B-spline FIR filters

In this work, theoretical design of a novel band pass filter based on the turning-around-point long period fiber grating (TAP-LPFG) having cladding index modulation is proposed and demonstrated. Cladding modes are excited by introducing the incident light into the fiber cladding of the input end of the TAP-LPFG. At the grating region, only those cladding modes that satisfy the phase matching condition couple back to the fiber core to obtain the band pass transmission. It is shown that a band pass filter with –3 dB width of from ~115 to ~198 nm with the center wavelength of ~1554.4 nm can be obtained, and the suppression of more than 10 dB for the side-lobes is achieved in a wide wavelength range. This novel TAP-LPFG based device can find applications in optical communications for wide band pass filter.

A novel composite FIR-based filter structure is proposed to reduce the complexity of echo cancellers. The proposed filter consists of an FIR filter, an interpolated FIR (IFIR) filter, and a tap-weight overlapping method. The FIR filter is used to model the short rapidly changing head echo portion while IFIR filter is for the long slowly decaying tail echo. About 55% complexity reduction is obtained compared to a conventional transversal filter while this design inherits stable convergence advantages. Simulation results show that an average 75.1 dB ERLE performance is achieved for the 2320-kbps SDSL system.

Two new approaches to the design of predictive FIR filters are presented. First, we discuss the design of predictors and estimators for narrow-band signals based on the interpolated FIR (IFIR) filter approach. The transfer function of the IFIR predictor is of the form H(z)=P(z/sup L/)G(z) where P(z) is a predictor and G(z) is an interpolating estimator. The general-purpose design procedure for efficient IFIR predictors is described, and demonstrated for polynomial predictors. The resulting predictors, optimized for white noise attenuation, have much lower computational complexity than the corresponding direct-form FIR predictors. Secondly, an IIR filter-based implementation of sinusoidal FIR predictors is presented. As an application, a zero-crossing detector for 50 Hz thyristor drives is designed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The main objective of this work is the study, design and simulation of a narrow-band compact band pass filter using the technique of a rectangular-shaped linear resonator closed on a capacitive load and based on magnetic coupling. This filter is intended for wireless communication systems (Wi-Fi, Bluetooth, RFID, and ISM). It is attractive considering the substrate and tracks used and also in terms of size (7.485 × 8.18) mm2. It also has good selectivity (300 MHz bandwidth) and low insertion loss (−0.01 dB).

Planar microwave bandpass filters (BPFs) are an essential component in many communication systems. Traditional BPF design focuses on the application of frequency-invariant K-/J-inverters inserted between the two resonant modes or served as the external coupling to feed the resonators. This design method is most suitable for narrow bandwidth BPFs, but for wideband cases it is difficult for a direct application. To solve this problem, a synthesis method based on a modified general Chebyshev function and the Richard’s transformation has been proposed to characterize the frequency response over the whole frequency range for the wideband BPF designs. As for the corresponding circuit structure, short-circuited stepped-impedance multi-mode resonators (MMRs) serve as the foundation to the designs in this dissertation. By parallel-connecting or folding the MMRs, a class of dual-wideband BPFs has been developed. Based on the above discussion, this dissertation presents the wideband BPF designs in two aspects, the proposed filter synthesis procedure and a new class of circuit structures to realize the target filtering responses. As the foundation of this research work, short-circuited MMRs have been researched in the first place for a single-wideband BPF design. n sections of cascaded commensurate lines are used to group the resonances, and short-ended stubs are shunt on its two sides to inductively feed the MMR. For the filter design, a Chebyshev filtering function is used to characterize the frequency response of the circuit. By equating the filtering function to the transfer function of the circuit, the design parameters are obtained. The first set of dual-wideband BPFs is formed by parallel-connecting two dissimilar single-wideband BPFs, both formed by stepped-impedance MMRs. The two transmitting paths of 180o phase difference are used to generate up to two pairs of transmission zeroes (TZs) with symmetry to the dual-wide passbands. By appropriately choosing the characteristic impedances of the two paralleled MMRs, one pair of TZs is located in real frequencies contributing to the attenuation between the two passbands, whereas the second pair of TZs is located in imaginary frequencies adjusting the group delay within the passbands. The short-circuited stubs, in shunt connection on the two sides of the MMR, act as the inductive loading element to feed the MMR and to flatten the passband. In the meanwhile, they introduce TZs at multiple of π to suppress the DC-component. Following a similar design principle, the second set of dual-wideband BPF has been proposed as an improved design in terms of realizing a more compact size, the greater flexibility in terms of reflection zeros in the passband and an extra degree of freedom in choosing characteristic impedances. The generic structure of the proposed filters is formed by folding a MMR along its symmetrical plane and by coupling a pair of short-circuited stubs on the two ends of the MMR. Thus, two signal transmitting paths, one from the folded MMR and another from the loaded stubs, are used to generate additional TZs between the two passbands. By increasing sections of the loaded MMR, the reflection zeros in the passband is enlarged. Under fully-coupled structure, the merit of compact size and extra design freedom is obtained. For these two sets of dual-wideband BPFs mentioned above, the even-/odd-mode analysis method has been used to derive the transfer function to characterize their frequency responses. Given the properties of the proposed filters, the commonly used generalized Chebyshev filtering function as well as its transferred dual-band function is not appropriately used herein. Instead, a generalized Chebyshev filtering function, originally developed for a single-wideband BPF design, is readily applied. By directly formulating a filtering function with mirror to the origin, it has dual passbands respectively located at positive and negative frequency ranges. To accurately account for the wideband response, a TZ is assigned at the origin. Next, the Richard’s transformation is applied to transfer the normalized frequency response to its dual-band counterpart. With this proposed synthesis procedure, the targeted filtering function is characterized by a ratio of two polynomials. By equating these two aforementioned functions, which are the ideal filtering function from the specifications and the transfer function from the circuits, all the circuit design parameters are obtained. Finally, the proposed single-/dual-wideband bandpass filters have been synthesized and designed for practical implementation. The experimental results of the fabricated filter circuits have strongly verified these new filter structures and their corresponding synthesis method proposed.

