Band Bandstop Filter Research Articles

Improvement of rejection band with Defected Microstrip Line and Ground plane Resonators

In this paper first a dual band bandstop filter is proposed using a unique spiral defect at the signal plane for Wi-Fi communication and remote sensing applications. The spiral defects is studied, simulated and measured. Next proposed spiral defect is combined with the hexagonal head defected resonators at ground plane to improve the rejection band. In addition a study is also done to observe the effects of the proposed defects at both signal plane and ground plane. A comparison is done among the response of individual defects filters and combined defect filter. It is observed that later shows improved overall bandwidth with compactness. The proposed combined defect filter with improved stopband displays 92.6% FBW and 112.5 dB/GHz sharpness factor with very compact in size as 0.26 λ0 × 0.25 λ0. All measurement results are in good agreement with the simulated results.

E-Plane dual band bandstop waveguide filter for possible X-band applications

ABSTRACT This paper presents, a novel second order E-plane planar insert based dual band bandstop waveguide filter. The circular shape with two T-shape resonators are printed on Roger RO4350 dielectric substrate to form planar insert. The insert are placed in such a way that positioned in E-plane of the standard WR-90 rectangular waveguide. The independent resonant frequency and bandwidth of the stopband can be adjusted by tuning the resonators. To achieve second order dual band bandstop filter response four asymmetrical circular shape with two T-shape resonators are designed on dielectric substrate to form different stopbands and separated by some specific distance to eliminate the unwanted coupling between them. The numerical analysis of the proposed filter is carried out using CST microwave studio. To validate the numerical analysis of the proposed filter, resonator, WR-90 rectangular waveguide is fabricated and measured. The measured results shows stopband characteristics having centre frequencies f 01g = 8.56 GHz and f 02 = 11.21 GHz and exhibits the bandwidth of 0.4146 GHz and 0.3824 GHz. The simulated and measured result are in good agreement.

Compact Dual Bandstop Filter Using Folded Lines and Genetic Algorithm

A novel method for creating a dual band bandstop filter with a meandering architecture is presented. Proposed bandstop filter shows two notch bands, one at 5.6 to 7.2 GHz and the other at 8 to 11 GHz. The designed filters simulated on HFSS software and fabricated on FR-4 substrates, filter dimensions have been optimized using GA. Filter shows S11 of 1dB and S21 of -18 dB at notch frequency 6.4 GHz and S11 of 1.2dB and S21 of -38 dB at notch frequency 9 GHz. The suggested filter has two pass bands one is up to 5 GHz for wireless communication and another is from 7.4 to 7.9 GHz for C band applications.

Tunable ultra-narrow band band-stop filter based on metal–insulator–metal​ plasmonic waveguide with square resonator

A tunable ultra-narrow band-stop filter based on metal–insulator–metal (MIM) plasmonic waveguide with square resonator is proposed and numerically investigated using Finite-Difference Time-Domain (FDTD) simulations. Different from straight waveguides with the same width, the proposed waveguide is composed of straight waveguides and ring waveguides with different widths. It is demonstrated that the proposed structure has a full width at half maximum (FWHM) of 9 nm at wavelength of 1261 nm. The influence of the structural parameters of the waveguides and square resonator on the transmission characteristics were analyzed in detail. The resonant wavelength can be tuned by changing the refractive index in the cavity or adding a square metal in the center of the cavity, where adding a square metal in the center of the cavity can make the resonant wavelength change proportionally. Combining the two schemes can achieve specific modulation of the resonance wavelength. Such waveguide filter may have potential applications in highly integrated optical circuits.

An ultra‐wideband bandstop filter with circularly etched stub resonator

AbstractIn this letter, an ultra‐wide band bandstop filter (BSF) with three transmission zeros and one reflection zero is presented. The role of the circular etched shaped stub as a notch pass response is investigated. Further, a compact size of 13 mm × 24.30 mm (0.219λg× 0.410λg) is achieved by employing an interdigital capacitor to increase coupling between the lines. Furthermore, the transmission line model of the filter is proposed, and consequently even and odd mode impedance is calculated analytically. The proposed filter offers an ultra‐wide bandwidth of 6.1 GHz (3.7 GHz‐9.8 GHz) with a rejection depth of 20 dB over the entire rejection band. Moreover, the upper skirt factor of 47.2 dB per GHz is achieved. A prototype of the proposed BSF is fabricated and measured. Simulated and measured results are in good agreement which validates the proposed design.

Design and analysis of angular stable antipodal F‐type frequency selective surface with multi‐band characteristics

This article presents frequency selective surface (FSS) with multi-band characteristics that features tri band band-stop and dual-band passband filter. The proposed FSS unit cell comprises the F-type resonance elements disposed of antipodal (diametrically opposed to) one to another on both layer and a square loop surrounding all resonators on the top layer of the dielectric substrate. The structure is specifically designed to filter out some extensively used broadband communication signals, such as, WiMAX and WLAN while enabling C-band satellite communication in the earth station and provides three stopbands operating at 2.4, 5.2, and 5.9 GHz besides two passbands of 4.1 and 5.5 GHz. Although this structure has a multi-band structure, it exhibits high stable performance for oblique incidence ranging from 0° to 60° for both transverse electric (TE) and transverse magnetic (TM) polarizations. Considering the resonant frequency deviation (RFD) at the incidence waves with different angles of arrivals, it was found that RFD at 60° is less than 0.6% on average and very low when compared with existing studies about multi-band FSS. The detailed equivalent-circuit model (ECM) is employed to predict and analyze the transmission characteristic of the proposed structure, and a good agreement between the simulated and measured transmission coefficients is obtained.

