Stopband Attenuation Research Articles

Design of Modulated Filter Banks and Transmultiplexers With Unified Initial Solutions and Very Few Unknown Parameters

This brief proposes a method for designing modulated filter banks (FBs) with a large number of channels. The impulse response of the long prototype filter is parameterized in terms of a few short impulse responses, thus significantly reducing the number of unknown parameters. The proposed method starts by first obtaining an FB with a few channels. The solution of this FB is then partly reused as an initial (very close to final) solution in the design of FBs with a large number of channels. The number of unknown parameters hence drastically reduces. For example, we can first design a cosine modulated FB (CMFB) with three channels whose prototype filter has a stopband attenuation of about 40 dB. We can then reuse the solution of this CMFB in the design of a CMFB with 16 384 channels whose prototype filter has a similar stopband attenuation. With our proposed method, we need to reoptimize only 14 parameters to design the CMFB with 16 384 channels.

Performance of different window functions for designing quadrature mirror filter bank using closed form method

In this paper, a closed form method for designing two-channel linear phase Quadrature Mirror Filter (QMF) bank presented by Kumar et al. is examined and improved by exploiting different window functions for designing the prototype filter for QMF bank. In this method, the optimum pass-band edge frequency is determined via empirical formula instead of using single or multivariable optimisation technique for the given stop-band attenuation and roll-off factor (RF). This method reduces the overall computational time with minimum amplitude distortion to make suitable design of QMF bank for applications, which are carried out in real or quasi-real time. Simulation results presented in this paper how enhanced performance of this algorithm over the other existing algorithms.

Coplanar Waveguide Filter using Stub Resonators for Ultra Wide Band Applications

The paper presents a compact coplanar waveguide filter employing stub resonators for ultra wide band applications. A cascade connection of series and shunt stubs quarter wavelength long is used for achieving bandpass characteristics. The performance requirement of the filter decides the number of cascaded sections. The filter has reduced insertion loss in its passband and good attenuation in lower and upper stopbands. The flat group delay in the passband ensures its use in communication applications. Measured frequency response of the fabricated prototype shows good agreement with simulated response.

A Novel Design Method for Compact UWB Bandpass Filters

In this letter, a new design method of ultra wideband bandpass filter (UWB BPF) is proposed. Based on a symmetrical structure of a simple uniform line loaded by a stepped-impedance open stub (SIS) connected at its center, the proposed design method employs simultaneously the optimization of a defined objective function in the range of frequency 3.1-10.6 GHz and the transmission zeros at cut-off frequencies for a rapid convergence. Obtaining different filter sizes with good performance, the compact UWB BPF is simulated, fabricated, and measured. A good agreement between simulation and measurement is obtained while achieving good performances such as a return loss better than 10 dB, an upper stopband attenuation higher than 20 dB up to 17.6 GHz, and a sharp selectivity.

Compact planar UWB filter using cascaded resonators

This paper presents a planar ultra wide band filter employing chip inductors and complementary split ring resonators. Asymmetric interdigital coupled lines are used for achieving bandpass characteristics. Lower side transmission zeros are introduced using LC resonators consisting of chip inductors and circular patch capacitors. The filter has low insertion loss and flat group delay in its passband, steep roll off rate and good stopband attenuation. Measurement results for transmission and reflection characteristics of the fabricated filter are in good agreement with simulated response.

A New Class of Low Complexity Low-Pass Multiplierless Linear-Phase Special CIC FIR Filters

This letter presents a new class of selective low-pass multiplierless linear-phase special CIC FIR filter functions of low complexity given in an explicit cascaded compact form. Several examples of the proposed filters are illustrated. They are compared in a fair way with conventional CIC FIR filters for the equal values of group delay and the same number of cascade sections. An example of the new class of the proposed seventh order filter with nine cascades is presented, where its stopband attenuation has high value of 143.82 dB, while corresponding conventional CIC FIR filter with the same filter order and the number of cascades has only 115.18 dB.

