Digital High Pass Research Articles

O040 Investigating the effects of airflow signal filtering on non-invasively quantified estimates of flow limitation

Abstract Introduction We previously reported a method to estimate flow limitation (FL, range 0-~1) from the airflow signal recorded within a polysomnogram. This method utilised high quality nasal pressure signals, without high-pass (HP) filtering. However, many clinical recording systems implement HP filtering on airflow signals. We hypothesised that FL estimates would be adversely affected when airflow signals have HP filtering present. Methods Within our existing framework for estimating FL, we manipulated the airflow signal by applying digital HP filtering (Butterworth, 4th order) at commonly used cutoff frequencies (0.005, 0.01, 0.03, 0.1Hz). At each HP filter cutoff, performance was assessed at the breath-level (pooled, all patients) and patient-level (median, sleep only) using coefficient of determination (R²) and root mean squared error (RMSE) comparing FL estimates with HP filtering against reference data without HP filtering. Results In N=96 individuals, R² decreased while RMSE increased as HP filter cutoff increased. For HP filter cutoffs at 0.005, 0.01, 0.03 and 0.1Hz, breath-level R² was 0.923, 0.879, 0.740, and 0.483; while RMSE was 0.062, 0.079, 0.129, and 0.219, respectively. Similarly, patient-level R² was 0.994, 0.977, 0.843, and 0.738; while RMSE was 0.015, 0.030, 0.100, and 0.170. Discussion Increasing HP cutoff frequency resulted in a reduction of consistency of FL estimates when compared to those made using an unfiltered airflow signal. Further work including reference to ‘gold standard’ is required, however, in line with current AASM recommendation (“Direct current (DC) or ≤0.03Hz”), this study suggests HP filter cutoff frequency for nasal pressure should be minimised, preferably avoided.

Adaptive Delay-Free Filtering Based on IMU for Improving Ship Heave Measurement.

Ship heave motion measurement is crucial for ensuring vessel stability, navigation precision, and maritime engineering safety. In order to achieve accurate heave motion measurement, a method based on an adaptive digital high-pass filter is proposed. The approach involves constructing a ship heave motion model, conducting an analysis of heave motion, determining the optimal cutoff frequency for the adaptive filter based on an analysis of filtering and sensor errors, and designing an adaptive delay-free digital high-pass filter. Through simulation experiments in various sea conditions and platform tests, the method demonstrates superior performance. In comparison to fixed-parameter complementary filters, it exhibits a reduction of over 50% in maximum error and mean square error.

저 관성을 가지는 공작기계의 터렛 서보 시스템에서 과도상태의 진동억제를 위한 댐핑 보상기법

In general, rotor inertia has an inversely proportional relationship with proportional gain and bandwidth in a turret speed control system of machine tools; thus, this system has a disadvantage, such as weak disturbance caused by a decrease in the damping ratio and an increase in bandwidth due to low rotor inertia. This paper proposes a damping compensator that is resistance to disturbances in order to improve the above problems. The proposed damping compensator reduces the residual vibration induced in the transient state by using a digital high-pass filter. The experimental results showed that the overshoot was reduced by about 5.5% in the speed response and by about 20% in the torque response in the no-load condition. Under the load condition of 4.8 N.m, the torque response showed that the undershoot was reduced by about 26%.

Quantum 3D FFT in Tomography

The Radon transform constitutes the conventional tool for tomosynthesis, i.e., the composition of cross-sections of an object from its projections. It is actually a version of the Fourier Transform, which is accompanied by the appropriate digital high pass filters for correct distribution of energy among the reconstructed frequency components. The Radon transform and its inverse are employed in their 2D and 3D versions, respectively, and the whole procedure is verified by the a priori known cross-sections to be reconstructed (known fandom). Usually, 3D medical image cubes, which are to be reconstructed, require powerful computational tools since the 2D projections are of high-resolution containing millions of pixels. Although the 3D FFT is very fast, the large number of projections will result in a 3D spectrum of very large dimensions. Inverting this spectrum with the inverse 3D FFT is extremely time consuming. In this work, the implementation of the 2D Radon transform using the 2D Quantum Fourier Transform is analytically presented. Simultaneously, its inverse version is realized by means of the Quantum inverse 3D FFT. For this purpose, a review of the necessary quantum computational units is presented for the implementation of the quantum 3D FFT and simultaneously simple examples of tomosynthesis are given by means of the quantum version of the 2D Radon transform and its inverse 3D counterpart. The whole procedure of the quantum tomosynthesis is analytically described.

