Showing papers on "Low-pass filter published in 2005"

Microstrip bandpass filters for Ultra-Wideband (UWB) wireless communications

Abstract: A new technique is developed for designing a composite microstrip bandpass filter (BPF) with a 3 dB fractional bandwidth of more than 100%. The BPF is suitable for ultra-wideband (UWB) wireless communications. The design utilizes embedding individually designed highpass structures and lowpass filters (LPF) into each other, followed by an optimization for tuning in-band performance. The stepped-impedance LPF is employed to attenuate the upper stopband and quarter-wave short-circuited stubs are used to realize the lower stopband. Two such BPFs are fabricated and measured to demonstrate the performance.

An ultrawideband bandpass filter using broadside-coupled microstrip-coplanar waveguide structure

Abstract: This paper presented an ultra-wideband (UWB) bandpass filter using broadside-coupled microstrip-coplanar waveguide structure. The filter consists of a microstrip line coupled to a coplanar waveguide (CPW) that was fabricated on the ground of the microstrip line. The proposed filter has been simulated, fabricated and measured for UWB system. The measured results demonstrated the UWB properties from 3.0 GHz to 10.63 GHz (-10 dB bandwidth) and the potential to be wider. A threesection filter shown insertion loss at central frequency is about 0.32 dB and very flat over the whole band. The group delay, which is important to an impulse radio UWB system, is about 0.42 ns over the most central band and less than 0.95 ns over the whole band. The filter also exhibited a good performance outside the band, both at low frequency end (to meet FCC limit) and high frequency end higher than 18 GHz with insertion loss larger than 30 dB.

Tunable combline filter with continuous control of center frequency and bandwidth

Abstract: A new combline filter structure with a continuous tunability for both the center frequency and bandwidth is presented in this paper. The passband-width tunability is achieved by placing variable coupling reducers between the filter resonators. The coupling reducers, operating as bandwidth control subnetworks, are designed as detuned resonators made up of a line segment ending in a variable capacitor. The proposed filter structure is experimentally validated with the design, construction in suspended stripline technology, and characterization of a low-cost filter prototype for terrestrial digital video broadcasting receivers operating in the UHF band (470-862 MHz). Other relevant factors, such as the intermodulation distortion produced by the varactors used to control the bandwidth electronically or the power-handling performance of the constructed filter, are also discussed. The reconfigurable filter module described in this paper is very suitable for the design of flexible multifunction receiver subsystems simultaneously supporting signals with a different bandwidth.

A 6.6-kV transformerless shunt hybrid active filter for installation on a power distribution system

Abstract: This paper presents a fully-digital-controlled shunt hybrid filter for damping of harmonic propagation in power distribution systems. The harmonic propagation is caused by resonance between line inductances and power capacitors installed for power factor correction. A possible solution to damping out harmonic propagation is based on installation of a shunt pure active filter at the end of a feeder. This paper proposes a shunt hybrid active filter characterized by series connection of a seventh-tuned LC filter per phase and a small-rated three-phase active filter. Like the pure filter, the hybrid filter is connected to the end bus of a feeder. The capacitor of the LC filter imposes a high impedance to the fundamental frequency, so that the fundamental voltage appears across the capacitor. This unique feature allows us to directly connect the hybrid filter to the 6.6-kV power line without step-down transformers. Furthermore, the capacitor used in this hybrid filter is lighter, cheaper and smaller than the transformer used in the pure filter. Theoretical analysis, along with experimental results obtained from a 200-V, 20-kW laboratory system, verifies the viability and effectiveness of the proposed hybrid filter.

Method and device for amplification of data signals over power lines

Abstract: A device for bi-directional amplification of data signals over power lines is disclosed. In one embodiment, the device includes a bandpass filter, a frequency converter and an amplifier. The bandpass filter filters out undesired frequencies and the frequency converter converts the frequency band of the data signals to a different frequency band. The output of the filter is provided to the amplifier for amplifying the frequency converted data signals for transmission over power line.

Low-loss ultra-wideband (UWB) filters using suspended stripline

Abstract: Two types of suspended stripline ultra-wideband bandpass filters are described, one based on a standard lumped element (L-C) filter concept including transmission zeroes to improve the upper passband slope, and a second one consisting of the combination of a low-pass and a high-pass filter.

Current controlled third order quadrature oscillator

Abstract: A novel current controlled third order translinear-C quadrature oscillator based on a new second order high input impedance voltage-mode low-pass filter is proposed. The circuit with grounded capacitors enjoys electronically tunable, non-interactive frequency and condition control, generates four quadrature current outputs at high impedance nodes and two quadrature voltage outputs. Design verifications are included using CBIC-R process parameters of AT & T transistors with attractive results.

