Parallel Bandpass Filters Research Articles

A low-cost, wireless, 4-channel EEG measurement system used in virtual reality environments

The combination of Virtual Reality (VR) technology and Electroencephalography (EEG) measurements has shown tremendous potential in the fields of psychology and neuroscience research. However, the majority of EEG measurement devices currently available are expensive, bulky, uncomfortable to wear, and difficult to integrate with VR headsets. These limitations have hindered the development of related research fields. This study describes a low-cost (60.07 USD), small-sized, wireless, high-precision, low-power consumption 4-channel EEG measurement system (NeuroVista) for frontal area EEG measurements, which can be used with a VR headset, enabling EEG measurements in VR environments. The system has an input-referred noise of less than 0.9480 μVrms, a common mode rejection ratio of over 96 dB, a measurement resolution of less than 0.1 μV, a bandwidth of 0.5 ∼ 45 Hz, and works at a sampling rate of 250 Hz. It also supports metal dry electrodes and includes a built-in analog bandpass filter, right-leg drive circuit, and built-in digital lowpass filter and notch filter, which can reduce noise during measurement. Researchers can reconstruct the electrode system to measure regions of interest according to their needs.

Development of a low-cost, compact, wireless, 16 - channel biopotential data acquisition, signal conditioning and arbitrary waveform stimulator.

The health and fitness of the human body rely heavily on physiological parameters. These parameters can be measured using various tools such as ECG, EMG, EEG, EOG, among others, to obtain real-time physiological data. Analysing the bio-signals obtained from these measurements can provide valuable information that can be used to improve health-care in terms of observation, diagnosis, and treatment. In bio-signal pattern recognition applications, more channels provide multiple information simultaneously. Different biosignal acquisition devices are available in the market, most of which are designed for specific signals like ECG, EMG, EEG etc The gain of the amplifiers and frequency of the filters are designed as per the targeted signals; due to which one device cannot be used for other signals. Also, most of the systems are wired system which is not comfortable for animal studies. In this paper, a low-cost, compact, wireless, 16 channel biopotential data acquisition system with integrated electrical stimulator is designed and implemented. There are several novel and flexible design approaches were incorporated in the proposed design like (1) It has user selectable digital filter in each channel based on the signal frequencies like ECG, EMG, EEG, EOG. The same system will be used to acquire different signals simultaneously. (2) It has variable gain with a configurable analog bandpass filter. (3) It can acquire signals from 4 patients simultaneously. (4) The system is capable to acquire signal from both two-electrode as well as three-electrode configurations. (5) It has integrated stimulator with trapezoidal, charge-balanced, biphasic stimulus output with near zero DC level and user selectable pulse duration or frequency of the stimulus. The developed system has the ability to acquire and transmit data wirelessly in real-time at a high transfer rate. To validate the performance of the system, tests were conducted on the acquired signals using a simulator.

CONSTRUCTION AND VERIFICATION OF A DIGITAL EQUALIZER MODEL

An approach to the development of an equalizer by building its mathematical model based on a microcontroller is proposed. All operations, including signal processing and equalizer kernel calculation, are performed by a single microcontroller. Thanks to the created mathematical model of the equalizer, the calculation of the kernel is reduced to multiple uses of relatively simple operations, which saves time and memory of the program. The equalizer provides satisfactory processing quality at a small filter order which is selected as a digital filter with final impulse response (FIR) because of its linear phase-frequency response, a guarantee of stability at the complex amplitude-frequency response, and also its associativity and linearity allowing it easily reproduce a complex amplitude-frequency response. Schematic implementation is based on parallel bandpass filters and a low-pass filter followed by adding filtered and amplified signals. It is the distributive property of the FIR filter that makes it possible to obtain a new kernel that includes all the amplified ranges by the sum of the corresponding kernel elements, instead of adding amplified ranges. The associativity and linearity of the FIR filter gives the opportunity to easily implement different types of filters on the basis of a low-pass filter, for the calculation of which the cardinal sine function is used together with the window function, which in combination gives qualitative frequency characteristics. The low-pass filter kernel and equalizer model are verified in the GNU Octave environment, which is an open-source analogue of Matlab. The model is checked by setting the frequency response of the test equalizer, and for individual filters the allowable width of the transition band and the maximum value of pulsation in the suppression band are set. The low-pass filter kernel is created with an arbitrary cutoff frequency, and the filter consists of 129 elements, which were multiplied by the Kaiser window with a value of parameter equal to 4.5. As a result of verification of the mathematical model in the GNU Octave environment, the width of the transition band and the maximum value of pulsation in the suppression band meet the specified conditions. The simulated equalizer kernel fully corresponds to the specified frequency response. Verification of the mathematical model confirmed its efficiency and compliance of the obtained characteristics of the equalizer with the specified requirements.

