Showing papers on "Low-pass filter published in 2008"

A complementary filter for attitude estimation of a fixed-wing UAV

Abstract: This paper considers the question of using a nonlinear complementary filter for attitude estimation of fixed-wing unmanned aerial vehicle (UAV) given only measurements from a low-cost inertial measurement unit. A nonlinear complementary filter is proposed that combines accelerometer output for low frequency attitude estimation with integrated gyrometer output for high frequency estimation. The raw accelerometer output includes a component corresponding to airframe acceleration, occurring primarily when the aircraft turns, as well as the gravitational acceleration that is required for the filter. The airframe acceleration is estimated using a simple centripetal force model (based on additional airspeed measurements), augmented by a first order dynamic model for angle-of-attack, and used to obtain estimates of the gravitational direction independent of the airplane manoeuvres. Experimental results are provided on a real-world data set and the performance of the filter is evaluated against the output from a full GPS/INS that was available for the data set.

Underwater Acoustic Communications: Design Considerations on the Physical Layer

Abstract: Acoustic propagation is characterized by three major factors: attenuation that depends on the signal frequency, multipath propagation, and low speed of sound (1500 m/s). The channel has a sparse impulse response, where each physical path acts as a time-varying low-pass filter, and motion introduces additional Doppler spreading and shifting. Because propagation is best supported at low frequencies, acoustic communication systems are inherently wideband. The way in which these facts influence the design of signal processing methods is considered for single-carrier and multi-carrier systems. Moreover, the facts that the available bandwidth and transmission power depend heavily on the distance, and that channel latency is high, bear important implications on the design of network architectures and related protocols.

A Power Optimized Continuous-Time $\Delta \Sigma $ ADC for Audio Applications

Abstract: We present design considerations for low-power continuous-time modulators. Circuit design details and measurement results for a 15 bit audio modulator are given. The converter, designed in a 0.18 mum CMOS technology, achieves a dynamic range of 93.5 dB in a 24 kHz bandwidth and dissipates 90 muW from a 1.8 V supply. It features a third-order active-RC loop filter, a very low-power 4-bit flash quantizer, and an efficient excess-delay compensation scheme to reduce power dissipation.

Steady-State and Dynamic Study of Active Power Filter With Efficient FPGA-Based Control Algorithm

Abstract: A new approach using field-programmable gate array (FPGA) to implement a fully digital control algorithm of active power filter (APF) is proposed in this paper. This FPGA-based controller integrates the whole signal-processing function of an APF, including synchronous-reference-frame transform, low-pass filter, three-phase phase-locked loop, inverter-current controller, etc. By case studies on the principle, performance, and architecture, these control blocks are implemented in real-time and synthesized into a medium-scale FPGA chip by adopting some useful digital-signal-processing techniques, such as pipelining, folding and strength reduction, with respect to minimization of hardware resource and enhancement of operating frequency. As a result, the whole algorithm needs around 5000 logic elements and can run at synchronous system-clock rates of up to 65 MHz. Experimental results on a laboratory prototype are given to demonstrate performance of the proposed approach during steady-state and dynamic operations.

Digital Lock-In Detection for Discriminating Multiple Modulation Frequencies With High Accuracy and Computational Efficiency

Abstract: We introduce a novel digital lock-in detection technique for simultaneously measuring the amplitude and phase of multiple amplitude-modulated signals. Using particular modulation and sampling constraints and averaging filters, we achieve optimal noise reduction and discrimination between sources of different modulation frequencies. Furthermore, it is shown that the digital lock-in technique can be performed as a simple matrix multiplication, which considerably reduces the computation time. The digital lock-in algorithm is described and analyzed under certain sampling and modulation conditions, and results are shown for both numerical and experimental data.

A Three-Phase Four-Wire Power Filter Comprising a Three-Phase Three-Wire Active Power Filter and a Zig–Zag Transformer

Abstract: Active power filters (APFs) have been developed to solve the problems of harmonic suppression and reactive power compensation simultaneously, In this paper, a three-phase four-wire power filter comprising a three-phase three-wire APF and a Zig-Zag transformer is developed. A hardware prototype is implemented and tested to verify the performance of the proposed power filter under various ideal and non-ideal power conditions. Experimental results show that this three-phase four-wire power filter has the desired performance under limited zero sequence utility voltage.