The design of inphase power divider based on transversal signal interaction technique

A wideband inphase power divider based on signal interaction technique and slotline technique is proposed in this article. On the one hand, this power divider breaks conventional quarter-wavelength slotline configuration so that the lumped resistor can be soldered. On the other hand, quarter-wavelength short-ended coupled line and three quarters-wavelength transversal transmission line are introduced to obtain a bandpass filtering response. A prototype inphase power divider is designed and fabricated to demonstrate the performance of the proposed wideband power divider. The simulated and measured results show that there is a good performance in passband 3.9–10 GHz. In addition, the stopband (attenuation more than 20 dB) reach up to about 4.8 GHz (11.2–16 GHz) from the experimental data.

Wide passband/stopband bandpass filter based on transversal signal interference concepts and modified branch-line structure

A high selectivity wide passband filter with a broader stopband based on transversal signal-interaction concepts and modified branch line structure (MBLS) is developed in this article. Two transmission paths, that is, one half-wavelength transmission line and one MBLS, are used to realize signal transmission from Port 1 to Port 2. Then, two transmission zeros are introduced at both lower and upper sides of the passband, which are used to improve the passband selectivity greatly. The filter bandwidth can be easily controlled by reasonable adjusting the coupling coefficient of the coupled lines. Furthermore, with four stubs connected at the input/output ports, the stopband attenuation level is improved greatly. Finally, one prototype filter having 69.1% of 3 dB fractional bandwidth is fabricated with advantages of sharp selectivity and high out-of-band rejection. The EM simulated and measured results are presented, and an excellent agreement can be obtained. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:330–336, 2015.

Lattice FBAR Filters: Basic Properties and Opportunities for Improving the Frequency Response

The paper contains a relatively detailed consideration of lattice filters with bulk acoustic-wave resonators (FBAR): basic theory, investigation and improving of their design. First FBARs and their parameters are introduced briefly. Then the basic structure of lattice filters and its modification with twice lower number of resonators are introduced. A theory of lattice FBAR filters is presented, which allows unified explanation of many of their properties: condition for small or large gain of the filter; existence of maxima of the filter frequency response; emergence of transmission zeros; etc. The effect of using two different resonators instead of a single resonator in the arms of the lattice filter is investigated next. It is demonstrated that this approach suggests extension of the passband bandwidth and increasing the stopband attenuation. The properties of the considered filters are illustrated by comparing their frequency responses. Similar comparison between some good representatives of lattice and ladder filters is also given at the end, accompanied by comments about the benefits of both filter architectures. KeywordsFilm Bulk Acoustic-Wave Resonators (FBAR); RF Filters; FBAR Filters; Circuit Theory

Compact microstrip bandpass filter with fragment‐loaded resonators

ABSTRACTMicrostrip bandpass filter with fragment‐loaded resonators is proposed and designed using multiobjective evolutionary algorithm based on decomposition combined with enhanced genetic operators (MOEA/D‐GO). When loaded by fragment‐type structures, microstrip resonators may have compact size and operate at different modes. By properly setting the modes of fragment‐loaded resonators in objectives of MOEA/D‐GO, stopband attenuation and spurious passband suppression of the microstrip bandpass filter can be readily adjusted and controlled. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2896–2899, 2014

A VCSEL-Composed Tunable Optical Band-Pass Filter for Long-Reach Optical Single Sideband Transport Systems

This paper proposes a novel long-reach optical single sideband (OSSB) transport system based on a phase modulator and a vertical-cavity surface-emitting laser (VCSEL)-composed tunable optical band-pass filter (TOBPF). Experimental results show that the VCSEL-composed TOBPF can provide an approximately 5 GHz pass-band window, 350 GHz detuning frequency, and more than 13 dB stop-band attenuation to convert an optical phase-modulated radio frequency signal from optical double sideband (ODSB) format to OSSB format. Error-free transmissions and clear eye diagrams are experimentally obtained when a 1.25 Gbps/10 GHz RF signal is transmitted over a 60 km single mode fiber. The proposed system is shown to be efficient in promoting radio-over-fiber (RoF) transmission in long-distance passive optical networks.

