scispace - formally typeset
Search or ask a question

Showing papers on "Prototype filter published in 2015"


Journal ArticleDOI
TL;DR: Practical guidelines for recognizing common adverse filter effects and filter artifacts are presented and best practices for selecting and reporting of filter parameters, limitations, and alternatives to filtering are discussed.

429 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the results of harmonic assessment and harmonic filter design for a typical high-speed train line in China, and validate the results by detailed simulations based on the train timetable by counting the 95% index of the 24-h profile of harmonic results.
Abstract: In order to make high-speed trains (HSTs) lighter and more reliable, LC or LCL high-pass filters, which are widely adopted to mitigate high-order harmonics, are not installed in most of China HSTs. Therefore, the harmonic problem is a concern, because of the significant adverse impacts it has on the tractive drive system of the train and power quality of the utility system. The harmful harmonic distortions in high-speed railways (HSRs) are mainly caused by harmonic resonance and massive characteristic harmonics emission. This paper presents the results of harmonic assessment and harmonic filter design for a typical HSR line in China. Harmonic penetration analysis (HPA) is implemented and carried out to determine the harmonic distorted types for a wide range of possible train-operating conditions in a timetable. Both statistical field test and numerical calculation are used in passive filter design for HSRs. A C-type filter is designed here to address these typical harmonic distortions. The studies will be validated by detailed simulations based on the train timetable by counting the 95% index of the 24-h profile of harmonic results.

110 citations


Journal ArticleDOI
TL;DR: In this paper, a 5-band waveguide bandpass filter based on spherical resonators has been designed, and fabricated by 3-D printing, and a special topology has been proposed to relieve the impact of the first three higher order modes in the resonator and ultimately to achieve a good out-of-band rejection.
Abstract: A fifth order X-band waveguide bandpass filter, based on spherical resonators, has been designed, and fabricated by 3-D printing. In comparison with rectangular waveguide, spherical resonators have a higher unloaded quality factor, but at the same time suffer from closer higher order modes. In this letter, a special topology has been proposed to relieve the impact of the first three higher order modes in the resonator and ultimately to achieve a good out-of-band rejection. Stereolithography based 3-D printing is used to build the filter structure from polymer and a 25 $\mu{\rm m}$ thick copper layer is deposited to the filter. The measurement result of the filter has an excellent agreement with the simulations. The filter is also considerably lighter than a similar metal filter.

109 citations


Journal ArticleDOI
Fei Li1, Xing Zhang1, Zhu Hong1, Haoyuan Li1, Changzhou Yu1 
TL;DR: In this paper, a new kind of high-order filter, named LCL - LC filter, is presented, and a parameter design method on the base of the resonant frequency characteristics of the filter is also proposed.
Abstract: In order to further cut down the cost of filter for grid-connected pulsewidth modulation (PWM) converter under the more and more stringent grid code, a new kind of high-order filter, named LCL - LC filter, is presented in this paper. The resonant frequency characteristics of the filter are analyzed, and a parameter design method on the base of the characteristics is also proposed in the paper. The proposed parameter design method can easily make full use of the existing research results about the traditional LCL filter parameter design. And then a parameter robustness analysis method based on four-dimensional graphics is proposed to analyze parameter robustness of the presented filter. Compared with the traditional one, the proposed analysis method can analyze the filter performance under variations of several parameters at a time without any iteration. The comparative analysis and discussion considering the LCL filter, the trap filter, and the LCL - LC filter, are presented and verified through the experiments on a 5 kW grid-connected converter prototype. Experiment results demonstrate the accuracy of theoretical analysis and prove that the presented filter has a better performance than two others.

89 citations


Journal ArticleDOI
Abstract: An original and simple approach to the design of fully reconfigurable multi-band microwave bandpass filters (BPFs) with an arbitrary number of passbands is reported in this paper. It exploits the use of an innovative quasi-BPF configuration made up of different sets of controllable mono-frequency resonators to separately shape each tunable passband. Thus, high-selectivity multi-band bandpass filtering transfer functions exhibiting independent control in terms of center frequency, bandwidth, and transmission zeros can be synthesized. Furthermore, as an unprecedented frequency-agility feature of the proposed reconfigurable multi-band BPF structure when compared to the state-of-the-art, its passbands can be merged together to form broader, and for certain realizations, higher order transmission bands. This allows even more degrees of reconfiguration to be achieved in the devised circuit, which can also operate as ultra-wideband BPF with flexible in-band notches or self-equalized flat-group-delay quasi-elliptic-type BPF. The theoretical foundations of the described reconfigurable multi-band BPF scheme, along with guidelines for its design and a triple-passband filter synthesis example based on the coupled-node formalism, are expounded. In addition, as an experimental proof-of-concept, two microstrip prototypes with high- $Q$ tuning implemented through mechanically variable capacitors are manufactured and tested. They are a wideband dual-band BPF and a quadruple-band BPF with narrow-bandwidth passbands.

