Showing papers on "Butterworth filter published in 2000"

New cross-coupled filter design using improved hairpin resonators

Abstract: Stepped-impedance resonators have been thoroughly studied in this paper. Two equations for odd- and even-mode resonance are derived from a new network model. The size and resonant frequencies of the resonator could then be designed based on these two equations. A new resonator-embedded cross-coupled filter, constructed by stepped-impedance hairpin resonators and miniaturized hairpin resonators is presented. This new filter is very compact and has lower spurious response. A 0/spl deg/ feed structure, which adds two transmission zeros to the filter response, is also studied. The two zeros are so close to the passband that the selectivity and out-of-band rejection of the filter are significantly increased. The design has been verified by experiment results.

Widely programmable high-frequency continuous-time filters in digital CMOS technology

Abstract: We present design considerations for programmable high-frequency continuous-time filters implemented in standard digital CMOS processes. To reduce area, accumulation MOS capacitors are used as integrating elements. The filter design problem is examined from the viewpoint of programmability. To allow frequency scalability without deterioration of noise performance and of the frequency response shape, we employ a technique called "constant-capacitance scaling," which assures that even parasitic capacitances remain invariant when transconductors are switched in and out of the filter. This technique is applied to the design of a programmable fourth order Butterworth continuous-time filter with a bandwidth programmable from 60 to 350 MHz implemented in a 0.25-/spl mu/m digital CMOS process. The filter has a dynamic range of 54 dB, dissipates 70 mW from a 3.3-V supply, and occupies an area of 0.15 mm/sup 2/.

A compact semi-lumped low-pass filter for harmonics and spurious suppression

Abstract: A semi-lumped parallel resonance circuit was employed to design a very compact low-pass filter. The semi-lumped shunt arm consists of a capacitor and a transmission line section. In such an arrangement, two finite attenuation poles can be generated near the passband edge. As a result, the proposed filter enjoys sharper cutoff and fewer filter orders than those of the conventional low-pass filters. In addition, these two attenuation poles can be properly designed to suppress the second and third harmonics generated from power amplifier and frequency source. A low-temperature cofired-ceramic (LTCC) multilayer-ceramic (MLC) low-pass filter and a PCB low-pass filter with a 0402 chip capacitor were designed and tested. Experimental results demonstrate the capability of this filter in harmonics and spurious suppression.

Subband acoustic feedback cancellation in hearing aids

Abstract: A new subband feedback cancellation scheme is proposed, capable of providing additional stable gain without introducing audible artifacts. The subband feedback cancellation scheme employs a cascade of two narrow-band filters Ai(Z)and Bi(Z)ng with a fixed delay, instead of a single filter Wi(Z)and a delay to represent the feedback path in each subband. The first filter, Ai(Z), is called the training filter, and models the static portion of the feedback path in ith subband, including microphone, receiver, ear canal resonance, and other relatively static parameters. The training filter can be implemented as a FIR filter or as an IIR filter. The second filter, B?I?(Z), is called a tracking filter and is typically implemented as a FIR filter with fewer taps than the training filter. This second filter tracks the variations of the feedback path in the i?th? subband caused by jaw movement or objects close to the ears of the user.

Image interpolation and decimation using a continuously variable delay filter and combined with a polyphase filter

Abstract: A filter structure is provided that facilitates the use of the filter as either a continuous delay Farrow filter or a selectable delay polyphase filter. The less complex polyphase filter is used when the desired scale substantially corresponds to a defined phase of the polyphase filter, or when time or power is not available to achieve the desired scale exactly; otherwise, the continuous delay Farrow filter is used. By providing an ability to switch to a continuous delay, the number of stages of the polyphase filter can be reduced. Additionally, an inversion of a Farrow filter is presented that provides for a continuous delay decimation filter with substantially reduced computational complexity compared to a direct embodiment of a Farrow filter. This inverted filter is also configurable as a polyphase filter, to provide selectable scale-resolution capabilities.

Compact dual-mode elliptic-function bandpass filter using a single ring resonator with one coupling gap

Abstract: A novel microwave dual-mode elliptic-function bandpass filter with one coupling gap structure is proposed. This filter has a 4.7% bandwidth at 1.805 GHz with 1.73 dB insertion loss. The filter provides less field perturbation of the ring resonator than conventional filters. Without the output coupling gap between the feed line and the ring resonator, a low insertion loss has been obtained. This compact, high performance filter is useful for mobile and personal communication systems.

Design of digital filters and filter banks by optimization: A state of the art review

Abstract: The many advancements in the area of numerical optimization in conjunction with the ever-increasing power of computers have made optimization-based filter design an increasingly important field of research. In this paper, several recent optimization methods for the design of FIR and IIR digital filters and filter banks are reviewed.

