Response Filter Research Articles

$$\alpha$$-order universal filter realization based on single input multi-output differential voltage current conveyor

Two voltage-mode topologies single input multi-output universal fractional filters with high input impedance are proposed. The proposed analog filters consist of three DVCC+ blocks, two grounded capacitors and two resistors targeting the minimum passive elements. The proposed topologies provide a realization for all standard fractional filter functions (HP, LP, BP, AP and notch filter). The effect of Fractional order on filter responses in the range of $$\alpha$$ from 0.7 to 1.2 was studied. Fractional order has been investigated for different filter responses in terms of cutoff, gain, phase and noise. The central frequency was designed to be 110 KHz for the first topology, while that of the second topology is around 100 KHz. The proposed filters are simulated using Cadence TSMC 130nm with dual supply voltages $$\pm \,0.75V$$ . A performance comparison between the proposed topologies and the topologies in the literature shows that the proposed architecture gives an acceptable performance.

A Differentially Fed Dual-Polarized Filtering Patch Antenna With Good Stopband Suppression

A differentially-fed dual-polarized filtering patch antenna with no extra filtering circuits involved is proposed. The filtering response is realized by symmetrically loading four short strips and a long cross-type strip, and a square ring slot to insert radiation zeros on the dual-polarized antenna element. The short and long strips can generate two transmission zeros at lower and upper band edges, respectively, leading to a sharp skirt selectivity. In addition, the long cross-type strip and the square ring slot can respectively introduce an extra resonance close to the original one, broadening the impedance bandwidth. Also, the equivalent circuit is presented to show that the two zeros can be brought by the two equivalent series resonant circuits extracted from the short/long strips resulting in the bandpass response. We may note that the proposed filtering structure owns the merits of simple, compact and complete symmetry, thus it can be well integrated with the dual- polarized antenna. Consequently, a compact and high-gain dual- polarized filtering antenna with good stopband suppression, low cross-polarization level and symmetrical radiation patterns is obtained. It can achieve an impedance bandwidth about 15% and a maximum gain of 8.4 dBi. The simulated cross-polarization level is below -40 dB, and the measured one is lower than -22 dB. Moreover, the upper stopband can be up to 2.6 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the center frequency of the antenna), where the stopband radiations from all the directions can be suppressed and the measured suppression ratio can reach 90%.

Analysis and Design of Microstrip Filters Using Photonic Band Gap Ground Plane with Fractal Periodic Pattern (Dept.E)

In the present work, four different techniques are used in designing the microstrip low pass filters (LPF). These techniques include LPF with fractal defected ground structure (DGS), LPF with continuous minkowiski fractal element, multi-stop band filter with discontinuous minkowiski element, and finally a wide multi-stop filter with separated interdigcap shape. A microstrip PBG filter of minkowiski element and interdigcap shape was designed to operate as a multifrequency band stop filter. With an appropriate fractal geometry of minkowiski and interdigcap elements, a wide stop-band at different frequencies are obtained. A continuous sinusoidal fractal slots are designed to work as a wide LPF. A novel fractal DGS for the microstrip LPF is proposed. The proposed fractal DGS can provide better band gap, and slow-wave characteristics. The numerical results show that a LPF of continuous and discontinuous fractal minkowiski elements in ground plane is obtained with a bandwidth 0 - 3 GHz for a slot width 0.5mm. However, if the slot width is taken equal 0.2 mm, the bandwidth is increased up to 10 GHZ. With suitable choice of number of elements, one can control the filter bandwidth. With a discontinuous fractal minkowiski and interdigcap element in ground plane, the filter response is forced to have a stop band at resonance frequency of fo and repeated at 2fo, .. etc. The numerical results obtained using an analytical technique with the aid of a numerical package (Sonnet) which is used in microstrip analysis.

