Elliptic Filter Research Articles

Current-Mode FPAA with CMRR Elimination and Low Sensitivity to Mismatch

This article introduces a current-mode field-programmable analog array (FPAA) architecture with its programming methods. The biggest benefit of the proposed approach is solving the problem of implementing reconfigurable analog circuits in modern nanometre technologies. It is achieved thanks to adopting a switched-current (SI) technique which allows to implement the array using transistors based only on the standard digital CMOS technology. The work describes an implementation of a reconfigurable current mirror basing on using a digital-to-analog converter. The article addresses a routing problem of current-mode modules working in a balanced mode. Author proposes methods for CMRR compensation in a huge array architecture. The array was programmed taking into consideration parasitic elements of the layout with the emphasis on topography mismatch. Examples of implementing a 10-bit digital–analog converter, an elliptic filter with SNR,=,40.42 dB, 2D-DCT processor with PSNR,=,53.05 dB and RGB-to-YCrCb converter with PSNR,=,46.95 dB are presented. The elaborated array can be used as IPcore in a larger mixed-signal system or can act as a dedicated circuit.

Multiscale and Multidirectional Multilooking for SAR Image Enhancement

With the steadily increasing spatial resolution of synthetic aperture radar images, the need for a consistent but locally adaptive image enhancement rises considerably. Numerous studies already showed that adaptive multilooking, able to adjust the degree of smoothing locally to the size of the targets, is superior to uniform multilooking. This study introduces a novel approach of multiscale and multidirectional multilooking based on intensity images exclusively but applicable to an arbitrary number of image layers. A set of 2-D circular and elliptical filter kernels in different scales and orientations (named Schmittlets) is derived from hyperbolic functions. The original intensity image is transformed into the Schmittlet coefficient domain where each coefficient measures the existence of Schmittlet-like structures in the image. By estimating their significance via the perturbation-based noise model, the best-fitting Schmittlets are selected for image reconstruction. On the one hand, the index image indicating the locally best-fitting Schmittlets is utilized to consistently enhance further image layers, e.g., multipolarized, multitemporal, or multifrequency layers, and on the other hand, it provides an optimal description of spatial patterns valuable for further image analysis. The final validation proves the advantages of the Schmittlets over six contemporary speckle reduction techniques in six different categories (preservation of the mean intensity, equivalent number of looks, and preservation of edges and local curvature both in strength and in direction) by the help of four test sites on three resolution levels. The additional value of the Schmittlet index layer for automated image interpretation, although obvious, still is subject to further studies.

Millimeter-Wave Thin Lens Employing Mixed-Order Elliptic Filter Arrays

This communication presents a novel approach for designing a simplified and cost-effective millimeter-wave thin lens by reducing the number of substrates and metal layers for a given tunable range of the phase shift. It is demonstrated that this can be achieved by employing mixed-order elliptic filter arrays where the different orders of the filter are responsible for different tunable ranges of the phase shift. The key features of the elliptic filters and their mixed-order array are introduced. It is found that constructively utilizing the interlayer coupling between the metal layers renders an elliptic filter response, and the mixed-order configuration of the elliptic filter array can be utilized to design the devised thin lens. The design procedure for the affordable thin lens configuration is discussed. The empirical and simulated results demonstrate that the conventional planar lens can be further simplified in terms of the number of substrates and metal layers, maintaining the tunable range of the phase shift. It is confirmed that the fabricated mixed-order lens is less than 0.05 $\lambda 0$ in total thickness and has a gain of up to 12 dB with $f/D = 0.7$ .

A Narrow Band Pass Filter Using Technology Surface Mount Technology on Radar Frequency Generators

A BPF using SMT components. A cut-off frequency on a filter under cooling below LPF which works at freq 310 MHz, while the cut-off frequency below a filter under cooling HPF which works at freq 306 MHz, so that the width of the band This filter is a type of narrow bandwidth filter 4 MHz. An 7 poles filter order with the aim to increase the steepness of the filter is generated, using the elliptic filter family or causer. Stop band width (Fs) to filter under cooling below about 20% in the frequency range 372 MHz, with stop band depth (As) of about 55 dB, while the stop band width (Fs) to filter under cooling of about 20% in the frequency range 245 MHz, with stop band depth (As) of about 55 dB. This filter is designed to pass the signal frequency division results DRO with a CF of 9856 MHz. Using SMT components, this circuit becomes very small and compact and has a high Q. The results of the simulation are generated, then this filter can realized system FMCW radar frequency generator.

