High Stopband Attenuation Research Articles

On design of preprocessing and postprocessing in cascaded-resonator-based harmonic analyzers and filter banks

The cascaded-resonator (CR)-based filter structure provides high attenuation in the stopbands thanks to the serially coupled resonators, which is an advantage in many applications of harmonic analyses and/or filtering. In addition to that, it has good properties provided by its parallel structure. On the other side, there are applications which besides the high stopband attenuation need wider (or even flat-top) passbands, lower group delays, etc. These performances can be modified/improved by preprocessing and postprocessing through reshaping of the primary CR-based filter bank frequency responses. The numerical complexity is also an important aspect where infinite impulse response (IIR) filters provide implementation with a smaller number of numerical operations, but involving nonlinearity of the phase responses and stability control issue. Although most of these issues have been discussed in the previous papers dealing with the design of the CR-based harmonic filtering and/or filter banks, the aim of this paper is to highlight them all together. In addition, some improvements of the previously described design techniques are suggested too.

Wideband and Highly Selective BandPass Filter Using Substrate Integrated Waveguide Technology for Ku-Band Applications

A new compact design of bandpass filter using substrate integrated waveguide (SIW) is proposed and analyzed in this paper. It offers good in-band return loss, low insertion loss, wide passband, and high stopband attenuation. The filtering response is achieved by loading a couple of inverted tuning fork-shaped defected ground structures (DGS) on the bottom of the SIW cavity. DGS is utilized to enhance the upper stopband performance. To validate, the filter is fabricated using Rogers RT/Duroid 5880 with 0.508 mm thickness and tested. The filter has a center frequency of 15.44 GHz with 19% fractional bandwidth (FBW). The return loss is more than 20 dB and the insertion loss is about 1.2 dB. It finds its application in Ku band satellite communication.

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.

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.

0.7-1.0-GHz Switchable Dual-/Single-Band Tunable Bandpass Filter Using a Switchable J-Inverter

Cognitive radios require tunable band-switchable bandpass filters to respond to the dynamically changing operating frequencies in cognitive systems. This study presents a novel switchable dual-/single-band tunable bandpass filter using a single switchable J -inverter. The proposed filter configuration can be easily converted from a two-pole dual-passband mode to a four-pole single-passband mode using the single J-inverter with switches. This is achieved through a novel dual-band bandpass filter configuration using hybrid resonators that consist of two parallel resonators and one J-inverter. In addition, two bandwidths and two center frequencies of the dual-passband mode are designed, and a high stopband attenuation level is achieved due to a transmission zero between the two passbands. The proposed filter is built on a Duroid substrate with a dielectric constant of 3.48 and a thickness of 30 mil. The tuning of the center frequency and the passband number change are carried out using silicon varactors and PIN diodes. In the four-pole single-passband mode, a center frequency tuning of 0.75-1.08 GHz is achieved with 1-dB bandwidths of 105-158 MHz. The two-pole dual-band bandpass filter mode has a center frequency tuning of 0.69-0.9 GHz (low-band) and 0.85-1.07 GHz (high-band). It has potential for application in wideband cognitive radios.

Least squares linear phase FIR filter design and its VLSI implementation

In this work we present least squares (LS) approach to design linear phase Finite Impulse Response (FIR) filter. Since the design of FIR digital filters is non-analytic, we aim at ideal zero-phase magnitude response and minimize the weighted error in passband and stopbands. The problem of least squares can then be solved non-iteratively by solving system of linear equations. Solution of which yields impulse response that is both real and symmetric. Frequency response of the proposed LS FIR filter shows a flat passband, and higher stop-band attenuation than traditional window based FIR design and comparable attenuation with Parks–McClellan method of the same order. In addition we have implemented LS FIR filter on FPGA based VLSI architectures. Performance evaluation of proposed LS FIR design on VLSI architecture shows comparable throughput, area and power consumption compared to classical filter design approaches.

