Showing papers on "Butterworth filter published in 2002"

Synthesis of direct-coupled-resonators bandpass filters for WDM systems

Abstract: A simple technique for the exact synthesis of selective bandpass filters for wavelength division multiplexing (WDM) systems is presented. The filters consist of direct-coupled ring resonators or cascaded Bragg gratings. The proposed technique permits the calculation of the physical dimensions of the optical structures given the desired frequency response of the filter in terms of bandwidth, free spectral range, out-of-band rejection, and frequency characteristic. The technique, explained in detail for Butterworth and Chebyshev frequency responses, is exact, uses closed-form formulae, and is physically well based. The resulting devices are very compact, have a high out-of-band attenuation, and are suitable for high-density integrated optics. Several filters for applications such as channel add-drop, channel selection, demultiplexing, multichannel filtering, and interleavers are designed, analyzed, and discussed in the paper.

A medium-voltage transformerless AC/DC power conversion system consisting of a diode rectifier and a shunt hybrid filter

Abstract: This paper proposes a 3.3-kV transformerless AC-to-DC power conversion system consisting of a three-phase six-pulse diode rectifier and a shunt hybrid filter. The hybrid filter is formed by a single tuned LC filter per phase and a small-rated three-phase active filter, which are directly connected in series without any matching transformer. The required rating of the active filter is much smaller than that of a conventional standalone active filter be. In addition, no additional switching-ripple filter is required for the hybrid filter because the LC filter functions not only as a harmonic filter tuned at the seventh harmonic frequency but also as a switching-ripple filter around 10 kHz. Experimental results obtained from a 200-V 5-kW laboratory system and simulation results of a 3.3-kV 300-kW system confirm the validity and effectiveness of the system.

Performance of a planar filter using a 0/spl deg/ feed structure

Abstract: The advantage of using a 0/spl deg/ feed structure in filter design is that two extra transmission zeros are created in the stopband while the passband response remains unchanged. This feed structure is analyzed by using transmission matrices. A new lumped-circuit model for a coupled resonator filter is then proposed to take into account the effects of this feed structure. Finally, the feed structure is applied to the design of a cross-coupled filter. All the theoretical analysis and design procedures have been successfully verified by experiment results.

A tunable filter and method of tuning a filter

Abstract: A bandpass filter is tuned by converting the filter into an oscillator using a negative resistance circuit, tuning the oscillator by using conventional tuning techniques such as tuning a varactor via a phase locked loop, sampling and holding the tuning signal and switching off the negative resistance circuit to convert the oscillator back into a bandpass filter.

A CMOS highly linear channel-select filter for 3G multistandard integrated wireless receivers

Abstract: A new approach for designing digitally programmable CMOS integrated baseband filters is presented. The proposed technique provides a systematic method for designing filters exhibiting high linearity and low power. A sixth-order Butterworth low-pass filter with 14-bit bandwidth tuning range is designed for implementing the baseband channel-select filter in an integrated multistandard wireless receiver. The filter consumes a current of 2.25 mA from a 2.7-V supply and occupies an area of 1.25 mm/sup 2/ in a 0.5-/spl mu/m chip. The proposed filter design achieves high spurious free dynamic ranges (SFDRs) of 92 dB for PDC (IS-54), 89 dB for GSM, 84 dB for IS-95, and 80 dB for WCDMA.

Ultra-selective 22-pole 10-transmission zero superconducting bandpass filter surpasses 50-pole Chebyshev filter

Abstract: An ultra-selective filter for third-generation (3G) and fourth-generation wireless application is presented. The demonstrated filter consists of 22 resonators and five cross couplings that produce ten transmission zeros. The filter was designed at 1950-MHz center frequency with a 20-MHz bandwidth to meet existing 3G wireless applications. The measured filter data shows excellent selectivity, better than 30-dB/100-kHz skirt slopes, and 90 dB of rejection at 350 kHz from the band edge. This filter performance surpasses the performance of a 50-pole Chebyshev filter. In order to fit a large number of resonators into a limited wafer area, a new compact resonator was developed. The filter was fabricated using a YBCO thin film on a 2-in MgO wafer.

