Showing papers on "Linear phase published in 2022"

Epileptic Spike Detection Using Neural Networks With Linear-Phase Convolutions

Abstract: To cope with the lack of highly skilled professionals, machine learning with proper signal processing is key for establishing automated diagnostic-aid technologies with which to conduct epileptic electroencephalogram (EEG) testing. In particular, frequency filtering with the appropriate passbands is essential for enhancing the biomarkers-such as epileptic spike waves-that are noted in the EEG. This paper introduces a novel class of neural networks (NNs) that have a bank of linear-phase finite impulse response filters at the first layer as a preprocessor that can behave as bandpass filters that extract biomarkers without destroying waveforms because of a linear-phase condition. Besides, the parameters of the filters are also data-driven. The proposed NNs were trained with a large amount of clinical EEG data, including 15 833 epileptic spike waveforms recorded from 50 patients, and their labels were annotated by specialists. In the experiments, we compared three scenarios for the first layer: no preprocessing, discrete wavelet transform, and the proposed data-driven filters. The experimental results show that the trained data-driven filter bank with supervised learning behaves like multiple bandpass filters. In particular, the trained filter passed a frequency band of approximately 10-30 Hz. Moreover, the proposed method detected epileptic spikes, with the area under the receiver operating characteristic curve of 0.967 in the mean of 50 intersubject validations.

A Preliminary Step to Realize Digital Filter for Electrocardiogram Signal Denoising

Abstract: The electrocardiogram (ECG) is one of the most commonly used technique in the assessment of cardiovascular disease. Cardiovascular disease is one of the major cause of death in many countries so it is important for interpretation of heart beat. The ECG signal during its acquistion gets commonly affected by baseline drift that hinders physician in the correct diagnosis of heart condition. In this work, ECG signal is preprocessed to alleviate noise. Digital filters such as Infinite Impulse Response (IIR) and Finite Impulse Response (FIR) filter are designed for the purpose of removal of artifacts from the signal. The IIR Butterworth low pass filter and least square linear phase low pass FIR filter are designed to reduce the baseline drift artifact in ECG signal. The preprocessing block is designed in MATLAB filter design and analysis tool. The corresponding model is realized in simulink environment. The performance measures of IIR and FIR filter are analyzed. The corresponding HDL code is generated and is targeted to a field programmable gate array board to observe the simulation results.

Minimum phase finite impulse response filter design

Abstract: The design of minimum phase finite impulse response (FIR) filters is considered. The study demonstrates that the residual errors achieved by current state-of-the-art design methods are nowhere near the smallest error possible on a finite resolution digital computer. This is shown to be due to conceptual errors in the literature pertaining to what constitutes a factorable linear phase filter. This study shows that factorisation is possible with a zero residual error (in the absence of machine finite resolution error) if the linear operator or matrix representing the linear phase filter is positive definite. Methodology is proposed able to design a minimum phase filter that is optimal—in the sense that the residual error is limited only by the finite precision of the digital computer, with no systematic error. The study presents practical application of the proposed methodology by designing two minimum phase Chebyshev FIR filters. Results are compared to state-of-the-art methods from the literature, and it is shown that the proposed methodology is able to reduce currently achievable residual errors by several orders of magnitude.

Phase Error Analysis for First-Order Linear Differential Microphone Arrays

Abstract: First-order Linear Differential Microphone Arrays (LDMAs) are sensitive to sensor imperfections such as phase errors. This paper analyses the impacts of both bounded and unbounded phase errors on first-order LDMAs. We propose a tolerance threshold that allows bounded phase errors to take various values. Moreover, White Noise Gain (WNG) thresholds for preventing mainlobe misorientation are obtained. Our work provides guidance for the design of robust first-order LDMAs.

Three-Order Band Pass Filter with flat group delay using U-shaped Negative Group Delay Circuits

Abstract: In order to achieve the full-passband linear-phase characteristic, the negative group delay circuit (NGDC) is applied to suppress the noticeable group delay at the edge of the passband of the traditional band-pass filter. This paper introduces the fundamental principle of the U-shaped negative group delay circuit, and configures them into a traditional band-pass filter for observation. From the simulation results, the GD fluctuation of the filter is reduced by 0.54ns, from 0.69ns to 0.17ns, and the insertion loss change is less than 3dB within the frequency range from 2.17GHz to 2.85GHz. It enables the traditional BPF to achieve a flat group delay in the entire passband, and realizes the full-passband linear-phase characteristic, which is suitable for applications.

