Blind adaptation of stable discrete-time IIR filters in state-space form

Blind deconvolution consists of extracting a source sequence and impulse response of a linear system from their convolution. In the presence of system zeros close to the unit circle, which give rise to very long impulse responses, infinite-impulse-response (IIR) adaptive structures are of use, whose adaptation should be carefully designed in order to guarantee stability. In this paper, we propose a blind-type discrete-time IIR adaptive filter structure realized in state-space form that, with a suitable parameterization of its coefficients, remains stable. The theory is first developed for a two-pole filter, whose numerical behavior is investigated via numerical experiments. The proposed structure/adaptation theory is then extended to a multipole structure realized as a cascade of two-pole filters. Computer-based experiments are proposed and discussed, which aim at illustrating the behavior of the filter cascade on several cases of study. The numerical results obtained show the proposed filters remain stable during adaptation and provide satisfactory deconvolution results.     

Detection of spicules on mammogram based on skeleton analysis

Existence of spicules is one of important clues of malignant tumors. This paper presents a new image processing method for the detection of spicules on mammogram. Spicules can be recognized as line patterns radiating from the center of tumor. To detect such characteristic patterns, line skeletons and a modified Hough transform are proposed. Line skeleton processing is effective in enhancing spinal axes of spicules and in reducing the other skeletons. The modified Hough transform is applied to line skeletons and radiating line structures are obtained. Experiments were made to test the performance of the proposed method. The system was designed using 19 training images, for which one normal case was recognized to be star-shaped. The other case were recognized correctly. Another experiments using 34 test images were also performed. The correct classification rate was 74%. These results shows the effectiveness of the proposed method.     

基于混合滤波器组的时间交替采样技术

时间交替采样技术对通道失配误差十分敏感,而基于混合滤波器组的采样技术降低了对通道失配误差的敏感,但前端模拟分析滤波器的稳定性难于设计限制了其工程应用。结合时间交替和混合滤波器组采样技术,提出了一种易于工程实现的基于混合滤波器组的时间交替采样技术。仿真结果表明,该技术能显著提高采样系统的精度。     

Current mode single-input multi-output MOSFET-only filter

In this paper, a very simple topology of a current mode MOSFET-only filter with single-input and multi-output is proposed. It is very important to emphasize that it is possible to obtain five of the filter functions, namely low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) using the proposed topology without using external passive elements. The core circuit of the proposed filter employs only four MOS transistors; therefore, it occupies very small chip area. It is also possible to adjust the filter gain with the biasing voltage. In addition, the circuit exhibits a very low input impedance and also high output impedances which make it possible for cascading. The MOSFET capacitances which determine the transfer functions are all grounded, so physical capacitances can be used instead of MOSFET parasitic capacitances to operate the filter at very low frequencies. Moreover, proposed filter structure has low supply voltage as 1 V in order to be applicable to low voltage operations. Detailed simulation results, including noise and Monte Carlo analysis, are provided using 0.18 µm TSMC technology parameters to verify the feasibility of the filter circuit.     

Parametric cumulant based phase estimation of 1-D and 2-Dnonminimum phase systems by allpass filtering

This paper proposes a parametric cumulant-based phase-estimation method for one-dimensional (1-D) and two-dimensional (2-D) linear time-invariant (LTI) systems with only non-Gaussian measurements corrupted by additive Gaussian noise. The given measurements are processed by an optimum allpass filter such that a single Mth-order (M⩾3) cumulant of the allpass filter output is maximum in absolute value. It can be shown that the phase of the unknown system of interest is equal to the negative of the phase of the optimum allpass filter except for a linear phase term (a time delay). For the phase estimation of 1-D LTI systems, an iterative 1-D algorithm is proposed to find the optimum allpass filter modeled either by an autoregressive moving average (ARMA) model or by a Fourier series-based model. For the phase estimation of 2-D LTI systems, an iterative 2-D algorithm is proposed that only uses the Fourier series-based allpass model. A performance analysis is then presented for the proposed cumulant-based 1-D and 2-D phase estimation algorithms followed by some simulation results and experimental results with real speech data to justify their efficacy and the analytic results on their performance. Finally, the paper concludes with a discussion and some conclusions     

METEOR: a constraint-based FIR filter design program

It is proposed to specify a filter only in terms of upper and lower limits on the response, find the shortest filter length which allows these constraints to be met, and then find a filter of that order which is farthest from the upper and lower constraint boundaries in a minimax sense. The simplex algorithm for linear programming is used to find a best linear-phase FIR filter of minimum length, as well as to find the minimum feasible length itself. The simplex algorithm, while much slower than exchange algorithms, also allows the incorporation of more general kinds of constraints, such as concavity constraints (which can be used to achieve very flat magnitude characteristics). Examples are given to illustrate how the proposed and common approaches differ, and how the proposed approach can be used to design filters with flat passbands, filters which meet point constraints, minimum phase filters, and bandpass filters with controlled transition band behavior     

Stability analysis of a series active filter integrated with adouble-series diode rectifier