An efficient and simple method for designing prototype filters for cosine-modulated pseudo-QMF banks

Abstract: We present a new method to design prototype filters for conventional cosine-modulated pseudo-quadrature mirror filter (QMF) banks. This method is based on windowing, and sets the 3-dB cutoff frequency of the filter obtained at /spl pi//2M. In this way, the filter bank performance can be significantly improved compared to other existing design methods.

Optimum Compensation Method and Filter Cutoff Frequency in Myocardial SPECT: A Human Observer Study

Abstract: Attenuation, photon scatter, and distance-dependent collimator-detector response are major degrading factors in myocardial SPECT images. The current study investigated whether compensation for these factors improves perfusion defect detectability, and compared the results for human observers with a previous study using a mathematical observer. Methods: Four methods were investigated: attenuation compensation (AC); attenuation and detector response compensation; attenuation and scatter compensation; and attenuation, detector response, and scatter compensation (ADSC). For ADSC, 4 three-dimensional postreconstruction Butterworth filter cutoff frequencies were investigated for a pixel size of 0.62 cm: 0.12, 0.14, 0.16, and 0.22 pixel−1. Five observers read images reconstructed using the 4 compensation methods. Receiver operating characteristics (ROC) analysis was used to determine the area under the ROC curve in each treatment studied. Results: Reconstruction methods that incorporated scatter and detector response compensation had higher indices of detectability than AC alone. Over the range studied, a filter cutoff frequency of 0.14 pixel−1 was optimal. A comparison of human observer results with an earlier channelized Hotelling observer study performed with the same images showed excellent agreement in trend and ranking of defect detectability. Conclusion: Compensation for detector response and scatter improves defect detectability compared with AC alone, although detectability may depend on phantom population choice and noise level. An optimal filter cutoff was found that is lower than what is typically used in a clinical setting. The channelized Hotelling observer is a good predictor of human observer performance and may reduce the need for tedious, time-consuming studies with human observers.

A high-speed, programmable, CSD coefficient FIR filter

Abstract: A new high-speed, programmable FIR filter is presented, which is a multiplierless filter with CSD encoding coefficients. We propose a new programmable CSD encoding structure to make CSD coefficients programmable. Compared with the conventional FIR structure with Booth multipliers, this coding structure improves the speed of filter and decreases the area. We design a 10-bits, 18-taps video luminance filter with the presented filter structure. The completed filter core occupies 6.8 /spl times/ 6.8 mm of silicon area in 0.6 /spl mu/m 2P2M CMOS technology, and its maximum work frequency is 100 MHz.

Frequency spectrum based low-area low-power parallel FIR filter design

Abstract: Parallel (or block) FIR digital filters can be used either for high-speed or low-power (with reduced supply voltage) applications. Traditional parallel filter implementations cause linear increase in the hardware cost with respect to the block size. Recently, an efficient parallel FIR filter implementation technique requiring a less-than linear increase in the hardware cost was proposed. This paper makes two contributions. First, the filter spectrum characteristics are exploited to select the best fast filter structures. Second, a novel block filter quantization algorithm is introduced. Using filter benchmarks, it is shown that the use of the appropriate fast FIR filter structures and the proposed quantization scheme can result in reduction in the number of binary adders up to 20%.

Efficient excitation quantization in noise feedback coding with general noise shaping

Abstract: In a Noise Feedback Coding (NFC) system having a corresponding ZERO-STATE filter structure, the first ZERO-STATE filter structure including multiple filters, a method of producing a ZERO-STATE response error vector. The method includes: (a) transforming the first ZERO-STATE filter structure to a second ZERO-STATE filter structure including only an all-zero filter, the all-zero filter having a filter response substantially equivalent to a filter response of the ZERO-STATE filter structure including multiple filters; and (b) filtering a VQ codevector with the all-zero filter to produce the ZERO-STATE response error vector corresponding to the VQ codevector.

