Suppression Of Spurious Responses Research Articles

Suppression of spurious responses near anti-resonance of TC-SAW resonators by selective thinning of SiO2

This paper discusses the generation mechanism and suppression of spurious resonances near the anti-resonance in temperature compensated surface acoustic wave devices using the SiO2/128°YX-LiNbO3 structure. Detailed field analysis is performed for the spurious resonances, and the result indicates that the spurious modes are caused by excitation and/or scattering near the electrode finger edges, and can be suppressed well by thinning of the SiO2 layer selectively in the gap region. It is also shown that most of spurious responses can be suppressed for the piston design using the Cu dots with the SiO2 selective thinning. In contrast, this selective SiO2 thinning does not work well for the piston design using the Cu stripes.

Spurious response suppression in wideband bandpass filters using chirality

A simple chiral medium is used to enhance the response of a conventional microstrip coupled line bandpass filter (BPF). The approach is applicable to both narrowband and wideband BPFs using the presented chiral topology. The topology is based on an ultra-subwavelength planar chiral particle that is utilized in the interface between two slabs of substrate. More specifically the medium realizes the suppression of the second spurious response of the filter at a large bandwidth, which enables its practical application in wideband coupled-line based BPFs. The effect of the chiral particles on the substrate's effective permittivity and on the phase velocities of the even and odd mode of two coupled transmission lines on top of the substrate structure is explicitly used in the design of the filter. The methodology is applicable to any coupled-line BPF order. Two wideband microstrip coupled-line prototype filters are designed, fabricated, and measured, one involving a substrate without particles and one involving the chiral substrate. Measurement results are in good agreement with the simulations. The chiral medium based filter results in a wide fractional bandwidth (FBW) of 81% for a 1 GHz center frequency and a measured suppression level of −60 dB.

An improved simplified composite right‐/left‐handed zeroth‐order resonator and its application to design a compact microstrip bandpass filter with enhanced upper stopband

AbstractAn improved simplified composite right‐/left‐handed (SCRLH) zeroth‐order resonator (ISZOR) is introduced, comprising two lateral parallel capacitors and a centred T‐type inductor circuit. Starting from the lumped circuit of the ISZOR, its miniature microstrip layout can be generated with on more than three times full‐wave simulations by virtue of the implicit space mapping technique. Multi‐solutions of the microstrip ISZOR with identical fundamental mode are obtained by sweeping key physical and electrical parameters, uncovering the relationship among physical sizes, resonant modes, unloaded quality factors and circuit elements. A three‐pole microstrip Chebyshev bandpass filter (BPF) with ultra‐wide upper stopband is further designed. By choosing the constituent ISZORs with identical base frequency but different higher resonant frequencies and applying the over‐coupled I/O terminals, wideband spurious response suppression in the upper stopband is achieved. The target BPF centers at 3.1 GHz with a relatively bandwidth of 5%, which is optimised through a customised aggressive space mapping iterative process. The optimal BPF layout dimensions are automatically obtained with just a few time‐consuming full‐wave simulations. A prototype measurement shows the BPF features good bandpass selectivity in a simple and easy‐to‐fabricate structure, with a transversal size reduction of more than 65% compared to a former counterpart and a rejection level better than 15 dB over 40.0 GHz.

Suppression of spurious harmonic responses in superconducting microstrip spiral filters using gold overlay and stagger tuning

The higher order resonances of microwave superconducting filters with spiral resonators were suppressed, giving a very wide stop-band. In one filter spirals were modified to have equal fundamental resonances, but different higher order resonances, by adding stubs and using non-uniform line width. The higher resonances were reduced to −39 dB, in a stop band up to 4.3 times the pass band centre. In another filter, parasitic resistive resonators were added, suppressing the responses to −57 dB. The resistance is provided by patterning the 200 nm gold overlay already required for the external contacts. The increase in pass band loss is not measurable. Measurements of a single spiral resonator with a gold-YBCO bi-layer (200 and 600 nm respectively) suggest that the resistivity of the gold layer at 15 K is the order of 22 times that of bulk gold, a slight advantage for the present application. At 100 K, it is about double.