89 citations


Journal ArticleDOI
TL;DR: In this paper, the authors review the techniques for implementing both incoherent and coherent tunable and reconfigurable microwave photonic filters, which can be implemented either in an incoherent operational regime or in a coherent operational regime.
Abstract: Extensively researched in recent years, microwave photonic filters can be implemented either in an incoherent operational regime or in a coherent operational regime. In the incoherent regime, a delay-line configuration is usually used with a finite-impulse response (FIR) or infinite-impulse response (IIR); to avoid optical interference, an incoherence light source or a laser array is used. Filter tuning and reconfiguration are achieved by changing the time delay and the tap coefficients. In the coherent regime, however, a single wavelength is needed, and the filter?s spectral response is translated directly from the spectral response of an optical filter. Thus, a coherent microwave filter requires a well-defined optical filter with a precisely controlled spectral response. This article reviews the techniques for implementing both incoherent and coherent tunable and reconfigurable microwave photonic filters.

88 citations


Journal ArticleDOI
TL;DR: In this article, the left and right-hand-side stopband terminations are coupled to each other using a two-port sub-network, which increases the stopband attenuation per filter cell and steepens the cutoff response without disrupting the reflectionless property or increasing the insertion loss in the passband.
Abstract: This paper expands on the previously described reflectionless filters—i.e., filters having, in principle, identically zero reflection coefficient at all frequencies—by introducing a wide variety of new reflectionless structures that were not part of the original publication. In addition to extending the lumped-element derivation to include transmission line filters, this is achieved by the introduction of a novel method wherein the left- and right-hand-side stopband terminations are coupled to each other using a two-port sub-network. Specific examples of the sub-network are given, which increase the stopband attenuation per filter cell and steepen the cutoff response without disrupting the reflectionless property or increasing the insertion loss in the passband. It is noteworthy that a common feature of all the structures derived by these methods is that most, if not all, of the reactive elements are of equal normalized value. This greatly simplifies the tuning requirements, and has facilitated their implementation as monolithic microwave integrated circuits (MMICs). A number of examples of MMIC reflectionless filters constructed in this way are presented and their results compared to the theory.

83 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a new filter based on substrate integrated folded waveguide (SIFW) technology, which exhibits compact size and good out-of-band rejection.
Abstract: This letter presents a new filter, based on substrate integrated folded waveguide (SIFW) technology, which exhibits compact size and good out-of-band rejection. The filter is based on a SIFW cavity, which guarantees size reduction, and the out-of-band rejection is controlled by the suppression and tuning of the high-order cavity modes. A detailed investigation of the cavity mode spectrum is presented, to illustrate the operation principle and the design of the filter. The interesting feature of this filter is the possibility to design the pass band and the return band by simply tuning the mode spectrum of the cavity, which is practically unaffected by the connection to the excitation ports. The fabrication and testing of a prototype operating at 4.5 GHz validate the proposed filter topology.

65 citations


Journal ArticleDOI
TL;DR: In this article, a tri-band bandpass filter with a wide stopband using asymmetric stub-loaded resonators (ASLR) is presented, where the harmonic responses are suppressed effectively by forming an uncoupled section at the end of the ASLRs, and the stopband region is formed from 3.7 to 7 GHz.
Abstract: This letter presents a tri-band bandpass filter (BPF) with a wide stopband using asymmetric stub-loaded resonators (ASLR). A tri-band filter sample was fabricated by using two ASLRs with coupled I/O ports. By properly tuning the electrical length ratios of the ASLRs ( $\alpha$ and $\gamma$ ), three passbands can be designed at 1.4, 2.4, and 3.5 GHz. The harmonic responses are suppressed effectively by forming an uncoupled section at the end of the ASLRs, and the stopband region is formed from 3.7 to 7 GHz with a rejection level of 30 dB. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

