Showing papers on "Band-stop filter published in 2004"

Effective negative-/spl epsiv/ stopband microstrip lines based on complementary split ring resonators

Abstract: In this letter a super-compact stopband microstrip structure is proposed. The frequency gap is produced by an array of complementary split ring resonators (CSRRs)-a concept proposed here for the first time-etched on the ground plane. This behavior is interpreted as due to the presence of a negative effective dielectric permittivity in the vicinity of resonance. The resulting device produces a deep rejection frequency band with sharp cutoff, and a pass band that exhibits very low losses and good matching. Due to the sub-lambda operation of CSRRs, the electrical size of the device is very small.

Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique

Abstract: A synthesizing method is presented to design and implement digital dual-band filters in the microwave frequency range. A dual-band filter consists of a bandstop filter and a wide-band bandpass filter in a cascade connection, wherein the transfer functions of both the bandpass filter and bandstop filter are expressed in the Z domain. The bandstop filter is implemented by using a coupled-serial-shunted line structure, while the wide-band bandpass filter is constructed by using a serial-shunted line configuration. In particular, the bandwidth of each passband of the dual-band filter is controllable by adjusting the characteristics of both the bandpass filter and bandstop filter. By neglecting the dispersion effect between microstrip lines of different widths over a wide bandwidth, a dual-band filter is realized in the form of microstrip lines and its frequency responses are measured to validate this method.

Design and analysis of UWB bandpass filter with ring filter

Abstract: To realize an Ultra Wideband (UWB) bandpass filter (BPF) in wireless communications[1], a device is developed using a new Ring Filter. The Ring Filter is compact, with low insertion loss, sharp rejection and a constant group delay within the UWB passband. The Ring Filter is made to control the attenuation pole frequency by adjusting both the ring and the stub impedance. A center frequency and a bandwidth of the 5-stage UWB BPF are designed based on the transmission line model. The circuit conditions of two attenuation poles at either side of the passband are given together with controlling them.

An adaptive notch filter for frequency estimation of a periodic signal

Abstract: Online frequency estimation of a pure sinusoidal signal is a classical problem that has many practical applications. Recently an ANF with global convergence property has been developed for this purpose. There exist some practical applications in which signals are not pure sinusoidal and contain harmonics. Therefore, online frequency estimation of periodic but not necessarily sinusoidal signals espoused by such applications becomes quite important. This note presents an alternative stability analysis for a modified ANF that permits the presence of harmonics in the incoming signal. Also, this stability analysis is simpler and alleviates the problem complexity even in the case of pure sinusoidal signal. Simulation results confirm theoretical issues.

Active interference cancellation technique for MB-OFDM cognitive radio

Abstract: Ultra Wideband transmit power (in-band) is regulated to be -41.25 dBm/MHz (in the United States), but in the future, it may be flexibly relaxed subject to the cognitive-radio spectrum policy. However, in close proximity of a protected radio service, transmission at the relaxed power might inflict an excessive degradation on the service quality. Applying the general analog or digital notch filter in the UWB transmitter (baseband) is the simplest but not a favorable approach due to the increased cost and the power consumption of the device. In OFDM, turning off the interfering tones has been studied as the alternative solution, but the inter-carrier interference may limit the notch depth to 5-10 dB. This paper discusses a new approach that enables the accurate notch bandwidth and depth control for the general OFDM transmitter. The technique demonstrates the fundamental advantage of the OFDM-based UWB solution[l] for the future cognitive ratio.

Varactor-loaded split ring resonators for tunable notch filters at microwave frequencies

Abstract: It is demonstrated that the resonant frequency of split ring resonators (SRRs) can be tuned using varactor diodes. The resulting particle, which is called a varactor-loaded split ring resonator (VLSRR), is applied to the design of a tunable notch filter at S-band. The device consists on a microstrip transmission line with VLSRRs placed at both sides of the conductor strip. Owing to the proximity of the particles to the line the rings are excited and a transmission notch arises. It is shown that simply using two VLSRRs pairs, rejection levels above 20 dB are achieved in a 0.5 GHz tuning interval centred at 2.85 GHz. The proposed device is the first tunable notch filter based on SRRs.