A novel active power filter for harmonic suppression

Abstract: In this paper, a novel active power filter is proposed and implemented by using a voltage-source power converter with a series connected inductor and capacitor set. The power converter is controlled to generate a compensating voltage that is converted into a compensating current via the series connected inductor and capacitor set. The compensating current flows into the power feeder in order to suppress the harmonic currents generated by nonlinear loads. The salient advantages of the proposed active power filter are lower voltage rating of dc capacitor and power switching devices, smaller filter inductor, smaller dimension, light weight, better filter performance and low electromagnetic interference (EMI). A three-phase 100 kVA active power filter is developed to demonstrate the performance of the proposed method. The results show that the proposed active power filter has the expected performance.

Varactor-tunable frequency selective surface with resistive-lumped-element biasing grids

Abstract: A novel tunable frequency selective surface (FSS) is presented consisting of vertically and horizontally positioned convoluted dipole FSS elements. Each of the latter incorporates a varactor diode, which is biased via novel resistive-lumped-element biasing grids that suppress undesirable resonances and improve the filter's low-pass response. The proposed design is shown, numerically and experimentally, to perform well. It is expected that this letter will assist research work in low-cost, large-scale tunable FSS.

Compact microstrip low-pass filter with sharp rejection

Abstract: This letter presents a compact multisection sharp-rejection microstrip low-pass filter. Each section consists of a microstrip line section and an interdigital capacitor. The analysis for optimizing the attenuation poles by adjusting the finger number, and the width and length of the microstrip line section, is presented. The cascaded four-section low-pass filter has a return loss of better than 17 dB and an insertion loss of less than 0.7 dB from DC to 1.6 GHz. The rejection is better than 20 dB from 2.1 to 7.5 GHz.

A Novel Design Method of LCL Type Utility Interface for Three-Phase Voltage Source Rectifier

Abstract: LCL type filter becomes more and more attractive as utility interface for grid-connected voltage source rectifier (VSR). Compared to L type filter, LCL type filter can render better switching harmonics attenuation using lower inductance, which makes it suitable for higher power applications. However, LCL filter design is complex and needs to consider many constraints, such as current ripple through inductors, total impedance of the filter, switching harmonic attenuation, resonance phenomenon and reactive power absorbed by filter capacitors, etc. Try-error method is inconvenient and time-consuming. This paper proposes a novel method for LCL type filter design, which makes the task very convenient. At first, the total inductance should be determined according to current ripple requirement. With filter capacitor insertion, total inductance is split into two parts. A set of equations is obtained to represent the relationship between the impedances at switching frequency with consideration of switching harmonic attenuation and reactive power constrains. The other constraints are considered as the limitation for solvability condition for equations. So the overall design can be easily done by solving the equations. Step-by-step design procedure is described as a design example, which is verified on the experimental set-up

A G/sub m/-C low-pass filter for zero-IF mobile applications with a very wide tuning range

Abstract: A third-order G/sub m/-C Butterworth low-pass filter implementing G/sub m/-tuning and G/sub m/-switching to maximize the tuning range is described. This filter is intended to be used as a channel-selection/anti-aliasing filter in the analog baseband part of a zero-IF radio receiver architecture for multimode mobile communications. Its G/sub m/-switching feature allows extending the tuning range and adapting the power consumption. The filter's cutoff frequency ranges from 50 kHz to 2.2 MHz. An Input IP3 of up to +18 dBV/sub p/ is achieved, for a total worst-case power consumption of 7.3 mW for both I and Q paths, and an effective area of less than 0.5 mm/sup 2/ in a 0.25-/spl mu/m SiGe BiCMOS process. A new figure of merit is introduced for comparison of published low-pass tunable filters including noise, linearity, and tuning range.

Quasi-lumped suspended stripline filters and diplexers

Abstract: This paper demonstrates a general concept and different types of filters and a diplexer realized in suspended stripline using quasi-lumped elements. Very small low-pass, bandpass, and high-pass filters with typically low loss are designed, fabricated, and tested; even transmission zeroes can easily be included into the design by additional coupling structures. Finally, a low-pass and high-pass filter are combined to form a diplexer of very small size.