It has been demonstrated by several authors that the well-known weighted least squares (WLS) approximation can be equiripple if a suitable weighting function is applied. In the pre- sent paper, the WLS algorithm is generalized to SAW filter syn- thesis with prescribed magnitude and phase specifications. Several weighting techniques producing quasi-equiripple designs are pre- sented. The frequency sampling technique is used for SAW filter frequency response approximation to reduce the number of the optimized variables. The WLS algorithm rapidly converges both for linear and non-linear phase SAW filters. Typically, no more than 5-10 iterations are required to obtain the WLS solution to accuracy better than 0.5-1 dB in the stopband when compared with the optimum Chebyshev approximation. Moreover, it is shown that the WLS technique can be effectively applied for sec- ond-order effect compensation.

The everyday broadening field of signal processing has digital filters to play a major role. Linear phase FIR filters are used in vast number of applications due to their nature of phase linearity as well as frequency stability. The traditional nonoptimization methods available for filter design suffer from the problem of need for analog to digital conversion and also the inefficient control of frequency response. The conventional gradient based optimization methods are unable to solve non-differential functions and converges to local optimum solution. Thus this paper presents the evolutionary optimization technique of Particle Swarm Optimization (PSO) for the design of linear phase digital low pass (LP) FIR filter. Given the specifications of desired filter to be realized, PSO algorithm results in an optimal coefficient set for linear phase FIR filter approximating the ideal specifications. In this paper PSO algorithm is used with constriction factor approach to solve the multimodal, highly non-linear filter design problem. This method has the property of parameter independence and thus ensuring convergence while fully exploring the solution space. The velocity and position updating rules of original PSO algorithm is used for the design of low pass FIR filter of order 20. The extensive simulation results obtained from the proposed method shows superiority of the algorithm.

One of the very popular medical imaging techniques used in present-day radiology is the magnetic resonance imaging (MRI) which is based on the phenomenon of nuclear magnetic resonance (NMR) in the hydrogen atoms present in the body. There is ever-increasing research in electronic circuit design for biomedical applications using NMR. Earlier magnetic resonance imagers operated at a magnetic field strength of 0.3 T. The present imagers operate at a magnetic field of 1.5 T, the resonance frequency of the nuclei being 64 MHz. This article presents a CMOS bandpass filter (BPF) design for NMR applications. The overall BPF design is realised in 180 nm CMOS technology which occupies an active area of 24.23 × 33.125 µm2 and consumes 0.165 mW of power from a 1.5 V supply.

A complementary coupled spiral transmission line with center via is proposed to design band pass filter with compact and simple profile, low group delay, and low insertion loss. A compact wideband band pass filter is designed and fabricated for demonstration which has 26% bandwidth, 0.3 dB insertion loss, and compact size as 0.41 × 0.23 λg with very low group delay, 0.28 ns. These good specifications prove the capability of the proposed approach to design of band pass filter compared with the literatures.