Audio input system

Abstract: A method for reducing noise associated with an audio signal received through a microphone sensor array is provided. A first filter enhances a target signal component of the audio signal. A second filter is blocking the target signal component. The output of the first filter and the output of the second filter are combined in a manner to reduce noise without distorting the target signal. An acoustic set-up associated with the audio signal is periodically monitored. The first filter and the second filter are both calibrated based upon the acoustic set-up. Preferably the calibration of the filters includes a blind source separation scheme using second order statistics calculation. Preferably the first filter is an adaptive beam-forming module enhancing a target signal component and the second filter is an inverse adaptive beam-forming module blocking the target signal component. The system can be included in a video game controller.

Design and analysis of UWB band pass filter with ring filter

Abstract: To realize an ultra wideband (UWB) bandpass filter (BPF) in wireless communications, a device is developed using a new ring filter. The ring filter is compact, with low insertion loss, sharp rejection and a constant group delay within the UWB pass band. The ring filter is made to control the attenuation pole frequency by adjusting both the ring and the stub impedance. A center frequency and a bandwidth of the 5-stage UWB BPF are designed based on the transmission line model. The circuit conditions of two attenuation poles at either side of the passband are given together with controlling them.

All-optical bandpass microwave filter based on an electro-optic phase modulator

Abstract: A novel all-optical microwave filter with a frequency response equivalent to a bandpass filter is presented. An electro-optic phase modulator combined with a dispersive device is employed to eliminate the baseband resonance of a typical lowpass filter. A two-tap bandpass transversal microwave filter with a null-to-null bandwidth of 8.8 GHz and a 35-dB notch rejection level is demonstrated.

Passive enhancement of resonator Q in microwave notch filters

Abstract: The lumped-element bridged-T notch filter concept is extended to reciprocal distributed-element microwave filters. A prototype microstrip bridged-T notch filter employing single-mode resonators is described that enhances the effective resonator Q/sub u/ by a factor of 325, while a different microstrip filter topology with a triple-mode resonator is described that enhances the effective resonator Q/sub u/ by a factor of 89. The new notch filters can be either partly reflective or fully absorptive within the stopband. Additional enhanced-Q/sub u/ notch filter topologies, such as a hybrid-coupler notch filter, that include at least two resonances and at least two signal paths are suggested.

An implementation of harmonic-suppression microstrip filters with periodic grooves

Abstract: In this paper, a new parallel-coupled-line microstrip band pass filter (BPF) improving the harmonic suppression performance of the second harmonic signal (2f/sub o/, twice the passband frequency) is described. It is found that the desired passband performance is improved and the harmonic passband signal is diminished by enforcing the consecutive patterns in coupled-line and increasing the number of grooves to the optimum values. The recalculation of design parameters such as space-gap between lines, line widths and lengths is not required due to the simple modification of the conventional filter by inserting periodic patterns. To evaluate the validity of this novel technique, order-3 Butterworth BPF centered at 2.5 GHz with a 10% fractional bandwidth (FBW) and order-5 Chebyshev BPF centered at 10 GHz with a 15% FBW were used. When five and three square grooves are used, over 30-dB suppression at second harmonic signal is achieved in simulation and experiment. Finally, the comparison between the characteristics of filters with square and semicircular periodic grooves has been carried out by using the simulated results.

Power system having a phase locked loop with a notch filter

Abstract: A power system having a phase locked loop (PLL) with a notch filter for synchronous reference frame sequence separation. The notch filter includes a generalized integrator tuned to the notch frequency. The output of the generalized integrator is summed with the filter input signal and the output of the summer is fed back to the integrator input. In one embodiment, the notch filter is programmable by a control signal generated in response to the filter output signal, thereby causing the filter to self-regulate to a frequency related to the PLL input signal. Illustrative power systems include active VAR generators and active rectifiers. One or more additional notch filters may be used to remove harmonic components from derived synchronous reference frame sequence components.