Power Quality Transient Detection and Characterization Using Deep Learning Techniques

Power quality issues can affect the performance of devices powered by the grid and can, in severe cases, permanently damage connected devices. Events that affect power quality include sags, swells, waveform distortions and transients. Transients are one of the most common power quality disturbances and are caused by lightning strikes or switching activities among power-grid-connected systems and devices. Transients can reach very high magnitudes, and their duration spans from nanoseconds to milliseconds. This study proposed a deep-learning-based technique that was supported by convolutional neural networks and a bidirectional long short-term memory approach in order to detect and characterize power-quality transients. The method was validated (i.e., benchmarked) using an alternative algorithm that had been previously validated according to a digital high-pass filter and a morphological closing operation. The training and performance assessments were carried out using actual power-grid-measured data and events.

Master-slave synchronous control method for attenuating dual mode electromechanical transmission system torsional vibration

The high-power electromechanical transmission (EMT) system is a typical dual-mode hybrid power transmission system. The torque fluctuation of internal combustion engine causes serious shock and vibration problems of EMT. Suppressing torsional vibration based on high dynamic motor torque regulation is an important way to improve the working life and stability of EMT system. First, a lbased on the lumped parameter linear dynamic model,the torsional vibration characteristics are analyzed. Second, a fluctuating speed estimation method is proposed based on the uniformly accelerated motion model and linear regression, and a digital high pass filter is designed. Then, a master-slave coupling active torsional vibration control strategy is proposed, and a PD control algorithm based on speed feedback is designed. The variation rules of control parameters is analyzed. Finally, the control effect is verified by experiments. The results show that the lever coefficient K ab and differential coefficient K d of master-slave control can change the natural frequency of torsional vibration of the system, thus significantly changing the vibration response of the system. Selecting appropriate control parameters can achieve peak clipping of EMT torsional resonance.

Denoising electrocardiogram signals using multiband filter and its implementation on FPGA

The electrocardiogram (ECG) signal carries vital information related to cardiac activities. While measuring ECG using electrodes, the signal is contaminated with powerline interference (PLI) from harmonics, baseline wandering (BW), motion artefacts (MA) and high frequency (HF) noise. The extraction of the ECG signal, without the loss of useful information from the noisy environment, is required. Therefore, the selection and implementation of an efficient filter design is proposed. The Finite Impulse Response (FIR)-based multiband needs separate digital filters, such as Lowpass, Highpass, and Bandstop Filter in cascade. The coefficients of the FIR multiband filter are optimised using a least squares optimisation method and realised in a direct form symmetrical structure. The capability of the proposed filter is evaluated on a Physionet ECG ID database, having records of inherent noisy ECG signals. The performance is also verified by measuring the power spectrum of the noisy and filtered ECG waveform. Also, the feasibility of the proposed multiband filter is investigated on Xilinx ISE and the design is implemented on a field programmable gate array (FPGA) platform. A low order simple multiband filter structure is designed and implemented on the reconfigurable FPGA device.

Virtual Instrument Based Real Time ECG Monitoring Device

This study presents a real-time ECG monitoring system based on a virtual instrument. The device was designed using surface electrode, lead wire, instrumentation amplifier (IN114), and passive low pass filter with cut-off frequency (fc, 180 Hz). Thereafter, the ECG signal was transferred via DAQ card by initializing the analog input and sampling rate to the Labview for further analysis. Further, digital notch filter (fc, 47 to 53 Hz), bandpass filter (fc, 0.05 to 20 Hz), and FIR high pass filter using Kaiser window (order-56, and fc – 3.5 Hz) was employed in order to remove the power line interference, detect fiducial point from ECG, and eliminate the baseline wondering. In addition, we examined the various wavelet to choose the best to use wavelet denoise based on signal-to-noise ratio (SNR). Finding suggests the SNR (58.75 dB) of sym8 wavelet was higher comparing with another wavelet. Hence, the wavelet denoising was implemented into the developed device to remove the distortion and to detect the better peak in real time. Further, multiresolution analysis with Haar wavelet with the decomposing level of 1 was incorporated into the developed ECG monitoring device to detect the R-R peak, followed by automatic heart rate detection. Thus, this finding suggests the promising result that has the potential to assess the cardiovascular conditions. In future, the developed device will be tested with healthy subjects in order to standardize the functionality and significant features will be extracted from the morphology of ECG waveform for the analysis of cardiovascular diseases.

