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Showing papers on "Low-pass filter published in 1999"


Journal ArticleDOI
TL;DR: Experimental results for quantized low-order position reference trajectories, which are commonly used in industrial systems, demonstrate the effectiveness of the proposed discrete-time tracking controller.
Abstract: Design and implementation of a discrete-time tracking controller for a precision positioning table actuated by direct-drive motors is considered. The table has acceleration capabilities in excess of 5 G, positioning accuracy at the micron level, and is used in applications such as semiconductor packaging. The controller proposed uses a disturbance observer and proportional derivative (PD) compensation in the feedback path and a zero phase error tracking controller and zero phase low-pass filter in the feedforward path. The existing disturbance observer design techniques are extended to account for time delay in the plant. Practical difficulties with excessive feedforward gains are examined and a low-order filter design method is proposed. Experimental results for quantized low-order position reference trajectories, which are commonly used in industrial systems, demonstrate the effectiveness of the approach.

577 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed a procedure for objectively determining the optimum cutoff frequency for the Butterworth low-pass digital filler, and evaluated the cutoff frequencies derived from the residual analysis, using a set of knee flexion-extension angle data in normal gait.
Abstract: The purposes of this study were (a) to develop a procedure for objectively determining the optimum cutoff frequency for the Butterworth low-pass digital filler, and (b) to evaluate the cutoff frequencies derived from the residual analysis. A set of knee flexion-extension angle data in normal gait was used as the standard data set. The standard data were sampled at different sampling frequencies. Random errors with different magnitudes were added to the standard data to create different sets of raw data with a given sampling frequency. Each raw data set was filtered through a Butterworth low-pass digital filter at different cutoff frequencies. The cutoff frequency corresponding to the minimum error in the second time derivatives for a given set of raw data was considered as the optimum for that set of raw data. A procedure for estimating the optimum cutoff frequency from the sampling frequency and estimated relative mean error in the raw data set was developed. The estimated optimum cutoff frequency signif...

271 citations


Journal ArticleDOI
TL;DR: A quadratic-constrained design method for prototype filters yielding PR with arbitrary length and system delay is derived, and design examples are presented to illustrate the tradeoff between overall system delay and stopband attenuation (subchannelization).
Abstract: This paper presents a general framework for maximally decimated modulated filter banks. The theory covers the known classes of cosine modulation and relates them to complex-modulated filter banks. The prototype filters have arbitrary lengths, and the overall delay of the filter bank is arbitrary, within fundamental limits. Necessary and sufficient conditions for perfect reconstruction (PR) are derived using the polyphase representation. It is shown that these PR conditions are identical for all types of modulation-modulation based on the discrete cosine transform (DCT), both DCT-III/DCT-IV and DCT-I/DCT-II, and modulation based on the modified discrete Fourier transform (MDFT). A quadratic-constrained design method for prototype filters yielding PR with arbitrary length and system delay is derived, and design examples are presented to illustrate the tradeoff between overall system delay and stopband attenuation (subchannelization).

186 citations


Patent
15 Sep 1999
TL;DR: In this paper, a notch EMI filter capacitive element is integrated in a co-planar relationship with a ceramic feedthrough filter capacitor assembly, which is particularly effective in an implantable medical device such as a cardiac pacemaker or implantable cardioverter defibrillator (ICD) against passage of external interference signals.
Abstract: A novel electromagnetic interference (EMI) filter is designed to attenuate one or more specific frequencies in order to provide electromagnetic compatibility of an electronic device while in the presence of an electromagnetic emitter operating at the same or similar frequencies. The EMI filter of the present invention combines an EMI low pass filter with one or more “notch” EMI filters tuned to the specific frequencies of interest. When combined in this fashion, the notch EMI filter can effectively attenuate the electromagnetic field of a powerful low frequency emitter which is outside the effective attenuation frequency range of the low pass filter, which is itself effective at filtering a broad range of higher frequencies. In a preferred embodiment, the notch EMI filter capacitive element is integrated in a co-planar relationship with a ceramic feedthrough filter capacitor assembly. This combined notch and low pass filter arrangement is particularly effective in an implantable medical device such as a cardiac pacemaker or implantable cardioverter defibrillator (ICD) against passage of external interference signals, such as those caused by both digital cellular phones and electronic article surveillance systems operating at low frequencies.

