Complex Bandpass Filter Research Articles

Frequency/Sequence Selective Filters for Power Quality Improvement in a Microgrid

A microgrid is capable of providing highly reliable power supply to sensitive loads like semiconductor fabrication or computer data processing equipment. This is especially required when the sensitive loads are located in distribution systems that also contain several single-phase and/or nonlinear loads. Voltage source inverter (VSI) based distributed energy resources can provide power quality conditioning support. They require filters to accurately detect unbalance and harmonics in the system. The state-of-the-art filtering techniques in three-phase power systems involve employing complex bandpass filters that pass frequencies within a band without much attenuation. Such methods however give good dynamic performance only when there is a wide separation between the desired and undesired frequencies. In power distribution systems containing imbalances and harmonic generating loads, the gap between the two frequencies may be very small, and therefore such methods don't offer good performance. This paper proposes improved methods of filtering signals in three-phase, three-wire power systems, especially when there is a narrow gap between the desired and undesired frequencies. The proposed techniques contain both complex bandpass and bandstop sections and are designed on three-phase space-vector quantities. Simulation and experimental results are presented to validate these novel filtering concepts.

G<sub>m</sub>-C Complex Band-Pass Filter with Tuning Circuit in 0.18μm CMOS

This paper presents a 0.18μm CMOS based Gm-C complex band-pass (CBP) filter with tuning circuit. Active-Gm-C structure with Nauta transconductor and phase-locked loop (PLL) architecture are adopted by the filter and the tuning circuit respectively which can achieve accurate frequency response. The layout size is 970μm×920μm. Under a 1.8V supply voltage, measurement results show that the pass-band gain and the ripple of the filter is 3.1dB and 3dB respectively. The bandwidth after tuning is 32.5MHz, image rejection ratio (IRR) is about 47dB, and the power dissipation of the filter is about 21.6mW.

A 1-V 1.2-mW CMOS medradio receiver for biomedical applications

An ultra-low-power low-voltage 401–406 MHz Medical Device Radiocommunications Service (MedRadio) receiver for continuous wireless communication in biomedical applications is demonstrated using 0.18-μm CMOS technology. Although using a low-IF architecture, careful consideration is done for individual block-level circuit design to minimize the overall power consumption. The receiver chain consists of a complementary current-reuse LNA, an in-phase/quadrature folded mixer, an eighth-order complex bandpass filter, a limiting amplifier chain with RSSI, and a frequency synthesizer with a quadrature VCO. The proposed receiver achieves a gain of over 80 dB, noise figure of 14 dB, image rejection of 32 dB, and phase noise of −106 dBc/Hz at 100 kHz offset while consuming less than 1.2 mW from a 1-V supply voltage with 1.8 mm2 of core die area. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2821–2825, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27205

A 1.8-V, 5-mA reconfigurable analog baseband circuit for low-IF multi-mode multi-band receivers

A 1.8-V, 5-mA reconfigurable analog baseband circuit for low-intermediate frequency multi-mode multi-band receivers is presented. It consists of four fixed-gain amplifiers, four programmable gain amplifiers, a complex band-pass filter (CBPF) with reconfigurable bandwidth and a received signal strength indicator (RSSI). CBPF is implemented as the third-order Bessel active resistor–capacitor structure to provide the image rejection with flat group delay, and one on-chip automatic frequency tuning circuit is utilised to set the accurate frequency characteristics and overcome the effects of the process and temperature variations. The reconfigurable analog baseband circuit has been implemented in 0.18 µm complementary-symmetry metal–oxide–semiconductor. The measured results show that the presented circuit could provide 34 dB variable gain, 2 MHz/1 MHz/0.5 MHz reconfigurable bandwidth and accurate RSSI indicator. The analog baseband circuit is powered with a 1.8-V supply and totally draws a current of 5 mA.

MULTISTAGE FILTERS FOR IDENTIFICATION OF EUKARYOTIC PROTEIN CODING REGIONS

A class of multistage filters, namely, real narrowband bandpass filter (RNBPF) has been previously used for identification of protein coding regions. This filter passes the frequency component at 2π/3 along with its conjugate. This conjugate frequency component may degrade the identification accuracy. To improve the identification accuracy, two types of multistage filters are proposed in this paper. A complex narrowband bandpass filter (CNBPF) is proposed for suppressing the conjugate frequency component which, in turn, reduces the background noise present in the deoxyribonucleic acid (DNA) spectrum and improves identification accuracy. By cascading RNBPF with moving average filter (RNBPFMA), another type of multistage filter is proposed. As moving average filter smooth out the rapid variations in the DNA spectrum, RNBPFMA improves the identification accuracy. The computational complexity of RNBPFMA is less than that of CNBPF. The RNBPF and proposed multistage filters are compared with previously reported short-time discrete Fourier transform (ST-DFT) method in terms of computational complexity. It is found that multistage filters reduce the computational load to a greater extent compared to ST-DFT method. The identification accuracy of the proposed CNBPF and RNBPFMA methods is compared with existing anti-notch filter and RNBPF methods. The results show that proposed methods outperform existing methods in terms of identification accuracy for benchmark data sets.