Multifunctional translinear-C current-mode filter

Abstract: A multifunctional current mode filter using three current controlled conveyors and two grounded capacitors is described. The filter realizes high pass, band pass and low pass second order current transfer functions, and provides independent pole-ω 0, and pole-Q 0 tuning through external current control. The filter also displays low incremental parameter sensitivities. The simulation results on the filter support the theory.

Robust Signal Quality Monitoring and Detection of Evil Waveforms

Abstract: The ability to monitor and detect problematic distortions in the received GPS-SPS signal is a task of critical importance. Detection of these satellite signal anomalies or “evil waveforms” can be accomplished using detailed monitoring of the correlation peak. Using the “Second- Order Step” threat model for evil waveforms, previous analysis has attempted to show that monitoring sufficient to satisfy GBAS and SBAS requirements for Category I precision approaches may be obtained from a receiver design that requires minimal modifications to existing GPS hardware. A “robust” signal quality monitor (SQM) design methodology has been developed for this purpose. This report evaluates the best current evil waveform (EWF) signal quality monitoring configuration, SQM2b, using this methodology. First, it compares the maximum regional pseudorange errors (PRE’s), computed at varying elevation angles, to the maximum allowable pseudorange (MERR) errors. Second, it examines the sensitivity of these results to differential group delay variations of up to 150ns. In addition, it examines the effects of user filter magnitude response. Using SQM2b, neither group delay variations nor changing MERR’s were found to pose a threat to standard E-L correlators in any of the four protected regions. However, they did induce some small, unacceptable ∆∆ receiver errors. To account for this, a “notch” was removed from the critical protected region to exclude those unprotectable ∆∆ receiver configurations. It was also shown that user PRE’s were sensitive to transition bandwidth variations. To mitigate this sensitivity it was recommended that the minimum airborne filter transition bandwidth be upper-bounded by that of the 6th-order Butterworth filter.

Insensitive current-mode universal filter using dual output current conveyors

Abstract: A new current-mode universal filter with single input and three outputs employing only three dual output current conveyors and five grounded passive elements is presented. The proposed filter realizes three filter functions simultaneously, all at high impedance outputs. No component matching is required and all the passive and active sensitivities are low. Furthermore, the filter can also realize the notch and all-pass responses. Orthogonal control of the natural angular frequency and the quality factor is achieved.

A 16-bit 250-kHz delta-sigma modulator and decimation filter

Abstract: This paper describes a delta-sigma analog-to-digital converter (ADC) capable of converting input frequencies up to 250 kHz. It consists of a fifth-order switched-capacitor delta-sigma modulator and a decimation filter. Various design optimizations in the modulator are presented. The decimation filter consists of a comb filter followed by a novel, highly efficient and scalable finite impulse response filter. The ADC was implemented in 0.6-/spl mu/m CMOS technology. It achieves a dynamic range of 94 db.

Electronically tunable current-mode active-only biquadratic filter

Abstract: This paper presents a realization of current-mode active-only filter. The proposed filter is constructed employing operational amplifiers and operational transconductance amplifiers (OTAs). The circuit can realize biquadratic transfer function, and the circuit characteristics can be electronically tuned through adjusting the transconductance gains of the OTAs. An example is given together with simulated result by PSPICE. The circuit configuration is very suitable for implementation in both bipolar or CMOS technologies.

Active polyphase filter with transconductor cross-coupling of filter sections

Abstract: The invention is an improved implementation of an active-RC polyphase band-pass filter with transconductor cross-coupling between filter sections. The polyphase filter has first to fourth inputs, first to fourth outputs, two filter sections, and a block of transconductor pairs. The four input signals to the polyphase filter succeed one another in phase by 90 degrees. The two filter sections have reactances comprised of active balanced operational amplifiers with matched capacitors in their feedback loops. The block of transconductor pairs is coupled between corresponding reactances of each filter. The transconductance of each transconductor pair is set as the product of a desired radian center frequency and the capacitance of the corresponding matched capacitors. In the preferred embodiment, the transconductors are Gm cells and the transconductance of at least one Gm cell is field adjustable. The filter sections of the preferred embodiment can be a pair of low-pass third-order active-RC gaussian filters or a pair of low-pass sixth-order active-RC gaussian filters.