158 citations


Journal ArticleDOI
Abstract: In this brief, a design algorithm for real-valued and complex-valued oversampled filter banks which yield a low level of inband alias and enable simple subband adaptive structures is presented. The filter banks are either based on complex modulation of a real-valued low-pass prototype or on the direct or modulated setups of real-valued filter banks. If real-valued filter banks are required, then the different channels will have different subsampling ratios so that the bandpass sampling theorem is not violated. This brief also presents design examples of real-valued and complex-valued filter banks.

154 citations


Journal ArticleDOI
TL;DR: The design for testability (DFT) of active analog filters based on oscillation-test methodology is described and the DFT techniques investigated are very suitable for automatic testable filter synthesis and can be easily integrated in the tools dedicated to automatic filter design.
Abstract: The oscillation-test strategy is a low cost and robust test method for mixed-signal integrated circuits. Being a vectorless test method, it allows one to eliminate the analog test vector generator. Furthermore, as the oscillation frequency is considered to be digital, it can be precisely analyzed using pure digital circuitry and can be easily interfaced to test techniques dedicated to the digital part of the circuit under test (CUT). This paper describes the design for testability (DFT) of active analog filters based on oscillation-test methodology. Active filters are transformed to oscillators using very simple techniques. The tolerance band of the oscillation frequency is determined by a Monte Carlo analysis taking into account the nominal tolerance of all circuit under test components. Discrete practical realizations and extensive simulations based on CMOS 1.2 /spl mu/m technology parameters affirm that the test technique presented for active analog filters ensures high fault coverage and requires a negligible area overhead. Finally, the DFT techniques investigated are very suitable for automatic testable filter synthesis and can be easily integrated in the tools dedicated to automatic filter design.

141 citations


Journal ArticleDOI
TL;DR: Numerical experiments for 1-D and 2-D implementations confirm the theoretically predicted accuracy and efficiency properties of the NFFT, and a numerically optimized filter shows the best results.
Abstract: The nonuniform discrete Fourier transform (NDFT) can be computed with a fast algorithm, referred to as the nonuniform fast Fourier transform (NFFT) In L dimensions, the NFFT requires O(N(-lne)L+(∏𝓁=1LM𝓁)∑𝓁=1LlogM𝓁) operations, where M𝓁 is the number of Fourier components along dimension 𝓁, N is the number of irregularly spaced samples, and e is the required accuracy This is a dramatic improvement over the O(N∏𝓁=1LM𝓁) operations required for the direct evaluation (NDFT) The performance of the NFFT depends on the lowpass filter used in the algorithm A truncated Gauss pulse, proposed in the literature, is optimized A newly proposed filter, a Gauss pulse tapered with a Hanning window, performs better than the truncated Gauss pulse and the B-spline, also proposed in the literature For small filter length, a numerically optimized filter shows the best results Numerical experiments for 1-D and 2-D implementations confirm the theoretically predicted accuracy and efficiency properties of the algorithm

141 citations


Proceedings ArticleDOI
30 Nov 1999
TL;DR: In this paper, a new photonic bandgap unit structure for microstrip line was proposed and the equivalent circuit parameters were extracted by using the circuit analysis method, by employing the extracted parameters, the wide-band harmonic rejection low-pass filter was designed.
Abstract: A new photonic bandgap unit structure for microstrip line is proposed. The equivalent circuit for the proposed photonic bandgap unit structure is derived by means of three dimensional field analysis methods. The equivalent circuit parameters are extracted by using the circuit analysis method. By employing the extracted parameters, the wide-band harmonic rejection low-pass filter is designed. The experimental results show the excellent agreements with theoretical results.

