Stopband Attenuation Research Articles

Realization of a novel dual-band bandpass filter with coupled series gaps and stepped impedance complementary split ring resonators

In this article, a bandpass filter (BPF) is proposed by etching stepped impedance complementary split ring resonators (SICSRRs) pairs in parallel with series gaps on the top side of a coplanar waveguide (CPW). The Nicolson-Ross-Weir (NRW) method is used to analyze the left-handed (LH) behavior of the filter. The effects of the resonators parameters on the left-handed BPF are studied. The parameters and number of the resonators are adjusted properly to obtain the desired filter characteristics. Split ring resonators (SRRs) are magnetically coupled to the BPF to realize a novel left-handed dual-band bandpass filter. Besides, The dual-band filter is described by means of the lumped-element equivalent circuit model. Also, the quasi-static analysis is used to obtain the equations for the resonant frequencies of the resonators. The efficient electrical size of the dual-band filter is 0.51λg × 0.42λg where λg represents the guided wavelength at the first passband center frequency. The prototype of the compact dual-band BPF is fabricated and measured. The measured results reveal low insertion loss and high return loss at the passbands along with wide upper stopband attenuation. The measured result is in a good agreement with the corresponding simulation result.

Effectual seizure detection using MBBF-GPSO with CNN network.

EEG is the most common test for diagnosing a seizure, where it presents information about the electrical activity of the brain. Automatic Seizure detection is one of the challenging tasks due to limitations of conventional methods with regard to inefficient feature selection, increased computational complexity and time and less accuracy. The situation calls for a practical framework to achieve better performance for detecting the seizure effectively. Hence, this study proposes modified Blackman bandpass filter-greedy particle swarm optimization (MBBF-GPSO) with convolutional neural network (CNN) for effective seizure detection. In this case, unwanted signals (noise) is eliminated by MBBF as it possess better ability in stopband attenuation, and, only the optimized features are selected using GPSO. For enhancing the efficacy of obtaining optimal solutions in GPSO, the time and frequency domain is extracted to complement it. Through this process, an optimized features are attained by MBBF-GPSO. Then, the CNN layer is employed for obtaining the productive classification output using the objective function. Here, CNN is employed due to its ability in automatically learning distinct features for individual class. Such advantages of the proposed system have made it explore better performance in seizure detection that is confirmed through performance and comparative analysis.

A Novel Approach for Polyphase Filter Bank Design Using ABC Algorithm

Polyphase filter banks (PFBs) are the most preferred multirate structures for subband coding in Digital Signal Processing (DSP) and communication. For PFB design, there are many important design parameters such as filter length and frequency selectivity. Also, to realize the desired frequency response in designs, stopband and passband attenuation are of considerable importance. In PFB design, researchers and practitioners frequently use iterative and meta-heuristic optimization methods. Heuristic techniques have a significant problem-solving ability in continuous and discrete solution space. Therefore, they give better results than other suggested methods, and their performance depends on the control parameters. In this study, Artificial Bee Colony (ABC) algorithm was employed for suggested design problem of PFB. In the first stage, the control parameters of the ABC algorithm were examined to improve the performance of the proposed PFB problem. In the second stage, the analysis was carried out by changing filter lengths (8-256) and filter band frequencies (0.3-0.7/0.4-0.6). All results obtained were also compared with the Particle Swarm Optimization algorithm (PSO) and the Genetic algorithm (GA). Finally, a DSP application of PFB was carried out according to best results achieved by the ABC algorithm for filter lengths and frequencies.

Design of FRM-Based Nonuniform Filter Bank With Reduced Effective Wordlength for Hearing Aids.

This paper presents a design method for frequency response masking (FRM)-based nonuniform filter bank with reduced effective wordlength. Instead of designing prototype filters separately, we propose to model the filter bank design problem as a nonlinear programming problem and jointly design the prototype filters in the FRM structure. Moreover, in this work, all the filters are designed directly in the finite wordlength space, such that they can be directly implemented using efficient fixed-point arithmetic without any quantization. By simultaneously considering all the subband constraints during optimization, the proposed method is able to guarantee the desirable stopband attenuation for all subbands and achieve optimal effective wordlength (EWL) for the coefficients, reducing the hardware complexity for very large-scale integration (VLSI) implementation. Experimental results show that the hardware complexity of filter banks can be reduced without sacrificing the audiogram compensation performance for hearing aid applications.