Low-power CSD linear phase FIR filter structure using vertical common sub-expression

Abstract: A high-speed/low-power canonic signed digit (CSD) linear phase finite impulse response (FIR) filter structure using vertical common sub-expression is proposed. In the conventional linear phase CSD filter, the horizontal common sub-expression method (see Hartley, 1996) has been widely utilised due to the inherent symmetrical filter coefficients. However, use has been made of the fact that the most significant bits of adjacent filter coefficients in the linear phase filter are also equal since they have mostly similar values. Through the example, it is shown that the proposed structure is more efficient in the case where bit precision of implementation is lower.

Directly tuned filter and method of directly tuning a filter

Abstract: A Method for filter tuning using direct digital sub-sampling is provided. The tuning is accomplished in the digital domain by determining the filter characteristics from the shape of the transfer function. The input signal (1) is passed through the filter (3) and is then sub-sampled by and Analog-to-digital Converter (ADC) (5). The sub-sampled signal (6) is then processed in the digital domain using a digital circuit (7) that is used to determine the center frequency (Fc) and Quality factor (Q) and/or other important filter parameters. The Fc, Q and/or other important filter parameters are then adjusted by generating digital control signals (8) that can be converted to analog signals (10) using Digital-to-analog Converters (DACs) (9).

New wide-band DC-block cymbal bandpass filter

Abstract: A new low-loss dc-blocking parallel-cascaded bandpass filter is presented. The filter is much easier to use and fabricate, more compact, and simpler to design than the conventional end- or parallel-coupled line filters. The filter has a wide passband with a 2:1 voltage standing-wave ratio bandwidth of around 10% and an insertion loss of 0.5 dB at 10 GHz. Simulated results agree very well with experimental results.

An efficient approach for designing nearly perfect-reconstruction low-delay cosine-modulated filter banks

Abstract: A systematic multi-step approach is described for optimizing the stopband response of the prototype filter for low-delay critically sampled cosine-modulated filter banks in the least-mean-square sense subject to the maximum allowable aliasing and amplitude errors. In this approach, filter banks having several channels are designed by starting with a filter bank with a small number of channels. Then, the number of channels is gradually increased and a new prototype filter is optimized using the modified version of the prototype filter of the previous step as a good start-up solution. Several examples are included illustrating the flexibility of the proposed approach for making compromises between the required filter orders, the required filter bank delays, and the aliasing and amplitude errors. These examples show that by allowing very small amplitude and aliasing errors, the stopband performance of the resulting filter bank is significantly improved compared to the corresponding perfect-reconstruction filter bank. Alternatively, the filter bank delay and the order of the prototype filter can be significantly reduced while still achieving practically the same filter bank performance.

Integrated tunable filter for broadband tuner

Abstract: A tunable filter circuit includes a first differential pair biased by a first current, a second differential pair biased by a second current, a first capacitor and a second capacitor. The tunable filter circuit of the present invention can be configured as a bandpass filter or a bandstop filter by connecting the input voltage signal to different input nodes of the tunable filter circuit. The tunable filter circuit can be tuned by adjusting the values of the first current and the second current. In an alternate embodiment, frequency tuning is achieved either by switching capacitive loads or changing resistive impedances introduced at the emitter of the differential pairs, which also extends the input voltage range of the filter. This emitter resistance is implemented using MOS switches whose on-resistance can be controlled for a precise tuning within a large frequency range.