128 citations


Patent
12 Nov 1999
TL;DR: In this article, an integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit is described, where the filters are tuned using local oscillators to tune a substitute filter, and frequency scaling during filter component values to those of the filter being tuned.
Abstract: An integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit is described. A receiver front end provides programable attenuation and a programable gain low noise amplifier. Frequency conversion circuitry advantageously uses LC filters integrated onto the substrate in conjunction with image reject mixers to provide sufficient image frequency rejection. Filter tuning and inductor Q compensation over temperature are performed on chip. The filters utilize multi track spiral inductors. The filters are tuned using local oscillators to tune a substitute filter, and frequency scaling during filter component values to those of the filter being tuned. In conjunction with filtering, frequency planning provides additional image rejection. The advantageous choice of local oscillator signal generation methods on chip is by PLL out of band local oscillation and by direct synthesis for in band local oscillator. The VCOs in the PLLs are centered using a control circuit to center the tuning capacitance range. A differential crystal oscillator is advantageously used as a frequency reference. Differential signal transmission is advantageously used throughout the receiver.

120 citations


Patent
14 Jul 1999
TL;DR: In this paper, a noise control system includes an error detector for detecting an error signal between the control sound and noise, an adaptive filter for outputting a control signal; and a coefficient updator for updating a coefficient of the adaptive filter.
Abstract: A noise control system includes: a control sound generator for generating a control sound; an error detector for detecting an error signal between the control sound and noise; a noise detector for detecting a noise source signal; an adaptive filter for outputting a control signal; and a coefficient updator for updating a coefficient of the adaptive filter. The coefficient updator includes at least a first digital filter, a first coefficient update calculator, a second digital filter, a phase inverter, a third digital filter, and a second coefficient update calculator. Alternatively, the coefficient updator includes at least a first digital filter, a second digital filter, a third digital filter, a coefficient update calculator, a phase inverter, a first adder, and a second adder. In either case, the coefficient updator has a function of suppressing an increase in a coefficient gain of the adaptive filter in a predetermined frequency band.

104 citations


Journal ArticleDOI
TL;DR: In this paper, an eight-pole planar high-temperature superconducting (HTS) bandpass filter with a quasi-elliptic function response is described.
Abstract: This paper presents recent developments of an eight-pole planar high-temperature superconducting (HTS) bandpass filter with a quasi-elliptic function response. A novel planar filter configuration that allows a pair of transmission zeros to be placed at the band edges is described. The miniature HTS filter has a fraction bandwidth less than 1% and is designed for mobile communication base-station applications to increase sensitivity and selectivity. Design considerations including filter characteristics, design approach, sensitivity analysis and unloaded quality factor of resonators are addressed. The filter was fabricated using double-sided YBCO thin film on an MgO substrate of size 0.3/spl times/22.5/spl times/39 mm. Very good experimental results were obtained with the filter cooled using liquid nitrogen. The minimum passband loss was measured to be approximately 1 dB. The passband width at points 1 dB down from the minimum loss point was 12.8 MHz for a center frequency of 1738.5 MHz. High selectivity was achieved with a 30-dB rejection bandwidth of 16 MHz.

Proceedings ArticleDOI
27 Jun 1999
TL;DR: In this paper, the authors proposed a method of estimating the positive and the negative sequence voltages separately without a significant delay by utilizing the weighted least squares estimation (WLSE) method having the covariance resetting technique.
Abstract: If a negative sequence is generated by a voltage sag and/or unbalance, it appears as an oscillating error in a synchronous reference frame (SRF). In power conditioning equipment, an exact value of positive sequence is needed for achieving the desired goal of the system, e.g., unity power factor and constant output voltage, whereas the exact value of negative sequence is needed for compensation. To measure the positive sequence separately from the negative sequence, one uses normally a low pass filter having a narrow bandwidth. However, such a filter causes a lot of phase delay or measurement delay, thus the response time of the system tends to be lengthened. The authors propose a method of estimating the positive and the negative sequence voltages separately without a significant delay by utilizing the weighted least-squares estimation (WLSE) method having the covariance resetting technique. They demonstrate through simulation and experiment the superior performance of the proposed scheme in measuring the positive and the negative sequence voltages at the time of abrupt transition. This method can be applied to UPSs, PWM AC/DC converters, active filters, series voltage compensators, etc.