58 citations


Journal ArticleDOI
TL;DR: In this paper, two types of modified open-or short-circuited stub-loaded $\lambda/4$ resonators and their applications to second-order dual-band bandpass filters are presented.
Abstract: Two types of modified open- or short-circuited stub-loaded $\lambda/4$ resonator and their applications to second- order dual-band bandpass filters are presented in this letter Based on the resonance characteristics analysis, it is found that the first two resonant frequencies of the two resonators can be independently controlled Furthermore, different frequency ratios can be achieved by loading different stubs Finally, to illustrate the proposed idea, two second-order dual-band filters with controllable bandwidths are designed, fabricated and measured The measured results are in good agreement with the full-wave simulation results

58 citations


Journal ArticleDOI
TL;DR: A hardware efficient finite impulse response (FIR) filter design using differential evolution (DE) and common sub expression (CSE) elimination algorithm and compared the performances with recently best published works in terms of area, delay, power and power-delay-product.
Abstract: In this paper, we present a hardware efficient finite impulse response (FIR) filter design using differential evolution (DE) and common sub expression (CSE) elimination algorithm. With the DE algorithm, we first found a set of filter coefficients with reduced number of signed-power-of-two (SPT) terms without compromising on quality of the filter response. After obtaining coefficients, we applied CSE elimination algorithm, and determined the hardware cost in terms of adders. The filters were designed using DE for various word lengths, and the same were implemented in transposed direct form (TDF) structure. The implemented filters were synthesized in Cadence RTL compiler using UMC 90 nm technology. We compared the performances of our filters with recently best published works in terms of area, delay, power and power-delay-product ( PDP ). One of the proposed filters found to improve a PDP gain of 29% compared to Remez algorithm. The proposed approach showed improvements in filter design for the given specifications.

Journal ArticleDOI
TL;DR: In this article, a bandstop-to-band-pass microwave photonic filter using a phase-shifted fiber Bragg grating (PS-FBG) and a dual-drive Mach-Zehnder modulator (DD-MZM) is proposed and experimentally demonstrated.
Abstract: A bandstop-to-bandpass microwave photonic filter (MPF) using a phase-shifted fiber Bragg grating (PS-FBG) and a dual-drive Mach–Zehnder modulator (DD-MZM) is proposed and experimentally demonstrated. The PS-FBG has an ultra-narrow notch in the reflection band. The DD-MZM is employed to generate a phase-modulated or a quasi-single-sideband (QSSB) optical signal by controlling the bias voltage. By applying the phase-modulated or QSSB signal to the PS-FBG to suppress one sideband, a bandpass or a bandstop MPF is implemented. The MPF can be continuously tuned from bandstop to bandpass or vice versa by controlling the bias voltage applied to the DD-MZM. The frequency tuning can be simply done by tuning the wavelength of the optical carrier. The proposed MPF is experimentally evaluated. Continuous tuning from a bandstop to bandpass filter with a bandstop rejection as high as 60 dB and frequency tuning with a frequency tunable range as large as 10 GHz are demonstrated.

Proceedings ArticleDOI
29 Oct 2015
TL;DR: In this paper, the authors presented a modeling technique for a hybrid commonmode (CM) filter, which is composed of an active filter and a passive filter to reduce the size and weight of conventional passive EMI filters.
Abstract: Hybrid electromagnetic interference (EMI) filters (HEFs) which are composed of an active filter and a passive filter, have been proposed to reduce the size and weight of conventional passive EMI filters. However, accurate models that can be used to predict the stability and performance of HEFs have not been developed. To cope with this, this paper presents a modeling technique for a hybrid common-mode (CM) filter. The technique can be applied to the modeling of other HEFs. Critical component models were first developed for the HEF. HEF's overall model is further developed based on these individual component models. Experimental results validated that the developed model can successfully predict the stability and performance of the hybrid CM filter.

