Stopband Attenuation Research Articles

Varactor‐tunable dual‐band filtering low‐noise amplifier

AbstractDesign and development of a tunable dual‐band filtering LNA has been presented in this paper. The center frequency of the lower band is continuously tuning with applied dc voltages. The center frequency of lower band has a tuning range of 2.0–2.5 GHz; while that of upper band is fixed at 5 GHz. Power consumption of our circuit is 28 mW. Overall size of proposed device is 0.96λg × 0.34λg, where λg is the guided wavelength at lower frequency. One ATF36163 GaAs HEMT is used as the active device in our circuit. Measured per stage gain of lower band is varying from 8 to 1.6 dB; while that of upper band is 5.4 dB. Measured noise figure of lower band is 2.4–3.4 dB; while that of upper band is 2.5 dB. Proposed filtering LNA has improved selectivity and spurious harmonic suppression with measured stopband attenuation of 45 dB. To author's knowledge, the investigation of tunable multiband and multifunctional device for highly improving the level of integration of the multiband RF front‐end design is reported for the first time.

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

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

Designing an Easy-to-Deploy Improved DVB-C Set-Top Boxes With a Backward Compatible Square-Root Nyquist Filter

The set-top boxes based on the digital video broadcasting-cable (DVB-C) standard have been deployed worldwide for decades, and the square-root raised cosine filter is specified as its receive filter. Recent years, plenty of the preferable square-root Nyquist filters have been developed. It is eagerly desired to upgrade the filter in DVB-C system. However, because a great number of the set-top boxes are still in operation, the upgraded new set-top boxes are required to coexist with the already deployed old ones. Theoretically, it requires the receive filters in both the old and new set-top boxes satisfy the Nyquist criterion with the same transmit filter. Up to now, there is no acceptable solution to this problem. This paper proposed a backward compatible square-root Nyquist filter design method, which enables the old set-top boxes to coexist with the upgraded new one. Theoretical analysis shows that the proposed filter enables both the old and new set-top boxes to work properly, in terms of satisfying the Nyquist criterion, achieving the required stop-band attenuation and satisfying other requirements defined by the DVB-C standard. The experimental tests and simulation results have also demonstrated that the proposed filter has increased the spectrum utilization by 14% compared with the DVB-C standard, and with much lower computational complexity.

Enhancement of the Comb Filtering Selectivity Using Iterative Moving Average for Periodic Waveform and Harmonic Elimination.

A recurring problem regarding the use of conventional comb filter approaches for elimination of periodic waveforms is the degree of selectivity achieved by the filtering process. Some applications, such as the gradient artefact correction in EEG recordings during coregistered EEG-fMRI, require a highly selective comb filtering that provides effective attenuation in the stopbands and gain close to unity in the pass-bands. In this paper, we present a novel comb filtering implementation whereby the iterative filtering application of FIR moving average-based approaches is exploited in order to enhance the comb filtering selectivity. Our results indicate that the proposed approach can be used to effectively approximate the FIR moving average filter characteristics to those of an ideal filter. A cascaded implementation using the proposed approach shows to further increase the attenuation in the filter stopbands. Moreover, broadening of the bandwidth of the comb filtering stopbands around −3 dB according to the fundamental frequency of the stopband can be achieved by the novel method, which constitutes an important characteristic to account for broadening of the harmonic gradient artefact spectral lines. In parallel, the proposed filtering implementation can also be used to design a novel notch filtering approach with enhanced selectivity as well.

A Design of Two Sub-Stage Square-Root Nyquist Matched Filter

A pair of matched filters whose cascade response satisfies the Nyquist criterion can guarantee the inter-symbol interference (ISI)-free transmission for band-limited communication systems. For a linear phase finite impulse response square root Nyquist filter, it is necessary to strike a balance between the stop-band attenuation (SBA) and ISI performance. This paper proposes a novel approach for obtaining the square root Nyquist filter by adopting two sub-stage cascade filters group, which is known as the compensated half-band (HB) filter group (CHFG). The first sub-stage of the CHFG is a HB filter which can guarantee the required SBA performance on low computational complexity; whereas, the second sub-stage is an ISI compensation filter to ensure that the cascaded response of two CHFGs satisfies the Nyquist criterion. Theoretical analysis and experimental results show that the proposed CHFG can either achieve better SBA/ISI performance or reduce the computational complexity.