Journal ArticleDOI
TL;DR: In this article, a new procedure was proposed to automatically determine the cutoff frequency for low-pass filtering of biomechanical data, based on the properties of the autocorrelation function of white noise.
Abstract: This article presents and evaluates a new procedure that automatically determines the cutoff frequency for the low-pass filtering of biomechanical data. The cutoff frequency was estimated by exploiting the properties of the autocorrelation function of white noise. The new procedure systematically varies the cutoff frequency of a Butterworth filter until the signal representing the difference between the filtered and unfiltered data is the best approximation to white noise as assessed using the autocorrelation function. The procedure was evaluated using signals generated from mathematical functions. Noise was added to these signals so mat they approximated signals arising from me analysis of human movement. The optimal cutoff frequency was computed by finding the cutoff frequency that gave me smallest difference between the estimated and true signal values. The new procedure produced similar cutoff frequencies and root mean square differences to me optimal values, for me zeroth, first and second derivative...

Journal ArticleDOI
TL;DR: In this article, a new current mode universal biquadratic filter using only two second generation current conveyors and a minimum number of passive components is presented, which can realize the second-order low pass, high pass, band pass and band reject responses simultaneously.

Patent
19 Aug 1999
TL;DR: In this article, a method and apparatus for tuning control loop parameters in a motion control system is presented, which can automatically predict, or simulate, the effects of the proposed parameters on bandwidth, gain margin and phase margin, based upon the composite data.
Abstract: A method and apparatus for tuning control loop parameters in a motion control system, is provided. In one embodiment, tuning of the proportional and integral gains of a servocontroller's velocity loop compensator is provided, as well as tuning of the cutoff frequencies of the servocontroller's low pass filters. In this embodiment, random noise excitation is added to the velocity command during a plurality of movement types for a machine tool axis. During each movement type, frequency response measurements are taken. Then, a composite frequency response can be selected by concatenating portions of the various frequency response measurements, so as to simulate a worst case scenario for the machine tool axis. From this composite response, an open loop response can be calculated and displayed, as well as bandwidth, phase margin, and gain margin values. The user can then enter the compensator parameters which were used when this data was taken, as well as proposed parameters. The system can automatically predict, or simulate, the effects of the proposed parameters on bandwidth, gain margin, and phase margin, based upon the composite data. Accordingly, the user need not actually try out the proposed parameters on the machine. Moreover, the simulated responses for the proposed parameters are based upon actual frequency response data taken during actual operating conditions of the system, and, accordingly, the inaccuracies of using mathematical assumptions are avoided.

Proceedings ArticleDOI
03 Oct 1999
TL;DR: In this paper, an FFT was used to measure the resonant frequency of a dual inertia spring system and tune an infinite impulse response notch filter to reduce the torsional oscillations in both the motor and load velocities.
Abstract: This paper presents a technique to measure the resonant frequency of a dual inertia spring system using an FFT. The resonant frequency measurement and anti-resonant frequency calculation are utilized to tune an infinite impulse response notch filter to reduce the torsional oscillations in both the motor and load velocities. The simplicity and easy tuning of the filter makes it practical to implement in a DSP. The baseband performance of a resonant system would greatly improve.

Proceedings ArticleDOI
13 Jun 1999
TL;DR: In this paper, a novel lowpass filter with a uniplanar, compact photonic band-gap structure etched in the ground plane has been proposed and demonstrated, which has a deep attenuation and spurious-free response.
Abstract: A novel lowpass filter with a uniplanar, compact photonic band-gap structure etched in the ground plane has been proposed and demonstrated. This new filter has a deep attenuation and spurious-free response. A drain mixer using this novel filter suppresses the LO leakage by over 10 dB compared to a reference mixer with a conventional filter.