Journal ArticleDOI
TL;DR: In this article, a novel quad-band bandpass filter (BPF) using short stub loaded E-Type resonators is proposed, and two sets of resonators are utilized and respectively designed to realize Filter 1, operating at 2.4 and 3.5 GHz, and Filter 2 with two very closely spaced passbands, Operating at 5.2 and 5.8 GHz.
Abstract: In this letter, a novel quad-band bandpass filter (BPF) using short stub loaded E-Type resonators is proposed. Two sets of resonators are utilized and respectively designed to realize Filter 1, operating at 2.4 and 3.5 GHz, and Filter 2 with two very closely spaced passbands, operating at 5.2 and 5.8 GHz. Then the two dual-band BPFs are combined by common feed lines with interdigital capacitance structure for quad-band responses, and two more transmission zeros (TZs) are achieved by strengthening the source-load coupling. The measured result of the fabricated filter agrees well with the simulation, which shows that the proposed structure is a good candidate for quad-band BPF designs and validates the proposed design flow well.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a balanced microstrip wideband bandpass filters by means of aggressive space mapping (ASM) optimization, based on multisection mirrored stepped impedance resonators coupled through quarter-wavelength transmission lines acting as admittance inverters.
Abstract: The automated and unattended design of balanced microstrip wideband bandpass filters by means of aggressive space mapping (ASM) optimization is reported in this paper. The proposed filters are based on multisection mirrored stepped impedance resonators (SIRs) coupled through quarter-wavelength transmission lines, acting as admittance inverters. Such resonant elements provide transmission zeros useful for the suppression of the common mode in the region of interest (differential filter pass band) and for the improvement of the differential-mode stopband (rejection level and selectivity). Due to the limited functionality of the inverters, related to the wide fractional bandwidths, the automated filter design requires a two-step process. With the first ASM, the filter schematic satisfying the required specifications (optimum filter schematic) is determined. Then, the layout is synthesized by means of a second ASM algorithm. Both algorithms are explained in detail and are applied to the synthesis of two filters, as illustrative (and representative) examples. With this paper, it is demonstrated that the two-step ASM optimization scheme (first providing the optimum schematic and then the layout), previously applied by the authors to wideband single-ended filters, can be extended (conveniently modified) to common-mode suppressed differential-mode bandpass filters. Thus, the value of this two-step ASM approach is enhanced by demonstrating its potential for the unattended design of complex filters, as those considered in this paper.

Journal ArticleDOI
TL;DR: In this paper, stepped-impedance resonators are used in a coaxial cavity filter to generate dual-band response, and two key merits of the proposed filter are the helical feeding structure and the introduction of mixed coupling for coupling control and generation of transmission zero.
Abstract: In this letter, stepped-impedance resonators are used in coaxial cavity filter to generate dual-band response. Two key merits of the proposed filter are the helical feeding structure and the introduction of mixed coupling for coupling control and generation of transmission zero. The helical feeding structure makes it possible to conveniently control the external quality factors of two bands. To illustrate the concept, a third-order dual-band coaxial cavity filter is designed, fabricated and measured. The measured results are in good agreement with the full-wave simulation results.

Proceedings ArticleDOI
17 May 2015
TL;DR: In this paper, a methodology for designing all-passive higher-order N-path filters is described, and a tunable, nominally 6th-order, high-Q Npath bandpass filter based on this methodology has been implemented in 65nm CMOS.
Abstract: In this paper, a methodology for designing all-passive higher-order N-path filters is described. The methodology extends known filter synthesis techniques for LC filters to N-path filters through the use of lumped quarter-wave transmission-line (t-line) equivalents that enable series-LC-like N-path structures. The quarter-wave t-line equivalents also isolate N-path filters from each other, allowing N-path sections to be cascaded to realize filters of arbitrary order. A tunable, nominally 6th-order, high-Q N-path bandpass filter based on this methodology has been implemented in 65nm CMOS. The filter has an insertion loss of 4.7–6.2dB, a tuning range of about 35% from 600MHz to 850MHz, and bandwidth that ranges from 9–15MHz, resulting in a Q that ranges from 40–90. The filter achieves an out-of-band (OOB) rejection of 30–50 dB, input-referred in-band (IB) and OOB 1dB compression point of 0dBm and +14dBm, and input-referred IB and OOB IIP3 of +7 and +17.5dBm respectively. The clock path DC power consumption at 700MHz is 75mW from a 1.2V supply.

Journal ArticleDOI
TL;DR: In this paper, a lowpass filter using a hexangular shaped resonator is presented, which has a −3 dB cutoff frequency of 2.97 GHz and the insertion loss in the passband is <0.06 dB.
Abstract: A compact lowpass filter using a hexangular shaped resonator is presented. The designed lowpass filter has a −3 dB cutoff frequency of 2.97 GHz. The stopband bandwidth for the attenuation level of −20 dB is from 3.32 GHz up to 21 GHz, and the circuit only occupies 10.04 × 10.92 mm2. The structure is simulated, fabricated and measured. Both simulation and measured results are presented and compared and there is good agreement between them. The insertion loss in the passband is <0.06 dB and the fabricated filter presents a sharp transition band from 2.97 to 3.32 GHz for the attenuation level of −3 and −20 dB, respectively.

