Showing papers on "Band-stop filter published in 2003"

Direct repetitive control of SPWM inverter for UPS purpose

Abstract: A novel repetitive controller directly combined with an open loop SPWM inverter is presented in this paper. To cope with the high-resonant peak of the open loop inverter that may cause instability, a zero-phase-shift notch filter other than the inverse transfer function of the inverter or a conventional second-order filter is incorporated in the controller. The proposed method has good harmonic rejection and large tolerance to parameter variations. To further reduce the steady-state error, a low-pass-filter Q(z) algorithm is applied. The DC bias problem is also taken into consideration and solved with the repetitive controller itself. The method is implemented with a digital signal processor and achieves low THD% (1.4%-1.7%) with nonlinear loads and fast error convergence (3-5 fundamental periods). It proves to be a cost-effective solution for common UPS products where high-quality output voltage is more stressed than fast dynamic response.

Compact, low insertion-loss, sharp-rejection, and wide-band microstrip bandpass filters

Abstract: This paper presents a new compact, low insertion-loss, sharp-rejection, and wide-band microstrip bandpass filter. A bandstop filter is introduced that uses a ring resonator with direct-connected orthogonal feed lines. A new bandpass filter based on the bandstop filter uses two tuning stubs to construct a wide-band passband with two sharp stopbands. Without coupling gaps between feed lines and rings, there are no mismatch and radiation losses between them and, therefore, the new filters show low insertion loss. In addition, a dual-mode characteristic is used to increase the stopband bandwidth of the new filters. A simple transmission-line model used to calculate the frequency responses of the filters shows good agreement with measurements. The filter using three cascaded rings has 3-dB fractional bandwidth of 49.3%, an insertion loss of better than 1.6 dB in the passband, a return loss of larger than 13 dB from 4.58 to 7.3 GHz, and two rejections of greater than 40 dB within 2.75-4.02 and 7.73-9.08 GHz. The high-performance, compact-size, and low-cost filter was designed for reducing the interference in full duplex systems in satellite communications.

Miniaturized coplanar waveguide stop band filters based on multiple tuned split ring resonators

Abstract: A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology.

Tunable microstrip bandpass filters with two transmission zeros

Abstract: This paper presents an analytical technique for positioning the locations of two transmission zeros for a microstrip bandpass filter. In addition, this paper discusses how the tapping positions of asymmetric feed lines affect the coupling between resonators. The bandpass filter uses two resonators with two transmission zeros to obtain lower insertion loss than a conventional cross-coupled microstrip filter. Also, by using four resonators, the bandpass filter has better out-of-band rejection than the conventional cross-coupled microstrip filter. The filter designs using four cascaded resonators provide a sharp passband that can be tuned using a piezoelectric transducer to change the effective dielectric constant. The filters demonstrate high selectivity, compact size, and can be used in many wireless communication systems.

Overlapped complex-modulated transmultiplexer filters with simplified design and superior stopbands

Abstract: A simple method for the design of the finite-impulse-response prototype filter for maximally decimated overlapped complex-modulated transmultiplexers with near perfect reconstruction property is presented. The procedure is unified for all values of overlap factor and leads to a prototype filter with excellent frequency selectivity and fast sidelobe fall-off rate. The high stopband attenuation and fast sidelobe fall-off rate, which is justified analytically, make the proposed filters suitable candidates for high-speed data communication applications employing multicarrier modulation.

Method and apparatus for channel equalization

Abstract: A method and apparatus is disclosed to overcome the effects of intersymbol interference during data transmission. Overcoming the effects of intersymbol interference makes possible higher data transmission rates for a given error rate. In one embodiment a receiver-transmitter pair is configured with a precode filter at the transmit side and a feed forward filter and a feedback filter at the receive side. Filter coefficients are calculated to reduce the undesirable effects of the channel, such as intersymbol interference. In one embodiment a training process occurs with the feedforward filter and a feedback filter, such that the first N coefficients of the feedback filter are set to zero. Thereafter, the coefficients of the feedforward filter are subject to spectral factorization and separated into minimum phase roots and maximum phase roots. The minimum phase roots comprise the precode filter coefficients and the maximum phase roots are established as feedforward filter coefficients.