Journal ArticleDOI
TL;DR: In this paper, an efficient cascaded integrator-comb (CIC)-based decimation filter for programmable downconverter is proposed, which is a cascade of a CIC filter, an interpolated second-order polynomials (ISOP), a modified halfband filter (MHBF), and a programmable finite impulse response filter.
Abstract: Interpolated second-order polynomials (ISOPs) are proposed to design efficient cascaded integrator-comb (CIC)-based decimation filters for a programmable downconverter. It is shown that some simple ISOPs can effectively reduce the passband droop caused by CIC filtering with little degradation in aliasing attenuation. In addition, ISOPs are shown to be useful for simplifying halfband filters that usually follow CIC filtering. As a result, a modified halfband filter (MHBF) is introduced which is simpler than conventional halfband filters. The proposed decimation filter for programmable downconverter is a cascade of a CIC filter, an ISOP, MHBFs, and a programmable finite impulse response filter. A procedure for designing the decimation filter is developed. In particular, an optimization technique that simultaneously designs the ISOP and programmable FIR filters is presented. Design examples demonstrate that the proposed method leads to more efficient programmable downconverters than existing ones.

Patent
12 Nov 1999
TL;DR: In this paper, an integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit is described, where the filters are tuned using local oscillators to tune a substitute filter, and frequency scaling during filter component values to those of the filter being tuned.
Abstract: An integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit is described. A receiver front end provides programmable attenuation and a programmable gain low noise amplifier. Frequency conversion circuitry advantageously uses LC filters integrated onto the substrate in conjunction with image reject mixers to provide sufficient image frequency rejection. Filter tuning and inductor Q compensation over temperature are performed on chip. The filters utilize multi track spiral inductors. The filters are tuned using local oscillators to tune a substitute filter, and frequency scaling during filter component values to those of the filter being tuned. In conjunction with filtering, frequency planning provides additional image rejection. The advantageous choice of local oscillator signal generation methods on chip is by PLL out of band local oscillation and by direct synthesis for in band local oscillator. The VCOs in the PLLs are centered using a control circuit to center the tuning capacitance range. A differential crystal oscillator is advantageously used as a frequency reference. Differential signal transmission is advantageously used throughout the receiver.

Patent
David G. Cason1
16 Feb 1999
TL;DR: In this paper, a nonlinear two-filter voice detection algorithm was proposed, in which one filter has a low time constant (the fast filter) and one filter had a high time constant(the slow filter).
Abstract: A system for detection of voice activity in a communications signal, employing a nonlinear two filter voice detection algorithm, in which one filter has a low time constant (the fast filter) and one filter has a high time constant (the slow filter). The slow filter serves to provide a noise floor estimate for the incoming signal, and the fast filter serves to more closely represent the total energy in the signal. The absolute value of incoming data is presented to both filters, and the difference in filter outputs is integrated over each of a series of successive frames, thereby giving an indication of the energy level above the noise floor in each frame of the incoming signal. Voice activity is detected if the measured energy level for a frame exceeds a specified threshold level. Silence (e.g., leaving only noise) is detected if the measured energy level for each of a specified number of successive frames does not exceed a specified threshold level. The system enables voice activity to be distinguished from common noise such as pops, clicks and low level cross-talk.

Journal ArticleDOI
TL;DR: A voltage-mode low-pass, band- pass, and high-pass filter with single Input and three outputs, employing only two compound current conveyors, two grounded capacitors, and three resistors, is proposed.
Abstract: A voltage-mode low-pass, band-pass, and high-pass filter with single Input and three outputs, employing only two compound current conveyors, two grounded capacitors, and three resistors, is proposed. The proposed circuit offers the following advantageous features: realization of voltage-mode low-pass, band-pass, and high-pass filter responses from the same configuration; no requirement of critical component matching conditions; employment of grounded capacitors ideal for integration; low sensitivity characteristics; and simpler configuration due to the use of only two compound current conveyors.