Compact Bandpass Waveguide Filters with Inductive Couplings with E-plane Symmetry and without E-plane Symmetry

Introduction. Modern satellite communication systems continue to impose stricter requirements on the frequency response, weight, and size of filters. In this paper, several designs of bandpass filters with inductive couplings on corrugated waveguides are considered. Although such filters have been described previously, this paper considers their possible implementations based on narrow cross-section waveguides, as well as on structures with and without electric field symmetry.Aim. To study filters with inductive couplings with and without electric field symmetry, as well as to assess the filter stopband width and attenuation.Materials and methods. Numerical studies were carried out by the finite element method (FEM) and the method of final difference in the time domain (FDTD).Results. Modeling of filters with inductive couplings with and without electric field symmetry was carried out. Filters without electric field symmetry were found to exhibit higher characteristics in terms of weight and size, at the same time as having a narrower stopband. The conducted modeling also showed that filters with stubs of the same cross section allow stopband attenuation to be improved by almost 20 dB compared to filters with stubs of varied cross section. The frequency responses of filters with inductive couplings obtained by electrodynamic modeling were established to agree well with those obtained experimentally. A ten-order ultra-compact filter with inductive couplings without electric field symmetry was considered, with the bandwidth loss of not more than 0.7 dB, the attenuation of at least 80 dB in the frequency range from 7.9 to 8.4 GHz, and the filter length of 30 mm.Conclusion. The use of filters with inductive couplings allows their mass and dimension characteristics to be significantly improved without increasing losses in the bandwidth at the same time as maintaining a high level of attenuation in the stopband.

Class‐F power oscillator based on complementary split ring resonator for sub‐6 GHz fifth generation and multistandard applications

SummaryA coupled complementary split‐ring resonator (CSRR) has been proposed. The proposed resonator consists of two coupled 50‐Ω transmission lines and complementary split rings in the ground plane (bottom layer) as defected ground structure (DGS). The proposed bandpass filter (BPF) has a measured stopband attenuation loss of less than −20 dB in the frequency band between 2.3 and 2.9 GHz and a low insertion loss of 1.15 dB. The measurement is carried by a VNA (vector network analyzer) meter of model ZVA67. Then, the proposed resonator (BPF) is utilized with an active device (SiGe BFP 640) as an output matching network of a class‐F oscillator. Fundamentally, this research aims to design and model an optimum achievement of BPF for optimum oscillator performance. The design simulation of the CSRR oscillator has been obtained by ADS and CST programs. The proposed band pass filter is designed and fabricated on a Rogers (RO4003C) micro‐strip material printed with a dielectric constant epsilon of 3.38 and a thickness of 0.813 mm. Depending on this study, the oscillator displays a minimum phase noise of −109.3 dBc/Hz at 1 MHz offset frequency and maximum dBm output power equals 13.4 dBm at 2.45 GHz oscillation frequency. The power dispassion of the proposed oscillator equals 8.3 mW from a 2 V supply voltage. The obtained maximum dBm output power and minimum phase noise is a benefit for power charger wireless applications, sub‐6 GHz fifth generation applications, and multistandard applications.

Optimal High Pass FIR Filter Based on Adaptive Systematic Cuckoo Search Algorithm

Abstract This paper presents the design of a desired linear phase digital Finite Impulse Response (FIR) High Pass (HP) filter based on Adaptive Systematic Cuckoo Search Algorithm (ACSA). The deviation, or error from the desired response, is assessed along with the stop-band and pass-band attenuation of the filter. The Cuckoo Search algorithm (CS) is used to avoid local minima because the error surface is typically non-differentiable, nonlinear, and multimodal. The ACSA is applied to the minimax criterion (L∞-norm) based error fitness function, which offers a better equiripple response for passband and stopband, high stopband attenuation, and rapid convergence for the developed optimal HP FIR filter algorithm. The simulation findings demonstrate that when compared to the Parks McClellan (PM), Particle Swarm Optimization (PSO), CRazy Particle Swarm Optimization (CRPSO), and Cuckoo Search algorithms, the proposed HP FIR filter employing ACSA leads to better solutions.