Integrating Signals With High Sampling Rates for Transmission Line Protection in Digital Substations

Travelling wave based protection functions require significantly higher sampling rates than protection functions based on time-domain superimposed quantities or fundamental frequency phasors. Integrating these high sampling rates in digital substations leads to a significant increase of the communication load of process-level networks and causes high computational cost for centralized protection systems. This paper builds on a distributed signal processing approach, which allocates the filtering operations among standalone merging units (SAMU). In particular, the paper presents a decimation filter design to integrate signals with high sampling rates at the process-level. Thereby, signal sequences with high, medium and low sampling rates are provided according to the requirements of the respective protection function. The decimation filter structure is optimized with respect to time delay by the Remez exchange algorithm and with respect to computational cost by a multistage approach and a sparse filter design algorithm. In addition, the filter response is verified against the accuracy constraints defined in IEC 61869-6 and IEC 61869-13. The paper shows that it is feasible to distribute the filtering operations among SAMUs, while keeping the time delay below the maximum allowable processing delay of 2 ms.

Advanced Cognition-Driven EM Optimization Incorporating Transfer Function-Based Feature Surrogate for Microwave Filters

This article proposes an advanced cognition-driven electromagnetic (EM) optimization incorporating transfer function-based feature surrogate for EM optimization of microwave filters. The proposed optimization technique addresses the situations where the response of the starting point for design optimization is far away from the design specifications. This article proposes to extract transfer function-based feature parameters for optimization to address the challenge that the features cannot be clearly and explicitly identified from the filter response. Multiple transfer function-based feature parameters are extracted and used to develop the feature surrogate model for the proposed cognition-driven optimization. Furthermore, we derive new objective functions for the cognition-driven optimization directly in the feature space. The proposed cognition-driven optimization incorporating transfer function-based feature surrogate can achieve faster convergence than the existing feature-assisted EM optimization methods. Two examples of EM optimizations of microwave filters are used to demonstrate the proposed technique.

Physics-Based Deep Learning for Fiber-Optic Communication Systems

We propose a new machine-learning approach for fiber-optic communication systems whose signal propagation is governed by the nonlinear Schrodinger equation (NLSE). Our main observation is that the popular split-step method (SSM) for numerically solving the NLSE has essentially the same functional form as a deep multi-layer neural network; in both cases, one alternates linear steps and pointwise nonlinearities. We exploit this connection by parameterizing the SSM and viewing the linear steps as general linear functions, similar to the weight matrices in a neural network. The resulting physics-based machine-learning model has several advantages over “black-box” function approximators. For example, it allows us to examine and interpret the learned solutions in order to understand why they perform well. As an application, low-complexity nonlinear equalization is considered, where the task is to efficiently invert the NLSE. This is commonly referred to as digital backpropagation (DBP). Rather than employing neural networks, the proposed algorithm, dubbed learned DBP (LDBP), uses the physics-based model with trainable filters in each step and its complexity is reduced by progressively pruning filter taps during gradient descent. Our main finding is that the filters can be pruned to remarkably short lengths—as few as 3 taps/step—without sacrificing performance. As a result, the complexity can be reduced by orders of magnitude in comparison to prior work. By inspecting the filter responses, an additional theoretical justification for the learned parameter configurations is provided. Our work illustrates that combining data-driven optimization with existing domain knowledge can generate new insights into old communications problems.

A Fast Segmentation Method for Fire Forest Images Based on Multiscale Transform and PCA.

Forests provide various important things to human life. Fire is one of the main disasters in the world. Nowadays, the forest fire incidences endanger the ecosystem and destroy the native flora and fauna. This affects individual life, community and wildlife. Thus, it is essential to monitor and protect the forests and their assets. Nowadays, image processing outputs a lot of required information and measures for the implementation of advanced forest fire-fighting strategies. This work addresses a new color image segmentation method based on principal component analysis (PCA) and Gabor filter responses. Our method introduces a new superpixels extraction strategy that takes full account of two objectives: regional consistency and robustness to added noises. The novel approach is tested on various color images. Extensive experiments show that our method obviously outperforms existing segmentation variants on real and synthetic images of fire forest scenes, and also achieves outstanding performance on other popular benchmarked images (e.g., BSDS, MRSC). The merits of our proposed approach are that it is not sensitive to added noises and that the segmentation performance is higher with images of nonhomogeneous regions.