Journal ArticleDOI
TL;DR: In this paper, a compact bandpass filter (BPF) with dual band-notch function for ultra wideband (UWB) applications is presented and discussed, where defected ground structure is used in order to improve the out-of-band performance of the filter.
Abstract: The procedure of attaining a compact bandpass filter (BPF) with dual band-notch function for ultra-wideband (UWB) applications is presented and discussed. In the proposed BPF, defected ground structure is used in order to improve the out-of-band performance of the filter. Also, four short-circuited bent stubs are employed in order to improve the selectivity of the filter at its cutoff frequencies. Dual band-notch function is added to the performance of the filter by coupling two short-circuited inverted T-shaped stubs to the filter main resonator. The fabricated filter satisfies well the demands of the Federal Communications Committee with two narrow band-notch functions at 5.5 and 8 GHz, which eliminates the interference of the UWB system with wireless local area network (WLAN) and satellite communication systems, respectively. The improved upper stop-band of the proposed filter with more than 20 dB attenuation level extends up to 20 GHz.

Journal ArticleDOI
TL;DR: In this article, the authors proposed an efficient and simple designs of non-uniform filter banks for digital hearing aid applications, which can be used to tune hearing aids individually to satisfy the requirements of hearing impaired persons.
Abstract: In this paper, efficient and simple designs of non-uniform filter banks for digital hearing aid applications are proposed. Hearing aids should be individually tuned to satisfy the requirements of hearing impaired persons. Cosine modulated filter banks are one popular filter bank having simple design procedure with efficient implementation structure. In the proposed structure for hearing aid, non-uniform subbands are obtained using two methods. The first method is by merging the adjacent channels of a uniform filter bank and the second method, is by using transition filters between two filters with different bandwidths. The advantages of the proposed structure are simple design procedure, less implementation complexity, greater flexibility in tuning the subbands for various types of audiograms and improved performance in terms of matching error.

Journal ArticleDOI
TL;DR: It is shown how to de-normalize the synthesized low-pass prototype by means of the generalized coupling coefficients, which allow to extend the usual de- normalization procedure also to networks with NRNs.
Abstract: In this paper, we present an approach to the synthesis of canonical cross-coupled prototype filters including resonant and non-resonant nodes (NRNs). The family of realizable topologies (including the folded and wheel configurations) is obtained through a recursive extraction technique and is characterized by all the couplings between adjacent nodes plus a number of cross-couplings between non-adjacent nodes (either resonant or non-resonant). The total number of distinct topologies that can be realized is ${\hbox{2}}^{({\rm np}-2)}$ with ${\rm np}$ order of the filter (i.e., number of poles). Some examples of synthesis are reported for illustrating the capabilities of the new proposed procedure. It is also shown how to de-normalize the synthesized low-pass prototype by means of the generalized coupling coefficients, which allow to extend the usual de-normalization procedure also to networks with NRNs.

Journal ArticleDOI
TL;DR: In this paper, a new type of absorptive bandstop filter (ABSF) design was proposed for absorbing the localoscillator-to-RF leakage of mixer in a heterodyne receiver.
Abstract: This paper presents a new type of absorptive bandstop filter (ABSF) design that is targeted for absorbing the local-oscillator-to-RF leakage of mixer in a heterodyne receiver The proposed ABSF is designed to absorb the input power at its Port 1, and it is achieved by introducing one lossy resonator to a conventional narrowband coupled-line bandstop filter Suitable equivalent circuit models and closed-form design equations are established to enable the direct synthesis of proposed ABSFs Specifically, a proposed microstrip ABSF with a stopband center frequency $f_{0}$ of 2 GHz is demonstrated The maximal stopband rejection is 348 dB with an input return loss of 277 dB, which implies that 998% of the input power is dissipated by the proposed ABSF