Seeker Optimization for Linear Phase Fir Filter Design

Abstract: In this paper, filter design procedure is analyzed using seeker optimization technique to design an optimal finite impulse response (FIR) filter with desired parameter specifications. Using these algorithms, the optimum impulse response coefficients of the different finite impulse response filter are determined to fulfill their exact output. A fitness function based on the error is generated in which we can specify the desired levels of δp and δs individually. Simulative results of these techniques are presented and compared in conformity with their select band and reject band ripples. The techniques developed are mainly useful for digital signal processing applications as clearly indicated by the results that it forms a good platform for newer applications.

Design of Optimal FIR Digital Filter by Swarm Optimization Technique

Abstract: Finite Impulse Response (FIR) digital filters are widely used in digital signal processing and other engineering because of their strict stability and linear phase. Aiming at the problems of low accuracy and weak optimization ability of traditional method to design digital filter, the newly proposed Grey Wolf Optimization (GWO) algorithm is used in this paper to design a linear-phase FIR filter to obtain the optimal transition-band sample value in the frequency sampling method to obtain the minimum stop-band attenuation, so as to improve the performance of the filter. And improved by embedding Lévy Flight (LF), which is the modified Lévy-embedded GWO (LGWO). Finally, the performance of traditional frequency sampling methods and optimization algorithms GWO and LGWO are compared. When the number of sampling points is 65 and 97, the stopband attenuation of LGWO is improved by 0.2029 dB and 0.2454 dB respectively compared with GWO algorithm. The better performance of LGWO is shown in the results.

A Broadband Transmitarray Antenna Element With Linear Phase Response

Abstract: In this paper, a broadband antenna element with linear phase response for transmitarray application is proposed. This element is based on receive-transmit configuration: the incident wave is received by the receiver, then go through the coupling slots and striplines. Finally, the incident wave is radiated into the free space by the transmitter. The proposed transmitarray element has high transmission efficiency within a wide frequency range. Meanwhile, more than 360° linear phase compensation is achieved by varing the phase delay lines. The proposed element has a lot of potential for wideband transmitarray antenna application due to its advantages of low insertion loss, broadband transmission magnitude and full 360° linear transmission phase.

A constant phase stable over the wideband for beam steering antenna applications

Abstract: A K‐band wideband self‐compensating phase shifter based on gap waveguide is presented. The traditional waveguide phase shifter cannot easily achieve a stable phase shift over wideband due to the dispersion effect. Accordingly, a short‐circuit structure and a slow‐wave structure are designed in this paper, and their phase shifts show a positive‐slope and a reverse‐slope with respect to frequency. The two structures are realized using the tuning screw technology, and different phase shifts of 0–140° are realized by adjusting the number of screws. Besides, two structures are combined with a high‐isolation power divider to realize a phase shifter with high phase and amplitude stability. The phase shifter is manufactured and measurement results of the eight phase shifts of the phase shifter show that the bandwidth of the phase changes within ±5° was greater than 30%. Finally, a four‐way feeding network has been designed, which is used to form a four‐element linear array. Generally, when the antenna beam is steered, the main‐beam directions of different frequencies are not consistent. Therefore, by compensating the slope of the phase shifter with respect to the frequency, an array antenna whose main‐beam direction does not change with respect to frequency is designed.

Assessment of Filter Design for 5G Applications

Abstract: This work investigates the projection of the Filter design for highly linear application design. In this paper, a simple configuration of the filters are utilized in design of phase shifter (PS), which can be used for designing a Analog Pre-distortion circuit, which henceforth, can be utilized for the highly linear power amplifier design. The combination of low pass filter and high pass filter produces the phase shift of a bout – 90 ° a t 3.5 GHz with bandwidth of 86%. Thus, this filter configuration can be utilized for designing highly linear Power Amplifiers which further can be used in the transmitter section of newer communication frequency band of 5G.