Design of two-channel filter bank using nature inspired optimization based fractional derivative constraints

In this article, a novel approach for 2-channel linear phase quadrature mirror filter (QMF) bank design based on a hybrid of gradient based optimization and optimization of fractional derivative constraints is introduced. For the purpose of this work, recently proposed nature inspired optimization techniques such as cuckoo search (CS), modified cuckoo search (MCS) and wind driven optimization (WDO) are explored for the design of QMF bank. 2-Channel QMF is also designed with particle swarm optimization (PSO) and artificial bee colony (ABC) nature inspired optimization techniques. The design problem is formulated in frequency domain as sum of L2 norm of error in passband, stopband and transition band at quadrature frequency. The contribution of this work is the novel hybrid combination of gradient based optimization (Lagrange multiplier method) and nature inspired optimization (CS, MCS, WDO, PSO and ABC) and its usage for optimizing the design problem. Performance of the proposed method is evaluated by passband error (ϕp), stopband error (ϕs), transition band error (ϕt), peak reconstruction error (PRE), stopband attenuation (As) and computational time. The design examples illustrate the ingenuity of the proposed method. Results are also compared with the other existing algorithms, and it was found that the proposed method gives best result in terms of peak reconstruction error and transition band error while it is comparable in terms of passband and stopband error. Results show that the proposed method is successful for both lower and higher order 2-channel QMF bank design. A comparative study of various nature inspired optimization techniques is also presented, and the study singles out CS as a best QMF optimization technique.

Design of Alias-Free Linear Phase Quadrature Mirror Filter Banks using Eigen value-Eigen vector Approach

An eigenvalue-eigenvector approach for the design of two-channel linear phase quadrature mirror filter (QMF) bank is proposed. To reduce the computational complexity, finite-duration impulse response (FIR) low-pass prototype filter of the filter bank is represented by polyphase components. The design problem is formulated to optimize the filter tap weights of the low-pass prototype filter of the QMF bank to minimize an objective function, which is the weighted sum of the square error of the filter bank transfer function at the quadrature frequency, pass-band error and stop-band residual energy of the low-pass prototype filter and measure of reconstruction ripple. The objective function has been minimized by an iterative algorithm. As compared to the existing design techniques, the proposed algorithm gives better performance in terms of mean square error in stop-band, number of iterations required and stop-band edge attenuation. Design examples are presented to validate the effectiveness of the proposed method.

Comb-Based RF Photonic Filters Based on Interferometric Configuration and Balanced Detection

We demonstrate a novel technique to improve radio frequency (RF) performance such as RF gain and noise figure (NF) for comb-based RF photonic filters. While conventional RF photonic links use a dual-output modulator and balanced detection, this RF photonic filter utilizes an interferometric configuration with double sideband suppressed carrier modulation and balanced detection. This technique can simultaneously provide filter tunability, 6-dB RF gain increase, and noise cancellation. The RF gain and NF of the RF photonic filter are improved to approximately 0 and 24 dB, respectively. With the improved RF performance, we perform the tuning of the filter center frequencies from 2 to 8 GHz with no baseband filter response (<;-38 dB), no RF power fading, while maintaining good filter shape (sidelobe suppression and stopband attenuation >32 dB).

Design of minimax robust broadband beamformers with optimized microphone positions

A new method for the design of robust minimax far-field broadband beamformers with optimized microphone positions is proposed. The method is formulated as an iterative optimization problem where the maximum passband1 magnitude response error is minimized and the microphone positions are optimized while ensuring that the minimum stopband attenuation is above a prescribed level. To maintain robustness, we constrain a sensitivity parameter, namely, the white noise gain, to be above prescribed levels across the frequency band. An additional feature of the method, which is quite useful in certain applications, is that it provides the capability of constraining the gain in the transition band to always lie below the maximum gain in the passband. Performance comparisons with existing methods show that the optimization of the microphone positions results in beamformers with superior performance.

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.