Proposal of channel-grouping wireless-transceiver architecture for suppressing local-oscillator phase noise

This paper proposes an architecture-level solution to suppress the phase noise of local oscillators in wireless-transceiver LSIs. Because a phase-looked loop (PLL) supplies only one local oscillator (LO) frequency for multiple channels, large loop bandwidth of the PLL can be used for suppressing the phase noise. Simulation results show that a sixteen-channel grouping can suppress the phase noise more than 24dB in narrow-band wireless systems. Channel selection in receive mode can be ensured by a variable intermediate frequency (IF) complex band-pass filter. Local-leak and image signals in transmit mode can be suppressed by a quadrature up-conversion mixer and radio frequency (RF) band-pass filter with high-IF configuration. A digital-analog converter, analog-digital converter, and digital LSI are in charge of modulation and demodulation of the variable-IF signals.

A New Approach to Complex Bandpass Sigma Delta Modulator Design for GPS/Galileo Receiver

In this paper, new complex band pass filter architecture for continuous time complex band pass sigma delta modulator is presented. In continuation of paper the modulator is designed for GPS and Galileo receiver. This modulator was simulated in standard 0.18 μm CMOS TSMC technology and has bandwidth of 2MHz and 4MHz for GPS and Galileo centered in 4.092 MHz. The dynamic range (DR) is 56.5/49 dB (GPS/Galileo) at sampling rate of 125 MHz. The modulator has power consumption of 4.1 mw with 3 V supply voltage.

Power-Scalable, Complex Bandpass/Low-Pass Filter With I/Q Imbalance Calibration for a Multimode GNSS Receiver

A power-scalable reconfigurable filter with in-phase/quadrature (I/Q) imbalance calibration for a multimode Global Navigation Satellite Systems (GNSS) receiver is presented. The filter is reconfigurable as either a fifth-order complex bandpass filter exhibiting a tunable intermediate frequency (4.092, 6.138, 10.23, 12.296, 13.29, 18.4, and 20.442 MHz) and bandwidth (2.2, 4.2, 8, 10, and 18 MHz) or a third-order low-pass filter with tunable bandwidth (5 and 9 MHz). A flexible current-reuse operational amplifier with a power-scaling technique is proposed to lower the power consumption, and the image-rejection ratio is improved by almost 20 dB by introducing an I/Q imbalance calibration circuit before the filter. The filter, which was implemented in 65-nm CMOS, consumes 2.9-19.5 mW in different modes, with the I/Q calibration circuit consuming 0.9 mW.

Adaptive Phasor and Frequency-Tracking Schemes for Wide-Area Protection and Control

The steady-state performance of phasor measurement units (PMUs) is well standardized in the recently issued revised IEEE Std. C37.118. The Western Electricity Coordinating Council (WECC) has developed dynamic performance requirements for PMU filters as a means to guarantee better, uniform PMU response under dynamic conditions, such as power swings and changing harmonics. These have been endorsed by North American Synchrophasor Initiative (NASPI) for its wide-area monitoring infrastructure. The main purpose of this paper is to present a new framework for designing PMU filtering algorithms capable of meeting or exceeding the WECC/NASPI requirements, while achieving an optimum transient response time. To this end, an adaptive complex bandpass filter derived from the exponentially modulated filter bank theory has been devised. It is built from freely chosen low-pass filter prototypes that fulfill the WECC requirements. The static and dynamic performances of two specific schemes dedicated to control and monitoring with 4- and 7-cycle response-time, respectively, are ascertained under noisy waveforms and changing harmonics with system frequency varying from 40 to 80 Hz. The center-frequency adaptation approach is shown to be intrinsically superior to the frequency compensation scheme, especially under fast varying frequency and changing harmonics.