Theory and design of a class of cosine-modulated non-uniform filter banks

Abstract: In this paper, the theory and design of a class of PR cosine-modulated nonuniform filter bank is proposed. It is based on a structure previously proposed by Cox (1986), where the outputs of a uniform filter bank are combined or merged by means of the synthesis section of another filter bank with smaller channel number. Simplifications are imposed on this structure so that the design procedure can be considerably simplified. Due to the use of cosine modulated filter banks as the original and recombination filter banks, excellent filter quality and low design and implementation complexities can be achieved. Problems with these merging techniques such as spectrum inversion, equivalent filter representations and protrusion cancellation are also addressed. As the merging is performed after the decimation, the arithmetic complexity is lower than other conventional approaches. Design examples show that PR nonuniform filter banks with high stopband attenuation and low design and implementation complexities can be obtained by the proposed method.

Accurate orientation for airborne mapping systems

Abstract: Stringent requirements on the accuracy of attitude determi- nation are currently a major challenge for strapdown INS/GPS integration, which is at the core of self-contained airborne remote sensing and mapping systems. This paper reviews the error models for INS/GPS integration and focuses i n detail on designingfiltering methodsfor improvingattitudeaccuracyin the bandwidth in which an inertial system does not benefit from frequent GPS position/velocity updates. Several fltering methods are designed based on the spec- tral analysis of the raw inertial signal in a dynamic environ- ment. These include a spectral technique for dither spike removal and a class of low-pass finite-impulse-response (FIR] filters operatinginforward/backward mannerfor achieving zero phase distortion. The orientation performance of the whole system with different filters i s evaluated b y comparing it to the "true" attitude information provided by a photo- grammetric block adjustment. Results show clearly that the choice of an appropriatefilter is decisivefor attitude accuracy. Overall, the INS/GPS integration combined with the most suitable pre-filtering method agrees with the external orien- tationreferenceto0.005"(19')RMS overthewholetestperiod, while the flight-line consistency is typically 0.003" (1U')RMS. The best filter in the comparison has an i?MS seven times smaller than the Butterworth filter which i s frequently applied i n the industrial designs of INS.

Algorithm for the Parameters of Double Tuned Filter and the Third Order Filter

Abstract: Algorithm for the parameters of double tuned filter and the third order filter was briefly introduced.Different from usual interactive method,this algorithm is an accurate analytic method and has been successfully applied in practical engineering.

A channel selection filter for a WCDMA direct conversion receiver

Abstract: A channel selection filter for a WCDMA direct conversion receiver is described. The 5th order Chebyshev low-pass filter with a 0.01dB ripple has the -3dB frequency close to 2MHz. The circuit uses two on-chip high-pass filters for offset compensation. The real pole of the prototype is realized with a passive RC element which is the first stage in the filter. The filter achieves +25dBV out-of-band IIP3, + 77dBV out-of-band IIP2 and 9.4nV/√Hz input-referred noise density. The maximum gain is 67.7dB and the circuit draws 4.3mA from a 2.7V supply.

First-order allpass sections-based current-mode universal filter using ICCIIs

Abstract: An inverting type current conveyor (ICCII) is presented and its usefulness in active filter synthesis illustrated by presenting a new current-mode universal filter using this element. The universal filter configuration based on the implementation of first-order allpass sections employs the absolute minimum number of passive and active components and hence leads to a filter circuit with very simple implementation.

A simplified analysis for high power microwave bandpass filter structures

Abstract: A method for computing the peak resonator voltages inside a bandpass filter and multiplexer is introduced based on the general cross-coupled lumped element prototype network of a filter. In this method, the resonator voltages are computed based on the circuit model and are shown to be related to the peak filter cavity voltages through an appropriate scale factor. Being circuit theoretical the method is simple and is considerably faster than techniques based on rigorous field theoretic tools. The proposed method is verified using direct calculation of voltages by commercial FEM software. This voltage estimation procedure would considerably simplify multipaction and power handling studies of critical filter based structures.

Fault detection methodology and BIST method for 2nd order Butterworth, Chebyshev and Bessel filter approximations

Abstract: This work proposes a new BIST scheme for 2nd order Butterworth, Chebyshev and Bessel filter approximations, using the transient analysis of simple input test vectors. A functional approach for fault modeling in 2nd order filters is presented and the transient response method is used for fault detection. The approach considers the filter as a 2nd order dynamic system where /spl omega/c and Qp deviations are faults to be detected. The peak time is the observed parameter that is evaluated in order to verify the filter correctness. The obtained results are very promising since all of /spl omega/c and Qp deviations as well as 100% of passive components are detected for this BIST scheme.

An analog CMOS high-speed continuous-time FIR filter

Abstract: A new analog CMOS high-speed continuous-time FIR filter is presented. The filter has five taps with 6- bit weights and operates at an effective sampling rate of 606 MS/s. The circuit was fabricated in a 0.5 µm CMOS process and dissipates 51 mW while operating from a single 3 volt supply.

