一种基于MMF-FRM的低复杂度信道化接收机结构

为实现时域重叠信号的全概率接收和跨信道信号重构，降低窄过渡带信道化结构的复杂度，提出一种基于调制屏蔽滤波器频率响应屏蔽（Modulation Masking Filter Frequency Response Masking, MMF-FRM）技术的信道化接收机结构.通过对原型屏蔽滤波器进行调制得到两个分支屏蔽滤波器，给出了基于MMF-FRM的窄过渡带滤波器设计方法 .推导出一种基于MMF-FRM的低复杂度信道化接收机结构，该信道化结构解决了多相分解受FRM(Frequency Response Masking)滤波器组限制的问题，并分析了该结构的有限字长性质和纹波系数.用Xilinx System Generator进行了硬件实现与仿真，在采样速率为1 GHz，信道数为8的条件下，提出的信道化接收机结构比多相信道化结构节省74.1%的乘法器资源，比FRM信道化结构节省13.5%的乘法器资源.     

基于神经网络的FRM滤波器优化设计研究

以频率响应屏蔽(FRM)技术为基础,提出了一种基于神经网络的窄过渡带FIR数字滤波器的优化设计新方法.该算法主要通过使频率响应平方误差函数最小化来获得FRM滤波器系数.文中详细介绍了基于神经网络的基本FRM滤波器和多层FRM滤波器的设计算法及设计步骤,证明了该算法的稳定性定理,给出了仿真实例,并与已有的设计方法进行了比较,设计结果表明用该方法设计的窄过渡带FIR数字滤波器性能更为优越.     

一种基于频率响应屏蔽技术的FIR滤波器设计新方法

提出了一种设计高效窄过渡带宽FIR滤波器的新方法。该方法以传统的频率响应屏蔽(FRM)方法为基础,通过选择特定的原型滤波器来降低合成的数字FIR滤波器的复杂度。本文研究了该方法的原理、实现结构和设计方法,并通过设计实例证明了此方法的有效性。     

基于频率响应屏蔽技术的采样率变换新结构

介绍了频率响应屏蔽(FRM)技术在采样率变换技术中的应用,分析了FRM的简化结构——内插滤波器的设计方法。将此滤波器应用于采样率变换中,并结合多相滤波思想提出了一种高效的FRM采样率变换结构,此结构能极大降低采样率变换实现复杂度。最后通过设计实例,验证了此结构的高效性。     

基于OTA的有源Gm-C复数带通滤波器的设计

设计了一种基于OTA的有源Gm-C复数带通滤波器,用以实现射频前端芯片中的中频滤波和镜像抑制功能,该滤波器采用Gyrator结构,将低通原型滤波器中的集总电感用有源电感进行替换,并依据复数变换理论,对浮地电容和接地电容进行复数变换,实现带通滤波器.滤波器中心频率为4.1 MHz,1 dB带宽2 MHz,带内增益13.27 dB,1.5倍带宽处抑制在40 dB以上,镜像抑制度40 dB.Gm-C滤波器集成度高,功耗低,适合于高频应用,是当前集成中频滤波器的热点.     

一种新型伪镜像滤波器组的实现方法

本文提出了一种新型２Ｍ个通道伪镜像滤波器组的结构和设计方法。本设计方法中，低通原型滤波器采用两级级联线性相位ＦＩＲ的结构，并使得整个分析／综合系统性能近于全恢复，无群时延失真。应用此方法设计伪镜像滤波器组，分析和综合滤波器组的结构和设计方法都比较简单，算法效率高，实现比较容易，这类滤波器组可用于语音的子带编码等。本文最后给出了一个实例。     

面向LTE-A的高性能低复杂度数字前端滤波器

LTE-A(Long Term Evolution-Advanced)以其优异的性能,成为未来4G的通信标准.然而LTE-A指标要求数字前端滤波器不仅要有很窄的过渡带,还要有很低的通带纹波,使数字前端滤波器的复杂度显著提升.采用基于频率屏蔽响应技术的FRM(frequency-response masking)滤波器,通过对其插值因子、滤波长度和纹波幅度的优化,实现了满足LTE-A性能的低复杂度前端数字滤波器.仿真结果表明,在LTE-A标准下,当带宽为1.4MHz、3MHz、5MHz、10MHz、15MHz和20MHz时,FRM滤波器的复杂度分别为68、79、87、87、87和87.与传统FIR滤波器相比,此FRM滤波器复杂度降低约50%,性能也优于FIR滤波器.     