Remote respiratory monitoring system based on developing motion magnification technique

Abstract The aim of this study is to detect and measure the rate and timing parameters of the respiratory cycle at a distance from different sleeping positions of a baby based on video imagery. This study relied on amplifying motion resulting from movement of the chest caused by inhalation and exhalation. A motion magnification technique based on a wavelet decomposition and an elliptic filter was used to magnify breathing movement that is difficult to see with the naked eye. A novel measuring method based on motion detection was used to measure respiratory rate and its time parameters by detecting the fastest moving areas in the magnified video frame sequences. The video frames were converted into a corresponding logical matrix. The experimental results on several videos for the baby at different sleeping positions show that the remote respiratory monitoring system has an accuracy of 99%. The proposed system has very low computational complexity, is feasible and safe making it suitable for the design of next generation non-contact vital signs monitoring systems.

A 5th order video band elliptic filter topology using OTRA based Fleischer Tow Biquad with MOS-C Realization

A new 5th order video band elliptic filter topology is presented. In video applications high order elliptic filters were used. The proposed 5th-order lowpass filter was simulated with PSPICE simulation program. The elliptic filter configuration consists of two cascade connected lowpass notch filters and a lowpass filter which is obtained using OTRA based Fleischer Tow biquad. After designing the 5th order video band elliptic filter topology, the MOS-C realization is obtained and used in PSPICE simulation.

Elliptic Filter and Iterative Inversion Method for Buried Object Detection Applications

In this paper, Forward-Backward Time-Stepping (FBTS) inversion method is used for detection, imaging and reconstruction of an unknown object in a region of interest. We consider the reconstruction parameter profiles of two-dimensional objects from measurement of the transient total electromagnetic field data contaminated with noise. A preliminary result of an Elliptic filter integrated in FBTS algorithm to suppress noise effect has been obtained. A circular shape in the region of interest is successfully detected and reconstructed.

A discrete time parametric model of auditory filters at peak sensitivity

The first stage of human auditory processing is the filtration performed by the ear. The middle ear, basilar membrane, and tectorial membrane contribute to a filter bank specialized for amplitude and frequency selectivity. Accurately modeling this system is of critical importance, because the properties of the cochlear filter bank determine what audio information is available to humans. Because the cochlea is such an intricate and non-linear system, many cochlear models are computationally taxing and unusable for real time applications. By making a judicious linear approximation of the system, digital filters modeled after the cochlea can be implemented efficiently in real time. However, the digital filter models presently in use (often eighth order gammatone or elliptic filters) do a poor job of capturing the most perceptually critical properties of the cochlear filter bank. In this report, a set of parametric digital filters are proposed, which accurately model cochlear filters at peak sensitivity from 80 Hz to 19.5 kHz best frequency. The filters were designed using a gradient of steepest descent method to fit target frequency responses generated by a physical model of the cochlea. The final result is a set of polynomial equations which describe the locations of the poles and zeros of the digital cochlear filter approximations as a function of normalized cochlear best place.

Perturbation Effect on IIR Filters

During the realization of digital FIR and IIR filters the finite word length in computers affects the accuracy of filter coefficients. This leads to change in actual desired poles and zeros of the system function. In this paper firstly the analog filter is converted to digital domain using bilinear transformation and then the filter coefficients are quantized to analyze the perturbation error and the finite word length effect.This paper analyzes the sensitivity to quantization of filter coefficients for 8-bit, 16-bit and 32-bit precisions up to order 7 for digital low pass Butterworth, Chebyshev (type I and type II) and Elliptic filters for direct form realization. In the end result shows that the Chebyshev type II filter yields the least perturbation error and Elliptic filter yields the maximum perturbation error for higher orders.

On the performance of advanced integrated microring filters for switching applications in next-generation elastic optical networks

We investigate the use of integrated advanced microring resonator-based sum-difference all-pass optical filters for switching applications in circuit-switched elastic optical networks. A practical design taking into account optical losses accordingly to typical reported values for strip waveguides in silicon-on-insulator technology is considered. By incorporating tuning elements (i.e., standard phase shifters), three different synthetized elliptic filters are emulated in the same physical structure showing the potential in terms of bandwidth configurability of the architecture. Practical filter design rules for standard silicon-on-insulator single-mode strip waveguides are also discussed. Beside possible advantages in terms of reduced fabrication costs, simulations performed on Nyquist PM-QPSK signals with different channel capacities over 50, 37.5 and 25 GHz frequency slots suggest that the proposed structure can achieve similar or better performance than commercial spectrum selective switch filters.