Journal ArticleDOI
TL;DR: The work shows that a wideband tunable diplexer can be realized using tunable bandpass filters and reconfigurable matching networks, and shows virtually no difference in the frequency response between a standalone filter and a filter placed in the tunablediplexers.
Abstract: An idea for implementing reconfigurable matching networks to realize a tunable diplexer is investigated and demonstrated. The reconfigurable matching networks ensure that the rejection band impedance of every filter is transformed to an open circuit over a wide range of frequencies, allowing two tunable filters to be connected together to form a tunable diplexer without affecting each other. The tunable diplexer is built using Schottky diodes and combline resonators on Duroid substrates, and can operate from 1.4 to 2.3 GHz with a closest frequency separation of 110 MHz. Measurements show virtually no difference in the frequency response between a standalone filter and a filter placed in the tunable diplexer. The work shows that a wideband tunable diplexer can therefore be realized using tunable bandpass filters and reconfigurable matching networks.

Journal ArticleDOI
TL;DR: In this paper, a low-pass-band-pass triplexer consisting of one lowpass channel and two bandpass channels is proposed, and the cut-off frequency of the LPF is chosen to be 1 GHz and the central passband frequencies are selected to be 2.4 and 5.8 GHz.
Abstract: This letter proposes a lowpass-bandpass triplexer consisting of one lowpass channel and two bandpass channels. Stepped-impedance stubs are used in the lowpass filter (LPF) design, which bring a sharp selectivity. Defected ground structures are utilized to increase the impedance of one transmission line in the lowpass section, giving improved performance. High Isolation is achieved by careful consideration of the input signal splitting structure. To illustrate the concepts, a lowpass-bandpass triplexer is designed, fabricated and measured. The cut-off frequency of the LPF is chosen to be 1 GHz. The central passband frequencies are selected to be 2.4 and 5.8 GHz. Simulated and measured results are found to be in good agreement with each other. Isolations among the three bands are better than 40 dB.

Journal ArticleDOI
01 Nov 2015
TL;DR: When the different design approaches for the design of the prototype filter in CMFB are compared, it is observed that the one using frequency response masking and meta-heuristic optimization techniques gives better performance in terms of implementation complexity, which in turn can lead to reduced chip size and power consumption.
Abstract: Cosine Modulated Filter Banks (CMFB) are very popular among the different maximally decimated filter banks due to their design ease and simplicity in implementation and the property that all the coefficients of all the filters are real. All the analysis and synthesis filters are derived from one or two prototype filters. Hence, recently, the design of the prototype filter in a CMFB has become a subject of interest in the field of multirate signal processing. Perfect Reconstruction (PR) filter banks are those which can produce at the output, a weighted delayed version of the input. But in most of the applications a near perfect reconstruction (NPR) is sufficient. This can reduce the computational complexity. Different approaches developed for the efficient and optimal design of the prototype filter in a NPR orthogonal CMFB are studied, classified and summarized in this paper. In today's applications, less space and low power consumption are very essential. When the different design approaches for the design of the prototype filter in CMFB are compared, it is observed that the one using frequency response masking(FRM) and meta-heuristic optimization techniques gives better performance in terms of implementation complexity, which in turn can lead to reduced chip size and power consumption. It is hoped that this review will be highly beneficial to the researchers working in the area of multirate signal processing. At the end, we also propose some novel design approaches for the design of low complexity prototype filter using FRM technique.

Proceedings ArticleDOI
28 Dec 2015
TL;DR: It is shown that Ramanujan filter banks have some important mathematical properties which allow them to reveal localized hidden periodicities in real-time data and these are compared with traditional comb filters which are sometimes used to identify periodicities.
Abstract: This paper studies a class of filter banks called the Ramanujan filter banks which are based on Ramanujan-sums. It is shown that these filter banks have some important mathematical properties which allow them to reveal localized hidden periodicities in real-time data. These are also compared with traditional comb filters which are sometimes used to identify periodicities. It is shown that non-adaptive comb filters cannot in general reveal periodic components in signals unless they are restricted to be Ramanujan filters. The paper also shows how Ramanujan filter banks can be used to generate time-period plane plots which track the presence of time varying, localized, periodic components.