Bandwidth and central frequency control on tunable bandpass filter by using MEMS cantilevers

Abstract: This paper deals with a tunable bandpass filter topology which controls independently and simultaneously both the central frequency and bandwidth. This tunable filter results from the association of MEMS cantilevers, used as variable capacitors, with an original passive topology. The latter is based on dual behavior resonators (DBRs), each of them is constituted of low- and high-frequency open-ended stubs. The associated filter electrical response is characterized by tunable frequency transmission zeros. A millimeter bandpass filter with central frequency and relative bandwidth tunability of about 10 and 75%, respectively, is presented.

Filtering intensity decision method, moving picture encoding method, and moving picture decoding method

Abstract: A moving picture encoding device includes an inter-pixel filter (114) having a filter A (114a), a filter B (114b), a filter C (114c), and a filter D (114d) each having different filtering intensity for filtering decoded image data and removing block distortion which is a high frequency noise in the vicinity of the boundary between blocks, and a filter processing control section (110) for deciding the filtering intensity of the inter-pixel filter (114).

Uniplanar compact wideband bandstop filter

Abstract: A uniplanar wideband bandstop filter is proposed using two bent open-end stubs. The proposed filter consists of the bent connecting line of /spl lambda//sub g//2 between two bent /spl lambda//sub g//4 stubs, which results in wideband design with a rejection bandwidth of 90% at 2.05 GHz. Further, the connecting line and stubs have the same characteristic impedance. The proposed filter compared to the conventional one is also more compact. The area of the novel filter is (/spl lambda//sub g//4)/sup 2/ at the center frequency of the stopband, while the area of the filter realized using the nonbent stubs and connecting line is 2(/spl lambda//sub g//4)/sup 2/ for the same stopband characteristics.

Photonic devices enabled by waveguide-mode resonance effects in periodically modulated films

Abstract: The chief properties and possible applications of periodic waveguides and their leaky modes are presented in this paper. After summarizing the basic physics of the guided-mode resonance, computed leaky-mode field patterns are provided to illustrate their structure and the high local focal field enhancement obtainable. An example fabricated bandstop filter is found to exhibit 90% efficiency, 1 nm linewidth, and low sidebands. Computed spectra for a single-layer bandpass filter operating at 1.55 μm wavelength yield low sidebands, extending 100 nm, and an angular aperture of ~1.7°. Resonant vertical-cavity surface-emitting lasers (VCSEL) are presented in which multilayer Bragg-stack mirrors are replaced with leaky-mode resonance layers. The use of guided-mode resonance mirrors provides optical power flow across and laterally along the laser active region. The round-trip gain is thereby increased resulting in high laser efficiency and relaxed mirror reflectivity constraints. As the GMR mirror achieves high reflectivity at resonance, the laser wavelength is locked at the resonance wavelength principally defined by the period. Example resonant VCSEL embodiments are shown along with their computed characteristics. Resonant biosensors are addressed last. The high parametric sensitivity of the guided-mode resonance effect, a potential limitation in filter applications, can be exploited for sensors as illustrated by several examples.

High input impedance voltage-mode universal biquadratic filter using two OTAs and one CCII

Abstract: A three-input and single-output voltage-mode universal biquadratic filter with high input impedance, using only two operational transconductance amplifiers (OTAs), one plus-type second-generation current conveyor (CCII) and two capacitors, is presented. The proposed circuit can realize all the standard filter responses, that is, highpass, bandpass, lowpass, notch and allpass filters, from the same configuration. The proposed circuit has no requirements for component matching conditions.

Wideband monolithic tunable high-Q notch filter for image rejection in RF application

Abstract: A notch filter with a high Q factor, which is integrated with a first and a second cascoded LNA, is totally contained on an integrated chip. The notch filter, comprising two Q-enhancement circuits, is coupled to the second differential LNA. The two Q-enhancement circuits are combined to generate sufficient negative impedance to compensate for the loss in the on-chip low Q inductors. To improve the image rejection of the notch filter in a wide frequency band, the notch filter uses an automatic current tuning circuit which consists of an analog multiplier and fixed and voltage controlled current sources. Furthermore, by modifying the connection and location of the tunable varactor, another wideband tunable notch filter is implemented. The notch filter can be applied in all current wireless receiver systems.