Coefficient decimation approach for realizing reconfigurable finite impulse response filters

Abstract: A new approach to implement computationally efficient reconfigurable finite impulse response (FIR) filter is presented in this paper If the coefficients of an FIR filter are decimated by M, ie, if every Mth coefficient of the filter is kept unchanged and remaining coefficients are changed to zeros, a multi-band frequency response will be obtained The resulting frequency responses will have centre frequencies at 2pik/M, where k is an integer ranging from 0 to M-1 If these multi-band frequency responses are selectively masked using inherently low complex wide transition-band masking filters, different low-pass, high-pass, bandpass, and bandstop filters can be obtained If every Mth coefficient is grouped together removing the zero coefficients in between, a decimated frequency response in comparison to the original frequency response is obtained In this paper, we also show the design of a reconfigurable filter bank using the above approach

Stopband-Expanded Low-Pass Filters Using Microstrip Coupled-Line Hairpin Units

Abstract: In this letter, a class of stopband-expanded low-pass filters (LPFs) is proposed via attenuation poles of microstrip coupled-line hairpin unit. By centrally tap-connecting this coupled-line unit and adjusting its coupling strength, three attenuation poles can be excited above the desired low passband. A coupled-line-oriented closed-form model is then constructed to provide a physical insight into the excitation of these poles and to execute an efficient synthesis design of this LPF. Two prototype filters with single and two units are finally designed with the specified cutoff frequency at 2.5 GHz. Measured results of the fabricated filters evidently demonstrate good LPF performance, sharp roll-off skirt, and a wide upper-stopband of 3.2 to 11.8 GHz with the insertion loss higher than 20.0 dB.

Time delay estimation

Abstract: A time differential is estimated between a plurality of signals by determining a filter response of a first electrical signal with a first filter array, determining a filter response of a second electrical signal with a second filter array, and determining, based at least on the filter response of the first electrical signal and the filter response of the second electrical signal, a time differential between the first electrical signal and the second electrical signal. A first optical signal is converted into the first electrical signal and a second optical signal is converted into the second electrical signal. The filter response of the first electrical signal and the filter response of the second electrical signal are sampled and the time differential between the first electrical signal and the second electrical signal is determined based at least on the sampled filter response of the first electrical signal and the sampled filter response of the second electrical signal.

Improved powder filters for qubit measurements.

Abstract: We designed and fabricated miniature low-pass metal powder filters suitable for noise-sensitive measurements at cryogenic temperatures. In comparison with previous powder filters, our filters have a much better frequency response and significantly smaller dimensions (0.7cm3 including the plugs) and can also be used as hermetic feedthroughs at low temperatures. Their transmission characteristics are smooth, contain no ripples, and have a steep decay above the cutoff frequency. At 4.2K the cutoff frequency of a single filter is fc=1MHz and the roll-off is −50dB per decade. All of the fabricated filters have identical frequency responses at 4.2K and their characteristics are reliably reproducible.

Filter design for grid connected PV inverters

Abstract: This paper proposes filter design guideline for single-phase grid-connected PV inverters By analyzing the instantaneous voltage applied on the filter inductor, the switching ripple current through the filter inductor is precisely calculated Therefore, filter inductance can be designed accurately which guaranties the switching ripple current under the target value Proposed filter design method is verified by experiment

Compact Elliptic-Function Low-Pass Filter Using Defected Ground Structure

Abstract: A novel elliptic-function low-pass filter (LPF) is presented, which consists of a dumb-bell-shaped defected ground structure (DB-DGS), a spiral-shaped defected ground structure (SP-DGS) and a broadened microstrip line. The DB-DGS provides the required wideband attenuation in stopband, while the SP-DGS provides steep transition from passband to stopband. A 2.4 GHz five-pole LPF is developed and experimental results show that it has a sharp cutoff frequency response. The measured passband insertion-loss is below 0.3 dB, and the rejection band over 20 dB is from 2.95 to 8.25 GHz.