Substrate integrated waveguide dual‐stopband filter

ABSTRACTA dual‐stopband filter in substrate integrated waveguide (SIW) technology is presented. The filter uses a uniform SIW transmission line loaded by three quarter‐wavelength H‐plane stubs spaced by quarter‐wavelength sections. The two stopbands contain three transmission zeros (TZs) each and are located at center frequencies of 10 and 12.2 GHz with corresponding bandwidths of 360 and 500 MHz, respectively. The center frequency and bandwidth of the passband, separating the two stopbands, are 11.03 and 1.26 GHz. A capacitive post is used to improve the return loss of this passband and the location of its reflection zeros (RZs). The filter is prototyped and measured, and good agreement between measured and simulated results is obtained. The measured results confirm the predictions in terms of locations of TZs and RZs as well as passband return loss and stopband attenuation levels. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1561–1563, 2014

Digital Stable IIR Band Pass Filter Design Using Seeker Optimization Technique

This paper presents a novel, control parameter independent evolutionary search technique known as Seeker Optimization Algorithm (SOA) for the design of a eighth order Infinite Impulse Response (IIR) Band Pass (BP) filter. A new fitness function has also been adopted in this paper to improve the stop band attenuation to a great extent. The performance of the SOA based IIR BP filter design has proven to be much superior as compared to those obtained by real coded genetic algorithm (RGA) and standard particle swarm optimization (PSO) in terms of highest sharpness at cut-off, smallest pass band ripple, highest stop band attenuation, smallest stop band ripple and also the fastest convergence speed with assured stability recognized by the pole-zero analysis of the designed optimized IIR filter.

The Design of Gm-C Low-Pass Filter for Micromachined Gyroscope

In this Paper, a 4th-Order Low-Pass Gm-C Filter is Presented. for the Design of Operational Tranconductance Amplifier(OTA), it Adopts the Techniques of Current Division and Current Cancellation. these Techniques can Help to Achieve a Low Transconductance Value. for the Architecture of the 4th-Order Gm-C Filter, it Consists of Two Biquads. the Two Biquads are Cascade Connected. the Gm-C Low-Pass Filter has been Implemented under 0.5 μm CMOS Process Model. the Final Simulation Results Show the Cutoff Frequency of the Filter is 100Hz and the Stop-Band Attenuation is Larger than 60dB. the Power Consumption is Lower than 1mW and the Total Harmonic Distortion(THD) is -55dB.

미앤더 마이크로스트립 전송선을 이용한 고감쇄 LPF 설계 및 제작

본 논문에서는 변형된 DCRLH 구조의 전송선로를 이용하여 저지대역에서 나타나는 고조파 공진 특성을 제거하고, 큰 감쇄 특성을 갖는 마이크로스트립 저역통과 필터를 설계하고 제작하였다. 저역통과 필터는 통과대역 신호를 잘 전달하고 저지대역 감쇄특성을 키우기 위한 병렬 개방스터브 선로와 고조파 통과특성을 제거하기 위한 직렬 단락스터브 선로를 복합적으로 사용하여 구성하였다. 이렇게 구성함으로써 저지대역에서 나타나는 불필요한 고조파신호를 억제시킬 수 있었고, 필터의 대역통과 성능을 개선할 수 있었다. 제작된 저역통과필터는 1.5 GHZ 이내의 통과대역에서 삽입손실 1.26 dB, 정재파비 1.65, 그리고 1.84 GHz에서 2.18 GHz의 저지대역에서 100 dB 감쇄, 20 와트 전력테스트에서 양호 평가를 얻어 모든 면에서 스펙에서 정한 규정 값 이상의 우수한 성능을 가질 수 있었다. 【In this paper, microstrip low pass filter using transmission line with the modified DCRLH structure is designed and fabricated to be removed a spurious resonant mode, and a deep attenuation in stop band. The low pass filter is composed of shunt open-stub to get a deep attenuation and series short-stub to eliminate the spurious harmonics in stop band. In this way, the spurious harmonics occurring on the higher order frequency are suppressed and the filter performance is improved. Insertion loss and VSWR of the fabricated microstrip low pass filter in the passband from DC to 1.5 GHz is 1.26 dB and 1.65, and attenuation on the stopband from 1.84 GHz to 2.18 GHz is less than -100 dB. And also this filter has a good performance for 20 watt power test.】