Very high frequency radio receiver preselector design

Objectives. The quality of a radio receiver preselector largely determines its main characteristics, including sensitivity. A preselector usually consists of linear elements: inductors, capacitors, low noise amplifiers, and switches. At high frequencies, the components cannot be considered as ideal ones, since active and reactive parasitic parameters significantly affect the frequency response of the components and, as a consequence, the network. Therefore, simulation of the networks requires more sophisticated component models, which take into account parasitic parameters. However, if refined components models are applied, it is still possible to obtain unsatisfactory results, since interconnections and footprints pads also affect the frequency response. This is true even if short lines with a length of about 5 mm are used at frequencies of about 100 MHz. These features must be taken into account for RF network design. The purpose of the work is to ensure the required characteristics of the preselector in the design process based on computer simulation.Methods. Egor Gurov’s methodology for analog VHF LC-filters was applied to radio receiver preselector design. The methodology contains the methods of discrete optimization, Monte-Carlo method, momentum analysis with Green’s functions. Experimental results were obtained by prototype implementation and measurement with a vector network analyzer. The purpose of the work is to ensure the required preselector characteristics in the design process based on computer simulation.Results. The article presents the preselector design process. The preselector contains two analog switches, an analog band-pass filter, an analog high-pass filter, and a low-noise amplifier. Simulation and experimental results with their comparison are presented in the article.Conclusions. Satisfactory results were obtained. It means that Egor Gurov’s method can be applied for more complex networks design such as radio receiver preselectors.

A comprehensive computational model of animal biosonar signal processing.

Computational models of animal biosonar seek to identify critical aspects of echo processing responsible for the superior, real-time performance of echolocating bats and dolphins in target tracking and clutter rejection. The Spectrogram Correlation and Transformation (SCAT) model replicates aspects of biosonar imaging in both species by processing wideband biosonar sounds and echoes with auditory mechanisms identified from experiments with bats. The model acquires broadband biosonar broadcasts and echoes, represents them as time-frequency spectrograms using parallel bandpass filters, translates the filtered signals into ten parallel amplitude threshold levels, and then operates on the resulting time-of-occurrence values at each frequency to estimate overall echo range delay. It uses the structure of the echo spectrum by depicting it as a series of local frequency nulls arranged regularly along the frequency axis of the spectrograms after dechirping them relative to the broadcast. Computations take place entirely on the timing of threshold-crossing events for each echo relative to threshold-events for the broadcast. Threshold-crossing times take into account amplitude-latency trading, a physiological feature absent from conventional digital signal processing. Amplitude-latency trading transposes the profile of amplitudes across frequencies into a profile of time-registrations across frequencies. Target shape is extracted from the spacing of the object’s individual acoustic reflecting points, or glints, using the mutual interference pattern of peaks and nulls in the echo spectrum. These are merged with the overall range-delay estimate to produce a delay-based reconstruction of the object’s distance as well as its glints. Clutter echoes indiscriminately activate multiple parts in the null-detecting system, which then produces the equivalent glint-delay spacings in images, thus blurring the overall echo-delay estimates by adding spurious glint delays to the image. Blurring acts as an anticorrelation process that rejects clutter intrusion into perceptions.