FIR Digital Filters Design: Particle Swarm Optimization Utilizing LMS and Minimax Strategies

Abstract: In this paper, a FIR filter is designed using particle swarm optimization (PSO). Two design cases are organized as follows: low-pass and band-pass filter. In addition, the authors examine the utility of various error norms such as least mean squares (LMS) and minimax, and their impact on convergence behavior and optimal resultant frequency response. The effect of different population and iteration in PSO based FIR filter design is investigated, too. Examples of 1-D FIR filters are given using the above methodologies to illustrate the usefulness and efficiency of the proposed techniques.

Efficient Acoustic Echo Cancellation With Reduced-Rank Adaptive Filtering Based on Selective Decimation and Adaptive Interpolation

Abstract: This paper presents a new approach to efficient acoustic echo cancellation (AEC) based on reduced-rank adaptive filtering equipped with selective-decimation and adaptive interpolation. We propose a novel structure of an AEC scheme that jointly optimizes an interpolation filter, a decimation unit, and a reduced-rank filter. With a practical choice of parameters in AEC, the total computational complexity of the proposed reduced-rank scheme with the normalized least mean square (NLMS) algorithm is approximately half of that of the full-rank NLMS algorithm. We discuss the convergence properties of the proposed scheme and present a convergence condition. First, we examine the performance of the proposed scheme in a single-talk situation with an error-minimization criterion adopted in the decimation selection. Second, we investigate the potential of the proposed scheme in a double-talk situation by employing an ideal decimation selection. In addition to mean squared error (MSE) and power spectrum analysis of the echo estimation error, subjective assessments based on absolute category rating are performed, and the results demonstrate that the proposed structure provides significant improvements compared to the full-rank NLMS algorithm.

Compact ultra-wideband bandpass filter with defected ground structure

Abstract: A compact planar microstrip ultra-wideband (UWB) bandpass filter is presented in this paper. The proposed UWB filter is realized by cascading a high pass filter (HPF) and a lowpass filter (LPF). HPF with short-circuited stubs is used to realize the lower stopband and a lowpass filter based on a defected ground array in the ground plane employed to attenuate the upper stopband. One such a bandpass filter is designed and simulated.

Power amplifying apparatus

Abstract: A power amplifying apparatus includes a high-speed low pass filter which inputs an envelope signal included in a transmission signal therein, a low-speed low pass filter which inputs the envelope signal therein, a determination unit which inputs the envelope signal therein and determines rising or falling of the envelope signal, a selecting unit which selects one of the high-speed low pass filter and the low-speed low pass filter according to a determined result of the determination unit, and a voltage supply unit which generates a voltage based on a signal input according to a selection by the selecting unit and supplies the voltage to a power amplifier which inputs the transmission signal therein so as to amplify a power of the transmission signal.

The Shiftable Complex Directional Pyramid—Part I: Theoretical Aspects

Abstract: This paper presents an over-complete multiscale decomposition by combining the Laplacian pyramid and the complex directional filter bank (DFB). The filter bank is constructed in such a way that each complex directional filter is analytical using the dual-tree structure of real fan filters. Necessary and sufficient conditions in order for the resulting multirate filter bank to be shift-invariant in energy sense (shiftability) are derived in terms of the magnitude and phase responses of these filters. Their connection to 2D Hilbert transform relationship is established. The proposed transform possesses several desirable properties including multiresolution, arbitrarily high directional resolution, low redundant ratio, and efficient implementation.

A 6 th -Order 100μA 280MHz Source-Follower-Based Single-loop Continuous-Time Filter

Abstract: The source follower is a well known basic building block for CMOS design. A capacitively loaded source follower acts as a 1st-order low- pass filter and exhibits excellent linearity, especially with reduced overdrive voltages. In these source-follower features have been used advantageously in the design of a 2nd-order (biquadratic) low-pass filter and a 4th- order filter, which was made by cascading two 2nd-order cells. We have used this technique to design single-loop high-order source- follower-based continuous-time filters that, like ladder filters, have transfer functions that are insensitive to component variations. An efficient CMOS realization demonstrates the principle an achieves lower power and smaller area than other solutions.