Multiple carrier adaptive notch filter

Abstract: A multiple carrier adaptive notch filter (ANF) module selectively filters a received wideband communication signal To determine the presence of narrowband interference, the multiple carrier ANF module scans various known narrowband channels that lie within the frequency spectrum of the wideband communication signal and determines signal strengths for each of the narrowband channels. The signal strengths from the narrowband channels are compared to a threshold that is derived from a statistical combination of the narrowband signal strengths. Narrowband channels having signal strengths that are greater than the threshold are determined to have interference.

Laterally coupled InP-based single-mode microracetrack notch filter

Abstract: We demonstrate an InP-based microracetrack notch filter with >25-dB extinction and 19-nm free-spectral range at 1550 nm. The curved section of the resonator has a radius of 2.25 /spl mu/m. To our knowledge, this represents the best extinction and the smallest radius of curvature for such a device to date.

An ultra-narrowband HTS bandpass filter

Abstract: This paper presents the measured results of an HTS ultra-narrowband bandpass filter with a 100 kHz bandwidth. This filter, with a fractional bandwidth of 0.014% and a center frequency of 700 MHz, represents a previously unrealized portion of filter parameter space. This filter was realized using a five-pole Chebyshev filter design and was fabricated using an HTS microstrip configuration. This filter required very high Q, very weak coupling, and a strong reduction in parasitics. Unloaded Qs of 135,000 were achieved with a resulting insertion loss of 1.37 dB. Even resonator Qs of 20,000 would lead to a filter loss of 9 dB. A noise figure of 1 dB was achieved for a complete system with this filter and a cryogenic low-noise amplifier.

Echo canceller with reduced requirement for processing power

Abstract: The present invention discloses an improved audio echo canceller processing echo, noise and near end talk in a narrower, but still intelligible, frequency band for reducing required processing power and complexity. In a preferred embodiment of the present invention, an input audio signal of captured sound in an audio communication system is decimated and then divided into a number of sub bands by an analyse filter. Each sub band is processed as in conventional audio echo cancelling by subtracting the signal with an echo estimate from a model of the acoustic signal in the respective sub band, except from that the signal is also bypassed, adjusted by an filter and subtracted from the processed signal. The resulting signals are then recombined by a synthesise filter and interpolated to the original sampling rate and bandwidth. Finally, the output from the synthesize filter is added to the input audio signal, which has been delayed and adjusted by an filter. The filters are controlled by an control algorithm detecting the presence of near end sound, far end sound and noise, so that the filters, and consequently the high pass filter of the echo canceller, only pass high frequency (above low pass frequencies) in cases where only near end sound is detected.

Cable detector with decimating filter and filtering method

Abstract: An electromagnetic cable detection or location device is disclosed comprising a detection stage (600) to produce a detection signal, a decimating filter (610) having an input and an output, the input being coupled to the receiving stage to filter the detection signal and output a down-sampled filtered signal with a decimation radio of N, and an output stage (620), coupled to the output of the decimating filter, to output an indication signal based upon the down-sampled filtered signal. The decimating filter used is a Finite Impulse Response (FIR) filter having a frequency response corresponding to that of a cascade of m SINC filters, wherein m is an integer greater than 1. A method of decimating a signal in a device is also disclosed.

Partial band reconstruction of frequency channelized filters

Abstract: A channelized filter design for partial band reconstruction having high dynamic range requirements. The analysis filter (505) and synthesis filter constraints of the present invention permit high performance signal detection with an alias free signal recombination capability for signals that span multiple frequency bins. The filter bank allows the use of a single wideband asset to provide for data channelized for detection processing with the ability to recombine one or more adjacent frequency bins into a wider bandwidth baseband time domain data stream suitable for exploitation processing. The present implementation allows the use of an efficient partial band reconstruction mechanism that allows signal reconstruction using only the frequency subchannels that pertain to the signal of interest that is to be copied. The filter design mechanism separates the specification of the analysis filter to support signal detection in environments of high dynamic range. The signal reconstruction (synthesis) filter uses fewer bins and allows a higher order filter.