Photodynamic Cancer Therapy Using Wavelet Based Monte Carlo Computation of Light Absorption with a Genetic Algorithm

Objective:The method to treating cancer that combines light and light-sensitive drugs to selectively destroy tumour cells without harming healthy tissue is called photodynamic therapy (PDT). It requires accurate data for light dose distribution, generated with scalable algorithms. One of the benchmark approaches involves Monte Carlo (MC) simulations. This gives an accurate assessment of light dose distribution, but is very demanding in computation time, which prevents routine application for treatment planning.Methods:In order to resolve this problem, a design for MC simulation based on the gold standard software in biophotonics was implemented with a large modern wavelet based genetic algorithm search (WGAS).Result:The accuracy of the proposed method was compared to that with the standard optimization method using a realistic skin model. The maximum stop band attenuation of the designed LP, HP, BP and BS filters was assessed using the proposed WGAS algorithm as well as with other methods.Conclusion:In this paper, the proposed methodology employs intermediate wavelets which improve the diversification rate of the charged genetic algorithm search and that leads to significant improvement in design effort efficiency.

Analyses of decimation filter stopband attenuation influence on subjective quality of audio signals

Analyses of decimation filter stopband attenuation influence on subjective quality of audio signals

Linear Phase Sharp Transition BPF to Detect Noninvasive Maternal and Fetal Heart Rate.

Fetal heart rate (FHR) detection can be monitored using either direct fetal scalp electrode recording (invasive) or by indirect noninvasive technique. Weeks before delivery, the invasive method poses a risk factor to the fetus, while the latter provides accurate fetal ECG (FECG) information which can help diagnose fetal's well-being. Our technique employs variable order linear phase sharp transition (LPST) FIR band-pass filter which shows improved stopband attenuation at higher filter orders. The fetal frequency fiduciary edges form the band edges of the filter characterized by varying amounts of overlap of maternal ECG (MECG) spectrum. The one with the minimum maternal spectrum overlap was found to be optimum with no power line interference and maximum fetal heart beats being detected. The improved filtering is reflected in the enhancement of the performance of the fetal QRS detector (FQRS). The improvement has also occurred in fetal heart rate obtained using our algorithm which is in close agreement with the true reference (i.e., invasive fetal scalp ECG). The performance parameters of the FQRS detector such as sensitivity (Se), positive predictive value (PPV), and accuracy (F1) were found to improve even for lower filter order. The same technique was extended to evaluate maternal QRS detector (MQRS) and found to yield satisfactory maternal heart rate (MHR) results.

Graphical User Interface Design of FIR Filter

FIR digital filter is a stable linear phase filter. Relying on the powerful computing power of MATLAB software and its GUI platform, this graduation project has completed the GUI design and implementation of FIR digital filter through programming. Through the FIR filter to achieve the program, you can design and implement a variety of amplitude characteristics of the FIR digital filter, according to the user input filter design indicators, select the corresponding filter design method (window function, frequency sampling method) to design the corresponding filter. According to the different amplitude characteristics, the parameters of the filter design parameters will change accordingly; when the Kaiser window design filter is selected, the user is allowed to input the stopband attenuation of the filter; when using the frequency sampling method to design the filter, the user must input the filter length and the transition zone sample value; when the parameter is entered incorrectly, the system will prompt for an error message. GUI can also provide intuitive filter amplitude characteristics, phase characteristics and the unit impulse response graphics to help users to confirm whether the design of the filter meets the design specifications; by setting the global shortcut keys, the user after all parameters and options is confirmed by the Shortcut keys to achieve the rapid implementation of filter design.