Development of A Low-Cost Arduino-Based 12-Lead Ecg Acquisition System And Accompanied Labview Application

In this paper, the design of a real-time digital multi--channel ECG signal acquisition system is presented. With the purpose of fabrication towards a simple, compact and low-cost tool for bioelectrical signal processing laboratories, the system is developed to acquire the 12 leads EGC signals and converted to numerical data based on an Arduino module named as Leonardo equipped 12 channels ADC. To observe the EGC waves, the ECG signals are amplified through designed amplifiers with the gain of 60 dB. To reduce the effects from the DC component as well as the baseline wandering and the high frequency noise, the active analog bandpass filter ranged in 0,05 Hz to 100 Hz was designed. The power line noise of 50 Hz also decreased with an active analog bandstop filter with attenuation -38 dB. Under the PC application was built using Labview programing, the low-cost digital ECG signal acquisition system was demonstrated with the requirement of observation in real-time. To clarify the small wave in the digital EGG signal, the limitation of the analog signal processing is improved through the digital filters parameterized in the software to increase the SNR from 1.4 dB to 27.6 dB. Practically, the system is evaluated through a series of experiments on a volunteer person resulting the ECG data is recorded and stored in a TDMS file. Since the system is designed as opened-system, a series of developments towards various applications in biomedical diagnosis based on digital signal analysis techniques is promised to be feasible in the near future.

Faults Detection in Active Analog Bandpass Filter Using OBIST Method

The main objective of this paper is to explain the principal of different analog circuit testing methods to examine the difficulties present in the analog circuit testing i.e. to test the analog parts in a mixed signal circuit. In this paper all possible catastrophic and parametric faults present in the analog bandpass filter are tested by OBIST method which does not requires test vector generator which reduces the test development. Bandpass filter is examined for all possible fault detection and verifying that OBIST approach can improve the overall percentage of fault detection.

Low cost, faster detection of cognitive radio through filter banks with bandpass sampling

In cognitive radio communication systems, fast and reliable detection of the idle channels which are not occupied by the primary users is the most fundamental requirement. In this paper, we first review some of the classical designs of cognitive radio receiver architectures and then propose a new solution using filter banks with the bandpass sampling technique. In conventional heterodyne receiver, a low rate analog to digital convertor (ADC) is used, which contains an analog bandpass filter. This results in a barrier in lowering detection time as significant time is used in the scanning operation. While the homodyne receiver has the capability of fast detection due to the use of high rate ADC, this is an unfeasible or very costly approach. Compressive sensing based receiver architectures are proposed in recent years, however those receivers do not work efficiently under the condition when the spectrum is congested and the number of channels are increased. In this work, we propose a filter banks based receiver with bandpass sampling architecture capable of fast detection and using a low rate ADC as well. In addition, comparative analysis of classical designs and the proposed architecture is carried out by considering performance parameters of detection time, signal to noise ratio and complexity of the receivers.

Harmonic Analysis of Fuzzy Logic Controller Based Active Filter Unit Using Resonant Current Control in Distributed Power System

Wide-ranging utilize of nonlinear loads creates harmonic resonance issues in radial distribution system. Harmonic amplification occurring at different locations in the radial line are due to the behavior of active filter as a harmonic admittance rather conductance. This paper presents fuzzy logic controlled active filter by using resonant current control to damp a harmonic resonance. For controlling active filter as an approximately pure harmonic conductance, collections of different parallel band-pass filters are tuned for resonant current controller at harmonic frequencies. A MATLAB/SIMULINK results illustrate that the fuzzy logic controller based active filter improves higher damping performance correlated with alternative techniques.

Separation of MiPS/MaPS spectrogram transformations in biosonar

Echolocating bats and dolphins differ in signals, sound emission, and reception pathways, and important aspects of the acoustic medium. They do, however, receive broadcasts and echoes through similar parallel bandpass filters in the cochlea, which impose integration-times of several hundred microseconds. Echoes consisting of several overlapping reflections from target glints (insect body-parts, fish swim bladders) interfere upon reception to form complex echoes with spectral interference patterns that characterize the target’s shape. Bats transform these patterns into images that depict the glints themselves along the range axis, a process called Spectrogram Correlation and Transformation (SCAT). Experiments with dolphins suggest two different scales for recognizing shape from echo spectra—macro- vs micro-power spectral features for ST (MaPS for short glint separations of <80 µs; MiPS for longer separations >80 µs). We tested this finding in big brown bats trained to distinguish between 2-glint echoes with long, MiPS-like and short MaPS-like spectral features and found that MiPS covers delay separations of about 25-500 µs from the frequency separation of spectral nulls, which have to fit into FM1 for ST to occur. At a deep level, dolphins and bats appear to share a common processing strategy for forming images. [Work supported by ONR.]