Reducing power line interference in digitised electromyogram recordings by spectrum interpolation.

Abstract: Interference from power lines (50 or 60 Hz) is the largest source of extraneous noise in many bio-electric signals and is within the bandwidth of many such signals. In this study, two different methods were compared for their efficacy in removing 50 Hz noise added to surface electromyogram (EMG) signals free of power line interference. The first was a simple second-order recursive digital notch filter. The second was an approach called spectrum interpolation, in which it is assumed that the magnitude of the original 50 Hz component of the EMG signal can be approximated by interpolation of the amplitude spectrum of the signal. When the spectrum was based on records containing an integer number of cycles of 50 Hz interference, and the frequency resolution was finer than 1 Hz, spectrum interpolation performed similarly to, or significantly better than, the notch filter (p < 0.01). It was also possible to make spectrum interpolation more robust than the notch filter. The Pearson squared correlation coefficient r2 between clean signals and signals processed using the notch filter was reduced from 0.98 to 0.65 when the interference frequency was increased by 0.5 Hz, but r2 for spectrum interpolation at 0.2 Hz resolution was only reduced from 0.99 to 0.85 if spectral values between approximately 49.5 and 50.5 Hz were modified by interpolation.

A system and method for excluding narrow band noise from a communication channel

Abstract: A signal filtering system and method that may be used in conjunction with a repeater or an input stage of a base-station. The system may include an analog to digital converter adapted to sample a received signal and to produce a data stream corresponding to the received signal in the time domain, a filtering block having one or more digital filter elements, wherein each of said one or more filter elements is adapted to filter one or more sets of frequency bands associated with one or more communication channel, and a controller adapted to configure said one or more digital filter elements based on parameters stored on a database and/or based on parameters received via a modem.

Fast analytical design algorithms for FIR notch filters

Abstract: Fast analytical design procedures for finite impulse response (FIR) maximally flat (MF) and optimal equiripple (ER) notch filters are introduced. The closed form solution provides recursive computation of the impulse response coefficients of the filter. The ER FIR filters are optimal in the Chebyshev sense. The relation between the MF and ER notch filter is presented in order to emphasize the superior performance of the ER narrow-band filters over their MF counterparts. The discrete nature of the notch frequency in both filter types is emphasized. Four design examples are included to demonstrate the efficiency of the presented approach.

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

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

Dual-band-rejection filter for distortion reduction in RF transmitters

Abstract: A novel concept of dual-band-rejection filter (DBRF) is proposed with its circuit synthesis procedure and examples of its realization with dielectric resonators and microstrip resonators. A DBRF can make two closely spaced rejection bands and a passband between them, with lower loss than a bandpass filter having the same number of resonators and the same frequency selectivity just around the passband. The DBRF can be synthesized by applying novel frequency-variable transformations to a prototype LPF, and its physical size can be smaller than a simple cascade of two conventional band-rejection filters with different rejection bands. The DBRF can be especially applicable to distortion reduction filter in RF transmitters.

Performance for passive and active power filter in reducing harmonics in the distribution system

Abstract: This paper presents the results for the performance of passive and active power filter to reduce harmonics in the distribution system. The harmonics analysis is performed in order to observe the percentage reduction of amplitude current harmonics and total harmonic distortion for passive and active power filter at various loads. In addition to that the bidirectional switching is used as a strategy control in active power filter. Representative result of circuit simulations is carried out. The results show that the active power filter can simultaneously attenuate various frequencies and are compared with passive filter which is only filtering an individual harmonics. Also, the significant percentage of reduction for the amplitude current harmonics and total harmonic distortion by active power filter are compared to passive filter. Furthermore, the sinusoidal current waveform quality at distribution lines which filtered by active power filter is better compared with passive filter. Therefore, the active power filter is good to reduce harmonics in the electrical distribution systems.