The Implementation of MSK Based on DSP and Complex Bandpass Processing

A novel method of minimum frequency shift keying (MSK) which based on digital signal processing (DSP) and complex bandpass processing is proposed in the article. According to the bit value of the input data, the MSK complex bandpass signal is directly produced and then is complex bandpass filtered, the real part of the complex bandpass signal is fetched to achieve the MSK modulation. The receiving signal of MSK is sampled, and then complex bandpass filtered to attain the complex bandpass signal. The complex bandpass signal and conjugate signal of its delayed version and the phase shift factor are multiplied together. According to the imaginary part of the product, the original data is recovered. The design method of complex bandpass filter is introduced also.

A reconfigurable OTA-C baseband filter with wide digital tuning for GNSS receivers

The design of a digitally-tunable sixth-order reconfigurable OTA-C filter in a 0.18-μm RFCMOS process is proposed. The filter can be configured as a complex band pass filter or two real low pass filters. An improved digital automatic frequency tuning scheme based on the voltage controlled oscillator technique is adopted to compensate for process variations. An extended tuning range (above 8:1) is obtained by using widely continuously tunable transcon-ductors based on digital techniques. In the complex band pass mode, the bandwidth can be tuned from 3 to 24 MHz and the center frequency from 3 to 16 MHz.

Estimation of the instantaneous amplitude and the instantaneous frequency of audio signals using complex wavelets

This work presents a method of analyzing and synthesizing audio signals that uses complex wavelets. In the method, the input signal is filtered by a complex bandpass filter bank through a discrete version of the complex continuous wavelet transform. A general theoretical signal with time-dependent amplitude and phase has been analyzed. The analysis of the information provided by the modulus and the phase of the complex continuous wavelet transform was used to develop an additive analysis/synthesis algorithm for audio signals called complex wavelet additive synthesis. To illustrate the method, this new algorithm has been used to analyze the following four synthetic, non-stationary signals that have different frequency variation laws: a linear chirp, a quadratic chirp, a hyperbolic chirp and an FM signal with a sinusoidal excursion. Finally, the validity of the algorithm has been tested by comparing the results of an analysis of two real sounds with the proposed algorithm and with one existing technique, namely spectral modelling synthesis (SMS).

Design of Complex BPF with Automatic Digital Tuning Circuit for Low-IF Receivers

This paper describes the architecture and implementations of an automatic digital tuning circuit for a complex bandpass filter (BPF) in a low-power and low-cost transceiver for applications such as personal authentication and wireless sensor network systems. The architectural design analysis demonstrates that an active RC filter in a low-IF architecture can be at least 47.7% smaller in area than a conventional gm-C filter; in addition, it features a simple implementation of an associated tuning circuit. The principle of simultaneous tuning of both the center frequency and bandwidth through calibration of a capacitor array is illustrated as based on an analysis of filter characteristics, and a scalable automatic digital tuning circuit with simple analog blocks and control logic having only 835 gates is introduced. The developed capacitor tuning technique can achieve a tuning error of less than ±3.5% and lower a peaking in the passband filter characteristics. An experimental complex BPF using 0.18µm CMOS technology can successfully reduce the tuning error from an initial value of -20% to less than ±2.5% after tuning. The filter block dimensions are 1.22mm × 1.01mm; and in measurement results of the developed complex BPF with the automatic digital tuning circuit, current consumption is 705µA and the image rejection ratio is 40.3dB. Complete evaluation of the BPF indicates that this technique can be applied to low-power, low-cost transceivers.

Latency analysis of single auditory evoked M100 responses by spatio-temporal filtering

Appropriate spatial filtering followed by temporal filtering is well suited for the single-trial analysis of multi-channel magnetoencephalogram or electroencephalogram recordings. This is demonstrated by the results of a single-trial latency analysis obtained for auditory evoked M100 responses from nine subjects using two different stimulation frequencies. Spatial filters were derived automatically from the data via noise-adjusted principle component analysis, and single-trial latencies were estimated from the signal phase after complex bandpass filtering. For each of the two stimulation frequencies, estimated single-trial latencies were consistent with results obtained from a standard approach using averaged evoked responses. The quality of the estimated single-trial latencies was additionally assessed by their ability to separate between the two different stimulation frequencies. As a result, more than 80% of the single trials can be classified correctly by their estimated latencies.