Millimeter-Wave Dual-Band Dual-Polarized SIW Cavity-Fed Filtenna for 5G Applications

This article presents a millimeter-wave (mmWave) dual-band dual-polarized filtenna, which can achieve desirable out-of-band rejection for 5G applications. The dual-band dual-polarized antenna element consists of two fully-shielded quarter-mode substrate integrated waveguide (FSD-QMSIW) cavities and a dual-band stacked ring antenna. Two parts are coupled through the slot on the ground. The cavities are completely enclosed by the metal holes and copper cover to eliminate radiation loss. The loaded slots can tune the frequencies of the first two modes in the FSD-QMSIW cavity for dual-band operation. The inherent transmission null between the dual modes is generated to improve the stopband attenuation. To verify the proposed method, a dual-band dual-polarized filtenna with a three-order filtering function and four radiation nulls is designed and fabricated. The −10 dB impedance bandwidth can effectively cover 5G n258 (24.25–27.5 GHz) and n260 (37–40 GHz) bands in the measurement. The gains of two polarizations drop over 20 dB between the two bands. A four-element filtenna array is constructed to test its beam-scanning ability and further integrated with active beamformer integrated circuits (ICs). The measured results show that the fabricated filtenna array maintains satisfactory out-of-band rejection performance and can be one of the most promising 5G communication candidates.

Design of a novel compact highly selective wideband bandstop RF filter using dual path lossy resonator for next generation applications.

This article presents the design of a wideband bandstop RF filter intending to improve selectivity and compactness. Conventional bandstop filter topology with finite unloaded quality factor produces degraded bandstop filter performance due to dissipation loss. In the proposed filter design, a novel dual path Capacitive Coupled Step Impedance Resonator (CCSIR) structure is used to obtain an infinite stopband attenuation. A uniform impedance resonator is used in Path 1, whereas Path 2 contains a resonator that is twice coupled to the transmission lines. The electrical length of both paths is chosen to be out of phase, resulting in a high rejection level at higher frequencies. It has been analyzed that the selectivity can be improved by increasing the order of the dual coupled step impedance resonator. The proposed design produces a wideband BSF centered at 5.25 GHz with a high rejection level of 104.3 dB and fractional bandwidth of 58.5%. The results have demonstrated that the resonant frequencies are regulated by varying the electrical length of CCSIR. Moreover, it has been realized that out of phase signal cancellation due to the dual path is involved in producing the finite frequency transmission poles, which further enhances the filter selectivity. However, the same electrical performance can only be achieved from coaxial cavities and waveguides due to the high-quality factor. The proposed topology is fabricated and measured on a high-frequency microstrip substrate having a low-quality factor with a compact output and better electrical performance compared to coaxial cavities or waveguides. Due to its high electrical performance and small size, the proposed BSF is appropriate for 4G and 5G (FR1) applications. The measurement shows good concurrence with the full-wave EM simulated results. The fabricated prototype of third order BSF has a compact size of (0.7 × 0.77)λg at 5.25 GHz.

A Low Complexity and High Modularity Design for Continuously Variable Bandwidth Digital Filters

ABSTRACT Digital filters with variable bandwidth can be used for a variety of applications. Arbitrary change in the bandwidth of a digital Finite Impulse Response (FIR) filter can be acquired using sampling rate converters. In this paper, a sampling rate converter is proposed which is generated from Pascal structure, a fractional delay filter having low hardware complexity and high modularity. The proposed sampling rate converter requires lesser number of multipliers for implementation when compared with the sampling rate converters in the literature. A low pass filter having a single bandwidth sandwiched between two sampling rate converters can contribute multiple bandwidths in such a way that each bandwidth is an arbitrary variation of the original bandwidth. A two stage Frequency response masking approach (FRM) is used for the hardware efficient design of the original low pass filter. A low complexity and high modularity novel design for a continuously varying bandwidth of a digital FIR filter is proposed in this paper using the proposed sampling rate converter. The modularity of the Pascal structure can be used to control both pass band ripple as well as stop band attenuation of the continuously variable bandwidth FIR filter design. Different communication standards in a Software defined radio (SDR) channelizer is realized using the proposed design of continuously variable bandwidth filter.

Design and Optimization of Butterworth and Elliptic Band Pass Filters in 5G Application

Filters are two-port networks that may pass or attenuate frequencies within defined ranges and can alter the frequency response of any system. In the present research study, the goals and optimization controller embedded with (ADS2019) are used to design Butterworth and Elliptic bandpass filters with frequency ranges of (18GHz – 38GHz), a bandwidth of (7GHz), stopband attenuation of (S21=-60dB), and passband attenuation of (S21=-1dB). Three types of each filter (Hp-Lp 6th order – 3rd order – 6th order) are simulated and optimized to choose the best (C, L) values. The selected filters are redesigned using the Design Filter Guide, and the simulation during this phase yields different values for (C, L). The designed circuit is then transformed into a microstrip model using transmission lines for open and short circuits. The study investigates the differences between each filter in BW-f center- attenuation at the stopband.In the last phase of the study, the circuit of each filter is transformed using a microstrip transmission line to obtain the (W, L) for each component of each filter. Finally, the study compares past studies and research projects in this field.