Transmitter filter arrangement for multiband mobile phone

Abstract: A filter arrangement for use in a multiband dual-mode mobile phone. In particular, the mobile phone is operable in a W-CDMA mode and a band-reject filter comprising at least a series and a shunt acoustic-wave resonators is used to create a deep notch at the receive frequency band. The band-reject filter further includes a plurality of inductive elements for matching static capacitance of the resonators at the passband frequency. The mobile phone is also operable in 1800 and 1900 GSM bands. The band-reject filter is operatively connected to a harmonic trap in order to eliminate the third harmonic of these GSM bands. The mobile phone is also operable in the lower GSM band, for which a harmonic filter can share an antenna path with the band-reject filter.

Method and apparatus for single burst equalization of single carrier signals in broadband wireless access systems

Abstract: A receiver implementing a single carrier single burst equalization (SC-SBE) method is capable of achieving near optimal reception of individual single carrier RF bursts by making an accurate estimate of the burst's propagation channel impulse response (CIR). The SC-SBE method uses a CIR based coefficient computation process to obtain filter coefficients for a minimum mean square error decision feedback equalizer (MMSE-DFE). The MMSE-DFE filter computation process computes a sufficiently large number of coefficients for the DFE filters, i.e., the feed forward filter (FFF) and feedback filter (FBF), so that each filter spans the maximum anticipated length of the CIR. In order to implement the filters efficiently, a coefficient selection process eliminates less significant computed FFF and FBF coefficients. The resulting FFF and FBF are sparse filters in that most of the taps in the filter delay lines do not have a filter coefficient. Such filters may be efficiently implemented in the time domain.

Electronic switchable bandpass filter using PIN diodes for wireless low cost system-on-a-package applications

Abstract: A reconfigurable band-pass filter for wireless applications has been designed and demonstrated. The topology has been designed on Duroid, a low cost organic substrate intended for system-on-a-package (SOP) applications. The design achieves discrete bandwidth tuning by direct manipulation of its geometry and implements PIN diodes as switching elements. The filter was designed with a centre frequency of 5.8 GHz and a passband tunablity ratio of 2:1. Several tests such as one-tone power handling and two-tone intermodulation measurements were conducted to investigate the filter's response to different power signal levels as well as the level of signal distortion. The filter produced third-order intermodulation intercept points (IIP3s) greater than 46 dBm around the centre frequency for tones separated by 1 MHz. The resulting circuit presented here does not produce significant distortion and it is capable of handling signals with power levels greater than 2 W. The two distinct bandwidths produced by the filter were 10.12% with an insertion loss of 3.95 dB and 5.43% with an insertion loss of 4.73 dB. The physical size of the fabricated filter layout including the realisation of bias circuitry is comparable to the size of a conventional filter.

Active noise cancellation system

Abstract: In an active noise cancellation system having an adaptive filter that outputs a control signal, first and second speakers that emit a canceling signal generated based on the control signal, a microphone that detects an error signal, a correction filter that corrects the base signal by a correction value to generate a reference signal and a filter coefficient updater that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter coefficient, while enabling to maintain an area in which noise can be reduced to the same level as that obtained before reducing the number of microphones.

Fbar band pass filter, duplexer having the filter and methods for manufacturing the same

Abstract: A duplexer including an FBAR band pass filter that can be easily embodied in single chip, and a method for manufacturing the same are disclosed. The duplexer of a mobile communication device includes a transmitting band pass filter, formed on an upper portion of a substrate, having at least two FBARs electrically connected to each other, a receiving band pass filter, formed on an other side of the substrate, having at least two FBARs electrically connected to each other, and a page shifter electrically connected with the transmitting band pass filter and the receiving band pass filter. Since the transmitting and receiving band pass filter and the inductor can be integrated into one chip, a duplexer with minimized size can be provided in response to the request of miniaturization and lightness of various mobile communication device. Moreover, since the transmitting or receiving band pass filter according to the present invention can be embodied in a remarkable size in comparison with the conventional SAW band pass filter as well as has a low insertion loss and low power consumption. Thus, an interface design and a terminal operating programming can be easily achieved, and a region of a board with a duplexer is mounted in a mobile communication device can be remarkably reduced.