Design and Implementation of a Novel Microstrip Filter

Microwave filters are circuits which perform signal processing functions, particularly to eliminate unwanted frequency components from the signal, to enhance wanted ones, or both. Electronic filters can be passive or active(depends on components used) Analog or digital(depends on input signal) High-pass, Low-pass, Band-pass, Band-stop or all other pass (depends on frequency) Infinite impulse response (IIR type) or Finite impulse response (FIR type) (Depends on response) Microstrip is a type of electrical transmission line which can be fabricated using printed circuit board technology, and is used to convey microwave frequency signals. Microwave components such as antennas, couplers, filters, power dividers etc can be formed using microstrip line. This paper aims on filter design, using microstrip transmission line, with a Non-Periodic technique especially using Defected Microstrip Structure to be operated in the C – Band frequency.

Intensity-curvature functional based digital high pass filter of the bivariate cubic B-spline model polynomial function

This research addresses the design of intensity-curvature functional (ICF) based digital high pass filter (HPF). ICF is calculated from bivariate cubic B-spline model polynomial function and is called ICF-based HPF. In order to calculate ICF, the model function needs to be second order differentiable and to have non-null classic-curvature calculated at the origin (0, 0) of the pixel coordinate system. The theoretical basis of this research is called intensity-curvature concept. The concept envisions to replace signal intensity with the product between signal intensity and sum of second order partial derivatives of the model function. Extrapolation of the concept in two-dimensions (2D) makes it possible to calculate the ICF of an image. Theoretical treatise is presented to demonstrate the hypothesis that ICF is HPF signal. Empirical evidence then validates the assumption and also extends the comparison between ICF-based HPF and ten different HPFs among which is traditional HPF and particle swarm optimization (PSO) based HPF. Through comparison of image space and k-space magnitude, results indicate that HPFs behave differently. Traditional HPF filtering and ICF-based filtering are superior to PSO-based filtering. Images filtered with traditional HPF are sharper than images filtered with ICF-based filter. The contribution of this research can be summarized as follows: (1) Math description of the constraints that ICF need to obey to in order to function as HPF; (2) Math of ICF-based HPF of bivariate cubic B-spline; (3) Image space comparisons between HPFs; (4) K-space magnitude comparisons between HPFs. This research provides confirmation on the math procedure to use in order to design 2D HPF from a model bivariate polynomial function.

Evaluation and Improvement of Active Stabilization Method for Matrix Converter Under Input Voltage Disturbances

For matrix converter (MC), real-time correction of duty cycles is a good solution to eliminate the effects of input voltage disturbances on output performance. However, MC adopting this solution suffers from stability deterioration. The typical active stabilization method is based on modifying output voltage reference with the filtered input voltage. In this paper, its performance is evaluated under input voltage disturbances. It is found that this method will introduce extra low-frequency harmonics into output reference voltage, degrading the output quality. The reason lies in the inability of the adopted digital high-pass filter to block the disturbances. To maintain a good output performance, the improved active stabilization method is proposed, which utilizes resonant controllers to eliminate the extra low-frequency harmonics. The principle and the implementation of the improved method are presented. The consideration of input frequency variation and the influence on input power quality are also discussed. Experimental results have verified the correctness of the performance evaluation and effectiveness of the proposed improvement.

A 100-km BOFDA Assisted by First-Order Bi-Directional Raman Amplification.

We present, to our knowledge for the first time, a 100-km Brillouin Optical Frequency-Domain Analysis (BOFDA) employing a 200-km fiber loop. Compared to our previous publication, enhanced sensor length, sensor accuracy and spatial resolution are presented. The performance improvements are achieved by applying distributed Raman amplification (DRA) and a digital high-pass filter. We report on temperature measurements over sensing distances of 75 km and 100 km both with a 12.5-m spatial resolution. Temperature changes of 5 C have been measured along 75 km sensing fiber. A temperature change of 30 C has been detected at 99.5 km.