A Second-Order Multibit Complex Bandpass AD Modulator with I, Q Dynamic Matching and DWA Algorithm

We have designed, fabricated and measured a second-order multibit switched-capacitor complex bandpass ΔΣAD modulator to evaluate our new algorithms and architecture. We propose a new structure of a complex bandpass filter in the forward path with I, Q dynamic matching, that is equivalent to the conventional one but can be divided into two separate parts. As a result, the AS modulator, which employs our proposed complex filter can also be divided into two separate parts, and there are no signal lines crossing between the upper and lower paths formed by complex filters and feedback DACs. Therefore, the layout design of the modulator can be simplified. The two sets of signal paths and circuits in the modulator are changed between I and Q while CLK is changed between high and low by adding multiplexers. Symmetric circuits are used for I and Q paths at a certain period of time, and they are switched by multiplexers to those used for Q and I paths at another period of time. In this manner, the effect of mismatches between I and Q paths is reduced. Two nine-level quantizers and four DACs are used in the modulator for low-power implementations and higher signal-to-noise-and-distortion (SNDR), but the nonlinearities of DACs are not noise-shaped and the SNDR of the ΔΣAD modulator degrades. We have also employed a new complex bandpass data-weighted averaging (DWA) algorithm to suppress nonlinearity effects of multibit DACs in complex form to achieve high accuracy; it can be realized by just adding simple digital circuitry. To evaluate these algorithms and architecture, we have implemented a modulator using 0.18 μm CMOS technology for operation at 2.8 V power supply; it achieves a measured peak SNDR of 64.5 dB at 20MS/s with a signal bandwidth of 78 kHz while dissipating 28.4 mW and occupying a chip area of 1.82 mm 2 . These experimental results demonstrate the effectiveness of the above two algorithms, and the algorithms may be extended to other complex bandpass ΔΣAD modulators for application to low-IF receivers in wireless communication systems.

A 20 mW 3.24 ${\hbox {mm}}^{2}$ Fully Integrated GPS Radio for Location Based Services

The challenges in the co-existence of a GPS receiver with cellular phones for location based services are addressed in this paper. A fully integrated GPS radio, realized in a 0.18 mum SiGe technology, demonstrates a 1 dB gain desensitization at 1.9 GHz of -8 dBm, a noise figure of 5 dB, with 20 mW power consumption. Chip area is 3.24 mm2. The receiver includes a highly selective LNA, key to minimize desensitization and reciprocal mixing due to the large cellphone leakage, a novel quadrature VCO topology capable of directly driving quadrature passive mixer with high swing and low power consumption, complex bandpass filter, variable gain amplifier, automatic gain control, 2-bit quantizer, and a fractional-N sigma-delta-based PLL that can lock to any crystal frequency.

Comparing a template approach and complex bandpass filtering for single-trial analysis of auditory evoked M100

Two methods for single-trial analysis were compared, an established parametric template approach and a recently proposed non-parametric method based on complex bandpass filtering. The comparison was carried out by means of pseudo-real simulations based on magnetoencephalography measurements of cortical responses to auditory signals. The comparison focused on amplitude and latency estimation of the M100 response. The results show that both methods are well suited for single-trial analysis of the auditory evoked M100. While both methods performed similarly with respect to latency estimation, the non-parametric approach was observed to be more robust for amplitude estimation. The non-parametric approach can thus be recommended as an additional valuable tool for single-trial analysis.

Recursive Algorithm for Real-Time Measurement of Electrical Variables in Power Systems

In this paper, a novel complex bandpass filter is presented which overcomes the pitfalls of the techniques in common use. This complex bandpass filter can correctly extract the phasor of the fundamental component and symmetrical components in voltage or current waveforms and then accurately estimate their instantaneous amplitude, phase angle, and frequency, even encountering various power disturbances. Further, a recursive algorithm is also developed for the complex bandpass filtering that updates current filtering output only using several previous sample values and filtering outputs. This attribute greatly reduces the computational complexity of complex bandpass filtering, which is the weakness of the continuous wavelet transform based on the well-known Morlet Wavelet. Thus, this recursive algorithm is highly desirable for real-time applications. The performance of the proposed technique is ascertained by using both simulated and practical power disturbance waveforms.

Adjacent Channel Interference Cancellation Scheme for Low-IF Receiver in Multi-Channel Reception

In this paper a new adjacent channel interference (ACI) cancellation scheme for multi-channel signal reception with low-IF receivers is investigated through the experiment. In the low-IF receivers, the signal in the mirror frequency causes interference to the desired signal. In the proposed analog-digital signal processing scheme, channel selection is made by analog complex band pass filter and the signal is reconstruct by Wiener filter to eliminate the interference effect in order to improve the performance.

General synthesis of complex analogue filters

General methods for the synthesis of complex band-pass and band-stop analogue filters are developed for implementation by active-RC, gm-C, switched-capacitor (SC) and switched-current (SI) techniques. These principles are extended to synthesis procedures for log-domain complex realisations. Circuits for filters and group delay equalisers are presented for both ladder and cascade-biquad realisations. These have been incorporated into the filter design software XFILTER. Various designs are compared, noise and sensitivity responses being shown.