A CMOS Continuous-Time Low-Pass Notch Filter for EEG Systems

Abstract: A CMOS OTA-C low-pass notch filter for EEG application is described. The pass-band covers four bands of brain wave and provides more than 65 dB attenuation for the 50 Hz power line interference. The OTA works in the weak inversion region and a low transconductance of 3 nA/V is achieved. The low transconductance enables using small capacitors in the OTA-C filter so that the filter is suitable for the multi-channel EEG integrated circuits. The measured results show the good performance of the filter for filtering the noise in acquired EEG signals.

Miniaturized dual-mode bandpass filter with harmonic control

Abstract: This letter presents a miniaturized dual-mode microstrip bandpass filter with the right crossed slots. The right crossed slots perturb and reduce the fundamental resonant frequency, but the second resonance is not affected. Therefore, the second resonance will be effectively higher than 2f/sub o/, where f/sub o/ is the fundamental frequency. Since the fundamental frequency is lower, the bandpass filter is smaller than the conventional filter. The proposed filter shows a 4.4% fractional bandwidth at 1.595GHz with a return loss of better than 10dB and an insertion loss of less than 2.5dB, while the second passband is located around 2.88f/sub o/= 4.6GHz. Compared with the conventional square patch filter, the proposed filter also shows a 58% size reduction.

A Frequency Selective Filter for Short-Length Time Series

Abstract: An effective and easy-to-implement frequency filter is proposed, obtained by convolving a raised-cosine window with the ideal rectangular filter response function. Three other filters, Hodrick--Prescott, Baxter--King, and Christiano--Fitzgerald, are thoroughly reviewed. A bandpass version of the Hodrick--Prescott filter is also introduced and used. The behavior of the windowed filter is compared to the others through their frequency responses and by applying them to both quarterly and monthly artificial, known-structure series and real macroeconomic data. The windowed filter has almost no leakage and is better than the others at eliminating high-frequency components. Its response in the passband is significantly flatter, and its behavior at low frequencies ensures a better removal of undesired long-term components. These improvements are particularly evident when working with short-length time series, which are common in macroeconomics. The proposed filter is stationary and symmetric, therefore, it induces no phase-shift. It uses all the information contained in the input data and stationarizes series integrated up to order two. It thus proves to be a good candidate for extracting frequency-defined series components.

Symmetric nearly shift-invariant tight frame wavelets

Abstract: K-regular two-band orthogonal filterbanks have been applied to image processing. Such filters can be extended into a case of downsampling by two and more than two filters provided that they satisfy a set of conditions. Such a setup allows for more degrees of freedom but also at the cost of higher redundancy. The latter depends directly on the number of the wavelet filters involved. Tight frame filters allow the design of smooth scaling functions and wavelets with a limited number of coefficients. Moreover, such filters are nearly shift invariant, a desirable feature in many applications. We explore a family of symmetric tight frame finite impulse response (FIR) filters characterized by the relations H/sub 3/(z)=H/sub 0/(-z) and H/sub 2/(z)=H/sub 1/(-z). They are simple to design and exhibit a degree of near orthogonality, in addition to near shift invariance. Both properties are desirable for noise removal purposes.

Sloshing suppression control of liquid transfer systems considering a 3-D transfer path

Abstract: In plants in many industries, there exist a lot of transfer systems with vibration mechanisms. While transfer without residual vibration is usually demanded in these plants, this requirement necessitates large numbers of sensors and complicated models for control design. Therefore, This work presents a trajectory control design method to suppress residual vibration in transfer systems without the need to directly measure vibration. The proposed method consists of two parts. First, the frequency characteristics of the controller, comprised of control elements with simple structures such as a notch filter and a low-pass filter, are shaped as needed to suppress vibration. Next, various parameters of the control elements are determined by solving an optimization problem with penalty terms expressed by the constraints of both the time and frequency domains. The proposed method is applied to a liquid container transfer system, with special consideration given to the suppression of sloshing (liquid vibration) as well as to the maintenance of a high-speed transfer on the container's three-dimensional transfer path. The obtained controller demonstrates good performance for all demands. The effectiveness of the control design method is shown by experiments.

GeoFilter: Geometric Selection of Mesh Filter Parameters

Abstract: When designing a lowpass filter to eliminate noise in a triangle mesh, the cutoff frequency is typically chosen by a cumbersome trial-and-error process. Therefore, it is important to provide a guideline in selectingfilter frequencies. Here, we explore the relation between the frequencies in a mesh filter and the geometric measures of user-selected features. In addition, by combining previously proposed implicit and explicit formulations, we develop a second order filter that can act as lowpass, bandpass, highpass, notch, and band exaggeration/reduction filters. The proposed GeoFilter framework allows the user to choose the frequencies for that filter based on the physical size of a blob (ellipsoid) automatically fit to a user-selected feature in the mesh. For example, the size of a bump in a noisy pattern can be used as a cutoff frequency in a lowpass filter, while the size of a nose may be used to smoothen a face or to exaggerate its features as in a caricature.