Design of optimal high pass and band stop FIR filters using adaptive Cuckoo search algorithm

This paper presents an efficient design of digital FIR high pass and band stop filters using an adaptive cuckoo search algorithm (ACSA). The important features of ACSA are — (i) the step size is independent and (ii) it is accurately decided from the current fitness value. The step size is decided according to the current fitness value within the iteration process. This increases the convergence speed. The other five global optimizers are also used for optimization. The optimal solutions obtained by the ACSA are compared with the other global optimizers. CEC 2005 benchmark test functions are considered for the comparison. The results are compared in terms of the convergence speed, accuracy, deviation from the desired response, minimum stop-band attenuation and maximum pass-band attenuation. The statistical analysis, i.e. t-Test is performed to claim the superiority of the proposed approach. The simulation results presented in this paper reveal the fact that the performance of the ACSA is better than the other algorithms.

Opposition aided Cat Swarm OptimizationAlgorithm for Optimal Digital IIR High PassFilter Design

1 ABSTRACT: This paper presents a solution methodology for the designing of optimal and stable digital infinite impulse response (IIR) high pass (HP) filter by employing the cat swarm optimization (CSO) technique with oppositional learning. Because of the presence of the denominator terms, the error surface of digital IIR filters is non linear and multimodal. Therefore, the traditional designing techniques usually got trapped in the local minim. CSO is a population based global optimization technique which has global as well as local search capabilities. Here, the multicriterion optimization is used as the design criterion that undertakes the minimization of magnitude approximation error and minimization of ripple magnitudes while satisfying the stability constraints that are imposed during the design process. For the intent of starting with an improved solution set, the opposition based learning strategy is included in CSO. The developed algorithm is used to design the digital IIR high pass (HP) filter and attempts to find the optimal filter coefficients which are approximately close to the desired filter response. The computational results shows that the proposed algorithm is capable of designing the stable and optimal digital IIR HP filter structure that is better to the designs presented by other algorithms.

Digital High-Pass Filters with Milder High-Pass Effect on Digital Images

Image filtering consists of modifying the original image by logically "reimaging" it with a mathematical imaging device in which spatial response can be controlled by the user. Image filtering is performed by a mathematical operation called convolution, which is simply the successive replacement of each point in the original image by a new value produced by a weighted combination of the original point and its surrounding neighbour points. Filtering generally requires definition of a filtering kernel or small matrix; often a few filtering kernels are predefined in imaging computer systems. The filtering kernel is generally square with a matrix size of 3×3 pixels, 5×5 pixels or 7×7 pixels. We consider the use of two-dimensional, second-order derivatives for image enhancement. The approach basically consists of defining a discrete formulation of the second-order derivative and then constructing a filter mask based on that formulation. Ten spatial high-pass filters (masks) are developed, then implemented and tested in our laboratory by using programs that were written in Borland c++ and visual Fortran. The results of the application of the developped Laplacian and Laplacian high-pass digital filters (masks) on digital images (either edge detection, sharpening of high frequency regions (fine details) accentuation), comparing between the effect of different dimensions filters 3×3 and 5×5 and milder high pass effect are presented and demonstrated. As the size of the filter (mask) gets larger and/or the weight of the center pixel of the kernel gets higher, the sharpenning effect becomes more and more. Second-order derivatives have a strong response to fine detail, such as thin lines and isolated points.

Implementing and Testing $d$– $q$ WPT-Based Digital Protection for Microgrid Systems

This paper presents the implementation and performance evaluation of a new digital protection for microgrid systems, The proposed digital protection is based on utilizing the wavelet packet transform (WPT) for extracting the first-level high-frequency subband contents present in the d-q-axis current components. The utilized WPT is realized by a half-band digital high-pass filter, whose coefficients are determined by the Daubechies db4 wavelet basis functions. The d-q WPT-based digital protection is implemented for offline and experimental performance evaluation. Offline tests are conducted using data collected from a simulation model of a microgrid located in Fermeuse, NL, Canada. The experimental tests are conducted on a laboratory microgrid system that is constructed as a scaled version of the Fermeuse microgrid. Several transient disturbances occurring in different parts of the test microgrid systems are investigated both offline and in experimentation. Performance results demonstrate significant abilities of the d-q WPT-based digital protection for fast, accurate, and reliable detection, classification, and response to different transient disturbances. In all tested faults, the developed digital protection is able to generate a trip signal in less than a quarter cycle based on the 60-Hz system operating frequency.