A novel digitally tunable microwave-photonic notch filter using differential group-delay module

Abstract: We demonstrate a digitally tunable microwave-photonic notch filter based on a differential group-delay module which produces a relative delay between two orthogonal polarizations. A maximum rejection level greater than 60 dB is obtained. The tunability of the filter is achieved through real-time electronic control of the relative delay time.

Wideband and compact bandstop filter structure using double-plane superposition

Abstract: A novel bandstop filter (BSF) structure is proposed and measured for wideband and compact circuit applications. The proposed BSF realizes the wide stopband (2-octave) characteristics by superposing two different photonic bandgap (PBG) structures into a coupled double-plane configuration. Only three cells of the proposed structure are enough for the measured 10 dB stopband from 4.3 to 16.2 GHz. We expect this novel BSF structure is widely used for compact and wideband circuit applications, such as compact high-efficiency power amplitiers using harmonic tuning techniques.

A Novel Mixed-Mode Current-Controlled Current-Conveyor-Based Filter

Abstract: A new mixed-mode biquad circuit is presented The circuit uses four dual-output second-generation currentcontrolled current-conveyors (DOCCCIIs) and two grounded capacitors and can realize lowpass, highpass, bandpass and notch responses from the same topology The circuit can be driven by voltage or current and its output can be voltage or current The parameters ωo and ωo /Qo enjoy independent electronic tunability Simulation results are included

Improving the signal data acquisition in condition monitoring of electrical machines

Abstract: The occurrence of a broken bar in induction machines causes an internal magnetic imbalance, which is reflected in the stator current. This effect may be detected by estimating the spectral signature of the stator current, particularly the sidebands around the fundamental frequency. However, the fundamental 60-Hz amplitude is considerably greater than the sideband amplitude, which usually requires an analog 60-Hz notch filter in the data acquisition system. Analog filters are sensitive to temperature variations, which, in this case, may shift the filter resonance frequency and degrade the desired response. It is proposed in this paper that the analog notch filter may be replaced by a digital/analog cancelling technique based on the recursive discrete-time Fourier transform. The technique is shown to attenuate the fundamental 60-Hz amplitude considerably before A/D conversion, leaving only the sidebands in the current signal.

Method and apparatus for optimizing dynamic range of a wideband analog-to-digital converter

Abstract: A direct down conversion receiver (100) includes a signal filter (105) having a selectable frequency response for receiving an input signal (102). The filtered signal is amplified by a variable gain amplifier (112), and the amplified signal is received as input by an analog-to-digital converter (114). The analog-to-digital converter generates a series of digital samples representative of the filtered signal. A controller (116) measures a corresponding peaking ratio of the filtered signal from the series of digital samples for each of a plurality of frequency bands and selects the frequency response of the signal filter as a function of the measured peaking ratios. The signal filter may include an adjustable highpass filter (108) and an adjustable lowpass filter (106). The cutoff frequency of the lowpass filter and the cutoff frequency of the highpass filter are selected to attenuate the level of the input signal in one or more of the plurality of frequency bands so that the signal presented to the analog-to-digital converter has a peaking ratio approximately equal to a selected peaking ratio threshold across the frequency range of the input signal.

Active type vibration noise controller

Abstract: PROBLEM TO BE SOLVED: To provide an active type vibration noise controller in which computational quantity required to obtain reference signals is reduced and which provides sufficient vibration noise control effect. SOLUTION: In the active type vibration noise controller, the filter coefficients of an adaptive notch filter 14 are successively updated so that error signals outputted by a microphone 18 are minimized based on the error signals and first reference signals, wherein the first reference signals are obtained by subtracting signals that are obtained by multiplying a sine correction value C1 based on the sine value of phase characteristics by reference sine wave signals of vibration noise frequencies from signals that are obtained by multiplying a cosine correction value C0 based on the cosine value of the phase characteristics in signal transmission characteristics from a loudspeaker 17 generating canceling vibration noise to the microphone 18 by reference cosine wave signals of vibration noise frequencies. Moreover, filter coefficients of an adaptive notch filter 15 are successively updated so that error signals are minimized based on the error signals and second reference signals, wherein the second reference signals are obtained by adding signals that are obtained by multiplying the reference sine wave signals by the cosine correction value C1 to signals that are obtained by multiplying the reference cosine wave signals by the sine correction value C0. COPYRIGHT: (C)2005,JPO&NCIPI