Dual‐band band‐stop microstrip filter with controllable bands based on unequal split ring resonators

In this study, a dual band band-stop filter based on split ring resonators (SRR) over a ground plane with unequal rings is proposed and characterised. The proposed SRR design method, which is demonstrated here, ensures the control of the resonance frequencies and their respective bandwidths. The lengths and coupling regions of each ring are arbitrary, making possible the control of, not only the separation between the two generated resonances, but also the bandwidth ratio between the pass-bands, or quality factors. The full characterisation of the resonators involves the computation of the resonant frequencies and the current distributions at the resonances. These current distributions are used to obtain the electromagnetic energy stored in the resonator that, in turn, is required to estimate the quality factor of each resonance. The dual band band-stop filter is composed by four proposed SRRs coupled to a transmission line showing that, indeed, both the centre frequencies and its bandwidth ratio can be controlled. The presented results confirm the reliability of the proposed method in the design of passive devices.

A compact dual stopband bandstop filter using defected SIR and Hilbert shape fractal structure

In this paper, a novel technique is proposed to design a dual band bandstop filter which is implemented with two defected stepped impedance resonators (SIRs) embedded on the input output transmission line. The embedded SIRs create a transmission zero at 2.5 GHz that generates the first stopband of the proposed filter. Introducing two Hilbert shaped fractal structure on the ground plane, the second stop band is employed at 3.5 GHz. The overall layout of the filter is realized with a size of 20 × 5 mm2. The proposed prototype is EM simulated and measured. The measured −10 dB bandwidth for first stopband is 0.1 GHz and for second stopband it is 0.14 GHz. The measured S-parameters exhibit an excellent out off band response with insertion loss less than 1.5 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1345–1347, 2016

Tunable Dual Band Filter with BST Capacitors

A tunable double band band-stop filter based on BST is presented. This configuration has a coplanar microstrip loaded with stepped impedance resonators. Ferroelectric BST parallel plate capacitors were loaded at the end of the stepped impedance resonators. When a DC voltage is applied to the BST capacitors, the change in capacitance shifts the resonance frequency of the stepped impedance transformers. The filters were designed with notch frequencies at 1.5 GHz and 3.5 GHz without loading them with BST capacitors. The filter circuits were simulated with Agilent ADS and were fabricated on FR-4 substrates. By loading the resonators with BST capacitors with no DC applied voltage, the first and second notch frequency shifts significantly. The first notch frequency can be tuned from 570 MHz to 781 MHz and the second notch frequency from 2.16 GHz to 2.55 GHz by applying the bias voltage of 5volts. The performance of the BST tuned filters were compared with filters tuned with p-n junction varactors.

Compact Low-Loss Tunable $X$-Band Bandstop Filter With Miniature RF-MEMS Switches

This paper presents a compact low-loss tunable <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band bandstop filter implemented on a quartz substrate using both miniature RF microelectromechanical systems (RF-MEMS) capacitive switches and GaAs varactors. The two-pole filter is based on capacitively loaded folded-λ/2 resonators that are coupled to a microstrip line, and the filter analysis includes the effects of nonadjacent inter-resonator coupling. The RF-MEMS filter tunes from 11.34 to 8.92 GHz with a - 20-dB rejection bandwidth of 1.18%-3.51% and a filter quality factor of 60-135. The GaAs varactor loaded filter tunes from 9.56 to 8.66 GHz with a - 20-dB bandwidth of 1.65%-2% and a filter quality factor of 55-90. Nonlinear measurements at the filter null with Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> = 1 MHz show that the RF-MEMS loaded filter results in > 25-dBm higher third-order intermodulation intercept point and P-1 dB compared with the varactor loaded filter. Both filters show high rejection levels ( > 24 dB) and low passband insertion loss ( <; 0.8 dB) from dc to the first spurious response at 19.5 GHz. The filter topology can be extended to higher order designs with an even number of poles.

Design of compact coplanar bandstop filter composed on open‐loop‐ring resonator and defected ground structure (DGS)

AbstractDesign of a novel compact bandstop filter composed on an open‐loop‐ring resonator and a defected ground structure (DGS) for coplanar waveguide is proposed and investigated. A simple coplanar open‐loop‐ring resonator has been designed and tested for the stop‐band from 3.9 to 4.3 GHz with tree transmission zeroes inside the stop‐band. Two almost symmetrical poles are obtained on both sides of the stop‐band. Then the proposed broad band bandstop filter based on the one open‐loop‐ring resonator has been transformed to the bandstop filter with a narrower stop‐band but with improved pass‐ and stop‐band characteristics. It is realized by adding a conventional rectangular DGS slot inside the open‐loop‐ring. The equivalent circuit model has been proposed to describe the behaviour of the bandstop filters. The improved bandstop filter introduces the stop‐band from 3.75 to 5.3 GHz with two transmission zeroes within and more than −20 dB rejection. The total size of the proposed structure is 13.8 × 13.4 mm2. Both bandstop filters have been fabricated and measured. Measurements are in good agreement with simulation results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 478–483, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24905