One of the possible errors in radar communication is the presence of unwanted frequencies that are still passed by the radar system, causing performance to decrease. This paper proposes a bandpass filter (BPF) design for S-Band radars that work in the range of 3 GHz. A Bandpass filter is designed using the microstrip hairpin technique plus the dumbbell-Defected Ground Structure (DGS) method. This study aims to prove that the selection of DGS forms and effectiveness in optimization can provide better results. The band-pass filter is realized using the RO4350-B material with a relative dielectric constant of 3.48 and a thickness of 1.524 mm. The results obtained from the realization of band-pass filters show S 11 of −31.822 dB, S 21 of −0.829 dB and VSWR of 1.502. Filters work on ranges 2.850 – 3.02 GHz with a bandwidth of 170 MHz. From the parameters of the results obtained, the filter designed is following the specifications specified. Addition of dumbbell-DGS also gives better results than the form of a square groove-DGS.

The contribution of this letter is to propose an evanescent-mode ultraminiaturized substrate integrated waveguide (SIW) cavity resonator and its application in bandpass filter (BPF) design. The proposed compact SIW cavity is composed of two dielectric substrates with three metal layers. The top and bottom metal layers form the cavity’s broadside walls, and the middle one is a circular patch that shorts to the bottom wall by a ring fence of vias (or a centered single via). This circular patch together with the ring-fence vias (or single via) provides cavity resonator a large loading capacitance to allow a dramatic frequency downshift. Two experimental four-pole BPFs are built to validate the circuit design. The achieved frequency downshift of the proposed SIW cavity, compared with that of its conventional SIW cavity counterpart, is 72.5% (82.3%) for the via-ring fence (single via) case. Not only is the associated area miniaturization factor (MF) comparable with the highest record in the literature, but also the BPFs implemented here are structurally simpler and exhibit a much wider relative upper stopband bandwidth than that of the SIW BPF with a record of high MF.

FIR filters have many advantages such as linear phase, high precision and good stability. However, when the performance is required to be high, usually a higher order is required, resulting in greatly increased hardware complexity of the FIR filter. Based on sparse FIR filter design algorithm and common subexpression elimination method, a novel algorithm to design the FIR filters with low complexity. First, a sparse FIR benchmark filter that fulfills frequency response specifications is yielded from the sparse filters design algorithm. Then, each quantized filter coefficient is represented in CSD. And the weight of all subexpressions and isolated nonzero digits of the quantized coefficient set are computed. Finally, the filter coefficient set with lower implementation cost is constructed by iteratively admitting subexpressions and isolated nonzero digits according to their weight. The simulation results show that the proposed algorithm can saves about 29% of adder compared with other low complexity filter design algorithms, which effectively reduces the implementation complexity and greatly saves the hardware cost.

The design of surface acoustic wave bandpass filters which utilize interdigital electrode transducers is reviewed. The impulse-response description of interdigital transducers is extended to allow calculation of transducer input admittance and filter frequency response with much less effort than required by earlier equivalent-circuit model approaches. The application of the impulse model to the straightforward design of VHF and higher frequency bandpass filters is discussed and several examples of high-performance surface-wave bandpass filters are given.

A novel bandpass filter (BPF) design based on vertical split‐ring resonators (VSRRs) was developed for single‐ and dual‐band applications. The filter is composed of VSRRs, transmission lines, and apertures. The characteristics of single‐ and dual‐band BPFs using a single VSRR and dual VSRRs, respectively, were investigated. The bandpass characteristics arising from VSSR resonance can be controlled by the VSRR dimensions, and the independent bandpass characteristics of dual VSRRs can be used to implement a dual‐band BPF. A full‐wave simulation and experimental measurements were used to measure their performance. The simulated results for the single‐ and dual‐band BPFs were in good agreement with the experimental results.

This paper presents a novel connecting-line coupling technique for the design of compact and low-loss bandpass filters (BPFs) with multiple controllable transmission zeros (TZs). Traditional gap-coupling methods are highly sensitive to fabrication errors and have limited design flexibility. By contrast, the proposed approach enables precise control of coupling strength without modifying resonator geometry. Such control is achieved through independent adjustments of the lengths, widths, and positions of connecting lines. Furthermore, the proposed approach facilitates the generation of up to n TZs for an nth-order BPF, thus considerably improving the BPF’s frequency selectivity and stopband attenuation. To validate the effectiveness of this method, four filters are designed and fabricated: a second-order stripline BPF, a fourth-order microstrip BPF, a fifth-order stripline BPF, and a sixth-order wideband microstrip BPF. The second-order BPF is based on asymmetric connecting-line coupling, whereas the fourth-, fifth-, and sixth-order BPFs are based on symmetric connecting-line coupling. Excellent agreement between simulation and measurement results is achieved for these designs, with low insertion loss, high roll-off rates, and high tolerance to fabrication variations being noted. The proposed technique is suitable for filters ranging from narrowband to ultra-wideband filters and across low to millimeter-wave frequency bands, making it a highly versatile and practical solution for modern RF and microwave communication systems.