A near-infrared heart rate measurement IC with very low cutoff frequency using current steering technique

Abstract: A near-infrared heart-rate measurement IC that processes the photoplethysmographic signal was designed using a 0.35-/spl mu/m CMOS technology. The IC consists of a current-to-voltage (I-V) converter, a buffer, a sample-and-hold circuit, a second-order continuous-time low-pass filter (CT-LPF), a comparator, and a timing circuit that is used to pulse the external light-emitting diode with a very low duty cycle to reduce its power consumption. The current steering technique is employed in the design of the CT-LPF to meet the requirement for very low cutoff frequency. The circuit operates from a 3-V lithium battery, occupies a core area of 0.46 mm/sup 2/ and has a power consumption of 4.5 mW. The measurement results corroborate with simulation results and show that the CT-LPF can achieve a cutoff frequency of as low as 0.25 Hz. This demonstrates the feasibility of current steering technique in the design of filter for low-frequency application.

A Gm-C low-pass filter for zero-IF mobile applications with a very wide tuning range

Abstract: A third-order G m -C Butterworth low-pass filter implementing G m -tuning and G m -switching to maximize the tuning range is described. This filter is intended to be used as a channel-selection/anti-aliasing filter in the analog baseband part of a zero-IF radio receiver architecture for multimode mobile communications. Its G m -switching feature allows extending the tuning range and adapting the power consumption. The filter's cutoff frequency ranges from 50 kHz to 2.2 MHz. An Input IP3 of up to +18 dBVp is achieved, for a total worst-case power consumption of 7.3 mW for both I and Q paths, and an effective area of less than 0.5 mm 2 in a 0.25-μm SiGe BiCMOS process. A new figure of merit is introduced for comparison of published low-pass tunable filters including noise, linearity, and tuning range.

Method and apparatus for removing baseline wander from an ECG signal

Abstract: According to one aspect of the invention, an improved ECG monitor includes a plurality of electrodes to be affixed to a patient's body to pick up ECG signals in an ECG signal band. The electrodes are electrically coupled to a plurality of input amplifiers. At least one analog to digital converter (“ADC”) is electrically coupled to the input amplifiers to digitize the ECG signals. A digital baseline wander filter has an internal finite impulse response (“FIR”) low pass filter characterized by a substantially trapezoidal impulse response. The baseline wander filter substantially removes a baseline wander signal component having a range of frequency components below the ECG signal band. The ECG waveform output signal is a baseline filtered ECG waveform representing the one or more of the ECG signals. The ECG waveform output signal from the improved ECG monitor is delayed less than 2 seconds from the ECG signals.

Miniaturized cross-coupled filter with second and third spurious responses suppression

Abstract: Novel miniaturized cross-coupled filter with second and third spurious responses suppression is proposed. This new filter structure is incorporated with the stepped-impedance resonator, which is beneficial for size diminution, and a proposed compact harmonic suppression cell that exhibits photonic bandgap (PBG) characteristics. When compared with a conventional cross-coupled filter, the proposed square stepped-impedance cross-coupled filter acquires more than 8% size reduction and spurious responses suppression simultaneously. Furthermore, the proposed filter performance shows almost 60-dB attenuation improvement to both second and third spurious frequencies.

Coding of coefficients of two-dimensional non-separable adaptive Wiener interpolation filter

Abstract: Standard video compression techniques apply motion-compensated prediction combined with transform coding of the prediction error. In the context of prediction with fractional-pel motion vector resolution it was shown, that aliasing components contained in an image signal are limiting the prediction accuracy obtained by motion compensation. In order to consider aliasing, quantisation and motion estimation errors, camera noise, etc., we analytically developed a two-dimensional (2D) non-separable interpolation filter, which is calculated for each frame independently by minimising the prediction error energy. For every fractional-pel position to be interpolated, an individual set of 2D filter coe±cients is determined. Since transmitting filter coefficients as side information results in an additional bit rate, which is almost independent for different total bit rates and image resolutions, the overall gain decreases when total bit rates decrease. In this paper we present an algorithm, which regards the non-separable two-dimensional filter as a polyphase filter. For each frame, predicting the interpolation filter impulse response through evaluation of the polyphase filter, we only have to encode the filter coefficients prediction error. This enables bit rate savings, needed for transmitting filter coe±cients of up to 75% compared to PCM coding. A coding gain of up to 1,2 dB Y-PSNR at same bit rate or up to 30% reduction of bit rate is obtained for HDTV-sequences compared to the standard H.264/AVC. Up to 0,5 dB (up to 10% bit rate reduction) are achieved for CIF-sequences.