Patent
Juha Ellä1
28 Dec 1999
TL;DR: In this article, a lattice configuration was proposed for a bulk acoustic wave filter structure, in which two of the filters have a different area than other two for creating very steep passband edges in the frequency response of the filter.
Abstract: The invention relates to resonator structures of radio communication apparatus, especially bulk acoustic wave filter structures. According to the invention, a bulk acoustic filter structure is constructed with a lattice configuration, in which two of the filters have a different area than other two for creating very steep passband edges in the frequency response of the filter. Preferably, the filter structure further comprises a second lattice structure for increasing the stopband rejection ratio of the filter structure, and for allowing the use of a simple mechanical structure. The cascaded configuration allows the construction of the filter structure in such a way, that the electrodes of the input and output port are at the same layer, thereby removing the need to make vias in the piezoelectric layer, which results in considerable simplification of the manufacturing process. Preferably, an acoustical mirror structure is used as the acoustical isolation in order to further simplify the mechanical structure of the filter structure.

Patent
19 Apr 1999
TL;DR: In this paper, a chopper stabilized amplified filter circuit is used to generate an offset compensation signal that corresponds to the residual offset within the output signal resulting from the amplifying and filtering of the input data signal.
Abstract: A switched capacitor filter circuit having reduced offsets and providing offset compensation when used in a closed feedback loop includes a chopper stabilized amplified filter circuit which amplifies and low pass filters its input data signal to produce an output signal with an out of band signal frequency component which is at the chop signal frequency and represents an offset and 1/f noise of the chopper stabilized amplified filter circuit. An output switched capacitor filter circuit which is synchronized with the chopper stabilized amplified filter circuit filters this signal with a stopband filter frequency response that virtually eliminates such out of band signal frequency component. When used in a closed feedback loop, this filtered signal is used to generate an offset compensation signal that corresponds to the residual offset within the output signal resulting from the amplifying and filtering of the input data signal. This offset compensation signal is then added to the input data signal prior to its amplification and filtering by the chopper stabilized amplified filter circuit.

Proceedings ArticleDOI
28 Jun 1999
TL;DR: The proposed scheme relies on the generalized Laplacian pyramid, which is a non-dyadic band-pass analysis structure unconstrained from the ground scales of the imaged data: for a p/q>1 ratio only one low-pass filter with cut-off at 1/p of the spatial frequency content is needed.
Abstract: Presents a general and formal solution to the problem of multisensor image data fusion and applies its results to a specific case study concerning multi-spectral observations: Landsat TM (30 m resolution) and MOMS-2P (18 m). The proposed scheme relies on the generalized Laplacian pyramid, which is a non-dyadic band-pass analysis structure unconstrained from the ground scales of the imaged data: for a p/q>1 ratio only one low-pass filter with cut-off at 1/p of the spatial frequency content is needed. Filter design is easy and noncritical for performances. Thus, the pyramid method is simple to be designed and generalized to images having whatsoever ground resolution, as in most applications involving new-generation sensors.

Journal Article
TL;DR: The Vold-Kalman filter as discussed by the authors allows for the high performance simultaneous tracking of orders in systems with multiple independent shafts, and using multiple tacho references, waveforms, as well as amplitude and phase may be extracted without the beating interactions that are associated with conventional methods.
Abstract: In this paper the filter characteristics of the Vold-Kalman Order Tracking Filter are presented. Both frequency response as well as time response and their time-frequency relationship have been investigated. Some guidelines for optimum choice of filter parameters are presented. The Vold-Kalman filter allows for the high performance simultaneous tracking of orders in systems with multiple independent shafts. With this new filter and using multiple tacho references, waveforms, as well as amplitude and phase may be extracted without the beating interactions that are associated with conventional methods. The Vold-Kalman filter provides several filter shapes for optimum resolution and stopband suppression. Orders extracted as waveforms have no phase bias, and may hence be used for playback, synthesis and tailoring.