Влияние режекторного фильтра на эффективность линеаризации фазочастотной характеристики аналогового полосового фильтра

The previously published works of the authors dealt with methods aimed at linearizing the phase frequency responses of analog filters using digital linearizing finite impulse response (FIR) filters. If the operating frequency band contains narrow-band interference, such interference often needs to be suppressed by using a narrow-band analog band-stop filter. However, when a band-stop filter is connected in series, the linearized phase frequency response may become distorted. The article examines the influence of a narrow-band analog band-stop filter on the effectiveness of linearizing the phase frequency responses of a complex analog band-pass filter using a complex band-pass linearizing digital FIR filter. The study was conducted using a circuit simulation program based on a model consisting of the following modules: a complex analog band-pass filter with a sixth-order Butterworth low-pass filter prototype, a narrow-band complex analog band-stop filter with a third-order Butterworth low-pass filter prototype, and a complex digital band-pass linearizing FIR filter. The article presents the results from studying the frequency band in which the phase frequency response linearity is distorted to an acceptable degree. A sharp change in the group delay time level takes place in the stopband vicinity. The frequency band in which the group delay ripple is larger than the pre-linearization group delay ripple is referred to as the linearization effect loss band. If the difference between the band-stop filter’s passband boundary frequencies is much (by dozens of times) smaller than the band of the complex band-pass filter, the linearization effect is retained over most of the passband. With the selected parameters and orders of the complex analog filter and band-stop filter, the frequency band in which the linearization effect vanishes is approximately seven times greater than the difference between the band-stop filter’s passband boundary frequencies. Such an approach is relevant in filtering narrow-band interference within the frequency band of broadband signals.

ТЕХНІЧНІ АСПЕКТИ РОЗРОБКИ ВБУДОВАНОГО ПРИСТРОЮ «РОЗУМНОГО ОСВІТЛЕННЯ» НА ОСНОВІ МІКРОКОНТРОЛЕРА MSP430

Urgency of the research. Lighting consumes around of 17.5% of the total volume of electricity produced on Earth. In some regions the consumption reaches to 50%. Improving of electronic devices and algorithms for autonomous lighting control reduces the consumption of more than a half (60%).Target setting. Existing "smart lighting" devices is supplied as a centralized system with closed protocols and managers by a powerful computer, or actively using existing communications network, which is not always provides for extension.Actual scientific researches and issues analysis. The centralized and decentralized solutions of the human indoors detection is performed by using the existing network devices for wireless communications (ZigBee), video surveillance, and audio range microphone. Particular attention was acted on how the technical implementation of the hardware and software parts, as well as technologies and algorithms that were used in those solutions, wavelet transform, pattern recognition and regulators non-classical structure.Uninvestigated parts of general matters defining. Still not researched class of decentralized "smart lighting" devices, that are embedded into a lighting device and use method of determining the presence of humans by the their noise sound spectrum.The research objective. Design a cheap and compact "smart lighting" device that can be built-in locally in each room, or even its part. Each device must have as less power consumption as possible and a minimal set of sensors.The statement of basic materials. For pre-amplification and filtering of sound signal the analog band-pass filter based on unipolar OpAmp was designed. The frequency responses (spectrums) of the noises caused by human activity, taking into account the classification of those activities, was experimentally measured. Combinations of existing software development tools that allows to develop and compile a project under any operating system, without using proprietary software was composed and assembled.Conclusions. The set of selection criteria for comparison decentralized "smart lighting" devices was done. The structure of the cheap and scalable device, which is easily modified unlike to existing models, was proposed. On the cost of sensor part the proposed device ahead of similar ones.