Different Methods of Linear Phase IIR Filer Realization

Abstract: Signal processing has become one of the most popular research topics. Researchers have designed a variety of digital filters to exclude unwanted random noises during the transmission or extract part of the signal in the desired range. There is a prevalent trend for digital filters to replace analog ones since they do not require hardwires. All the performances are operated on a single processor and are free from the effect of external factors. Finite impulse response (FIR) and infinite impulse response (IIR) filters in digital filters respectively provide infinite and finite impulse responses. In the application, it is preferred to have a linear phase digital filter, and FIR filters are naturally linear. However, FIR filters have higher orders and group delay than IIR filters, so researchers found various ways to implement linear phase IIR filters for improvement. This paper introduces and compares Powell and Chau Linear Phase IIR Filter, Kwan Linear Phase IIR Filter, and Xiao, Oliver, and Agathoklis Linear Phase IIR Filter.

Simple Method for Perfect Reconstruction QMF Filter Design

Abstract: The purpose of this work is the design of FIR QMF (Quadrature Mirror Filters) filters of perfect reconstruction and odd number of coefficients (even order). By design, these filters will have linear phase and integer delay. These filter pairs have many applications in wavelet transforms and other multi-frequency decompositions. Perfect reconstruction filters have been studied from long time ago but we still found publications about them.

Comparison of FIR Window Filter Variation Results on Pink Noise Audio

Abstract: IIR and FIR filters are the most used digital signal filters. The application of each filter type depends on the needs of the user. IIR filters are generally used for applications with limited memory. In comparison, FIR filters are usually used for applications where the linear phase is essential. In this study, the implementation of FIR filters on pink noise audio samples was observed. Various FIR window method filters such as rectangular, hamming, hanning, and Blackman will be compared. Each type of filter will have a different filter order due to computing the frequency cut-off point for each filter. The comparisons were made by observing the gain response, the time domain signal, the frequency response, and the phase response. The results indicated that the Hanning window method is a better filter because it produces low delay and good attenuation. Things to be considered in designing FIR filters are fluctuations in frequency response and phase shift. Alterations on cut-off points on the filters and delay usage can be deployed for some improvement

A New Method for Linear Antenna Array Design

Abstract: The inherent relation between the linear antenna array and the finite impulse response filter of digital signal processing is revealed and the least square linear-phase finite impulse response filter design method is introduced for the linear antenna array to obtain a similar main lobe width of uniform linear antenna array but much lower sidelobe level.

Using Interpolated FIR Technique for Digital Crossover Filters Design

Abstract: Digital filters design is an important aspect of the audio processing. They are used in several applications and the key point is not only the achieved final audio quality but also their computational complexity. In this context, the use of Interpolated Finite Impulse Response (IFIR) filters is proposed for the optimized implementation of a digital crossover network. In particular, the structure can be viewed as an analysis filter-bank that can be optimized introducing IFIR filters that allow to reach very narrow transition bands, with low computational complexity and linear phase, avoiding ripple between adjacent bands. Starting from a real-time implementation of the proposed crossover network, several experiments have been conducted to prove the effectiveness of the proposed approach in terms of computational complexity and obtained audio quality.

Minimum Phase Linear Antenna Array Design

Abstract: The paper considers the design of minimum phase discrete linear arrays. The paper introduces recent advances for the design of minimum phase Finite Impulse Response filters, as applied to the design of minimum phase linear arrays. The minimum phase linear array is demonstrated to require the least number of elements of all linear arrays that are able to achieve a given magnitude pattern specification. Three example designs are presented and compared to results from the literature.

A comprehensive estimation method of phase error in the frequency-interleaving digital-to-analog converter

Abstract: This letter studied the phase error in the frequency-interleaving digital-to-analog converter (FI-DAC) and proposed a comprehensive phase estimation method. Firstly, the model of FI-DAC system was established, and the phase error were considered that consists of three parts: time delay error, initial phase error and nonlinear phase error. By analyzing the phase function characteristics of the system, the least squares (LS) was used to linearly fit the phase functions of the non-overlapping bands to estimate both the time delay and initial phase of each sub-band channel. Then, the nonlinear phase error of the system was estimated by the difference between the system phase function and the estimated linear phase function. Finally, the effectiveness of the proposed estimation method was verified by the built FI-DAC test bench.