一种应用于限制零极点位置复数陷波器的迭代算法

基于最小均方误差准则(MMSE),本文推导出了一种修改限制零极点位置的一阶复数陷波器权值迭代算法,并进而提出了一种新的可应用于矩阵型高阶陷波器的自适应权值修改算法,该高阶陷波器由一阶陷波器作为陷波单元构成。该迭代算法直接修改陷波器权值的指数,因而在算法迭代过程中能够将高阶复数陷波器的极点始终限制在单位圆内,从而保证了陷波器的稳定工作。仿真结果表明,采用该算法的一阶和高阶复数陷波器工作稳定,对输入陷波器的宽带信号损伤小,且能快速跟踪和有效抑制其中的强单/多频信号。     

卫星导航接收机时域窄带干扰抑制滤波器设计与性能分析

针对卫星导航接收机时域窄带干扰的有效抑制问题,本文首先给出二阶格型IIR陷波器参数设计方法,通过陷波带宽的定量调整,既可以有效抑制窄带干扰,又可以降低卫星信号的失真;其次推导了二阶IIR格型陷波器相关输出信干噪比改善因子的闭合表达式,该表达式相比干扰抑制后信干噪比的改善,更为直观地反映了陷波器对卫星导航信号的影响。理论分析和仿真实验,二阶格型IIR陷波器相关输出信干噪比改善因子与陷波器的带宽参数有关,而与陷波频率无关,且二阶格型IIR陷波器的性能优于最优线性预测Wiener滤波器、最优线性插值Wiener滤波器、五系数FIR滤波器以及二阶直接型IIR陷波器。      

Complex notch filter design using allpass filter

Complex coefficient IIR notch filter design problems are investigated. The specification of a notch filter is first transformed into that of an allpass filter. An effective approach to the design of this desired allpass filter is developed. The realisation of the proposed notch filter is equivalent to the realisation of an allpass filter. Owing to the mirror-image symmetry relation between the numerator and denominator polynomials of allpass filters, the notch filter can be realised by a computationally efficient lattice structure with very low sensitivity     

Design of Digital Notch Filters

It is shown that a second-order digital notch filter is uniquely characterized by two distinct parameters, the notch frequency and the 3-dB rejection bandwidth. As a result, such a filter can be realized using only two multipliers. Methods are outlined to design a notch filter for a prescribed notch frequency and a prescribed 3-dB rejection bandwidth, along with procedures for postdesign adjustment of these parameters. All two-multiplier, canonic and noncanonic, notch filter configurations are developed using the multiplier extraction approach. These networks are then compared with regard to the effect of internal multiplication roundoff errors. Results of computer simulation of the notch filter configurations are also included.     

Elimination of AC interference in electrocardiogram using IIR notchfilter with transient suppression

A technique for suppressing the transient states of IIR notch filter is investigated. This technique uses the vector projection to find better initial values for notch filters. When a notch or comb filter is used to eliminate power line (AC) interference in the recording of electrocardiograms (ECG), the performance of the notch filter with transient suppression is better than that of the conventional notch filter with arbitrary initial condition. The improvements with this technique are at the cost of additional computation load at the beginning of filtering     

Photonic notch filter without optical coherence limitations

A new topology for a photonic notch filter that can solve the coherent interference problem in photonic signal processors is presented in this paper. It is based on a double-pass modulation technique. The key advantage of this new structure is that it completely removes the dominant phase noise limitation, which is a fundamental problem with existing incoherent processor approaches. It also enables arbitrary narrow-linewidth telecommunication-type lasers to be used with stable and robust filter operation. Extensions to obtain tunable notch frequency and wide-passband notch filter operation are presented. Results demonstrate robust notch filter operation with a narrow-linewidth source, no phase-induced intensity noise, and a vastly superior signal-to-noise ratio performance (i.e., a nearly 60-dB increase) compared with the conventional delay line notch filter. Tunable coherence-free operation of the notch filter is also shown. Finally, a new structure that not only operates without coherence limitations but also realizes a notch filter with a wide passband of more than 50% of the free spectral range is demonstrated.     

Simple millimeter wave notch filters based on rectangular waveguide extensions

A new efficient notch filter is proposed. Some details of notch filter operation at millimeter waves are discussed. A 110 GHz notch filter is numerically and experimentally tested.     