Mixed Lumped and Distributed Circuits in Wideband Bandpass Filter Application for Spurious-Response Suppression

Mixed lumped and distributed circuits (MCs) have been analyzed and applied in a wideband bandpass filter (BPF) synthesis procedure for spurious-response suppression. First, an MC is proposed and compared with the conventional commensurate line. With the even–odd mode analysis, the MC is decomposed into an inverter and the shunt stubs on the two sides, which finds its lowpass equivalent circuit. Then, constant and frequency mapping functions, simply formed by two basis functions, are derived to link the MC and its lowpass equivalent circuit. With this technique, the lowpass prototype filter can be mapped to its BPF counterpart. Finally, the BPF design variables are obtained by comparing the input admittances of the even/odd mode in the MC or the shunt stubs to the basis functions. A fifth-order ladder type BPF has been implemented following the proposed procedure. The experimental results accurately predict both wide passband and spurious-response rejection band.

Dielectric Constant Measurement of Low Loss Materials Using NB BPF with Modified Slow Wave Resonator

Compact wide-stopband narrow bandpass filter using modified slow wave resonators is proposed. The basic filter consists of an open-stub, transmission line and coupled line. Using transmission line theory and coupled line structure, the new design methodology of a narrowband BPF is employed and resonant frequency has been clearly explained. Experimental results show that the designed filter has a fractional-bandwidth of 2 %, an insertion loss about 0.38 dB and return loss better than 30 dB. Spurious response suppression is achieved until 5f0. The overall physical size of this filter is only 23.9 mm × 10.2 mm or 0.41 źg × 0.175 źg, having a smaller size compared with conventional narrowband pass filters. The bandwidth of this filter has capability of changing with the coupled lines used in the middle of the proposed filter structure, having tunable resonance frequencies. Due to the narrow bandpass property, the proposed filter is used as a sensor to measure the dielectric constant of materials. The resonant characteristics of resonator vary with dielectric constant of the material. The proposed filter is designed, simulated and fabricated. The measured and simulated results are well complied with each other.

A simple method for improving the stopband response for unequal‐length microstrip coupled‐line filters with stubs

ABSTRACTThis work demonstrates a simple method for improving the stopband response of microstrip coupled‐line bandpass filters in an extremely wide bandwidth. Substantial enhancement in the stopband response is achieved by constituting a filter with reduced‐length coupled lines of unequal length, which are loaded with open stubs. The lengths of these stubs are optimized to compensate for the reduction the reduction in the lengths of the coupled lines, and at the same time, to provide transmission zeros for further suppression of spurious responses. A rigorous mathematical analysis demonstrates a systematic method is verified experimentally with the experimental results obtained with third‐order Chebyshevy‐type bandpass filters that maintain the transmission level below −30 dB up to 17.8f0, where f0 is the center frequency. Even further enhancement can be achieved simply by increasing the filter order. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2477–2481, 2016

Suppression of spurious responses in microstrip half‐wavelength filters combining stagger tuning and resistive attenuation

ABSTRACTStagger tuning and resistive attenuation are combined to attenuate harmonic responses of microstrip filters with half‐wavelength resonators, extending the technique previously used for quarter‐wave resonators. In a measured filter with 0.93 GHz center frequency and 22% bandwidth, the worst spurious peak between 1.3 and 2.7 GHz is about 10 dB better than with stagger tuning alone, while the next two peaks at 2.75 and 3 GHz are suppressed by a further 5 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1955–1957, 2016

이중 급전 구조를 갖는 마이크로스트립 이중 모드 대역통과 필터

In this paper, a microstrip dual mode band pass filter with doubly fed line is proposed. The proposed filter consists of a corner truncated patch with right crossed slots and doubly fed lines. In general, the resonator with the right crossed slots simultaneously has size reduction and spurious response suppression. In order to improve the rejection performance in out of its higher stop band, the dual mode resonator is excited by using doubly fed line. Details of the filter characteristics are described, and both simulated and measured results of the designed filter are presented.