New high-efficiency 2.5 V/0.45 W RWDM class-D audio amplifier for portable consumer electronics

Abstract: A single-chip of Class-D audio amplifier with high-power efficiency is presented. It includes a rectangular wave delta modulator (RWDM) and bridge-tied load output gate-drivers. The RWDM has a multiple inputs floating-gate hysteresis comparator and a feedback integrator formed by the external L-R low-pass filter. This monolithic Class-D audio amplifier with a maximum power efficiency of 92% has a flat frequency response with /spl plusmn/0.3 dB up to 20 kHz, and is capable of delivering up to 0.45 W of continuous average power into an 8-/spl Omega/ load at less than 0.5% total harmonic distortion plus noise from a 2.5-V power supply in the high fidelity range (20 Hz-20 kHz).

6-15 GHz RF MEMS tunable filters

Abstract: Capacitive RF MEMS switches can be used to adaptively tune microwave filter elements for use in communications and radar. This work describes progress towards building a 6-15 GHz tunable bandpass filter bank. Three banks of tunable high-pass and low-pass filters covering 6-15 GHz were designed and tested. The low-pass filters showed loss ranging from 2 to 4 dB with rejection better than 60 dB. The high-pass filter showed insertion losses ranging from 3 to 5 dB with similar rejection. These filters were cascaded in series in three banks to obtain a tunable bandwidth/center frequency bandpass filter that covers 6-15 GHz.

Fabry-perot tunable filter systems and methods

Abstract: A spectral filter includes a two-dimensional array of Fabry-Perot cavity structures, a controller, and a sampling circuit used to switch the Fabry-Perot cavity. The filter receives an incoming image, the sampling circuit switches the cavity to generate a filter image, and the filtered image is detected by the photodetectors to convert a filtered image into digital data. The controller coordinates all the image captures functions of the spectral filter.

High-frequency magnetic microstrip local bandpass filters

Abstract: This paper presents results for a compact, local bandpass filter. We fabricated the filter using two different ferromagnetic materials, Fe and NiFe, in a microstrip geometry. The different values of saturation magnetization of the two ferromagnets give rise to different gyromagnetic resonance frequencies and provide a local bandpass region between them. The results show that the center frequency of the filter can be tuned over a wide range by adjusting the magnitude of the bias magnetic field. The filter’s bandwidth is almost constant (3.5±0.5GHz) over the entire tuning frequency range (6–26GHz). Theoretical calculations are in good agreement with the experimental results.

Frequency dependency of the relationship between perceived auditory source width and the interaural cross-correlation coefficient for time-invariant stimuli.

Abstract: Previous research has indicated that the relationship between the interaural cross-correlation coefficient (IACC) of a narrow-band sound and its perceived auditory source width is dependent on its frequency. However, this dependency has not been investigated in sufficient detail for researchers to be able to properly model it in order to produce a perceptually relevant IACC-based model of auditory source width. A series of experiments has therefore been conducted to investigate this frequency dependency in a controlled manner, and to derive an appropriate model. Three main factors were discovered in the course of these experiments. First, the nature of the frequency dependency of the perceived auditory source width of stimuli with an IACC of 1 was determined, and an appropriate mathematical model was derived. Second, the loss of perceived temporal detail at high frequencies, caused by the breakdown of phase locking in the ear, was found to be relevant, and the model was modified accordingly using rectification and a low-pass filter. Finally, it was found that there was a further frequency dependency at low frequencies, and a method for modeling this was derived. The final model was shown to predict the experimental data well.

A simple method for suppression of resonance oscillation in PWM current source converter

Abstract: This paper deals with a suppression method for the resonance oscillation in the ac side of a pulse-width modulation (PWM) current source converter. The converter is operated with the PWM switching pattern which is generated by the full digital control of computer software. The resonance current, caused by the LC low pass filter at the step change of the pattern, can be effectively suppressed by one pulse control of the pattern. The proposed method does not need to have the feedback loop of the current/voltage and does not offer the switching stress of the devices. The switching timing of the control is determined by pre-calculation of the off-line in consideration of the circuit constants. The experimental and the simulated results in the single-phase and the three-phase PWM converters are given, compared with those without the control, and show good response of the supply current.