A class of two-channel approximately perfect reconstruction hybrid analog/digital filter banks

Abstract: This paper introduces a class of two-channel hybrid analog and digital filter banks which find application in high-speed A/D conversion. The distortion caused by mismatch errors in time-interleaved A/D converters is attenuated using hybrid filter banks. The proposed class of filter banks satisfy perfect reconstruction within certain tolerances that can be controlled in the filter design. The filter design uses both linear and nonlinear programming.

Embedded programmable filter for disk drive velocity control

Abstract: A disk drive having a motor and a velocity control loop, which includes a frequency detector and a filter. The filter includes a filter section and an accumulator. The filter is programmable in that filter coefficient(s) are dynamically received by the filter section. One embodiment of the filter section is an infinite impulse response filter. One embodiment of the filter is a digital integrated circuit. A method for compensating a control loop by infinite impulse response filtering and accumulating. The control loop may be a position, velocity, acceleration or force control loop. A programmable digital integrated circuit for compensating a velocity control loop having a filter section cascaded with an accumulator. The integrated circuit may include memory for storing filter coefficient(s) for the filter section, thereby not requiring external components.

Top-down design of a switched-current video filter

Abstract: A case study for the design of switched-current filters is presented. While the emphasis is on the step-by-step numerical design of a video filter, the design flow is applicable to any switched-current filter. The chosen design example is a low pass elliptic ladder filter with the following specification: passband 0.5 dB equiripple, stop-band attenuation > 30 dB, –3 dB frequency of 8 MHz, sampling frequency of 80 MHz, signal-to-noise ratio of 60 dB. All aspects of the design are covered from filter specification, through filter synthesis, circuit definition and finally transistor sizing for CMOS implementation.

Band pass filter with improved group delay

Abstract: An electrical signal is applied to a band pass filter, a first notch filter, and a second notch filter in any order. The center frequencies of the notch filters straddle the pass band of the band pass filter. The notch filters improve group delay and steepen the skirts of the response curve of the band pass filter.

Determination of optimal filter parameters for filtering kinematic walking data using butterworth low pass filter

Abstract: INTRODUCTION: Noise in biomechanical displacement data are often reduced by digital filter routines. In literature the cross-validated quintic spline from Woltring (1986) and the Butterworth low pass filter are commonly used. Challis (1999) recently suggested a method for determining the optimal cut-off frequency of Butterworth low pass filters. This method is based on a combination of residual analysis and autocorrelation. The optimization of the filter order, however, is not discussed by Challis. Thus the purpose of this study was to determine optimal filter parameters (frequency and order) of a Butterworth low-pass filter using the approach of Challis applied to a kinematic data set in walking.

Method and system for linearization of MOEMS tunable filter scan

Abstract: One problem that arises in the context of controlling tunable filters, and more specifically, Fabry-Perot tunable filters concerns the control algorithms for these MOEMS devices. An optical filter system comprises a tunable optical filter that scans a pass band across a signal band to generate a filtered signal. A filter tuning voltage generator generates a tuning voltage to the optical tunable filter. A photodetector generates an electrical signal in response to the filtered signal. Finally, a controller, that is responsive to the photodetector, triggers the filter tuning voltage generator. To increase the ease at which the results of a scan of the signal band of a WDM signal can be analyzed and improve spectral resolution, the change in the pass band of the tunable filter as a function of time is linearized in frequency or wavelength. This is achieved through the use of essentially an arbitrary waveform generator as the filter tuning voltage generator. The generator is programmed with an inverse of the filter's tuning characteristic.

Optimum Laguerre filter design technique for sigma-delta demodulators

Abstract: As an alternative to conventional FIR filters, an optimal IIR filter architecture based on orthonormal Laguerre functions is proposed for Sigma-Delta (/spl Sigma/-/spl Delta/) demodulators. A Laguerre IIR filter design methodology is presented via the optimization of a quadratic function subject to a linear and a quadratic constraint. An efficient procedure to perform the optimization is discussed. The proposed IIR filter is easy to implement because it needs only a small number of components and therefore well suited for VLSI implementations. The impact of the selection of filter pole on the filter stability and phase linearity is discussed. The robustness issue of the Laguerre IIR filter is also addressed.

Optimization of the parameters of a pre-equalization low pass filter for a read channel

Abstract: A method is provided for defining programmed values of the boost and cut-off frequency parameters of a low pass filter of pre-equalization, of a read channel for a magnetic medium mass memory device, to ensure optimal functioning conditions of the adaptive filter of final equalization. The method includes pre-programming instantaneous digital values of the boost and cut-off frequency parameters of the low pass filter of pre-equalization for each magnetic medium, as a function of purposely sensed instantaneous operating parameters of the adaptive filter that carries out the definitive equalization of the signal during a trim scanning of the magnetic medium.