Kaiser ve Von-Hann Pencereleri Tabanlı Yeni bir Pencere Fonksiyonu ve Onun Sayısal Süzgeç tasarımındaki Performans Analizi

Digital filters, which are used in many signal processing applications, can be classified as recursive or nonrecursive. Since nonrecursive digital filters can provide inherent stability and exact linear phase characteristic, they have an important place in the literature. In this paper, a new hybrid function is proposed for the design of nonrecursive digital filters. This new window was obtained by combining two different window functions known as Kaiser and Von-Hann in the literature. First of all, the effects of two independent parameters of the proposed window function on the digital filter characteristic are analysed in terms of minimum stopband attenuation and transition bandwidth. Later, comparative examples for different filter lengths are given to compare the performance of the proposed window function in the design of digital filter with the well-known other two parameter window functions. Simulation results demonstrate that the proposed window function can provide a better filter design than Kaiser-Hamming, Saramaki, Kaiser, Dolph-Chebychev, Cosh, Exponential, and Gaussian window functions.

Universal Pseudo-Differential Filter Using DDCC and DVCCs

In the paper, a universal preudo-differential second-order filter operating in voltage mode, where both intup and output are differential, is presented. The circuit is formed by one differential difference current conveyor (DDCC), two differential voltage current conveyors (DVCCs), and five passive elements. The filter is characterized by high input impedance, minimum number of passive elements that are all grounded, and high common-mode rejection ratio (CMRR). The proposed filter structure is able to realize all five standard frequency filter responses. Non-ideal analysis has been performed by considering the real parasitic parameters of the active elements. The optimization of passive element values has been done in terms of minimal shift of the pole-frequency and to obtain the maximum stop-band attenuation of the high-pass filter response. Functionality is verified by simulations and experimental measurements using readily available integrated circuit UCC-N1B 0520. DOI: http://dx.doi.org/10.5755/j01.eie.23.6.19694

A New Design Method for Stable IIR Filters With Nearly Linear-Phase Response Based on Fractional Derivative and Swarm Intelligence

In this paper, a new design method based on fractional derivative (FD) is proposed for designing digital stable infinite impulse response (IIR) filters with nearly linear-phase response. In this method, the design problem is formulated as a phase error optimization of an all-pass filter connected in parallel with a pure delay function. FD is employed to improve the frequency response of the filter at some reference point $(\omega _{{0}})$ in the passband. Optimal values of FD constraints and reference points in passband are determined by minimizing the sum of error in passband $(E_{p})$ and stopband $(E_{s})$ of an IIR filter, using different evolutionary techniques such as particle swarm optimization (PSO), constraint factor inertia PSO (CFI-PSO), quantum PSO, artificial bee colony algorithm, and cuckoo search technique. Comparative study provides evidence that the proposed method, based on CFI-PSO, gives the best performance amongst the employed swarm-based techniques. Experimental results show the impact of the proposed method as compared to earlier reported techniques in terms of improved response in passband and sharper transition width. However, small reduction in stopband attenuation $(A_{s})$ is observed within the allowable limit when compared to nonfractional design approaches.

Lowpass filters with almost‐maximally flat passband and Chebyshev stopband attenuation

A class of the almost-maximally flat (AMF) lowpass filters with Chebyshev stopband attenuation, referred to as AMF filters, is discussed. Allpole lowpass filters’ transfer functions are first derived by using parameters α and β of modified Jacobi polynomials J n ( α β ) ( Ω ) such that passband attenuation is minimised, and obtained transfer functions are then augmented by adding one or several pairs of j Ω -axis transmission zeros. The magnitude characteristics of proposed filters are compared with those of the Chebyshev II filters and are found to be superior, both in the passband and in the stopband.

Wideband reconfigurable bandpass filter using coupled lines loaded with varactor loaded stubs

In this article, a novel reconfigurable bandpass filter with tunable passband edge and bandwidth is proposed. The bandpass filter enables the two band edges independently adjustable to meet the needs of different systems. The wide tuning range of the bandwidth is achieved by controlling the tuning mechanism to altering not only the coupling strength of the coupled lines but also the transmission zeroes positions of the resonator. The lower passband edge can shifts from 760 to 840 MHz with the upper passband edge keeping still and the upper edge of the passbands from 981 to 1107 MHz with the lower edge keeping still. The overall tuning range of 3 dB fractional bandwidth is from 15.5% to 36%. The upper stopband attenuation of the fabricated structure can reach to 40 dB within a wide frequency range.