Wideband suppression of spurious response for microstrip filters based on coupled lines of incommensurate lengths

This work demonstrates design methods that can achieve remarkable enhancement in the stopband response of microstrip coupled-line filters. The frequencies of resonance and/or the transmission zeros of a coupled-line section can be controlled by its length. Therefore, by constructing a filter with coupled lines of incommensurate lengths such that these frequencies do not overlap, substantial improvement in the stopband response can be obtained. Besides its compact structure and simple design procedure, an unprecedented performance is demonstrated experimentally in which the transmission level is maintained below −20 dB up to as high as 11.9 f0 for a third-order filter, where f0 is the center frequency.

COMPACT INTERDIGITAL CAPACITOR COUPLED DUAL-BEHAVIOR RESONATOR (ICDBR) FILTER WITH SUPPRESSION OF SPURIOUS RESPONSES

A compact interdigital capacitor coupled dual-behavior resonator (DBR) fllter with high spurious responses suppression is proposed in this paper. The technique is based on two equivalent topologies of J-inverter and dual-line equivalent circuit of open- circuited stubs. The flrst compact equivalent topology capacitive inverter is a high pass structure, and consequently, the spurious responses can be suppressed efiectively at low frequencies. The second equivalent topology …-network is employed in realizing a compact size and adding new transmission zeros dedicated to the spurious responses suppression at high frequencies. Further compactness is achieved with a dual-line equivalent circuit of open-circuited stubs. The relevant equations are given in the paper. Finally, a 3rd-order compact DBR fllter is designed and measured. This structure has a high degree of miniaturization (83%) in comparison to the classical one. Measurement results show good agreement with the simulated ones.

Spurious Suppression without Energy Dissipation in Aluminum–Nitride-Based Thin-Film Bulk Acoustic Resonator Using Thin Ring on Electrode Edge

We examined the suppression of spurious responses beneath the resonant frequency in an aluminum-nitride-based thin-film bulk acoustic resonator (FBAR) by a two-dimensional (2D) finite element method (FEM) and dispersion analysis of waves. The results confirmed that the 0th-order asymmetric mode (A0 mode) influences the resonance characteristics. As a result of these findings, we propose a structure having a thin ring on the electrode edge to take advantage of this A0 mode in suppressing spurious responses.

Periodic substrate structure suppresses spurious response in coupled line filters

Periodic perturbation of the dielectric medium following Bragg's law and equalizing mode velocities together suppress the first spurious response in coupled-line filters. The design parameters are calculated using the classical coupled-line filter design. Fabricating a Chebyshev filter; for the bisected unit cell, spurious response suppression of 35 dB is achieved. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2175–2178, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26999

Stepped-Impedance Coupled Resonators for Implementation of Parallel Coupled Microstrip Filters With Spurious Band Suppression

A parallel-coupled microstrip bandpass filter based on the stepped-impedance coupled resonator (SICR) for suppression of harmonic spurious response is presented. The SICR relies upon the incorporation of different stepped impedances for the even and odd propagation modes of the coupled microstrip lines. This is to align the modal parallel resonance frequencies, and thereby effectively equalize the modal phase velocities. Its structural simplicity enables closed-form analytical formulation, and the derived equations are effectively utilized to explicitly guide parameters selection based on classical synthesis methodology of coupled microstrip filters. Practical feasibility of the SICR and the integrity of the analysis are demonstrated via designs and implementations of two third-order 0.01-dB ripple Chebyshev bandpass filters with a passband center frequency of 2.0 GHz and 3-dB fractional bandwidths of 15% and 25%. Good agreement between design, simulation, and measurement is obtained, where suppressions of the first harmonic spurious responses by more than 40 dB are achieved in both filters.

Design of Novel Dual-Band Bandpass Filter with Multi-Spurious Suppression for WLAN Application

In this paper, a new compact dual-band bandpass filter with multi-Spurious Suppression is proposed, which is composed of stub-loaded step impedance resonators. The stub-loaded SIRs are used to decrease the dimensions of the resonators and increase unwanted resonant frequencies. The even mode Resonance frequencies can be controlled with stub-loaded section; therefore the second resonance frequency can be tuned for WLAN application. A transmission zero is also created by stub-loaded section and used to suppress the unwanted spurious responses. The length of coupling and the gap size between stub-loaded SIRs are two freedom degrees for determining the realizable fractional bandwidth of the two passbands. A complete design procedure of dual-passband responses and suppression of spurious responses is described in detail. A third-order filter is designed and fabricated. The measured results show a rejection level of 24 dB up to more than 20 GHz (8.16f 1). Simulation and test results are in good agreement with each other.