一种适合于窄过渡带FIR滤波器设计的方法

介绍了一种适合于窄过渡带FIR(有限冲击响应)滤波器设计的方法———频罩法,首先设计一个原型滤波器,将该滤波器每个延迟部分延迟M点可产生尖锐过渡带,对其施加不同中心频率的低阶频罩滤波器,即可得到所需的尖锐带通滤波器,该方法实现窄带FIR滤波器所需的阶数仅为直接设计的50%左右;然后讨论了其VHDL(超高速集成电路硬件描述语言)实现算法,最后介绍了利用FPGA(现场可编程门阵列)实现此系统的设计方案,并分析了实际硬件设计过程中涉及的问题。     

全通多相网络滤波器组的理论和设计

本文进一步研究了应用全通滤波器实现均匀N带滤波器组的设计理论。我们提出了一种两级全通型滤波器组的结构,第一级为周期性镜像半带滤波器,第二级为两个N/2带的带通滤波器组。第一级的阻带恰好可以抑制第二级的不可控带,实现了全通型多相滤波器的连续阻带持性。并且给出了综合滤波器组的实现方案,可以使整个分析/综合系统完全消除混叠和幅度失真。最后本文给出了一个实例。     

低功耗Zigbee收发器镜像抑制滤波器设计

分析镜像抑制和带外衰减的要求,设计了适用于2.4 GHz Zigbee无线收发前端的镜像抑制滤波器.电路采用7阶巴特沃思OTA-C双二次结构.通过线性变换实现复数滤波.采用交叉耦合输入跨导器,扩大了输入线性范围.为减小滤波器频率偏差,设计了一种锁相环频率修调电路.电路利用0.18 μm CMOS工艺实现.测试结果表明,复数滤波器带宽2.54MHz,镜像抑制大于35 dB,偏移3.5 MHz抑制超过50 dB.在1.8 V电源电压下电流为0.86 mA.     

Design of high-resolution cosine-modulated transmultiplexers with sharp transition band

Due to the growing importance of multichannel modulation, there has been great interest in the design of high-performance transmultiplex systems. In this paper, a new cosine-modulated transmultiplex structure is proposed based on a prototype filter designed with the frequency-response masking (FRM) approach. This new structure leads to substantial reduction in the computational complexity (number of multiplications per output sample) of the prototype filters having sharp transition band and equivalently small roll-off values. The relation between the interpolation factor used in the FRM prototype filter and the decimation factor in the subbands leads to distinct structures. Examples included indicate that the reduction in computational complexity can be higher than 50% of the current state-of-art designs, whereas the reduction on the number of distinct coefficients of the prototype filter can be reduced even further (over 75%). As a result, the proposed approach allows the design of very selective subfilters for transmultiplexes with a very large number of subchannels.     

基于频率响应掩蔽法的宽带滤波器的设计

针对FIR滤波器设计中锐截止宽带滤波器阶数较高、计算复杂的问题,提出用频率掩蔽法,先设计一个过渡带为目标过渡带的L倍的原型滤波器,其实现复杂度远小于所要求的滤波器,依据L倍内插滤波器的过渡带宽是原型滤波器的1/L的原理,利用一对互补滤波器和掩蔽滤波器,得到了较低计算复杂度的锐截止宽带滤波器。     

Design of Computationally Efficient Sharp FIR Filter Utilizing Modified Multistage FRM Technique for Wireless Communications Systems

Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower stop band ripples offers alias-free switching among the preferred frequency bands. A computationally competent low pass filter (LPF) structure based on the multistage frequency response masking (FRM) approach is proposed for the design of sharp finite impulse response (FIR) filters which are suitable for wireless communications applications. In comparison of basic FRM with other existing multistage FRM structures, the proposed structure has a narrow transition bandwidth and higher stop band attenuation with significant reduction in terms of the number of computational steps. A design example is incorporated to demonstrate the efficiency of the proposed approach. Simulation results establish the improvement of the proposed scheme over other recently published design strategies.     

Two-Channel FIR Filter Banks Utilizing the FRM Approach

The frequency-response masking (FRM) approach has been introduced as a means of generating narrow transition band linear-phase finite impulse response (FIR) filters with a low arithmetic complexity. This paper proposes an approach for synthesizing two-channel maximally decimated FIR filter banks utilizing the FRM technique. For this purpose, a new class of FRM filters is introduced. Filters belonging to this class are used for synthesizing nonlinear-phase analysis and synthesis filters for two types of two-channel filter banks. For the first type, there exist no phase distortion and aliasing errors, but this type suffers from a small amplitude distortion as for the well-known quadrature mirror filter (QMF) banks. Compared to conventional QMF filter banks, the proposed banks lower significantly the overall arithmetic complexity at the expense of a somewhat increased overall filter bank delay in applications demanding narrow transition bands. For the second type, there are also small aliasing errors, allowing one to reduce the arithmetic complexity even further. Efficient structures are introduced for implementing the proposed filter banks, and algorithms are described for maximizing the stopband attenuations of the analysis and synthesis filters in the minimax sense subject to the given allowable amplitude and/or aliasing errors. Examples are included illustrating the benefits provided by the proposed filter banks.     