Journal ArticleDOI
TL;DR: In this paper, the step-impedance lowpass filter is modified by replacing the low-IMpedance lines with low-pass transmission lines, which is called a multi-stub lowpass filtering.
Abstract: The stepped-impedance lowpass filter is modified by replacing the low-impedance lines with lowpass transmission lines The modified stepped-impedance lowpass filter is called a multi-stub lowpass filter because it is largely composed of open-circuited stubs For experimental verification of the multi-stub filters, we design a 1 GHz seventh-order Butterworth LPF The proof-of-concept prototype is a compact design that fits into a circuit size of $009\lambda_{g}\times 0136\lambda_{g}$ on an RO4003 substrate The measurement results show that the multi-stub lowpass filter retains the characteristics of a Butterworth filter in the passband, while substantially improves the performance in the transition and stopband regions It achieves state-of-the-art performance compared to lowpass filters in the literature

Journal ArticleDOI
TL;DR: In this article, a quasi-elliptic response bandpass filter (BPF) with 3 dB fractional bandwidth of 39.8% for 2.4 GHz WLAN application is presented.
Abstract: This letter presents a novel quasi-elliptic response bandpass filter (BPF) with 3 dB fractional bandwidth of 39.8% for 2.4 GHz WLAN application. Four resonant modes from two stepped-impedance stub loaded shorted stepped-impedance resonators (SISLSSIRs) and one dual-mode shorted stub loaded stepped-impedance resonator (SSLSIR) can constitute an asynchronously tuned coupled-resonator circuit which support a wideband performance. Four transmission zeros (TZs), i.e., one TZ due to the mixed electric and magnetic coupling, one TZ due to the harmonic effects, and another two TZs owing to the cross-couplings, are realized on both sides of the passband, resulting in its quasi-elliptic response performance. The radial stubs and high-impedance open stubs are loaded at the middle position of SISLSSIRs to improve the in-band return loss of BPF. The fabricated filter has a compact size of $0.22\lambda_{\bf g}\times 0.22\lambda_{\bf g}$ and wide upper stopband from 2.62 to 7.69 GHz. Good agreement is shown between the simulated and measured results.

Journal ArticleDOI
TL;DR: It is shown, by means of examples, that the proposed filter bank can meet different needs of hearing loss cases with acceptable delay, and has extremely low complexity.
Abstract: The emerging demand for personalized hearing aids requires the filter bank of a hearing aid system to be capable of decomposing the sound waves in accordance with the characteristic of the patient’s hearing loss. In this paper, an efficient adjustable filter bank is proposed to achieve this goal. By careful design, the number of the subbands as well as the location of the subbands can be easily adjusted by changing a 4-bit control signal. The proposed filter bank has extremely low complexity due to the adoption of fractional interpolation and the technique of symmetric and complementary filters. Only one prototype filter is needed for each of the stages, the multiple passbands generation stage and masking stage. We show, by means of examples, that the proposed filter bank can meet different needs of hearing loss cases with acceptable delay.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a novel approach for the implementation of balanced ultra-wideband (UWB) bandpass filters with common-mode noise suppression, where the series branches of the balanced filter are implemented by means of inductive strips and patch capacitors, whereas the shunt sections are realized through mirrored stepped-impedance resonators (SIRs) and short transmission-line sections.
Abstract: This paper presents a novel approach for the implementation of balanced ultra-wideband (UWB) bandpass filters with common-mode noise suppression. To a first-order approximation, the differential-mode filter response is described by the canonical circuit model of a bandpass filter, i.e., a cascade of series-connected resonators alternating with shunt-connected parallel resonant tanks. Thus, the series branches of the balanced filter are implemented by means of inductive strips and patch capacitors, whereas the shunt sections are realized through mirrored stepped-impedance resonators (SIRs) and low-impedance (i.e., capacitive) short transmission-line sections. For the differential mode, the symmetry plane is a virtual ground, the wide strip sections of the SIRs are effectively grounded, and the SIRs behave as grounded inductors parallel connected to capacitors. However, for the common mode, where the symmetry plane is an open (magnetic wall), the SIRs act as shunt-connected series resonators, thus providing transmission zeros at their resonance frequencies. By properly tailoring the location of these transmission zeros, rejection of the common mode over the differential filter passband can be achieved. To illustrate the potential of the approach, an order-5 balanced bandpass filter covering the regulated band for UWB communications (3.1–10.6 GHz) is designed and fabricated. The filter exhibits common-mode rejection above 10 dB over the whole differential filter passband, with differential-mode insertion losses lower than 1.9 dB and return losses better than 10 dB. Since the proposed design approach is based on planar semi-lumped components, filter size is as small as 10.5 mm $\,\times\, $ 7.6 mm.