Current-mode leapfrog ladder filters using CDBAs

Abstract: In this paper, a possible realization of a current differencing buffered amplifier (CDBA) in the low-voltage operation is proposed A leapfrog simulation of the current-mode ladder network using the CDBAs as active circuit building blocks is then introduced In order to demonstrate that the CDBA considerably simplifies the leapfrog structure of the current-mode ladder filters, a fifth-order Butterworth low-pass filter and a sixth-order Chebyshev bandpass filter which require a minimum of active components will be presented PSPICE simulation results are employed to verify the correctness of the realization procedure

Apparatus and method for tuning a filter

Abstract: An apparatus and method for tuning a filter (11) with oscillator alignment for applications where the filter tuning signal (19,27) is generated independently of the local oscillator tuning signal and the tuning range is large, for example such as terrestrial and cable TV broadcasting (40 to 860MHz). The filter being adapted to a filter tuning modulation signal (25) having a first frequency (F1) and a second frequency (F2). Values of the output signal (28) are measured, a first value (S1) at the first frequency, and a second value (S2) at the second frequency, and a comparison signal (26) is generated in comparing the first value and the second value to adjust filter with the tuning control signal in response to the comparison signal, modulation signal and an approximate filter tuning signal to provide a desired signal at the output signal.

Realization of Current-Mode Third Order Butterworth Filters Employing Equal Valued Passive Elements and Unity Gain Buffers

Abstract: This paper describes current-mode third-order Butterworth filter topologies realized with unity gain active elements and minimum number of passive components. All capacitors and resistors are equal valued. The core of the circuit realizes HP, BP and LP functions easily. The filter exhibits high output impedance. Experimental results are included to verify theory.

Integrated low power channel select filter having high dynamic range and bandwidth

Abstract: A channel select filter circuit is disclosed using a current-mode transconductance-capacitor (gm-C) architecture, which is tuned by digitally controlled capacitor arrays. The main filter includes at least one transconductor-capacitor (gm-C) filter and a transresistance amplifier. A replica transconductor-capacitor (gm-C) filter and a phase detector are used to establish any phase shift in an input signal, and a state machine adjusts capacitor arrays in the the replica transconductor-capacitor (gm-C) filter and the at least one transconductor-capacitor (gm-C) filter in order to set a cut-off frequency of the channel select filter.

Surface acoustic wave device and communication apparatus

Abstract: A branching filter is a surface acoustic wave device in which a first filter having a relatively low bandpass frequency and a second filter having a relatively high bandpass frequency are connected to a common terminal. A junction-side resonator that is included in the second filter and that is connected in closest proximity to the common terminal is connected in series. The resonant frequency f sr of the junction-side resonator is higher than the center frequency f 0 , which is the center of the passband, of the second filter, and is more preferably set so as to satisfy the expression: f 0 +BW×0.2≦f sr ≦f 0 +BW×0.7, where BW is the bandwidth of the passband.

Polyphase filter with low-pass response

Abstract: A complex low-pass filter that reduces the influence of component mismatch. The filter includes a first filter section for effecting a first single pole transfer function and a second filter section for effecting a second single pole transfer function, where the first and the second single pole transfer functions collectively define a conjugate pair of poles. In higher order low-pass filters, an optimal cascade order follows a shoestring pattern.

A 57-dB image band rejection CMOS G/sub m/-C polyphase filter with automatic frequency tuning for Bluetooth

Abstract: A 7th order polyphase G/sub m/-C IF filter with automatic frequency tuning, implemented in a 0.35/spl mu/m CMOS process, is presented. The filter has a center frequency of 3MHz and a passband of 1MHz. The image band rejection is higher than 57dB, the stop band attenuation is at least 40dB. The in-band spurious free dynamic range is around 53dB. On-chip automatic frequency tuning provides more than 240% center frequency range (i.e., 1.6MHz-3.9MHz) of the filter. The filter is well suited for employment in the Bluetooth short-range radio.