A Band-Divided Memory Polynomial for Wideband Digital Predistortion With Limited Bandwidth Feedback

With a real analog bandpass filter (BPF) in the feedback loop, band-limited digital predistortion (DPD) normally uses a narrower bandwidth low-pass filter at baseband to further constrain the bandwidth of the power amplifier (PA) output signal. This discards the nonlinear information at the BPF's roll-off regions. The PA's spectral regrowth at the edge of the BPF is thus unable to be suppressed with the conventional band-limited DPD. To make efficient use of digital-to-analog converter/analog-to-digital converter sampling rate without losing information at the BPF's roll-off regions, this brief proposes a band-divided DPD method, in which the restricted feedback bandwidth is divided into two parts in frequency domain—center and border regions of PA's band-limited output. These two parts are characterized separately using two different basis functions with a band-divided memory polynomial (BDMP) model. It provides higher flexibility in selecting the digital band-limiting filter's bandwidth and also reduces the filter order. The measurement results for a class-AB GaN PA with orthogonal frequency division multiplexing signal of 60-MHz bandwidth have shown the superiority of BDMP DPD over the previous state-of-the-art.

Analog Filtering Method for Sensorless AC Machine Control With Carrier-Frequency Signal Injection

This paper analyzes the angle estimation errors for signal injection based sensorless control with an analog bandpass filter (BPF). The analog BPF has been used to reduce the level of the injection voltage. However, the frequency components of the current signal that have passed through the analog BPF have different phase delays. In addition, the injection voltage at the carrier frequency is distorted by the pulsewidth modulation. Because of these reasons, the angle estimation error includes the alternation at three or six times the rotating frequency and dc offset. The pattern of the angle estimation error depends on the quality factor of the analog BPF. In this paper, each cause of the angle estimation errors is studied and the experimental results verify these analyses. In addition, the filter design guide to reduce the angle estimation error is outlined.

FPGA Based Wavelet Trigger in Radio Detection of Cosmic Rays

Experiments which show coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays are designed for a detailed study of the development of the electromagnetic part of air showers. Radio detectors can operate with 100 % up time as, e.g., surface detectors based on water-Cherenkov tanks. They are being developed for ground-based experiments (e.g., the Pierre Auger Observatory) as another type of air-shower detector in addition to fluorescence detectors, which operate with only ∼10 % of duty on dark nights. The radio signals from air showers are caused by coherent emission from geomagnetic radiation and charge-excess processes. The self-triggers in radio detectors currently in use often generate a dense stream of data, which is analyzed afterwards. Huge amounts of registered data require significant manpower for off-line analysis. Improvement of trigger efficiency is a relevant factor. The wavelet trigger, which investigates on-line the power of radio signals (∼V2/R), is promising; however, it requires some improvements with respect to current designs. In this work, Morlet wavelets with various scaling factors were used for an analysis of real data from the Auger Engineering Radio Array and for optimization of the utilization of the resources in an FPGA. The wavelet analysis showed that the power of events is concentrated mostly in a limited range of the frequency spectrum (consistent with a range imposed by the input analog band-pass filter). However, we found several events with suspicious spectral characteristics, where the signal power is spread over the full band-width sampled by a 200 MHz digitizer with significant contribution of very high and very low frequencies. These events may not originate from cosmic ray showers but could be the result of human contamination. The engine of the wavelet analysis can be implemented in the modern powerful FPGAs and can remove suspicious events on-line to reduce the trigger rate.

An Optimization of the FPGA Based Wavelet Trigger in Radio Detection of Cosmic Rays

