得到了最高响应速度为138．89MHz的高速CIC梳状滤波器。其性能远优于DSP通用处理器的实现方式。     

基于FPGA的DDC中CIC滤波器的设计

文中基于多速率数字信号处理原理,设计了用于数字下变频技术的CIC抽取滤波器.通过分析CIC滤波器的原理及性能参数.利用MATLAB设计了符合系统要求的CIC滤波器,并通过FPGA实现了CIC滤波器的设计.     

基于多级CIC滤波器的相控阵延时算法设计

为实现超声相控阵精确延时的接收技术,基于多级级联积分梳状数字滤波器(Cascade Integrator Comb,CIC)设计了延时算法。利用数字信号的内插理论,通过多级CIC数字滤波器插值处理,提高信号延时精度,同时也减少硬件资源的消耗。通过现场可编程门阵列(FPGA)的实现,验证了延时算法的可行性。实验表明此方法在采样率为50MHz的条件下可以实现1.25ns延时精度,为精度要求高的相控阵接收系统提供了技术支持。     

Reducing periodic noise using soft morphology filter

A novel spatial domain method--soft morphology filter is presented for reducing the periodic noise in image processing. The simulation results are presented to demonstrate the effectiveness of the method in comparison with a frequency domain method and other spatial domain filters.     

Reducing ICI effect in OFDM system using low‐complexity Kalman filter based on comb‐type pilots arrangement

In OFDM systems, time‐varying channels destroy orthogonality between subcarriers causing Inter‐Carrier Interference. To reduce this effect, a Kalman filter, as a benchmark, is used for channel estimation, based on comb‐type pilot arrangements of the OFDM system. An advantage of comb‐type pilot arrangements in channel estimation is the ability to track the variation of the channel caused by Doppler frequency. Kalman method has been proposed to estimate the channel frequency response (CFR) at the pilot locations, then CFR, at data subchannels, is obtained by means of interpolation between estimates at pilot locations. The low‐complexity Kalman method is introduced to reduce the complexity of the system while achieving the same BER/SNR. Different types of interpolations have been also compared such as Low‐pass, Spline‐cubic and Linear interpolation methods. The BER/SNR performance of BPSK modulation schemes are considered for time varying Rayleigh fading channels. Our results has shown that the low‐complexity Kalman estimation, used with the pilot arrangement and a suitable interpolation method, gives almost the same performance as that of the Kalman method specially for low SNR values and hence the effect of Doppler shift effect is controlled. Copyright © 2010 John Wiley & Sons, Ltd.     

On design of a novel class of selective CIC FIR filter functions with improved response

The Cascaded-Integrator-Comb (CIC) filter is a non-recursive (FIR) filter which is multiplier free, consisting only of two building blocks (simple integrator stage and simple comb filter stage) and has a linear phase. This paper summarizes some key points of classical CIC filters and proposes a novel class of CIC FIR filter functions. A novel class of CIC filter functions maintains simplicity of FIR filters by avoiding the multipliers, but shows excellent performances in term of insertion loss in stopband and selectivity with respect to conventional CIC filters. A set of simulations along with illustrative examples is conducted in order to compare the attenuation characteristics of the classical CIC filter functions and the proposed novel class of selective CIC FIR filter functions. For the same level of a constant group delay τ = 45.5 s, a classical CIC filter function has insertion loss of 166.3 dB, and designed novel filter function has a higher level of insertion loss 206.55 dB.     

Reducing the computational load of a Kalman filter

The Kalman filter is a powerful tool in linear-systems analysis. The authors present a particular application in which there are more measurements than states. In such an application, the state-space system can be replaced by an equivalent one that has the same number of measurements as states. The Kalman filter will produce the same state estimates for both systems. Using the equivalent system leads to a substantial saving in computer operations     

Reducing the complexity of instruction-level power models for VLIW processors

Aim of this paper is to propose a high-level power exploration framework based on an instruction-level energy model for VLIW (Very Long Instruction Word) architectures. More specifically, the present paper deals with the reduction of the complexity of the energy model of K-issue VLIW processors from exponential with respect to the number of operations within the Instruction Set O(⫨ISA⫨ ^K ) to quadratic (O(K*⫨ISA⫨²)). The complexity of the energy model has been further simplified by automatically clustering the operations in the ISA with respect to their average energy. Globally, the proposed approach reduces the complexity of the characterization problem for a K-issue VLIW processor to quadratic (O(K*⫨C⫨²)) with respect to the number of operation clusters. In this way, a more efficient characterization of the VLIW core power consumption can been achieved, while preserving the accuracy of the power estimates. The proposed model has been further extended to provide early power figures and energy/performance trade-offs for multi-cluster VLIW architectures composed of multiple data-path units and a single instruction cache control unit. The proposed high-level power estimation methodology has been applied to the Lx 4-issue VLIW pipelined processor provided by STMicroelectronics.     