Closed-form unbiased frequency estimation of a noisy sinusoid using notch filters

Abstract: In this note, the problem of the frequency estimation of a sinusoid embedded in white noise is considered. The approach used herein is the minimization of the sample variance of the output of constrained notch filters fed by the noisy sinusoid. In particular, this note focuses on closed-form expressions of the frequency estimate, which can be obtained using notch filters having an all-zeros finite-impulse response (FIR) structure. The results presented in this note are as follows: 1) it is shown that the FIR notch filters obtained from standard second-order infinite-impulse response (IIR) filters are inadequate; 2) a new second-order IIR notch filter is proposed, which provides an unbiased estimate of the frequency; 3) the FIR filter obtained from the new IIR filter provides a closed-form unbiased frequency estimate; and 4) the closed-form frequency estimate obtained using the new FIR notch filter asymptotically converges toward the Pisarenko harmonic decomposition estimator and the Yule-Walker estimator.

A 5-GHz radio front-end with automatically Q-tuned notch filter and VCO

Abstract: A low-voltage receiver front-end for 5-GHz radio applications is presented. The receiver consists of a low-noise amplifier (LNA) with notch filter, a voltage-controlled oscillator (VCO), and a mixer. The LNA/notch filter has an automatic Q-tuning circuit integrated with it to provide good image rejection. On-chip transformers are used extensively in the receiver to improve performance and facilitate low-voltage operation. The receiver has a gain of 19.8 dB, noise figure of 4.5 dB, a third-order input intercept point (IIP3) of -11.5 dBm, and an image rejection of 59 dB, and the VCO had a phase noise of -116 dBc/Hz at 1-MHz offset.

A 4D frequency-planar IIR filter and its application to light field processing

Abstract: A 4D frequency-planar filter is described, having a steady-state frequency response with a pass band that approximates that of a 4D plane. It is shown that a light field containing Lambertian surfaces with no occlusions may be selectively filtered for depth using such a filter. Examples are given showing the effectiveness of the filter in scenes with and without occlusions. A technique for effectively reducing the length of the transient response of the filter is also proposed and the effectiveness of this technique is demonstrated.

Ultra selective HTS bandpass filter for 3G wireless application

Abstract: This paper presents an ultra selective HTS filter that meet existing 3G wireless band. The filter consists of 22 resonators and five cross coupling structures that produce ten transmission zeros near the band edges. A quadruplet cross coupling technique was introduced into the design for the transmission zero implementation. To accommodate twenty-two resonators within a limited wafer size, a compact new topological resonator was also developed. The filter was fabricated using a YBCO thin film on a 2-in MgO wafer. Measured skirt slope has exceeded 30 dB/100 kHz and the filter has a 90 dB out-of-band rejection at 350 kHz from its band edge. This filter surpasses the rejection of an ideal 50-pole Chebyshev filter.

Integrated circuit tuner with broad tuning range

Abstract: An integrated front end filter for a tuner provides an array of from several to a multitude of passbands, each for passing at least one but less than all channels designated in a band of frequencies. Each passband is exclusively selectable. The integrated front end filter can include at least one active filter unit with an active reactance element in either of fixed and variable filter configurations and a decoder coupled to said at least one active filter unit and being responsive to a control signal for selecting a one of the passbands. In one example, a multitude of active filter units of fixed filter configuration provide the multitude of passbands. In another example, a plurality of data corresponds to a like plurality of selectable passbands in combination with a filter element of the variable filter configuration. Each data is stored at a predetermined location and reproduced in response to a corresponding control data signal from a tuner controller. Each data characterizes one of the plurality of passbands. The filter element is switchable from one passband to another in response to the control data signal. Lower power dissipation and lesser requirements of an on-following integrated circuitry tuner permit a reduction of “off chip” connections and cost.