This paper deals with a harmonic current-free AC/DC power conversion system which is characterized by the integration of a small-rated series active filter with a large-rated double-series diode rectifier. The stability of the active filter based on feedback control is discussed theoretically, taking into account delay time in the control circuit. As a result, it is revealed that the delay time may produce a bad effect on stability, especially when the power conversion system is installed on a stiff power system with low system inductance. The authors propose a viable way of reducing the effect of delay time on the system stability. Analysis in the frequency domain enables us to know how much the system stability is improved in terms of gain and phase margins. A switching-ripple filter is designed to obtain good filtering performance without affecting the system stability. Experimental results obtained from a 20 kW laboratory system verify the validity of the developed theory, and confirm the viability and effectiveness of the proposed control circuit     

Multirate signal processing on finite fields

The paper addresses the problem of multirate signal processing over arbitrary fields. Studies of multirate systems and filter banks have proceeded in parallel, and a wealth of results are available in literature. The authors concentrate their attention on cyclic systems. These structures are ideally suited to generalising the concepts to finite fields. The perfect reconstruction property for quadrature mirror filter banks is obtained. It is shown how the cyclic wavelet transform (CWT) can be derived from such systems; the relationships between cyclic filter banks and CWTs are explored in detail. The results obtained are potentially very well suited for speech and image encoding, as well as for fast algorithms in signal processing     

用计算全息制作改进的Mexican-hat子波匹配滤波器实现二维光学子波变换

提出了应用计算全息制作改进的Ｍｅｘｉｃａｎ－ｈａｔ子波匹配滤波器,在一个光学４ｆ系统中实现了二维子波变换,给出了简要的理论分析和实验结果,实验结果与计算机模拟完全一致。     

An efficient digital implementation of multicarrier CDMA system based on generalized DFT filter Banks

In this paper, an efficient digital implementation of multicarrier transmission scheme based on generalized discrete Fourier transform (DFT) filter banks is presented for multicarrier code-division multiple-access (MC-CDMA) systems. Generalized DFT filter banks has been traditionally discussed for very high-speed digital subscriber lines (VDSL) wireline systems, received interest also for wireless applications. The design of the generalized DFT modulated filter banks is investigated and its fast implementation is derived in the time-domain for arbitrary integer sampling rate. Through the utilization of the generalized DFT modulated filter banks, one or more subcarriers, even noncontiguous subcarriers can be easily supported by system in both uplink and downlink, which facilitates the users to access the network in a frequency-division multiple-access manner. Simulation results show that the overall bit-error-rate performance of the proposed multicarrier transmission scheme well approaches that of a single-carrier system due to the negligible intercarrier interference introduced by an appropriate design of the generalized DFT modulated filter banks.     

锁相频率合成器的噪声优化设计

简要介绍了锁相环频率合成的原理,对环路内和环路外的噪声进行了详尽分析,提出为了使系统性能达到最优,应该采取哪些措施、选择哪些器件以及怎样设计匹配电路的原则和方法。使用PLL Design&Simulation仿真软件,对环路滤波器在采用有源滤波器和无源滤波器2种情况下鉴相器和VCO的输出信号进行了仿真,从仿真结果可以看出,环路滤波器应尽量选择无源滤波器。     

Multichannel Fast QR-Decomposition Algorithms: Weight Extraction Method and Its Applications

Multichannel fast QR decomposition RLS (MC-FQRD-RLS) algorithms are well known for their good numerical properties and low computational complexity. The main limitation is that they lack an explicit weight vector term, limiting themselves to problems seeking an estimate of the output error signal. This paper presents techniques which allow us to use MC-FQRD-RLS algorithms with applications that previously have required explicit knowledge of the adaptive filter weights. We first consider a multichannel system identification setup and present how to obtain, at any time, the filter weights associated with the MC-FQRD-RLS algorithm. Thereafter, we turn to problems where the filter weights are periodically updated using training data, and then used for fixed filtering of a useful data sequence, e.g., burst-trained equalizers. Finally, we consider a particular control structure, indirect learning, where a copy of the coefficient vector is filtering a different input sequence than that of the adaptive filter. Simulations are carried out for Volterra system identification, decision feedback equalization, and adaptive predistortion of high-power amplifiers. The results verify our claims that the proposed techniques achieve the same performance as the inverse QRD-RLS algorithm at a much lower computational cost.     

