Rapid interference suppression using Kalman filter approach

Directional interference suppression is based upon a recursive estimation procedure of the state of a filter generating the angular interference spectrum. This leads to an iterative solution of the Wiener-Hopf matrix equation. Simulation results compare the convergence rate of the proposed technique and the gradient method.     

Planar filter design with fully controllable second passband

New designs of the dual-band filter realized by distributed circuits are studied in this paper. Series and parallel open stubs are used as the resonators to fulfil the dual-band characteristics. Two dual-band inverters are proposed, which can be easily merged with adjacent resonators to reduce the circuit size. All the theoretical analysis and design procedures are discussed in detail and have been successfully verified by experiment results.     

Adaptive reduced-rank interference suppression based on themultistage Wiener filter

A class of adaptive reduced-rank interference suppression algorithms is presented based on the multistage Wiener filter (MSWF). The performance is examined in the context of direct-sequence (DS) code division multiple access (CDMA). Unlike the principal components method for reduced-rank filtering, the algorithms presented can achieve near full-rank performance with a filter rank much less than the dimension of the signal subspace. We present batch and recursive algorithms for estimating the filter parameters, which do not require an eigen-decomposition. The algorithm performance in a heavily loaded DS-CDMA system is characterized via computer simulation. The results show that the reduced-rank algorithms require significantly fewer training samples than other reduced- and full-rank algorithms     

Varactor-tuned active notch filter with low passband noise andsignal distortion

The frequency-tunable band-reject filter described in this paper is designed to suppress signal interference in receivers of frequency-agile systems, while offering maximum transparency at passband frequencies. The presented solution is based on a new channelized-active-filter architecture in which the portion of the circuit that determines passband behavior is free of semiconductor devices. This permits passband residual noise and intermodulation distortion to be reduced to that of a simple nonresonant passive network. The concept is demonstrated with a varactor-tuned hybrid-integrated filter whose 40-dB-deep rejection notch of constant 70-MHz width can be tuned over a 9.5-10.5-GHz frequency span. Included are measurements of pertinent small-signal transfer characteristics and noise properties, as well as detailed assessments of nonlinear effects, such as third-order intermodulation distortion and compression of notch depth as a function of drive level     

Lowpass filter with minimum integrated power-loss ratio in the passband

A class of lowpass filters with minimum integrated power-loss ratio in the passband is discussed. Comparisons with the usual Butterworth and Cheby?shev filters are also reported.     

Combined self-organising feature map-LMS adaptive filter fordigital co-channel interference suppression

The performance of the conventional LMS adaptive filter used for co-channel interference suppression degrades when the desired signal and the interference have similar characteristics. The authors propose a technique that uses a self-organising feature map to track the interference statistics, which are then used by the LMS adaptive filter to reject the interference. Simulation results and an analysis of the weight error power are presented     

New periodic-loaded electromagnetic bandgap coplanar waveguide with complete spurious passband suppression

In this work, coplanar waveguides (CPW) periodically loaded with shunt capacitances and periodically perturbed by varying the distance between the central strip (of constant width) and ground planes are studied. It is demonstrated that the multiple spurious passbands above the Bragg frequency, inherent to the presence of the reactive elements, can be completely and efficiently rejected by means of very simple geometry perturbation. This result is in contrast to previous works, where the rejection of multiple frequencies requires complex layout patterns and reveals that the elimination of spurious frequency bands in periodic loaded CPWs cannot be merely estimated from the Fourier transform of the perturbation geometry.     

Continuous-time analog filter with passband constant IIP3 based on common-gate amplifier

This paper presents an analog filter based on Rauch biquadratic cell. The filter exploits an improved analog stage that makes linearity performance uniform over the entire pass-band frequency region. All feedback analog filters suffer from poor linearity when the input tones frequency is in close proximity to the closed-loop poles frequency, where loop-gain reduces. This often forces an overdesign with higher current (higher power consumption) and/or higher overdrive voltages (lower dynamic range) in order to meet the linearity specifications over the whole filter pass-band region. The hereby proposed Rauch scheme resolves such a binding issue without power increasing and having the same IIP3 at low and at high frequency (up to the filter closed-loop poles frequency). Hence the linearity performance is in first approximation independent on the input tones bandwidth. In order to validate the hereby proposed idea a 4th-order 25 MHz ?3 dB bandwidth pseudo-differential filter has been designed and simulated in CMOS 28 nm technology. The prototype consumes 820 µW from 1 V supply voltage and has 15  and 13 dBm IIP3 at 5 and 6 and 20 and 21 MHz input tones, respectively.     