A Low-Power CMOS Front-End for Photoplethysmographic Signal Acquisition With Robust DC Photocurrent Rejection

Abstract: A micro-power CMOS front-end, consisting of a transimpedance amplifier (TIA) and an ultralow cutoff frequency lowpass filter for the acquisition of photoplethysmographic signal (PPG) is presented. Robust DC photocurrent rejection for the pulsed signal source is achieved through a sample-and-hold stage in the feed-forward signal path and an error amplifier in the feedback path. Ultra-low cutoff frequency of the filter is achieved with a proposed technique that incorporates a pair of current-steering transistors that increases the effective filter capacitance. The design was realized in a 0.35-mum CMOS technology. It consumes 600 muW at 2.5 V, rejects DC photocurrent ranged from 100 nA to 53.6 muA, and achieves lower-band and upper-band - 3-dB cutoff frequencies of 0.46 and 2.8 Hz, respectively.

Amplifier with integrated filter

Abstract: An amplifier with integrated filter (e.g., an LNA) is described. In one design, the amplifier may include a gain stage, a filter stage, and a buffer stage. The gain stage may provide signal amplification for an input signal. The filter stage may provide filtering for the input signal. The buffer stage may buffer a filtered signal from the filter stage. The amplifier may further include a second filter stage and a second buffer stage. The second filter stage may provide additional filtering for the input signal. The second buffer stage may buffer a second filtered signal from the second filter stage. All of the stages may be stacked and coupled between a supply voltage and circuit ground. The filter stage(s) may implement an elliptical lowpass filter. Each filter stage may include an inductor and a capacitor coupled in parallel and forming a resonator tank to attenuate interfering signals.

Efficient sampling of sparse wideband analog signals

Abstract: Periodic nonuniform sampling is a known method to sample spectrally sparse signals below the Nyquist rate. This strategy relies on the implicit assumption that the individual samplers are exposed to the entire frequency range. This assumption becomes impractical for wideband sparse signals. The current paper proposes an alternative sampling stage that does not require a full-band front end. Instead, signals are captured with an analog front end that consists of a bank of multipliers and lowpass filters whose cutoff is much lower than the Nyquist rate. The problem of recovering the original signal from the low-rate samples can be studied within the framework of compressive sampling. An appropriate parameter selection ensures that the samples uniquely determine the analog input. Moreover, the analog input can be stably reconstructed with digital algorithms. Numerical experiments support the theoretical analysis.

Single-ensemble-based eigen-processing methods for color flow imaging - Part I. The Hankel-SVD filter

Abstract: Because of their adaptability to the slow-time signal contents, eigen-based filters have shown potential in improving the flow detection performance of color flow images. This paper proposes a new eigen-based filter called the Hankel-SVD filter that is intended to process each slow- time ensemble individually. The new filter is derived using the notion of principal Hankel component analysis, and it achieves clutter suppression by retaining only the principal components whose order is greater than the clutter eigen- space dimension estimated from a frequency-based analysis algorithm. To assess its efficacy, the Hankel-SVD filter was first applied to synthetic slow-time data (ensemble size: 10) simulated from two different sets of flow parameters that model: (1) arterial imaging (blood velocity: 0 to 38.5 cm/s, tissue motion: up to 2 mm/s, transmit frequency: 5 MHz, pulse repetition period: 0.4 ms) and 2) deep vessel imaging (blood velocity: 0 to 19.2 cm/s, tissue motion: up to 2 cm/s, transmit frequency: 2 MHz, pulse repetition period: 2.0 ms). In the simulation analysis, the post-filter clutter- to-blood signal ratio (CBR) was computed as a function of blood velocity. Results show that for the same effective stopband size (50 Hz), the Hankel-SVD filter has a narrower transition region in the post-filter CBR curve than that of another type of adaptive filter called the clutter- downmixing filter. The practical efficacy of the proposed filter was tested by application to in vivo color flow data obtained from the human carotid arteries (transmit frequency: 4 MHz, pulse repetition period: 0.333 ms, ensemble size: 10). The resulting power images show that the Hankel-SVD filter can better distinguish between blood and moving- tissue regions (about 9 dB separation in power) than the clutter-downmixing filter and a fixed-rank multi-ensemble- based eigen-filter (which showed a 2 to 3 dB separation).