A robust hysteresis current-controlled PWM inverter for linear PMSMdriven magnetic suspended positioning system

Hysteresis current-controlled pulsewidth modulation (PWM) is very robust but it possesses nonconstant switching frequency, and it is difficult to use for high-performance position servo applications. This paper presents a robust hysteresis current-controlled PWM scheme for a magnetic suspended positioning system driven by an inverter-fed linear permanent-magnet synchronous motor having improved performance in these two areas. In the proposed control scheme, the conventional hysteresis PWM mechanism is augmented by a robust harmonic spectrum-shaping controller. The error signal, which represents the switching frequency deviated from the set one, is detected using a notching filter inverse model. Then, the current command is adjusted by a robust compensation signal. The hysteresis band can be equivalently varied to let the dominant harmonic frequency of inverter output be constant, wherein the frequency can easily be changed by tuning the center frequency of the notch filter. The gating signal of switches is not needed to be sensed for making the proposed control. The constant-frequency control performance yielded by the proposed controller is rather insensitive to the system disturbances and the neutral voltage variation due to isolated Y connection. Through applying the proposed PWM inverter, satisfactory position control requirements can be achieved by properly setting the dominant harmonic frequency according to the electromechanical model of the positioning system     

Anonymous Indoor Navigation System on Handheld Mobile Devices for Visually Impaired

An indoor positioning and navigation system based on measurements of received signal strength in wireless local area network is proposed. In the system, the location determination problem is solved by applying compressive sensing, which offers recovery of sparse signals from a small number of noisy measurements by solving an ?₁-minimization problem. The refined estimate is then used with a map-adaptive Kalman filter for real-time tracking. A navigation module integrated with the tracking system guides users to pre-defined destinations with voice instructions. Experimental results with a system that was implemented on a PDA shows that the proposed tracking system is lightweight so that it can be used on a resource constrained platform while outperforming the widely used traditional positioning and tracking systems. A pilot study was carried out with 30 visually impaired subjects from the Canadian National Institute for the Blind. Testing results show that the proposed system can be used to guide visually impaired subjects to their desired destinations with a very high success rate.     

Harmonic-suppression LTCC filter with the step-impedance quarter-wavelength open stub

An effective method to design a low-temperature co-fired ceramic RF bandpass filter with suppression of the harmonic frequency is demonstrated in this paper. The second harmonic, which appears in the frequency band of 4.8-5.0 GHz, is very significant and should be reduced in the 2.4-GHz wireless local area network and Bluetooth application. This feature of harmonic frequency suppression is very important in a communication system to improve linearity, output power, intermodulation performance, etc. The harmonic-suppression filter can be easily obtained by adopting the characteristic of equivalent quarter-wavelength resonators. The detailed three-dimensional layout of each layer is disclosed. By analyzing the influences of the dielectric constant and layer thickness of a ceramic sheet by electromagnetic simulation, the optimal condition for the filter design can be obtained. The measured results agree well with the simulation.     

A new motor speed estimator using Kalman filter in low-speed range

In this paper, a new machine drive technique using novel estimation strategy for the very low-speed operation to estimate both the instantaneous speed and disturbance load torque is proposed. In the proposed algorithm, a Kalman filter is incorporated to estimate both the motor speed and the disturbance torque. The Kalman filter is an optimal state estimator and is usually applied to a dynamic system that involves a random noise environment. The effects of parameter variations are discussed, and it is verified that the system is stable to the modeling error. Experimental results confirm the validity of the proposed estimation technique     

根升余弦脉冲成形滤波器FPGA实现

提出了基于电路分割技术实现通信系统发送端根升余弦波形成形滤波器查表法的FPGA结构,节省了ROM单元,讨论了其ROM初始化时形渡数据的组织方法,完成了该结构的VHDI。实现,给出了该设计在Modelsim环境下的时序仿真结果。通过对仿真结果分析,表明所述的设计方法是可行的。该设计方案不随波形样本数目的增多而使电路系统变得更为复杂,它所实现的成形滤波器满足于高速成形的应用需求。     

Scanning laser system for combined fluorescent diagnostics andphotodynamic therapy: structural design, preliminary trials, andpotentials

Photodynamic therapy (PDT) is commonly performed by administration of porphyrin photosensitizers selectively retained by malignant tumors. Subsequent photoexcitation with UV-blue light causes fluorescence useful for diagnosis. Excitation by red light destroys the cancer tissue. The use of high-speed scanning of laser light as an alternative to conventional PDT which employs dispersed light to achieve uniformity of treatment is proposed. It is shown that treatment with scanned light beams produces photochemical effects in malignant animal tissue that are virtually the same as those caused by comparable treatments with diffused light. It is argued that undesirable thermal effects can be reduced by the use of focused, scanned laser beams in lieu of diffused light. It is also shown how concurrent analysis and treatment can proceed using a system of two laser beams     

A low-power multi-mode and multi-output high-order CMOS universal Gm-C filter

This paper presents a new CMOS high-order Gm-C universal filter which can realize multi-mode (current, voltage, trans-resistance and trans-conductance) filtering functions, using grounded capacitors to absorbing shunt parasitic capacitances and a reduced number of active elements which leads to the minimum chip size and power consumption. Furthermore, in current-mode implementation, the proposed circuit produces simultaneously multiple filtering functions while uses just one configuration of inputs. Also, as the result of sensitivity analysis shows, the new filter structure has a very low sensitivity to the values of capacitors and trans-conductance elements. However, the proposed Gm-C filter is designed and simulated in HSPICE using 0.18 μm CMOS technology parameters and HSPICE simulation results have very close agreement with theoretical results obtained from MATLAB which justifies the design accuracy and low-power, multi-mode, multi-output universal filtering performance of the proposed circuit.