A novel singular spectrum analysis-based multi-objective approach for optimal FIR filter design using artificial bee colony algorithm

Effective filter design plays an important role in signal processing applications. Multiple parameters must be considered to control the over-frequency response of the designed filter. In this study, a novel multi-objective approach is proposed for windowing finite impulse response (FIR) filter design. The windowing FIR filters are commonly used due to its linear phase property, frequency stability and easier implementation. However, windowing method can only control the cutting frequency of filter, and it suffers from the problem of insufficient control of the transition bandwidth, pass and stop band cutoff frequencies. Therefore, the window function was optimized using a novel multi-objective artificial bee colony (ABC) algorithm based on singular spectrum analysis (SSA) to eliminate these disadvantages of the windowing method. The proposed method was compared to three other multi-objective ABC variants. Novel SSA-based multi-objective approach yielded the best performance among four approaches. The proposed multi-objective approach that uses the SSA method has a significant advantage since it does not require user experience, it is not dependent on parameters, and there is no weight determination problem. Also, it does not have sorting and pooling stages that increase the cost of calculation. The obtained results were compared with the published literature studies. The SSA-based multi-objective approach offered better alternative to other literature techniques in terms of calculating the fitness function that deals with finding the most reasonable solution considering all error terms. Finally, the performance of the designed filter was tested on electroencephalography (EEG) signal. The EEG signal was decomposed successfully into subbands using proposed filter design approach. Based on numerical results of this study, the proposed filter provided the low-pass band and stop band ripple, and high stop band attenuation value of all, while having well enough performance.

Design of Computationally Efficient Sharp FIR Filter Utilizing Modified Multistage FRM Technique for Wireless Communications Systems

Modern wireless communications gadgets demand multi-standard communications facilities with least overlap between different input radio channels. A sharp digital filter of extremely narrow transition-width with lower stop band ripples offers alias-free switching among the preferred frequency bands. A computationally competent low pass filter (LPF) structure based on the multistage frequency response masking (FRM) approach is proposed for the design of sharp finite impulse response (FIR) filters which are suitable for wireless communications applications. In comparison of basic FRM with other existing multistage FRM structures, the proposed structure has a narrow transition bandwidth and higher stop band attenuation with significant reduction in terms of the number of computational steps. A design example is incorporated to demonstrate the efficiency of the proposed approach. Simulation results establish the improvement of the proposed scheme over other recently published design strategies.

A High-Performance Common-Mode Noise Absorption Circuit Based on Phase Modification Technique

In this article, a high-performance common-mode noise absorption circuit (CMNAC) is proposed for solving electromagnetic interference (EMI) or radio-frequency interference (RFI) problems in high-speed differential digital systems. Instead of reflecting common-mode noises by conventional common-mode filters (CMFs), the common-mode noises can be absorbed in the proposed circuit. In addition, the phase modification technique is utilized to enhance the common-mode noise absorption rate and the differential-mode eye diagram in this CMNAC. In the common-mode half circuit (CMHC), the phase inversion of the subnetwork adds a destructive combination of the stopband energy, resulting in higher stopband attenuation. In the differential-mode half circuit (DMHC), the phase linearization leads to flat group delay, reducing the distortion in high-speed digital signal transmission in the lumped circuit. Using a standard integrated passive device (IPD) process, this CMNAC is implemented for the demonstration. The circuit occupies an area of only 1.138 mm $\times0.822$ mm. From the measured results, the proposed circuit exhibits the common-mode suppression level larger than 15 dB from 4 to 20 GHz and the absorption rate over 90% from 3.8 to 17.4 GHz with a fractional bandwidth 128%. In addition, the measured eye diagram shows that the proposed circuit can support high-speed transmission up to 10 Gb/s.

Dynamic Harmonic Synchrophasor Estimator Based on Sinc Interpolation Functions

This paper introduces a new dynamic harmonic synchrophasor estimator (DHSE) based on the Shannon sampling theorem. Each dynamic harmonic phasor is modeled as a weighted sum of a series of sinc interpolation functions. Based on this, a bank of finite impulse response filters is designed. They are used to estimate not only the dynamic harmonic synchrophasor but also the harmonic frequency and rate of change of frequency (ROCOF). A model parameter is properly selected to adapt filters’ passband and stopband performances for different order harmonics. Frequency responses and simulation tests are used to compare the performance of the DHSE and the Taylor–Fourier transform (TFT). The results show that the DHSE has lower passband ripples and higher stopband attenuation than the TFT. Moreover, under frequency deviation, harmonic oscillation, and frequency ramp conditions, the DHSE is more accurate than the TFT in dynamic harmonic synchrophasor, frequency, and ROCOF estimations.