Birefringent filter synthesis by use of a digital filter design algorithm

Abstract: We present an efficient method for designing birefringent filters comprising a number of birefringent sections with equal length and arbitrary orientation between two polarizers and for producing a specified spectral response in transmission. The method uses a digital filter design algorithm (i.e., the Remez algorithm) to determine an optimal polynomial approximation to obtain a specified finite impulse response, and a layer-peeling algorithm to calculate the filter structure parameters. The design procedure is demonstrated for a 14-section bandpass filter with sidelobes below -40 dB. The influence of errors in length and orientation of the birefringent sections on the filter's spectral response is also discussed.

Flat group-delay low-pass filter, mounting structure thereof, flat group-delay low-pass filter device, and optical signal receiver

Abstract: A flat group-delay low-pass filter includes a series element connected between an input terminal and an output terminal, and a shunt element with one end thereof grounded. Inductors define the series element, a parallel circuit including a capacitor and a series circuit including a resistor and a capacitor defines the shunt element. The flat group-delay low-pass filter thus eliminates the need for inserting a fixed attenuator to control the effect of reflections due to impedance mismatching between the filter and other components. The resulting flat group-delay low-pass filter and an optical signal receiver including the filter have very low manufacturing costs and component costs.

Gm-C tuning circuit with filter configuration

Abstract: A tuning circuit for an RF communications system and method includes a master block that outputs a control signal to a slave block. The master block can include a first filter having a high pass filter and a low pass filter that each receive the control signal, a first rectifier coupled to the high pass filter, a second rectifier coupled to the low pass filter, and a converter coupled to the first and second rectifiers that outputs the control signal. The first filter is preferably a gm-C poly-phase filter. Output signals of the gm-C poly-phase filter include high and low pass filtering signals resulting from similarly configured circuits so that the output signals have the same electrical characteristics, which results in an increased accuracy, for example, in a cut-off frequency.

Adaptive IIR filter design for single sensor applications

Abstract: The goal of this research was to investigate the theoretical design and physical implementation of a digital adaptive IIR filter to serve as an enhancement to the traditional active RC or passive RLC anti-aliasing filter. This all-digital filter will reside directly on the DSP engine. As explained in the paper, the adaptive IIR filter is designed to process an oversampled signal coming from a single sensor to reject noise in an acquisition system. Differentiation between the noise and the signal is obtained by exploiting the different auto-correlation functions of the two signals. In contrast to oversampling techniques employed in sampled data systems that are designed to relax the requirements of an analog anti-aliasing filter, this filter will track a signal in the frequency domain. Several power spectral density plots are given to illustrate the performance of the new filter. The results also indicate that the new filter performs well as compared to the Wiener filter in the stationary case.

Filter with improved intermodulation distortion characteristics and methods of making the improved filter

Abstract: Multi-stage electric filters with improved intermodulation-distortion characteristics and a method for designing such electric filters is provided. In general, the invention may include a multi-resonator electric filter in which one or more of the resonators have been intentionally designed to have a different IP and/or Q than the other resonators in the electric filter. In one case, the electric filters include a 4-resonator Chebyshev narrow pass-band filter with at least the first resonator (1105) having a Q and/or IP different from at least one other resonator (1110) in the filter. The filter thereby has improved IMD power over conventional designed filters while maintaining high Q. In a preferred embodiment the filter may include a superconducting material. The relative Q and IP of the respective resonators in the improved filter may depend on the relative strength of in-band and out-of-band signals. The performance and cost of the electric filter may be optimized by designing the filter to have a relative Q and IP required by the particular application.

Low power sigma delta decimation filter

Abstract: This paper presents an efficient design and implementation of a low power sigma delta digital decimation filter. We implement a low power decimation filter with a narrow transition finite impulse response (FIR) filter using a canonic signed digit number (CSD) system. We use multi-stage multi-rate signal processing to design and implement half-band filters and narrow transition band FIR filters. The decimation filter is designed using Simulink, DSP Blockset and simulated using Matlab. The FIR filter has been coded in Verilog and implemented using FPGA Xilinx 4000 technology. The power consumption of the proposed decimation filter is reduced by 67% compared to the conventional 4-stage comb-FIR architecture.