Substrate integrated waveguide filter showing improved stopband performance and fractional bandwidth using different input/output topologies

In this work bandpass filter based on SIW technology with an adequate fractional bandwidth as well as refinement in the stopband performance is presented. Its application lies with the receiver filter working in the Ka band used mainly in the ground terminal for satellite communication. Additionally analysis of divergent input/output arrangement is also demonstrated. Three SIW filter having a varying passband from 19.2GHz -21.2GHz depending on the input/output are synthesized on a planar substrate having height of 0.508mm RT/duroid 6002 using periodically arranged metal via holes through a regulated PCB process. Simulated outputs has a in-band insertion loss 0.9dB and the improved stopband attenuation within the frequency range of 29.5GHz – 31GHz is around 45 dB. It is observed that the experimented results coincide completely with the results simulated in HFSS/CST.

Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter.

In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter’s pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.

Flat optical frequency comb generation using polarization modulator and frequency shifter with double recirculating frequency shifting loops

A scheme to generate ultra-flat and stable optical frequency comb (OFC) based on multi-wavelength optical seed source and polarization-modulator-based complementary frequency shifter (PCFS) has been proposed and demonstrated. The OFC generation scheme includes two stages: 5-carrier light source is generated by utilizing a polarization modulator at the first stage, and the light source is then used as the seed light in the PCFS at the second stage. Compared with the previous flat OFC generator based on a recirculation frequency shifter, the proposed scheme can greatly reduce the recirculation times, and such a property makes the accumulated noise of the system enormously decrease. In order to achieve the frequency comb with the best flatness, the optical amplifier gain, filter stop-band attenuation and modulator drive voltage are optimized. Experiment simulations show that high-quality OFC with hundreds of frequency lines and power fluctuation within 2 dB can be achieved without direct-current bias control and wavelength-selective-switch.

Wide-stopband bandpass-filtering power divider with high-frequency selectivity

A wide-stopband bandpass-filtering power divider with high-frequency selectivity has been proposed in this paper. The input and output feeding lines and eight 1/4 wavelength resonators are used to realize the signal transmission. In order to obtain good frequency selectivity, source-load coupling transmission path is used to generate transmission zeros near the passband. A four-way power divider with bandpass-filtering response and high-frequency selectivity is designed, fabricated, and measured. The measured results agree with the simulated ones closely in the desirable frequency range. The measured center frequency of the power divider is 2.38 GHz with input return loss of 31.2 dB, while the measured insertion loss is about 1 dB (not including ideal 6 dB four-way power dividing insertion loss). Moreover, the measured 3-dB bandwidth is 12% and the measured stopband attenuation is >15 dB from 2.59 to 7.7 GHz. In addition, two transmission zeros of 1.9 and 2.8 GHz are located near the passband. The measured output isolations are all >15.7 dB.

$K$ -Band Substrate-Integrated Waveguide Filter Using TM21 Mode With Enhanced Stopband Attenuation

In this letter, we present a method for enhancing the stopband attenuation performance of a $K$ -band TM21 mode filter using substrate-integrated waveguide resonators. To improve the stopband response, we suppress and move spurious resonant peaks and produce transmission zeros. The step-by-step procedure of the proposed three-step method is shown in detail. The measurements show that when using the presented method, the filters exhibit better stopband performances than those in which the presented steps are not followed.

Design of sEMG-detecting circuit for EMG-Bridge.

A surface electromyography (sEMG) signal typically results from the electrical activities of many muscle fibers, and can be utilized as a signal source in prostheses due to its abundance of movement information. This paper proposes an sEMG-detection circuit for the acquisition of the controlling signal in EMG-Bridge (EMGB) systems. The detection circuit mainly comprises a preamplifier, a driven right leg (DRL) circuit, a high-pass filter (HPF), a low-pass filter (LPF), and a gain adjustable amplifying circuit. The common-mode rejection ratio (CMRR) of the circuit is higher than 120 dB, the input impedance is greater than 100 MΩ, the passband range is 20~450 Hz, and the frequency attenuation in stopband is not less than 120dB/dec.