High order stable infinite impulse response filter design using cuckoo search algorithm

In this paper, an efficient technique for optimal design of digital infinite impulse response (IIR) filter with minimum passband error (e p ), minimum stopband error (e s ), high stopband attenuation (A s ), and also free from limit cycle effect is proposed using cuckoo search (CS) algorithm. In the proposed method, error function, which is multi-model and non-differentiable in the heuristic surface, is constructed as the mean squared difference between the designed and desired response in frequency domain, and is optimized using CS algorithm. Computational efficiency of the proposed technique for exploration in search space is examined, and during exploration, stability of filter is maintained by considering lattice representation of the denominator polynomials, which requires less computational complexity as well as it improves the exploration ability in search space for designing higher filter taps. A comparative study of the proposed method with other algorithms is made, and the obtained results show that 90% reduction in errors is achieved using the proposed method. However, computational complexity in term of CPU time is increased as compared to other existing algorithms.

Triple-Mode Cavity Bandpass Filter on Doublet With Controllable Transmission Zeros

On the basis of doublet and its properties, a class of multiple-mode narrow band bandpasss filter is designed and fabricated by simultaneously exploiting the three resonant modes in a single rectangular cavity: TE101, TE011, and TM110 modes. The input/output ports of the proposed filter are fed by coupling a microstrip line to a slot on the side wall of a rectangular cavity. Different modes are excited by changing the position and shape of the two slots at input and output of the rectangular cavity without any intra-cavity coupling. Besides three poles within the passband, a pair of transmission zeros (TZs) is achieved, which can be controlled independently by setting the positions of the two TZs at the lower and/or upper stopband. High stopband attenuation and high filtering selectivity are achieved by considerably allocating three transmission poles and two zeros. In order to verify the proposed theory, two filter prototypes are fabricated and measured.

A Family of Square-Root Nyquist Filter With Low Group Delay and High Stopband Attenuation

A simple method for square-root Nyquist filter design with low group delay and high and fast decaying stopband attenuation is presented. The method is based on a frequency domain design procedure and can address various roll-off factors. The computation procedure is presented and justified analytically. Numerical results show that for a given group delay, the stopband attenuation performance of this proposed technique outperforms the most relevant existing techniques.

Design of Grooved Microstrip Patch Resonator Filters for Mobile Communication

In advanced communication technology the microstrip filter has an important job in terms of selectivity and elimination of the undesired signals. In microwave and RF frequency applications the design of filter is complex task as lumped components cannot be used in this range of frequency. Microstrip filters are always preferred over the lumped filters at larger frequency for their compact size, lighter weight, lower cost and higher performance. In this paper the design of grooved microstrip patch resonator bandpass filter is presented at mid-band frequency 1.8 GHz for L-Band applications. It also acts as a band-reject filter at center frequency 1.1 GHz, which is innovative concept in microstrip filter design. Band-pass filter has a high attenuation in stop band, small insertion loss of 0.5744 dB and high return loss of 26.52 dB in the pass band whereas Band-reject filter has a low attenuation, high insertion loss of 21.95 dB and low return loss of 0.2432 dB in the stop band. The result is encouraging and fabrication is also very easy.

Design of optimal band-stop FIR filter usingL1-norm based RCGA

Abstract In this paper, an optimal design of linear phase digital finite impulse response (FIR) band stop (BS) filter using the L 1 -norm based real-coded genetic algorithm ( L 1 -RCGA) is presented. Although RCGA has proved its ability to overcome the drawbacks associated with conventional gradient-based optimization methods of filter design, it is applied here with a novel fitness function based on the L 1 -norm. This leads to a global optimal solution along with the improvement in filter design with same specifications. The designed filter pursues a better response in terms of flat passband, high stopband attenuation and fast convergence. The simulation results justify that the proposed FIR BS filter using L 1 -RCGA outperforms the existing optimization techniques, the L 1 -method and particle swarm optimization (PSO) and the conventional methods such as least-squares (LS) approach, Kaiser window method and the Parks McClellan (PM) algorithm. A detailed analysis is performed to evaluate the performance of the designed filters.

Design and FPGA Implementation of Reconfigurable Linear-Phase Digital Filter With Wide Cutoff Frequency Range and Narrow Transition Bandwidth

Reconfigurable filters based on the spectral parameter approximation (SPA) technique and its combination with other techniques provide a continuous control over the cutoff frequency $(f_c)$ . However, when very wide $f_c$ range and narrow transition bandwidth is desired, these filters either fail to satisfy some of the specifications or have extremely high complexity. In this brief, we propose an interpolated SPA (ISPA) filter that overcomes all the limitations of all the existing SPA technique based filters, and achieves very wide $f_c$ range (equal to approximately the entire Nyquist band) and narrow transition bandwidth along with small passband ripple and high stopband attenuation. Comparison with the state-of-the-art reconfigurable filters is provided via a design example, which shows that the ISPA filter achieves more than 50% savings in the number of multipliers compared to the filter based on the combination of SPA and modified coefficient decimation techniques. The field-programmable gate array implementation results show that the ISPA filter has much lesser group delay and much higher operating speed, but incurs moderate penalty in terms of area compared to the filter based on the combination of frequency transformation and interpolation techniques.