Experiments that observe coherent radio emission from extensive air showers induced by ultra-high energy cosmic rays are designed for a detailed study of the development of the electromagnetic part of air showers. Radio detectors can operate with 100% up time as e.g. surface detectors based on water-Cherenkov tanks. They are being developed for ground-based experiments (e.g. the Pierre Auger Observatory) as another type of air shower detector in addition to the fluorescence detectors, which operate with only ~10% of duty in dark nights. The radio signals from air showers are caused by the coherent emission due to geomagnetic radiation and charge excess processes. Currently used self-triggers in radio detectors often generate a dense stream of data, which is analyzed afterwards. Huge amounts of registered data requires a significant man-power for the off-line analysis. An improvement of the trigger efficiency becomes a relevant factor. In this work, Morlet wavelets with various scaling factors were used for an analysis of real data from the Auger Engineering Radio Array and for an optimization of the utilization of the resources in an FPGA. The wavelet analysis showed that the power of events is concentrated mostly in a limited range of the frequency spectrum (consistent with a range imposed by the input analog band-pass filter). However, we found several events with suspicious spectral characteristics, where the signal power is spread over the full band-width sampled by a 200 MHz digitizer with significant contribution of very high and very low frequencies. These events may not origin from cosmic ray showers but can be human-made contaminations. The engine of the wavelet analysis can be implemented into the modern powerful FPGA and can remove suspicious events on-line to reduce the trigger rate.

Receiver Performances Considering Effects of Gain Control and Quantization in FDM-Based Narrowband Communication Systems

In wireless receivers, in order to prevent the saturation of a received signal in an analog-to-digital converter (ADC), an automatic gain control (AGC), which maintains the amplitude of an analog signal at an appropriate fixed level, is frequently employed. This paper discusses the effects of gain control and quantization in the AGC and ADC on the receiver performance in frequency division multiplexing-based narrowband communication systems. Each communication channel is very narrow in these systems, so the channels are packed without breaks, making it difficult to extract the desired signal using an analog bandpass filter. Therefore, other multiple communication signals are in-band interference signals in these systems. In comparison with a single interference signal, a peak amplitude of multiple interference signals is greater than the that of single interference signal given the same interference power. It is well known that signals having a large peak value cause the degradation of bit resolution due to the AGC and ADC processes. The purpose of this paper is to provide a theoretical and numerical analysis of the effects of gain control and quantization on the receiver performance in such an environment. The analysis results indicated that (i) in-band interference signals decreased the bit resolution of the desired signal amplitude because of these processes and (ii) the effects of these processes depend on the amplitude intensity and the number of in-band interference signals, given the same interference power.

Filter Design of Power Battery Resistance Measuring for New Energy Vehicle

In order to measure the internal resistance of new energy vehicle power battery precisely, the high quality factor analog band-pass filter circuit and switched-capacitor circuit was studied. And the circuit was redesigned by using a switched capacitor circuit for digital control. Combined with the requirements of vehicle battery internal resistance measurement, the resistance measurement system architecture which is based on microcontroller and programmable logic devices is proposed. Finally, the system is validated via error calculation and the actual experiments.

実験的変換行列を用いた平板の実時間衝撃荷重同定

This paper proposes a method for identifying the location and force history of an impact force acting on plate structures. The identification method is an experimental one so it does not require any analytical model of the structure. The impact location is identified using arrival times of the flexural wave to the PZT sensors. In order to determine the arrival times accurately and rapidly, an analog band-pass filter is used to obtain the wave with a specified frequency. Experimental transfer matrices, which relate the impact force and the sensor responses, are used to identify the force history. Here, the transfer matrices are preconstructed from the measured data obtained by impact tests conducted with an impulse hammer. The force history is identified by minimizing the deviation between the measured sensor responses and the responses estimated from the experimental transfer matrices. In order to verify the validity of the proposed method, impact force identification of aluminum plates and CFRP laminated plates are performed experimentally. The results reveal that the location and force history of the impact force can be identified accurately in real time using the proposed method.

A dual band-pass amplifier-filter circuit for simultaneous recording of spikes and local field potentials from live neuronal tissue using multielectrode arrays

The paper presents the design and test results of a novel circuit with dual band-pass filter for simultaneous recording of Local Filed Potentials and spikes from individual neurons. Single readout channel is built of an input AC-coupling circuit with the cut-off frequency below 0.1Hz, a low noise preamplifier and two parallel band-pass filters with nominal bandwidths from 2Hz to 100Hz and from 200Hz to 2kHz. The design is optimized for low noise, high dynamic range, and low power dissipation. The circuit has been designed and manufactured in a 0.35μm CMOS process as a multichannel chip comprising also an analog multiplexer for serialization of the analog output signals.