一种二阶锥规划通带线性相位FIR滤波器的设计

在有限冲激响应（Finite Impulse Response,FIR）滤波器设计中,如果系统只要求通带或某个频域区间具有线性相位而其他频域区间相位非线性,则系数对称的FIR滤波器设计方法不再适用。为此,提出了一种基于二阶锥规划（Second-Order Cone Programming,SOCP）的通带线性相位FIR滤波器设计方法。该方法使用二阶锥规划实现滤波器设计,其中优化目标为通带最小群延迟,约束条件为全频域振幅误差。实验结果显示,所提方法设计的FIR滤波器有着很好的幅频特性和通带线性相位,通带群延迟误差很小。该方法实现简单,计算复杂度低,可以广泛应用于数字信号处理领域。     

慢波结构SIR双频带通滤波器设计

本文通过分析阶梯阻抗谐振器（SIR）和慢波结构谐振器的特性,提出了利用SIR谐振器的寄生通带产生第二通带的双频带通滤波器设计方法,以达到滤波器小型化的目的;并基于0°馈电结构获取传输零点的原理对滤波器阻带性能进行优化。最后结合ADS仿真软件设计了一个中心频率在2.4GHz和5.2GHz的微带双频带通滤波器。仿真结果表明滤波器具有良好的带内带外特性。本文所设计的滤波器尺寸小,性能好,具有很好的实用价值。     

Cyclic and rectangular passband optical bandpass filter using AWG pair

A novel optical bandpass filter is proposed that consists of an arrayed-waveguide grating pair and an optical slit. A 200 GHz cyclic and 40 GHz passband optical filter using the proposed configuration, which is useful for WDM single sideband filtering, is successfully demonstrated.     

宽带HFC网络中的调制方式与窄带干扰抑制的分析

在整个5－42MHz回传通路频带内，对采用16QAM调制方式的HFC系统，构造了一个非线性窄带干扰抑制器，并应用非线性算法对带宽小于100kHz的窄带噪声进行非线性抑制。     

A maximally flat group delay recursive digital filter with improved passband magnitude response

A technique is proposed for the design of a recursive digital filter with maximally flat responses in both magnitude and group delay. In comparison to the previous designs [1]-[3], the magnitude and group delay always show smooth responses no matter what the difference is in the polynomial degrees of the numerator and denominator.     

Athermal Mach-Zehnder interferometer-synchronised arrayed waveguide grating multi/demultiplexer with low loss and wide passband

Described is a silica-based athermal 100 GHz-spacing 40-channel arrayed waveguide grating (AWG) with a Mach-Zehnder interferometer (MZI)-synchronised configuration that employs resin-filled grooves in the AWG and MZI. By suppressing the groove excess loss and using 1.5%-Delta waveguides, a low insertion loss of 3.2 dB and a wide 0.5 dB bandwidth of 45.9 GHz with athermal operation in the -5 to 65degC range and a compact chip size were achieved.     

Multiple-symbol differential detection with interference suppression

A multiple-symbol differential detector is formulated for M-ary differential phase-shift keying modulation where the channel state information is unknown to the receiver. The maximum-likelihood decision statistic is derived for the detector, and its performance is demonstrated by analysis and simulation. Under the Gaussian assumption for the aggregate interference plus noise, an exact expression for the symbol pairwise error probability is developed for M-ary differential phase-shift keying modulation over a diversity, slow-fading Rayleigh channel in the presence of an interference source. A simpler expression of the pairwise error probability is developed for the asymptotic case of large signal-to-noise ratio and small signal-to-interference ratio. It is shown that with an increasing observation interval, the performance of the differential detector over an unknown channel approaches that of optimum combining with known channel.     

基于特征空间的相干干扰抑制技术

该文把多线性约束和特征空间技术相结合,提出了基于特征空间的多约束最小方差波束形成器(EM-CMVB),该波束形成器可以有效抑制相干干扰。EMCMVB是利用估计得到的相干干扰方向和阵列信号相关矩阵特征分解来得到修改的信号子空间,再把多约束最小方差波束形成器(MCMVB)的权矢量向修改的信号子空间投影来得出新的权矢量。经分析表明,EMCMVB的性能优于MCMVB的性能。最后,给出了计算机仿真结果,证实了EMCMVB的优越性。     

Tunable microwave photonic filter for noise and interference suppression in UMTS base stations

A design of a tunable microwave photonic filter for noise suppression and channel interference mitigation in the front-end stage after the receiving antenna of an UMTS base station is presented. The filter provides a tunable and very high selective performance (5 MHz along the 1935-1977 MHz band) with 14 dB suppression in the stopband using 30 fibre Bragg gratings and a reconfigurable dispersive delay line.     

Comments on "Adaptive reduced-rank interference suppression based on the multistage Wiener filter"

For original article by M. L. Honig and J. S. Goldstein see ibid., vol.50, no.6, p.986-94, June 2002.     

Coherent interference suppression with complementally transformedadaptive beamformer

This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR). Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers     

CMOS filter with wide digitally programmable VHF range

A novel approach is presented for programmable filtering over the VHF range based on fully-balanced pseudo-differential continuous-time transconductors for applications in low-voltage systems. An example third-order G_m-C lowpass Butterworth filter using the proposed transconductor and accumulation MOS capacitors has been implemented using an AMS 0.35 mum CMOS process, achieving -3 dB cutoff frequencies ranging from 40 to 200 MHz. The active chip area is 0.06 mm ² per pole