A Novel Substrate Integrated Waveguide (SIW) Based Highly Selective Filtering Power Divider

Aims: In this paper, a novel Substrate Integrated Waveguide (SIW) based filtering power divider is presented. Objective: In the proposed power divider, filtering response is achieved by interleaving inductive posts in the SIW structure. The proposed structure reduces the size and the cost of the system, as the structure performs the function of the power divider as well as the function of a filter. Methods: Simulation of the proposed structure was carried out using commercial software Ansoft High Frequency Structure Simulator (HFSS), which is a three-dimensional full-wave solver utilizing the Finite Element Method (FEM). The proposed power divider structure was also fabricated and tested. Results: The measured return loss was found to be -21.78 dB with 3 dB Fractional Bandwidth (FBW) of 4.72% at the center frequency of 14.8 GHz. Moreover, the proposed structure showed an insertion loss of 0.96 dB, isolation of more than 18 dB; maximum amplitude and phase imbalance was observed to be 0.18 dB and 1.24° respectively within the operating frequency band. Conclusion: Good agreements are observed between the experimental results and the simulations.

A Novel Frequency Tunable RF Comb Filter

This letter presents a new filter to suppress radio frequency interference (RFI) in microwave remote sensing instruments, particularly a wideband autocorrelation radiometer (WiBAR). RFI increases the noise floor and results in a decreased signal-to-noise ratio (SNR) of the WiBAR delay peak. The proposed filter operates like a Fabry-Perot interferometer (FPI) in optics and has the frequency response of a comb filter with many evenly spaced alternating pass and stop bands. The frequencies of these bands are varied with an electrically adjustable phase shifter. The design of a comb filter with an airy finesse value of 20 has been verified by simulation and measurement.

An enhanced particle swarm optimization with distribution fields appearance model for object tracking

This paper presents an improved Particle Swarm Optimization tracker, representing target with Distribution Fields (DFs) to solve problems of how to effectively represent the appearance model and adapt to the change of environment. First, Categorized Particle Swarm Optimization (CPSO) makes good use of identifying selected object model by integrating based on the performance of categorized particles and it achieves an efficient algorithm in object tracking. Then, compared with the traditional target representation such as color, gradient, filter responses, etc. DFs build image descriptors that are able to make object smoothing and keep pixel values. To provide a better tracking result in different videos, this paper finds a more efficient way by using an appearance model which adopts the DFs layer with CPSO to build tracking procedure. The experiments show higher performances than another four state-of-the-art approaches on several sequences videos.

Sparsity-Aware Direct Equalization of Time-Varying Channels for V2V Communications

In this letter, we propose a new adaptive anti-interference equalization technique for fast time-varying channels. The equalization is implemented by basis expansion model (BEM) based time-varying (TV) finite impulse response (FIR) filters. By exploiting the sparsity of angle of arrival, we propose the idea of adaptive basis expansion for direct equalization. The optimization problem of the basis functions is formulated and solved by block orthogonal matching pursuit (BOMP) algorithm. We further propose a decision directed solution to improve the equalization performance. Simulation results show that the proposed methods exhibit a significant gain over conventional schemes.

Design of digital IIR filter: A research survey

This paper presents an overview on advancement made in designing of a digital infinite impulse response (IIR) filter. The design problem of an IIR filter was found to be challenging due to presence of poles in its transfer function. This makes the phase response of an IIR transfer function nonlinear and its magnitude response is also drifted due to quantization of coefficient values of denominator polynomials, which leads towards instability. Therefore, numerous efforts were made in order to acquire an optimal filter response using several optimization methods. Design problem of an IIR filter with various constraints was developed and solved using gradient based techniques, which resulted in optimal passband response with nearly linear phase or in some cases, absolute linearity was also achieved. However, the obtained solutions were sub-optimal in many cases due to transferring the multimodal design problem of an IIR filter into convex optimization. The solution was also affected due to the quantization of filter coefficients and in case of absolute linear phase response; a strong hick in magnitude response at beginning of transition edge frequency was obtained. To overcome the sub-optimality, researchers used evolutionary algorithms (EAs) for designing of an IIR filter. In time domain, system identification (SI) was adopted, whereas various error functions were developed in frequency domain for obtained magnitude responses close to desired response. This approach resulted in an optimal IIR filter response, however phase response linearity was not improved. Thus, EA approach was appropriated for lower order IIR filters. The design of various IIR filters like lowpass filter (LPF), highpass filter (HPF), bandpass filter (BPF) and bandstop filter (BSP) using an all-pass infinite impulse response (APF-IIR) was also reported. This approach is most appropriate, because the filter response is stable, nearly linear and magnitude response was also accurate. However, there is high error at the band edges of passband. Therefore, literature reveals that an APF based approach is most appropriate for various magnitude response filters.