Sparse FIR notch filter design and its application

A technique for designing a sparse FIR notch filter is presented. First, a sparse property of the ideal notch filter, whose notch frequency has the form (q/2p)π is derived, where p and q are coprime integers. Then, the Lagrange multiplier method is used to obtain the coefficients of the sparse notch filter which is optimal in the least-squares sense. Next, a design example is presented to demonstrate the effectiveness of this approach. Finally, a sparse notch filter is applied to eliminate the 60 Hz powerline interference superimposed on the electrocardiogram signals     

基于复数陷波器的窄带干扰抑制研究

研究了直接序列扩频通信系统中幅值相差较大的窄带干扰抑制问题,以一阶复数自适应陷波器为陷波单元,介绍了一种级联结构的陷波器,给出了系数迭代的自适应算法和理论分析。仿真实验表明,该陷波器能有效消除多个窄带干扰,迭代算法具有良好的收敛性能。     

Stable IIR notch filter design with optimal pole placement

This paper presents a two-stage approach for designing an infinite impulse response (IIR) notch filter. First, the numerator of the transfer function of the IIR notch filter is obtained by placing the zeros at the prescribed notch frequencies. Then, the denominator polynomial is determined by using an iterative scheme in which the optimal pole placements are found by solving a standard quadratic programming problem. For stability, the pole radius in the single notch filter design is specified by the designer, and in the multiple notch filter design, the pole radius is constrained by using the implications of Rouche's theorem. Examples are included to illustrate the effectiveness of the proposed techniques     

Multisim 2001在基于UAF42陷波器设计中的应用

目前地球物理勘探（物探）工作使用的专业电子仪器的工作频率都较低,所以在物探仪器中运用陷波器相当普遍,特别是用于压制50 Hz电力线的干扰方面.为了压制50 Hz的工频干扰,要在仪器的信号调理部分采用陷波器电路.为了设计和优化基于UAF42的新型陷波器电路,采用Multisim 2001进行仿真实验.Multisim 2001借助虚拟现实技术,使设计者能快速地模拟、分析、验证所设计电路的性能.与传统方法相比,这种虚拟技术既省时又经济,而且还可避免实验中发生的各种损坏和事故.本文利用基于UAF42设计的50Hz陷波器的仿真电路,对陷波器的频率响应进行了仿真.仿真结果表明,基于UAF42的50 Hz陷波器达到了设计目的和要求,并证明了Multisim 2001在电路设计中的重要作用.     

一种低复杂度的稀疏FIR陷波滤波器的设计方法

FIR陷波滤波器具有线性相位、精度高、稳定性好等诸多优势,然而当陷波性能要求较高时,通常需要较高的阶数,导致FIR陷波滤波器硬件实现复杂度大大提高。该文基于稀疏FIR滤波器设计算法和共同子式消除的思想,提出一种低复杂度的FIR陷波滤波器设计方法。该方法首先采用稀疏滤波器设计算法得到满足频域性能设计要求的FIR陷波原始滤波器系数,然后对其进行CSD编码,并分析CSD编码量化系数集中所有的2项子式和孤子的灵敏度,最后根据灵敏度的大小依次选择合理的2项子式或孤子直接合成滤波器系数集。仿真结果表明,新算法设计实现的FIR陷波滤波器比已有的低复杂度设计方法最多可减少51%的加法器,有效地降低了硬件实现复杂度,大大节省了硬件资源。     

Optical notch filter design based on digital signal processing

Based on digital signal processing theory,a novel method of designing optical notch filter is proposed for Mach-Zehnder interferometer with cascaded optical fiber rings coupled structure.The method is simple and effective,and it can be used to implement the designing of the optical notch filter which has arbitrary number of notch points in one free spectrum range(FSR).A design example of notch filter based on cascaded single-fiber-rings is given.On this basis,an improved cascaded double-fiber-ri...     