Design and Determination of Optimum Coefficients of IIR Digital Highpass Filter using Analog to Digital Mapping Technique

Digital Signal Processing (DSP) , there two types of filters are used to perform the filtering operations and they are the Infinite Impulse Response (IIR) filter and the Finite Impulse Response (FIR) filter. The present output sample of an IIR filter depends on the present input samples, past input samples and past output samples, i.e IIR filter is of recursive type. Now to design the Digital IIR filter, the coefficients are essentially required. There are a numbers of techniques available for designing the IIR filter. In this paper, the design and determination of the IIR filter coefficients are introduced using computer based approach. The program based on the algorithm proposed in this paper is simulated in Matlab which provides with the satisfactory results.

A lightweight sensing method of tooth-touch sound for disabled person using remote controller

To support disabled people to use remote controllers, several biological signals are used. The tooth-touch is one of desirable biological signals. This is because it is the simple and natural human behavior. However, a sophisticated signal processing to extract only the tooth-touch sound is needed since the tooth-touch sound is mixed with the voice sound. This paper proposes a lightweight sensing method extracting the tooth-touch without a sophisticated signal processing to eliminate only voice sound from the sound wave in which tooth-touch and voice are mixed. Instead of the audible sound wave, proposal uses a shock wave (i.e., ultrasonic wave) which is generated when the upper tooth and the lower tooth hit each other. Using the shock wave generated to detect the tooth-touch, a trivial high-pass filter can eliminate only voice sound in the lower frequency domain than in the ultrasonic domain including the tooth-touch. Through a preliminary experiment that uses a conventional microphone and well-known digital high-pass filter, we show that the used electret microphone can sense the tooth-touch as ultrasonic wave and the high-pass filter can extract only tooth-touch. Then, we show some robustness of our method by using the sound waves including the voice and tooth-touch. In addition, we design the filtering hardware to implement a small and cheap system-on-chip achieving a real-time operation. Through the implementation of Field Programmable Gate Array, and the simulation, we show that our hardware is small and performs well for a real-time operation.

Design of optimal linear phase FIR high pass filter using craziness based particle swarm optimization technique

In this paper, an optimal design of linear phase digital high pass FIR filter using Craziness based Particle Swarm Optimization (CRPSO) approach has been presented. FIR filter design is a multi-modal optimization problem. The conventional gradient based optimization techniques are not efficient for such multi-modal optimization problem as they are susceptible to getting trapped on local optima. Given the desired filter specifications to be realized, the CRPSO algorithm generates a set of optimal filter coefficients and tries to meet the desired specifications. In birds’ flocking or fish schooling, a bird or a fish often changes directions suddenly. This is described by using a ‘‘craziness’’ factor and is modeled in the CRPSO technique. In this paper, the realizations of the CRPSO based optimal FIR high pass filters of different orders have been performed. The simulation results have been compared to those obtained by the well accepted classical optimization algorithm such as Parks and McClellan algorithm (PM), and evolutionary algorithms like Real Coded Genetic Algorithm (RGA), and conventional Particle Swarm Optimization (PSO). The results justify that the proposed optimal filter design approach using CRPSO outperforms PM, RGA and PSO, in the optimal characteristics of frequency spectrums.

Novel approach to GPS/SINS integration for IMU alignment

Strapdown inertial navigation system (SINS) requires an initialization process that establishes the relationship between the body frame and the local geographic reference. This process, called alignment, is generally used to estimate the initial attitude angles. This is possible because an accurate determination of the inertial measurement unit (IMU) motion is available based on the measurement obtained from global position system (GPS). But the update frequency of GPS is much lower than SINS. Due to the non-synchronous data streams from GPS and SINS, the initial attitude angles may not be computed accurately enough. In addition, the estimated initial attitude angles may have relatively large uncertainties that can affect the accuracy of other navigation parameters. This paper presents an effective approach of matching the velocities which are provided by GPS and SINS. In this approach, a digital high-pass filter, which implements a pre-filtering scheme of the measured signal, is used to filter the Schuler cycle of discrete velocity difference between the SINS and GPS. Simulation results show that this approach improves the accuracy greatly and makes the convergence time satisfy the required accuracy.