Low-latency localization in the spherical harmonics domain using an iterative search method

Higher-order ambisonic microphones have attained considerable interest for their ability to allow spherical harmonic decomposition of soundfields. In taking advantage of this property, myriad methods have been produced for directional filtering and subsequent analysis, as well as localization and tracking of soundfields. This study introduces a technique to estimate direction of arrival of an acoustic signal by generating a set of spatial filters corresponding to randomly chosen orientations over the sphere, then iteratively reducing the region for orientation selection based on the maximum power obtained from the filter response. This method is distinct from existing mapping- and vector-based methods in that it produces accurate, low-latencyresults in the presence of moderate reverberation. Results obtained using both simulated and experimental data demonstrate viability of this technique for localization in large, reverberant spaces as well as accurate source identification under real-time conditions. [Work supported by NSF grants #1631674 and #1909229, and the RPI Cognitive and Immersive Systems Laboratory.]

A Study on Neural Network Detector in SMR System

We have previously proposed the waveform equalization using a two-dimensional finite impulse response (TD-FIR) filter and the inter-track interference (ITI) canceller as a signal processing method for shingled magnetic recording (SMR) system. In this study, we propose a neural network detector (NND) to automate the iterative decoding in the future and evaluate the performance of the NND in SMR system. The result shows that our proposed NND shows almost the same performances as a combined system with TD-FIR filter and soft-output Viterbi algorithm (SOVA) detector with signal-dependent noise predictor.

Design and Fabrication of a Band-Pass Filter With EBG Single-Ridge Waveguide Using Additive Manufacturing Techniques

A novel band-pass filter topology in waveguide technology is presented in this work. The proposed filter design is based on a periodic structure that uses modified sections of a single-ridge waveguide (SRW) as the unit cell to produce the desired frequency response. Two-step height profiles are included in the central part of the SRW, which provide useful parameters to yield a simple design method to achieve the required filtering characteristics. The suggested topology and design process are used to achieve band-pass filter responses with different fractional bandwidth and rejection characteristics. A 54% fractional bandwidth band-pass filter centered at 5.4 GHz is implemented using low cost 3-D additive manufacturing techniques, which allow fast prototyping and the fabrication of complex geometries. Experimental measurements are in agreement with the expected simulated response of the designed band-pass filter.

Deep Optimal Filter Responses for Multi-Spectral Imaging

Spectral recovery from measured camera signals based on deep learning lead to significant advancements of the potential reconstruction quality. However, most deep learning based approaches only consider RGB cameras and are targeting object classification in particular or remote sensing in general as their final application. Within this work, we analyze the influence of a joint filter optimization and spectral recovery for multi-spectral image acquisition with the underlying goal of capturing high-fidelity color images. An evaluation on the influence of the total camera channel count on the reproduction quality is provided. Finally, a possible normalization of spectral data is discussed.

Decisive structures for multirate FIR filter incorporating retiming and pipelining schemes