Universal Graph Filter Design Based on Butterworth, Chebyshev, and Elliptic Functions

Graph filters are crucial tools in processing the spectrum of graph signals. In this paper, we propose to design universal IIR graph filters with low computational complexity by using three kinds of functions, which are Butterworth, Chebyshev, and elliptic functions, respectively. Specifically, inspired by the classical analog filter design method, we first derive the zeros and poles of graph frequency responses. With these zeros and poles, we construct the conjugate graph filters to design the Butterworth high-pass graph filter, Chebyshev high-pass graph filter, and elliptic high-pass graph filter, respectively. On this basis, we further propose to construct a desired graph filter of low pass, band pass, and band stop by mapping the parameters of the desired graph filter to those of the equivalent high-pass graph filter. Furthermore, we propose to set the graph filter order given the maximum passband attenuation and the minimum stopband attenuation. Our numerical results show that the proposed graph filter design methods realize the desired frequency response more accurately than the autoregressive moving average graph filter design method, the linear least-squares fitting-based graph filter design method, and the Chebyshev FIR polynomial graph filter design method.

Design and Fabrication of Compact Microstrip Low-pass Filter with Thin Film Technique for Wideband Applications

This paper introduces a compact microstrip low-pass filter (LPF) with a very sharp rejection. The proposed LPF is designed to be used for electronic warfare in defense industry. It has 62 dB/GHz attenuation rate, 10 GHz of stopband width and 48.6 dB of stopband attenuation. Moreover, it also has a wide passband and has a high cut-off frequency (f_c) of 6 GHz. The designed filter has been fabricated using alumina (Al2O3) substrate and titanium-gold (Ti-Au) coating on top of that with thin film technique in a clean room. The experimental measurements of the proposed LPF show great agreement with the simulation results, which validates that the presented filter is convenient to be used for applications up to C-band in electronic warfare systems.

Compact filtering balun with ultra‐wide stopband based on π‐type capacitive networks

AbstractIn this letter, a new compact filtering balun with an ultra‐wide stopband is proposed on the ceramic substrate. Four coupled line units are utilized to design the distributed balun with a second‐order filtering response. Then, three‐/two‐port inductively loaded π‐type capacitive networks without high‐order harmonics are equivalent to distributed three‐/two‐port distributed coupled line units; therefore, the proposed compact lumped filtering balun based on these π‐type capacitive networks inherently have ultra‐wide stopband characteristics. To verify the design concept, a prototype with 15‐dB bandwidth across 0.85–1 GHz is designed at 0.95 GHz, and its amplitude and phase imbalances are 0.4 dB and E4.5°, respectively. The upper stopband attenuation higher than 20 dB of the balun is extended to 12.9 f0, where f0 is the center frequency, and its size is only 0.0025λg2, where λg is the guide wavelength.

A high-speed single-photon detection scheme based on frequency domain filtering

This paper presents a high-speed integrated circuit for narrow-gated single-photon detection. Due to the parasitic capacitor that exists in the avalanche photo-diode (APD), the avalanche signal pulse triggered by the received photon is easily mixed with unavoidable spike noise arising from the gated clock. The traditional double-ended architecture extracts avalanche signals by suppressing common-mode noise. In order to overcome the shortcomings of high cost and mismatch in the traditional architecture, this paper adopts a single-ended detection architecture and deals with the problem of spike noise from the perspective of the frequency domain. According to the difference between the frequency characteristics of the spike noise and the avalanche signal, the effective separation of the two signals can be realized in the frequency domain by a low-pass filter with a specific cut-off frequency. The signal-to-noise ratio of the detection system is improved by using the subsequent amplification and discrimination circuit, so as to realize sensitive detection of the avalanche signals. The proposed circuit is implemented in 180 nm complementary metal oxide semiconductor technology and occupies an effective area of 2.6 mm2. The test results show that the single-ended detection system can sensitively discriminate photon signals with an emission frequency below 20 MHz when the whole circuit, including the APD, is operated at room temperature, where the minimum voltage amplitude converted from the avalanche current of the APD is around 20 mV, and the stopband attenuation of the filter at 1 GHz frequency is −58.8 dB.