Design of multiplier-less sharp non-uniform cosine modulated filter banks for efficient channelizers in software defined radio

Forthcoming software defined radios require filter banks which satisfy stringent specifications efficiently with low implementation complexity. Cosine modulated filter banks (CMFB) have simple and efficient design procedure. The different wireless standards have different channel spacing or bandwidths and hence demand non-uniform decomposition of subbands. The non-uniform CMFB can be obtained from a uniform CMFB in a simple and efficient approach by merging the adjacent channels of the uniform CMFB. Very narrow transition width filters with low complexity can be achieved using frequency response masking (FRM) filter as prototype filter. The complexity is further reduced by the multiplier-less realization of filter banks in which the least number of signed power of two (SPT) terms is achieved by representing the filter coefficients using canonic signed digit (CSD) representation and then optimizing using suitable modified meta-heuristic algorithms. Hybrid meta-heuristic algorithms are used in this paper. A hybrid algorithm combines the qualities of two meta-heuristic algorithms and results in improved performances with low implementation complexity. Highly frequency selective filter banks characterized by small passband ripple, narrow transition width and high stopband attenuation with non-uniform decomposition of subbands can be designed with least the implementation complexity, using this approach. A digital channelizer can be designed for SDR implementations, using the proposed approach. In this paper, the non-uniform CMFB is designed for various existing wireless standards.

An Active Filter for Delta-Sigma-Modulated Josephson Waveforms

We present the design and electrical characteristics of an active low-pass filter. It will be used in a reference waveform source based on a programmable Josephson voltage standard with multilevel delta–sigma modulation to generate accurate and spectrally pure arbitrary waveforms. The filter has a fifth-order Butterworth characteristic with high input impedance, low distortion, high stopband attenuation, and stable passband performance, including dc.

Two-Stage Filter-Bank System for Improved Single-Channel Noise Reduction in Hearing Aids

The filter-bank system implemented in hearing aids has to fulfill various constraints such as low latency and high stop-band attenuation, usually at the cost of low frequency resolution. In the context of frequency-domain noise-reduction algorithms, insufficient frequency resolution may lead to annoying residual noise artifacts since the spectral harmonics of the speech cannot properly be resolved. Especially in case of female speech signals, the noise between the spectral harmonics causes a distinct roughness of the processed signals. Therefore, this work proposes a two-stage filter-bank system, such that the frequency resolution can be improved for the purpose of noise reduction, while the original first-stage hearing-aid filter-bank system can still be used for compression and amplification. We also propose methods to implement the second filter-bank stage with little additional algorithmic delay. Furthermore, the computational complexity is an important design criterion. This finally leads to an application of the second filter-bank stage to lower frequency bands only, resulting in the ability to resolve the harmonics of speech. The paper presents a systematic description of the second filter-bank stage, discusses its influence on the processed signals in detail and further presents the results of a listening test which indicates the improved performance compared to the original single-stage filter-bank system.

Optimal IIR filter design using Gravitational Search Algorithm with Wavelet Mutation

This paper presents a global heuristic search optimization technique, which is a hybridized version of the Gravitational Search Algorithm (GSA) and Wavelet Mutation (WM) strategy. Thus, the Gravitational Search Algorithm with Wavelet Mutation (GSAWM) was adopted for the design of an 8th-order infinite impulse response (IIR) filter. GSA is based on the interaction of masses situated in a small isolated world guided by the approximation of Newtonian’s laws of gravity and motion. Each mass is represented by four parameters, namely, position, active, passive and inertia mass. The position of the heaviest mass gives the near optimal solution. For better exploitation in multidimensional search spaces, the WM strategy is applied to randomly selected particles that enhance the capability of GSA for finding better near optimal solutions. An extensive simulation study of low-pass (LP), high-pass (HP), band-pass (BP) and band-stop (BS) IIR filters unleashes the potential of GSAWM in achieving better cut-off frequency sharpness, smaller pass band and stop band ripples, smaller transition width and higher stop band attenuation with assured stability.