PurposeVery large-scale integration (VLSI) digital signal processing became very popular and is predominantly used in several emerging applications. The optimal design of multirate filter with improvement in performance parameters such as less area, high speed and less power is the challenging task in most of the signal processing applications. This study aims to propose several effective multirate filter structures to accomplish sampling rate conversion.Design/methodology/approachThe multirate filter structures considered in this work are polyphase filter and coefficient symmetry-based finite impulse response filter. The symmetry scheme particularly brings down the complexity to significant extent. To bring improvement in speed, delay registers are inserted at appropriate path with the help of pipelining and retiming scheme.FindingsIn this paper, the three tasks have been considered. First, the polyphase coefficient symmetry and modified polyphase (MP) structure is designed. Second, the pipelining is applied to the polyphase structure and the obtained results are compared with the polyphase structure. In third, retiming is applied to the polyphase structure and the performance comparison is carried out. The structures are realized for various orders, and the comparative analysis is carried out with the filter order N = 12, 30, 42, 8, 11 and 24 and the results are stated. The performance of all the accomplished structures is analyzed using Altera Quartus with the family cyclone II, device EP2C70F672C6. The results show that the multirate filter using pipelining and retiming offers better performance when examining with the conventional structures. Retimed and pipelined MP structure achieves a speed enhancement of about 33.81% when examining with the conventional polyphase (CP) structure with retiming and pipelining for N = 24 and M = 5. Likewise, the 2/3 structure of pipelined coefficient symmetry approach offers area reduction of about 54.76% over 2/3 structure of pipelined polyphase approach for N = 30 with little reduction in power. The fine grain pipelined and retimed MP structure with N = 11 and M = 3 avails critical path delay reduction of about 28.15% when examining with the corresponding fine grain pipelined and retimed CP structure.Originality/valueThe proposed distinct structures offer better alternative to conventional structures because of the symmetric coefficients, performance enhancement using pipelining and retiming based rate conversion structures. The suggested structures can be used for achieving different rates in software radios.

Expressions for the Harmonic Transfer Functions of N-Path Filters With Arbitrary Source and Load Impedances

We derive analytical expressions for the harmonic transfer functions (HTFs) of N-path filters with arbitrary source and load impedances. We start with first-order approximations of the HTFs based on a simplified “Ohm's-law” characterization of filter operation, and then show how these can be corrected via a feedback visualization to obtain infinite-series expressions. We apply our expressions to study the impact of variations in the source and load impedances. Overall, our approach provides a way to visualize and understand the individual terms contributing to the HTFs and adds to the existing analytical methods to explore N-path filter response.

Single VDGA-Based Dual-Mode Multifunction Biquadratic Filter and Quadrature Sinusoidal Oscillator

This article relates to the realization of voltage-mode and/or current-mode multifunction biquadratic filter and quadrature oscillator circuits each using one voltage differencing gain amplifier (VDGA), two resistors and two grounded capacitors. The proposed dual-mode filter having one output and three inputs can provide the three standard biquadratic transfer functions with both voltage and current output filter responses simultaneously. It also has the independent tuning of the angular resonance frequency and the quality factor . With a slight modification of the proposed filter, a new dual-mode quadrature sinusoidal oscillator can be obtained. The proposed quadrature oscillator provides orthogonal resistive/electronic control of both oscillation condition and oscillation frequency. Non-ideal and parasitic conditions are also examined and their effects on the circuit performance are discussed. In order to confirm the theory, several computer simulation results with PSPICE program are given .

VLSI design of APT-VDF using novel variable block sized ternary adder and multiplier

Nowadays, Variable digital filters (VDF) play an essential role in the field of communication and signal processing. The desired frequency response of any prototype filter can be obtained by developing an All Pass Transformation (APT) based Variable digital filter (APT-VDF) that maintains an exhaustive control over the cut off frequency. The performance of the APT-VDF is limited by its speed and area utilization. In this paper, the pipelined APT-VDF is modified by developing a new Variable Block Sized Ternary Adder (VBS-TA) and a modified Ternary multiplier for the fast realization of the filter structure. Because, the fundamental arithmetic operations involved in the design of APT-VDF are addition and multiplication. The ternary logic transmits more data through interconnection wire, and hence the ternary logic based arithmetic requires fewer components and interconnections. The proposed VBS-TA increases the speed of the addition process by skipping the carry propagation with the help of ternary compound gates. This VBS-TA can also be used to boost up the speed of the multiplier circuit in the APT-VDF filter. Furthermore, the ternary multiplier is modified by introducing a divide and conquers approach in the partial product generation part. The simulation results show that the proposed APT-VDF overtakes the existing VDFs in terms of delay, power and area utilization. It consumes only 0.289Wpower with a latency of 9.24 ns. Also, it achieves an operating frequency of 210.87 MHz, and it is much better than the existing VDFs.