Selective digital filters with quadratic phase

SummaryA method for design of a new class of digital infinite impulse response filters realized as parallel connection of two all‐pass filters is presented in this paper. A new approach to approximation of quadratic phase of all‐pass filter at all frequencies is given. Chosen parallel structure offers opportunity for realization of filters with arbitrary shape phase. The presented algorithm is based on all‐pass filter phase approximation. Phases of both all‐pass filters approximate ideal quadratic phase in minimax sense at all frequencies. Such filters can be applied for chirp signal compression or expansion. Magnitude characteristic of described filters is very selective and elliptic‐like. Obtained filters are compared with elliptic filter and group delay corrector in cascade. For the same specifications, much better results are achieved by the proposed filters. Parallel connection of all‐pass filters introduces lower signal delay, and for a given maximal phase, approximation error demands less complex network. Examples to illustrate the proposed method are given. Copyright © 2016 John Wiley & Sons, Ltd.

Design of a Selective Filter-Antenna with Low Insertion Loss and High Suppression Stopband for WiMAX Applications

This paper presents a selective quasi–elliptic bandpass filter-antenna. The presented filter-antenna has a low insertion loss in the passband and relatively high stopband rejection. This structure consists of a quasi–elliptic bandpass filter direct coupled with patch antenna. The bandpass filter consists of four (λ/4) spiral square resonators. It has operates between (3.25–3.6) GHz so it is suitable for WiMAX applications. A CST Microwave Studio Suite software has used to simulate the filter-antenna circuit. The simulated results of the patch antenna and the results of the filter-antenna appears a good matching between the two circuits.

Design of Bessel low-pass filter using DGS for RF/microwave applications

ABSTRACTA synthesis method to design a defected ground structures (DGS)-based Bessel low-pass filter (LPF) using a triangular and an open-square (OS)-type DGS is reported. For the five-pole Bessel LPF at fc = 2.5 GHz, we get 10.6 dB/GHz selectivity using the triangular DGS; while the OS-type DGS provides 39 dB/GHz selectivity. For these two filters, the 10 dB impedance matching BW is 76% and 84%, respectively. It is a much wider BW that is obtained for a lumped element Bessel LPF. The maximum group delay (GD) variation within the pass band is 25pS and 28pS, respectively. The 20 dB rejection BW can be increased from 5.8 GHz to 18.8 GHz with increase in the order of filter from 5 to 11. We have also presented the design of a compact five-pole DGS-based elliptic filter with selectivity 38.2 dB/GHz and 17.8 dB return loss. Results on the DGS-based elliptic filter, Butterworth and Chebyshev filters are also presented. The experimental results are compared against the recently reported LPFs. Our reported filters perform better with respect to selectivity and group delay variation. The flatter GD and high selectivity, along with a wide 10 dB impedance matching BW, make the DGS Bessel filter a candidate for high-speed data communication, front end of a wideband communication system and efficiency improvement of a power amplifier.

Planar elliptic function lowpass filter with sharp roll-off and wide stopband

A compact planar elliptic function lowpass filter with sharp roll-off at 20 dB attenuation level and wide stopband using microstrip stepped-impedance polygonal patch resonators is developed and investigated. Electromagnetic simulation is used to optimize the performance of the filter. The filter using cascaded multiple patch resonators provides a very sharp attenuation near cutoff frequency with a high stopband suppression level. The rejection bandwidth is enhanced by introducing additional transmission zeroes and the results are validated by the experiment. The filter has a compact size of 17.6 mm × 12.2 mm. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:133–136, 2016

Silicon Micromachined Terahertz Bandpass Filter With Elliptic Cavities

In this paper, a 400-GHz silicon micromachined elliptic cavity waveguide filter with two transmission zeros on both sides of the passband is presented. The filter is cascaded by two elliptic cavities which are operating at quasi- ${\rm TM}_{110}$ mode. Each elliptic cavity can introduce a transmission zero near the passband of the filter. By adjusting the axial-ratio (AR) of the elliptic cavity, the position of the introduced transmission zero could be moved to the upper side or the lower side of the passband. The micromachining process of deep reactive ion etching (DRIE) is used for the fabrication. The measured 3-dB bandwidth of the filter is 7.52%, from 380.2 to 409.9 GHz, and the measured insertion loss is 2.84 dB, including extra waveguide of about 4.5 mm at the input and output ports. In addition, the insertion loss of straight waveguide is also measured and analyzed. Then, an analysis method for the loss property is summarized. According to the measurement, the unit length loss of the waveguide is about 0.144 dB/mm at 400 GHz.