Multiprocessor multipath recursive filter structure with noincrease in computational complexity

An efficient delayed multipath recursive filter structure is proposed. Compared with conventional multiprocessor approaches, the new structure can achieve much higher throughput rate owing to its low computational complexity. Experimental results are taken using a system with four digital signal processors (DSPs)     

Reducing the CMOS RAM test complexity withI DDQ and voltage testing

In this article, we outline a RAM test methodology taking into accountI _DDQ and voltage based March tests. RAM test cost forms a significantly large portion of its total production cost and is projected to increase even further for future RAM generations.I _DDQ testing can be utilized to reduce this cost. However, owing to architectural and operational constrains of RAMs, a straight forward application ofI _DDQ testing has very limited defect detection capability. These constrains are removed by creating anI _DDQ test mode in RAMs. All bridging defects in RAM matrix, including the gate oxide defects, are detected by fourI _DDQ measurements. TheI _DDQ test is then supplemented with voltage based March test to detect the defects (opens, data retention) that are not detectable usingI _DDQ technique. The combined test methodology reduces the algorithmic test complexity for a given SRAM fault model from 16n to 5n+4I _DDQ measurements.     

Reducing the Peak-to-Average Power Ratio of OFDM system with low complexity

This paper proposes a companding scheme, where small signals are enlarged and large signals are reduced, to reduce the Peak-to-Average Power Ratio（PAPR）. Computer simulation results show that the proposed technique has two advantages at least when compared with the conventional methods such as partial transmit sequence, selective mapping and the previous companding. First, it gets better PAPR performances with a lower complexity. Second, the scheme achieves greater performances gain with hardly any damnification of OFDM signals in some degree.     

Fast converging and low complexity adaptive filtering using anaveraged Kalman filter

Kalman filtering is applied to obtain a fast converging, low complexity adaptive filter that is of the matrix stepsize normalized least mean square (NLMS) type. By replacing certain variables with averages, the solution of an averaged diagonal Riccati equation allows optimal time varying adaptation gains to be precomputed or computed online with a small number of scalar Riccati equations. The adaptation gains are computed from prior assumptions on impulse response power and shape. This fact results in a systematic procedure for adaptation gain tuning in the time-varying matrix stepsize case. Simulations using music as input, show significant performance improvements as compared with the NLMS algorithm     

一种基于多视点视频的低复杂度自适应环路滤波算法

自适应环路滤波(ALF)是面向高清的多视点视频编码(MVC)中的一项新的滤波技术,虽然能提高视频压缩的主观质量和客观质量,但是其复杂度过高阻碍了其实时应用。本文提出了一种低复杂度的ALF算法,充分利用了视点间相关性和层间相关性以减少亮度和色度分量的分割次数,并且能自适应跳过大部分帧的块控制(DBC)处理过程。实验结果表明,所提出的算法能在保证视频主观质量和客观质量基本不变的情况下减少61%左右的ALF处理时间。因此,所提出的方法在编码效率和复杂度上做到了很好的折中处理,并且能很好地改善ALF的性能。     

Reducing the complexity of MPEG-4 global motion estimation using pixel subsampling

MPEG-4 uses a perspective model for global motion estimation. The region of support for global motion representation consists of the entire image frame. Estimating global motion parameters is very expensive computationally, since all the pixels in the frames are involved in the computation. Therefore, computationally efficient global motion estimation techniques are sought-after. It is shown that real-time global motion estimation in an MPEG-4 video codec can be achieved by using a pixel subsampling method based on regular subsampling patterns. Simulation results demonstrated that the proposed method was capable of speeding up the conventional all- pixel GME approach by more than 11 times, with a subsampling ratio of 1/16, without significant loss in estimation accuracy and compression efficiency.     

改进的高性能CIC抗混叠滤波器

这里对一种旋转锐化级联积分梳状滤波器(RSCIC,Rotated Sharpening Cascaded Integrator Comb Filter)进行了研究,RSCIC由锐化级联积分梳状滤波器(SCIC,Sharpening Cascaded Integrator CombFilter)和旋转内插滤波器(Rotated Sinc Filter)两部分构成。RSCIC可有效地提高传统积分梳状滤波器(CIC,Cascaded Integrator Comb Filter)的通带和阻带传输性能,特别适合采样率转化。仿真表明,在同等条件下,RSCIC滤波器的阻带衰减性能比传统的CIC滤波器提高了22 dB,通带抗衰减性能比传统的CIC滤波器提高了0.5 dB。