SAW-Less Direct RF Transmitter With Multimode Noise Shaping and Tri-Level Time-Approximation Filter

This article presents a multimode direct radio frequency (RF) transmitter capable of a high in-band dynamic range and a low out-of-band (OOB) noise floor. It features a hybrid digital-to-analog converter (DAC) with a reconfigurable dual-band delta–sigma modulator to lower the quantization noise floor at one or two frequency bands. Additionally, a tri-level time-approximation filter is proposed to further suppress OOB noise with high tunability and stopband attenuation. The objective is to demonstrate a low-noise floor without using a surface acoustic wave (SAW) filter. For a 256-quadratic-amplitude modulation (QAM) signal with 17.4-dBm average output power at a 2.2-GHz carrier, the silicon prototype achieves −40-dB error vector magnitude (EVM) and −169-dBc/Hz noise spectral density (NSD) at 68-MHz offset by consuming a total power of 1.2 W.

Design of Planar Wide-Stopband Bandstop Filters With Extra-High Attenuation

The novel microstrip bandstop filters with extra-high attenuation and wide stopband have been proposed. In order to realize the bandstop filter with broad stopband and great attenuation within the stopband, the coupled lines with single-ended ground have been adopted at both input and output ports. Moreover, for a greater fractional bandwidth, a higher impedance ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z_{ei}/Z_{oi}$ </tex-math></inline-formula> of two adopted coupled lines is required. Furthermore, by differentiating the even- and odd-mode impedances of coupled lines at the input and output ports, the attenuation within the stopband can be increased and the stopband’s bandwidth would be slightly narrower. Two bandstop filters, with the attenuations of 46 dB and 55 dB and a fractional bandwidths of 58.1% and 50.3%, respectively, have been developed to verify the proposed method.

Optimized design of windowed-sinc anti-aliasing filters for phase-preserving decimation of hydrophone data.

Passive acoustic monitoring generates large data sets for which decimation is beneficial to analysis and portability for data sharing. Among the goals for effective decimation are avoidance of aliasing in the passband, accurate and complete control of the attenuation profile, phase preservation, and high efficiency in processing. We present an approach to decimator design that addresses each of these goals, and we demonstrate its application to ocean audio recordings. Anti-aliasing is achieved by windowed-sinc filters that also preserve phase. Control of the passband attenuation profile is based on the specification of the maximum allowed attenuation at a certain percentage of the final output Nyquist frequency. The window type is selected to meet the stopband attenuation requirement. Efficiency is achieved through optimization of the anti-aliasing filters applied in each decimation stage, and through parallelization of processing. The best combination of the sinc function's cutoff frequency and the mainlobe bandwidth of the window function generates the shortest qualifying filter, optimizing the trade-off between filter performance and computational load. Parallelization is enabled by applying the overlap-add method to contiguous segments of audio data, consistent with the commonly used storage of contiguous audio data in files of limited duration. Beyond addressing common goals for effective decimation of audio data, the approach presented is deployable in open-source environments.

A novel approach to design optimal digital FIR filter based on logistic distribution based approximation

ABSTRACT This work proposes a novel methodology to design FIR lowpass filter (LPF) using logistic probability distribution function. Desired magnitude response of the FIR filter is approximated as sum of equi-spaced logical function waveforms with their mean varying at definite interval. The required number of logistic waveforms and its standard deviation depends on the parameters of designed filter specifications. Simulation results have been compared with optimal Method (Park McClellan) and windowing technique to show the superiority of the proposed method. It is found that ripples in pass band and stop band of the filter has been reduced iteratively, higher stop band attenuation is achieved. The proposed method also provides a close design way to link coefficients of the filter to design specification directly.

Optimization design of fractional‐order Chebyshev lowpass filters based on genetic algorithm

AbstractFractional‐order filters have received extensive attention from international scholars because of their greater design freedom and continuously stepped stopband attenuation rate. Based on genetic algorithm (GA), this paper proposes an optimum design approach for fractional‐order Chebyshev lowpass filters that meet design specifications. The fractional order and ripples attenuation of the normalized Chebyshev lowpass filter are calculated according to specifications, the integer order in the Chebyshev polynomial is replaced with the calculated fractional order, and then the fractional‐order Chebyshev polynomial is substituted into the magnitude response of the normalized Chebyshev lowpass filter along with the ripples attenuation to achieve the ideal response. The transfer function parameters of a fractional‐order filter are optimized using GA to make the magnitude response approximate the ideal response described above. This completes the optimized design of a fractional‐order Chebyshev filter that meets specifications. Given three different sets of design specifications, the fractional‐order Chebyshev filter designed using the proposed method is compared with one designed by another method in the literature. Finally, design examples are presented, stability analysis and Pspice simulations are performed, and an actual circuit is constructed to illustrate the effectiveness of the proposed method.