Adaptive notch filter design under multiple identical bandwidths

Digital notch filters are applied to remove or suppress the narrow-band interferences in digital signals, while preserving other components unchanged. Under the condition of the identical notch bandwidths, a novel design method is put forward in this paper to realize the adaptive notch filter with infinite-impulse response (IIR). Firstly, a specially simplified all-pass filter is introduced to construct an IIR non-adaptive notch filter, which serves as the core part in the adaptive one. Secondly, the criterion of least-mean-square (LMS) is applied to design the desired adaptive notch filter (ANF). The designed ANF can track and suppress multiple non-harmonic interference components simultaneously. Finally, the effectiveness and practicability of the proposed design method are verified by a set of experimental results.     

基于全相位陷波器解析设计的啸叫去除

为了快速且精准地抑制助听器中的啸叫效应,该文提出一种中心频率可以精确控制的全相位有限脉冲响应(FIR)陷波器解析设计。首先,为了获得较高的陷波精度,引入了整数部分m和小数部分λ来控制陷波的中心频率。然后,设计了一个偶对称的闭式解析式来计算陷波器系数。最后,为了保证输出信号的连续性和线性相位,进行数据延拓和截取操作。该陷波器具有线性传输特性,避免了非线性失真。为了检验陷波器的滤波性能,将其应用在助听器中去除啸叫。实验结果表明,该滤波器在啸叫频率下的衰减值可达–330 dB,信噪比达22 dB,输出波形质量好,算法复杂度低,鲁棒性高,具有一定的应用前景。     

罗兰C接收机中窄带干扰的抑制技术

针对目前的罗兰C接收机在抑制窄带干扰方面的缺陷,将基于LMS算法(最小均方准则)的自适应陷波器应用于罗兰C窄带干扰的抑制,通过仿真,将其与固定频率点的陷波器进行了比较,自适应陷波具有较好的抑制窄带干扰能力。     

Tunable notch filter using a thermooptic long-period grating

This paper proposes a tunable notch filter using a thermooptic long-period grating and investigates it theoretically. This notch filter is in the form of an integrated optical device and is based on a simple structure as compared with existing integrated optical notch filters. The thermooptic grating denotes a thermooptic index perturbation induced by periodic heaters. The attenuation of a resonance band in the transmission spectrum of the proposed notch filter can be controlled by adjusting the electric power applied to the periodic heaters. Employing the heat transfer theory and the coupled-mode theory, the proposed filter is designed and analyzed. The paper also presents analytic expressions for the temperature change due to a heater and the coupling coefficients due to the thermooptic grating. This filter may have potential as a compact dynamically controllable device like a tunable gain flattening filter.     

Selectivity of notch filters using nonuniform RC lines

The notch selectivity of a notch filter is defined as the halfpower selectivity of a feedback amplifier with an open-loop gain of 40dB and the notch filter in its feedback circuit. Parameters of the exponential, the trigonometric, and the hyperbolic RC lines for different selectivities are given.     

Design of three-dimensional adaptive IIR notch filters

This paper investigates a realization of a three-dimensional (3-D) adaptive notch filter. The procedures are mainly divided into two parts: frequency-detecting and sinusoidal interference removal. The detections are based on adaptive line enhancer on infinite impulse response (IIR) lattice structure. In the interference removal part, a non-separable version of a 3-D notch filter is effectively applied. The magnitude response of a 3-D adaptive IIR notch filter is illustrated. At the end of the paper, the implementation of an IIR notch filter on a 3-D image is also conducted in order to show how to remove a sinusoidal interference superimposed on a 3-D image.     

Tunable/adaptive second-order IIR notch filter

A modified second-order infinite impulse response (IIR) notch filter with constrained poles and zeros is presented to eliminate or retrieve sinusoids embedded in a broadband signal. Such a filter is ideally suited to either parallel or cascaded implementation. Two classes of problems are considered. The first is where the sinusoidal frequencies are known a priori. For this case a straightforward design procedure based on a set of design characteristic graphs is used to select tunable notch filter parameters. An interesting property of the notch filter model is that it can be converted to a line enhancer by interchanging the position of the poles and zeros. The second type of problem arises when the sinusoidal frequencies are unknown and possibly varying with time. This means that an adaptive solution is required and an important consideration is the parameter estimation accuracy. For this purpose, the paper derives the Cramer–Rao lower bound for the adaptive cascaded notch filter using a frequency-domain approach. Some simulation results are included to demonstrate the effectiveness of the proposed adaptive notch filter.