Implementation of a Dynamic Voltage Restorer System Based on Discrete Wavelet Transforms

Abstract: This paper presents an implementation of the discrete wavelet transform (DWT) using passive LC filters for operating a dynamic voltage restorer (DVR) system. The proposed implementation is based on designing Butterworth passive LC filters with cutoff frequencies that are identical to cutoff frequencies of DWT associated digital filters. These passive LC filters can detect abnormal conditions that may disrupt the quality of the power supplied to sensitive loads in a power system. Detecting any abnormal condition is realized through extracting high- and low-frequency components present in system voltages using high-pass and low-pass filters, respectively. The designed Butterworth passive LC passive filters are third-order systems to simplify their practical implementation as well as their integration with the test power system and the DVR. Simulation and experimental test results for transient voltage dip and steady-state harmonic distortion cases show significant performance improvement of the DVR system operated by the designed Butterworth passive LC filters. The proposed DWT-operated DVR system using Butterworth passive LC filters is implemented and tested for improving the power quality under different abnormal conditions.

Particulate substance detector

Abstract: PROBLEM TO BE SOLVED: To provide a particulate substance detector capable of detecting a particulate substance with high accuracy by using a sensor circuit by simple structure.SOLUTION: A particulate substance detector 100 includes: a voltage application circuit 22 which applies a voltage signal of a sine wave obtained by syntonizing a voltage signal of a square wave by a lowpass filter whose Q value is 1.5-3; a current voltage conversion circuit 26 which converts the applied voltage into current; a detection circuit 23 which decomposes output of the current voltage conversion circuit 26 into orthogonal components by synchronous detection of two or more phases to be detected; and characteristic measurement means 20 which has two or more calibration elements 24a and 24b electrically connected to the voltage application circuit 22 and the current voltage conversion circuit 26 at a state that the calibration elements can be switched to a pair of measurement electrodes 12a and 12b. The detector calculates a calibration matrix Q of the current voltage conversion circuit 26 from two or more calibration detection values measured by using the two or more calibration elements 24a and 24b, respectively and original true values of the two or more calibration elements, and calibrates a detection value which is measured between the pair of measurement electrodes 12a and 12b.

A Least-Squares Filter Design Technique for the Compensation of Frequency Response Mismatch Errors in Time-Interleaved A/D Converters

Abstract: This paper introduces a least-squares filter design technique for the compensation of frequency response mismatch errors in M-channel time-interleaved analog-to-digital converters The overall compensation system is designed by determining M filter impulse responses analytically through M separate matrix inversions The proposed technique offers an alternative to least-squares techniques that determine all filters simultaneously Several design examples are included for illustration

Resistorless first-order all-pass filter with electronic tuning

Abstract: A first-order all-pass filter (APF) with electronic tuning properties is presented The filter consists of only active components and a single-grounded capacitor The circuit is cascadable, has small sensitivities, and suitable for monolithic integration, and it can also operate at high frequencies

A 2.4-GHz ISM-Band Sliding-IF Receiver With a 0.5-V Supply

Abstract: We report an ultra-low-voltage RF receiver for applications in the 2.4 GHz band, designed in a 90 nm CMOS technology. The sliding-IF receiver prototype includes an LNA, an image-reject LC filter with single-ended to differential conversion, an RF mixer, an LC IF filter, a quadrature IF mixer, RF and IF LO buffers, and an I/Q baseband section with a VGA and a low-pass channel-select filter in each path, all integrated on-chip. It has a programmable overall gain of 30 dB, noise figure of 18 dB, out-of-channel IIP3 of -22 dBm. The 3.4 mm2 chip consumes 8.5 mW from a 0.5 V supply.

A Simple Ultra-Wideband Suspended Stripline Bandpass Filter With Very Wide Stop-Band

Abstract: This letter introduces a simple ultra-wideband suspended stripline filter with a pass-band from 3.1 to 10.6 GHz and a very wide stop-band up to more than 25 GHz. The filter is realized by capacitive coupling of a quasi-lumped low-pass filter to the I/O ports. Insertion loss in the pass-band is better than 0.5 dB. The filter has a length of 13.8 mm. Excellent agreement is achieved between measured and simulated results.

Analog finite impulse response filter

Abstract: According to one embodiment of the invention, a programmable finite impulse response (FIR) filter is implemented with differential isolation circuits to isolate parasitic capacitance from attenuating an output signal at both a first and second differential output terminals of the FIR filter. The FIR includes a summing circuit that provides operational advantages to the FIR filter.