Complexity Reduction By Decoupling The Masking Filters From The Bandedge Shaping Filter In The FRM Technique

In the frequency-response masking (FRM) approach, the complexity of two masking filters is heavily dependent on the interpolation factor and the cutoff frequencies of the bandedge shaping filter. In this paper, we propose a novel structure that decouples the masking filters from the bandedge shaping filter. The design equations together with the design procedures are presented. With the introduction of an additional decoupling stage, the complexity of the overall filter can be greatly reduced. Our example shows that more than 40% savings in the numbers of multipliers and adders can be achieved compared with the original FRM approach.     

低复杂度FIR数字滤波器设计方法

FIR滤波器具有绝对稳定性和线性相位的优势,然而当对滤波器的频域性能要求较高时,FIR滤波器通常需要很高的阶数,这使得FIR滤波器硬件执行的复杂度很高。为降低FIR滤波器的硬件执行复杂度,诸多研究者进行了探索。文章对低复杂度FIR滤波器设计方法进行研究,着重介绍比较典型的频率响应罩设计方法、外插脉冲响应设计方法和基于压缩感知的设计方法。     

On the synthesis of very sharp decimators and interpolators using the frequency-response masking technique

Decimation and interpolation are very common multirate signal processing operations. Conventional decimation or interpolation technique using polyphase filters has the advantage that for a given transition-band sharpness, the filter's computational complexity decreases with increasing interpolation or decimation factor. Nevertheless, if the transition band of the decimation or interpolation filter is very sharp, the complexity of the filter may still be very high. The complexity of a very sharp filter may be reduced using the frequency-response masking (FRM) technique. However, as shown in this paper, for a given transition-band sharpness, the computational complexity of the classical FRM method does not reduce as rapidly as the increase in decimation or interpolation factor. In this paper, we present a novel variant of the FRM technique for interpolation or decimation application. In this new variant, the computational complexity reduces as rapidly as the interpolation or decimation factor increases. The reduction in computational complexity increases with decreasing transition width. Over an order of magnitude reduction in computational complexity is achieved when compared with conventional polyphase approach in a particular example presented in this paper.     

Design Equations for Jointly Optimized Frequency-Response Masking Filters

The introduction of nonlinear optimization techniques to the design of a frequency-response masking (FRM) filter has changed the way in which an FRM filter is synthesized. It allows all subfilters in an FRM structure to be optimized jointly, resulting in further savings in the number of arithmetic operations. Under the joint optimization, a new set of design equations is necessary, not only for a more computationally efficient filter, but also for the simplification of the design process and the reduction of the design time. In this paper, we present a set of design equations that estimates the filter lengths and optimum interpolation factor in an FRM filter under joint optimization. It is shown, by means of examples, that the proposed design equations lead to a better estimation of the optimum interpolation factor compared with existing design equations.     

Optimum masking levels and coefficient sparseness for Hilbert transformers and half-band filters designed using the frequency-response masking technique

Hilbert transformers and half-band filters are two very important special classes of finite-impulse response filters often used in signal processing applications. Furthermore, there exists a very close relationship between these two special classes of filters in such a way that a half-band filter can be derived from a Hilbert transformer in a straightforward manner and vice versa. It has been shown that these two classes of filters may be synthesized using the frequency-response masking (FRM) technique resulting in very efficient implementation when the filters are very sharp. While filters synthesized using the FRM technique has been characterized for the general low-pass case, Hilbert transformers and half-band filters synthesized using the FRM technique have not been characterized. The characterization of the two classes of filter is a focus of this paper. In this paper, we re-develop the FRM structure for the synthesis of Hilbert transformer from a new perspective. This new approach uses a frequency response correction term produced by masking the frequency response of a sparse coefficient filter, whose frequency response is periodic, to sharpen the bandedge of a low-order Hilbert transformer. Optimum masking levels and coefficient sparseness for the Hilbert transformers are derived; corresponding quantities for the half-band filters are obtained via the close relationship between these two classes of filters.