Dual-band-rejection filter for distortion reduction in RF transmitters

Abstract: A novel concept of dual-band-rejection filter (DBRF) is proposed with its circuit synthesis procedure and an example of its realization with dielectric resonators at L-band. DBRF can make two closely-spaced rejection bands and a pass-band between them, with lower loss than a band-pass filter (BPF) having the same number of resonators and the same frequency-selectivity just around the pass-band. DBRF can be applicable to distortion reduction filter in RF transmitters.

Led light apparatus and methodology

Abstract: An LED light apparatus and methodology that can produce a collinear beam of light. The apparatus has a housing (102) with three sets of LED light assemblies (132, 133, and 134) each having several LED lights of the same color, being red, blue or green. Adichroic bandpass filter (116) and a dichroic notch filter (115) are incorporated along with a power supply. In one embodiment both filters intersect forming an x-pattern. Red light passes through both filters. The resulting light from the band pass filter combines with blue light and passes through the notch filter. This combined light stream then combines with green light to form a collinear beam of white or colored light.

Novel all-optical RF notch filters with equivalent negative tap response

Abstract: New all-optical radio-frequency notch filters with frequency response equivalent to two-tap negative tap notch filters are presented. Two topologies are described, based on a dual-output electrooptic modulator that undergoes double-pass modulation, and whose phase difference of the modulated signals at the outputs are used to obtain equivalent negative tap behavior in the notch filter response. Results are presented for the novel structures, which demonstrate the realization of an equivalent negative tap notch filter response, and which also show the important advantages of eliminating coherence and phase noise limitations in the operation of the processors.

Apparatus for and method of actively controlling vibratory noise, and vehicle with active vibratory noise control apparatus

Abstract: The filter coefficients of an adaptive notch filter are sequentially updated to minimize an error signal based on the error signal and a first reference signal which is produced by subtracting a signal which represents the product of a sine corrective value C1 and a reference sine signal, from a signal which represents the product of a cosine corrective value C0 and a reference cosine signal. The filter coefficients of an adaptive notch filter are sequentially updated to minimize the error signal based on the error signal and a second reference signal which is produced by adding a signal which represents the product of the reference sine signal and the cosine corrective value C0 and a signal which represents the product of the reference cosine signal and the sine corrective value C1 to each other.

Filter apparatus and frequency converter to which the filter apparatus is connected

Abstract: The invention provides a technique and a product in which for a frequency converter supplying electric power to, for example, a motor, a downsizing, lightening or the like of the frequency converter is realized while providing a filter apparatus reducing electromagnetic noises and the like. The filter apparatus reducing electromagnetic noises and the like is provided near a main circuit terminal board of the frequency converter, and the filter apparatus is connected directly to a main circuit terminal as a wiring drawing portion of the frequency converter. Part of a housing of the frequency converter and part of a filter housing are fitted to each other to fix the filter housing to the frequency converter.

A tunable GaInAsP-InP optical microring notch filter

Abstract: The authors demonstrate an ultracompact tunable GaInAsP-InP microring notch filter. The core of the device is a quantum-well superlattice and forms the intrinsic region in a p-n structure. The device has curved sections of radius 2.25 /spl mu/m and straight sections of length 1 /spl mu/m, making it the smallest microring filter ever reported. They obtain 0.8 nm (100 GHz) of tuning by reverse-biasing the diode structure over 8 V using the quadratic electrooptic effect.