MICROSTRIP LOW PASS FILTER DESIGNS USING DEFECTED GROUND STRUCTURE

The microwave filters play an important role in most RF/microwave applications. They are designed to remove undesired harmonics to reduce the system noise or to remove spurious mixing products. DGS slot with an interdigital shape are introduced here in two elliptic low pass filter designs. Here a fifth order low pass filter was designed, simulated and fabricated for a cut off frequency of 3GHz. Finally a prototype model were designed based on the simulation results obtained. These prototype filter designs have more than 20 dB of stop band rejection and a good return loss in the pass band. The fabricated results proved to be better than the simulation results. In the first low pas filter design the central aperture was replaced with the interdigital slot structure which improved the stop band response at the resonant frequency around 7.8 GHz. To improve the stop band rejection two interdigital structures were introduced in the bottom layer (Ground).

A New Wideband Elliptic Bandstop Filter With Cross Coupling

A novel fifth-order elliptic cross-coupled wideband bandstop filter (BSF) is proposed and designed in this letter. It is devised by introducing additional electric coupling into two nonadjacent quarter-wavelength shunt stubs of a conventional commensurate line BSF. The selectivity and stopband rejection can be effectively enhanced by two extra transmission zeros generated from the coupling. The proposed BSF is designed directly from the normalized lowpass prototype by using the design formulas, which are derived based on the rigorous correspondence between the BSF and its lumped prototype in the $S$ -plane. In order to demonstrate our design, a BSF example is developed, with a measured 27.2 dB stopband over a fractional bandwidth of 141.7%.

AN ANALYSIS TO DESIGN MERGED DELAY TRANSFORMED IIR DOWN SAMPLER FILTER: AN EFFICIENT DOWN SAMPLER FILTER ARCHITECTURE

An efficient architecture of Down Sampler Filter using Merged Delay Transformed Technique in terms of cost reduction and increase throughput has been proposed. The stability analysis of Merged Delay Transformed filters, finite word length effect on Transformed filters as well as conventional filters and peak error between the output from transformed IIR filters and from conventional filters have been investigated on the basis of commercially available software and mathematical calculations. The Butterworth, Chebyshev-1, Chebyshev-2 and Elliptic filters have been considered in this paper for the sake of comparison. The simulation results show that 84.59%, 73.56% and 50.83%&78.71%, 73.85% and 51.89% reduction in cost can be achieved with different specifications by using the proposed scheme when it is compared with conventional FIR filter, conventional IIR filter and conventional polyphase IIR filter, respectively. It has been elaborated that the stability of transformed IIR Decimation filters will not disturb as the Decimation Factor M increases. It is also shown that the transformed Elliptic filter is more stable and the transformed Chebyshev-2 filter is a marginally stable filter. The simulation results show that the peak error is in the range of 10 -10 to 10 -17 which increases with an increase in order of the filter. On the basis of simulation results and mathematical calculations, it is shown that the decomposition of higher order system into 1 st order and 2 nd order systems using parallel implementation architecture with Merged Delay Transform increases the processing rate of the filter and a reduction in the cost of implementation as well as peak error.

Design and Synthesis of Quasi Dual-mode, Elliptic Coaxial Filter

This article introduces the design of a novel quasi dual-mode, elliptic coaxial filter. The transfer function is mapped to a Generalized Chebyshev prototype with sym- metrically located transmission zeros (TZs) where the cou- pling values are extracted. Furthermore, the miniaturiza- tion is achieved by incorporating stepped-impedance coax- ial line with inductive element shunted at the center to ex- hibit a quasi dual-mode property. Theoretical analysis to- gether with experimental prototype is presented. The center frequency of the filter is 2.7 GHz. The simulated and mea- sured insertion loss/return loss are 1.2 dB / 15 dB and 2.5 dB / 11.5 dB respectively. Both theoretical and measured results show a very good agreement.

A systematic implementation of elliptic low-pass filters using defected ground structures

For the past decade, defected ground structures (DGSs) are largely used in the implementation of low-pass filters, without a systematic approach. In this paper, a simple systematic approach for the design of elliptic low-pass filters using DGSs is proposed. An empirical model for a simple rectangular slot DGS is extracted for its equivalent circuit. Using this model, low-pass filters for various orders are designed for critical filter specifications and optimized by reducing the parasitic effects induced by DGSs. This systematic implementation of DGS-based filters achieves more than 90% of the desired filter specifications. Due to the improved slow-wave factor and power handling capacity of DGSs, the filter is more compact and reliable than the conventional filters.