Novel Second-Order Dual-Mode Dual-Band Filters Using Capacitance Loaded Square Loop Resonator

This paper presents a novel approach for designing dual-mode dual-band bandpass filters using capacitance loaded square loop resonators (CLSLR). The CLSLR features compactness and spurious response suppression because of the loaded capacitance. A dual-band response is obtained via an extremely large perturbation in a single resonator and second-order dual-mode dual-band filters are realized by a new cascading principle. Coupling coefficients between two resonators in both bands can be controlled independently and external quality factors are also controlled by a particularly-designed coplanar waveguide (CPW) feed line. Three types of filters are designed to validate the analysis. They are direct coupling dual-mode dual-band filter, source-load coupling dual-mode dual-band filter with a better band-to-band isolation and CPW-feed dual-mode dual-band filter with a wider bandwidth. Measured results show good agreement with the design specifications.

WIDEBAND BANDPASS FILTERS USING PARALLEL-COUPLED SIRS WITH WIDE SPURIOUS SUPPRRESSION

This paper proposes parallel-coupled stepped impedance resonators (SIRs) used for wideband bandpass fllters with reduced size and improved spurious response suppression in out-of-band. The fllter design concept is demonstrated by both two- and four-parallel coupled line resonator structures with the same fundamental frequency (f0) of 6.5GHz. The flrst bandpass fllter has been designed using two resonators with ‚/2 slot and embedded slot feeds for spurious response suppression at 2f0 and 3f0, respectively. The measured insertion loss is around 0.3dB and the operation band is from 4.4 to 9.2GHz (FBW = 73.8%). For the second bandpass fllter, the embedded slot feeds and additional loaded open-stubs have been utilized to improve the wide spurious response suppression and sharp skirt characteristic in the passband. The measured passband of frequency response is from 4.2 to 8.6GHz (FBW = 67.7%). The insertion loss of passband is lesser than 0.25dB and the return loss is better than 15dB. The fllter designs are described in details. The simulated and experimental results are demonstrated and discussed.

Suppression of spurious responses in microstrip filters using a reduced number of resistors

The stop band of a microstrip filter was extended by suppressing its harmonics, using additional stubs together with a smaller number of resistors than in the previous work. The possibility of suppressing the second to the fifth harmonics with one resistor per resonator is investigated in a simulation. Equations for initial estimates for losses and required coupling coefficients for the new stub design are given. In a simulation of a fourth-order filter, a total of only two resistors were required to suppress the second, third and fourth harmonics to -35-dB; -29-dB was achieved in a fabricated filter. The pass band loss was only increased by 0.2-dB.

MINIATURIZED DUAL-MODE COMPOSITE-RIGHT/LEFT-HANDED LINE RESONATOR FILTER WITH WIDE HARMONIC SUPPRESSION

This letter presents a miniaturized dual-mode composite- right/left-handed line resonator with wide harmonic suppression. The pure right-handed microstrip transmission line adopt 36 - electrical length instead of 90 - , thus the size of the dual-mode fllter can be reduced signiflcantly meanwhile the spurious response suppression are improved efiectively. A prototype fllter is designed and implemented at 730MHz, which not only has a size reduction of 92% against a conventional dual-mode fllter, but also exhibits harmonic suppression characteristics over a decade bandwidth.

Improved microstrip hairpin-line bandpass filters for spurious response suppression

A new fractal technique is applied to hair-pin microstrip bandpass filters for the second spurious suppression. The coupled edges of hair-pin microstrip resonators are changed by a new fractal to equalise the odd-mode and even-mode phase velocities so that the nearest spurious harmonic can be suppressed. Simulated and measured results show that the second spurious level is reduced below 30 dB for a 1 GHz and 25% bandwidth bandpass filter. An analysis is presented to show the effects of tap point height on fundamental parameters of the filters. In addition, the circuit size is reduced by 11% in comparison to the conventional filter.