Patent
19 Feb 1999
TL;DR: A tunable optical signal device and method of using the same having at least two filter elements, each of said filter elements being made of a material having an adjustable parameter, wherein the adjustable parameter is maintained at slightly different values for adjacent filter elements as mentioned in this paper.
Abstract: A tunable optical signal device and method of using the same having at least two filter elements, each of said filter elements being made of a material having an adjustable parameter, wherein the adjustable parameter is maintained at slightly different values for adjacent filter elements.

Patent
31 Aug 1999
TL;DR: In this paper, a multi-band transceiver having a receiver portion and a transmitter portion includes a direct conversion receiver system for directly downconverting a signal to baseband frequencies.
Abstract: A multi-band transceiver having a receiver portion and a transmitter portion, wherein the receiver portion includes a direct conversion receiver system for directly downconverting a signal to baseband frequencies. The direct conversion receiver system includes a frequency translator having first and second inputs and an output. A first signal at a first frequency is applied to the first input. A second signal having a second frequency is applied to the second input. The first frequency is preferably an nth order subharmonic of the second frequency, wherein n is an integer greater than 1. A low pass filter is integral with or inherent to the first input, and a high pass filter is integral with or inherent to the second input. The corner frequencies of both the low pass and high pass filters is above the first frequency and below the second frequency.

Journal ArticleDOI
TL;DR: In this article, regression filters are used for ground clutter filtering with a class of cancelers that use regression, resulting in similar or better performance than the fifth-order elliptic filter implemented in the WSR-88D.
Abstract: This paper explores ground clutter filtering with a class of cancelers that use regression. Regression filters perform this task in a simple manner, resulting in similar or better performance than the fifth-order elliptic filter implemented in the WSR-88D. Assuming a slowly varying clutter signal, a suitable projection of the composite signal is used to notch a band of frequencies at either side of zero Doppler frequency. The complexity of this procedure is reduced by using a set of orthogonal polynomials. The frequency response of the resulting filter is related to the number of samples in each input block and the maximum order of approximating polynomials. Through simulations, it is demonstrated that the suppression characteristic of this filter is better than that of step-initialized infinite impulse response filters, whereby transients degrade the theoretical frequency response. The performance of regression filters is tested with an actual weather signal, and their efficiency in ground clutt...

Journal ArticleDOI
TL;DR: In this paper, a low-voltage channel selection analog front end with continuous-time low-pass filters and on-chip tuning for a receiver in an IS-95 cellular phone is described.
Abstract: This paper describes a low-voltage channel selection analog front end with continuous-time low-pass filters and on-chip tuning for a receiver in an IS-95 cellular phone. The filters were realized as balanced seventh-order elliptical g/sub m/C filters to achieve low current consumption. The transconductors were realized by using second-generation current conveyors (CCII) and resistors to achieve good intermodulation distortion performance. A novel CCII circuit topology was developed to fulfil the low supply-voltage requirement. The cutoff frequency tuning was implemented with capacitance matrices and a time-domain master-slave tuning circuit.

Patent
30 Apr 1999
TL;DR: In this paper, a circuit arrangement and control thereof for igniting a HID lamp, for reducing the high frequency ripple superimposed on the low frequency rectangular waveform lamp current after ignition, and for increased circuit efficiency.
Abstract: A circuit arrangement and control thereof for igniting a high intensity discharge (HID) lamp, for reducing the high frequency ripple superimposed on the low frequency rectangular waveform lamp current after ignition, and for increased circuit efficiency. The high frequency ignition voltage is only applied to the lamp during ignition phase and is mainly generated by the second stage of the low pass (LP) filter. The first stage of the LP filter whose resonant frequency is below the second stage further attenuates the high frequency ripple current through the lamp in normal operation. The resulting lamp current is a low frequency rectangular wave with less than 10% high frequency ripple. Acoustic resonance is avoided. The inductor in the first stage of LP filter is operated in discontinuous current mode. Doing so, the active switches are in zero current switching (ZCS) to maximize the circuit efficiency.