Compact Bandstop Filter Research Articles

L대역 불요파 저감을 위한, UHF대역 CRLH 대역통과 여파기와 소형 대역저지 여파기의 결합 설계

In this paper, we propose a way to improve the quality of L-band wireless communication from unfriendly influential factors lying in the neighboring RF bands. The UHF-band system has resonator components and they generate harmonics as the spurious in the L-band. Therefore, a metamaterial CRLH bandpass filter is designed for the purpose of system miniaturization and smaller insertion loss, and its spurious phenomenon is observed in the frequency domain. And its harmonics in the L-band are suppressed by a compact bandstop filter whose equivalent circuit is newly developed. The design methodology is validated by the equivalent circuit to be compared with commercial full-wave EM software simulations, where the spurious is dropped by 20dB. Also, the advantage of the proposed design is presented by the comparison where our filter is much smaller than the conventional parallel edge coupled filter by over 50%, with excellent harmonic suppression.

Very compact broad band-stop filter using periodic L-shaped stubs based on self-complementary structure for X-band application

Self-complementary structures are used to design a novel compact band-stop filter for X-band applications. By cutting a rectangular slot with five pairs of L-shaped protruded strips inside the slot on the ground plane and by inserting five pairs of L-shaped stubs in the microstrip transmission line, the self-complementary structure is created, hence a constant and flat impedance bandwidth at the X-band can be produced. The operating frequencies of the filter can be easily controlled by changing the dimensions of the protruded L-shaped strips and stubs, without changing the area taken up by the structure. Experimental results show good agreement with simulation results and demonstrate that excellent stop-band performance could be obtained through the proposed band-stop filter.

Comments on “Compact Wideband Bandstop Filter With Four Transmission Zeros”

In this paper the four zeros roll-off and stopband bandwidth performance of the compact wideband bandstop filter consisting of an open-ended coupled-line connected in parallel to a transmission line is obtained with three zeros BSF.

Novel compact size bandstop filter with shorted‐stub loaded ring resonator

AbstractA planar compact bandstop filter (BSF) and a miniaturized resonator structure are presented along with its analytical equation to obtain resonance. The resonator is miniaturized by means of a shorted‐stub which is loaded to a closed‐loop resonator. Design and implementation of a 2.1 GHz BSF with 6% fractional bandwidth is presented. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2766–2768, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26439

Compact wideband bandstop filter with multiple transmission zeros based on edge-coupled parallel line and transmission line signal interference

In this article, we demonstrate that the compact bandstop filter (BSF) configuration consisting of an edge-coupled microstrip line connected in parallel to a transmission line section can produce multiple transmission zeros in the stopband. A lossless transmission model is used to derive the condition for two, three, or four transmission zeros. A prototype BSF at 2 GHz achieving a wide 20 dB stopband bandwidth of 92.8% with sharp rejection along with a better than 30 dB return loss in the passband is fabricated for validation purposes. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2265–2268, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26258

Compact dual-band open-stub bandstop filter with suppression of spurious passbands

In this article, by replacing the series quarter-wavelength connecting line of conventional open-stub bandstop filter (BSF) with the equivalent P-shaped line, a compact dual-band BSF is proposed and designed. Furthermore, it suppresses a lot of spurious passbands of the open-stub BSF. Design equations of P-shaped line are achieved by ABCD matrixes. To validate the design concept, two full-wave electromagnetic simulators are used and the proposed filter is fabricated. The simulate results are in excellent agreement with measurement results. The circuit area of the dual-band BSF is only 50% of the conventional open-stub BSF.

Compact bandstop filter using coupled-line section

A new compact bandstop filter with a coupled-line structure is proposed. Stopband rejection depth and bandwidth can be controlled by the configuration of the coupling section, and good return loss is realised by properly adjusting the impedances of two open-circuited stubs. Design equations are obtained using a lossless transmission line model. To validate the analysis, a bandstop filter with about 72% fractional bandwidth at 5 GHz has been fabricated. The implementation area is 0.32λ g × 0.18λ g .

A novel compact bandstop filter using defected microstrip structure

AbstractIn this article, a new defected microstrip structure (DMS) which is used to design filter is introduced.Its resonant characteristics can be adjusted by changing the dimension of the structure unit. A novel bandstop filter is designed based on this structure. There are two transmission zeros located at about 4.08 GHz and 6.2 GHz, respectively. The measured results show a good agreement with the simulation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:433–435, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25708

Microstrip dual-band bandstop filter of defected ground structure and stepped impedance resonators

This article presents a compact microstrip dual-band bandstop filter (BSF), in which one λg/4 defected ground structure (DGS) pair is utilised to realise one stopband while two stepped impedance resonators (SIRs) help obtain another stopband and suppress the spurious harmonics. The design strategies and the equivalent circuits are introduced in detail. The measured results indicate 43.8% and 18.7% fractional bandwidth in the two stopbands (2.4 GHZ and 5.2 GHz) respectively, and the return loss is greater than 15 dB in the whole passband. In addition, size reduction can be conveniently achieved by adjusting the length of the SIRs and DGS.

Design of a new compact dual-mode multiband bandpass filter using multi-armed ring-open-loop resonators without coupling gaps

In this article, we proposed at first step a new compact dual-mode bandstop filter with broad stopband and low insertion loss in the passband using one ring resonator.Based of this microstrip ring resonator, a novel type of multibandpass filters is proposed. The idea of the proposed filters is to engineer the transmission band using multireject band resonators, which are implemented using multi-armed open-loop resonators that are directly coupled to the input/output ports. Each resonator pair of arms creates a reject band in the transmission response. By properly adjusting the multireject bands, appropriate multitransmission bands are created. The idea was verified by designing three different filters with multibandpass response. The designed and fabricated filters have compact size with good agreement between the measured and simulated responses. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2668–2672, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25576

Compact Planar Dual-Wideband Bandstop Filters with Cross Coupling and Open-Ended Stepped Impedance Resonators

This letter presents the design of a compact bandstop filter (BSF) operating at two frequencies. The proposed BSF consists of open-ended stepped impedance resonators (OSIR) and an end-shorted parallel-coupled microstrip line (E-PCML). The OSIRs are used to achieve the impedance-controlled stopband positions. The wide BSF bandwidths are achieved through enhanced coupling of the E-PCML. Explicit design guidelines are derived using a lossless transmission line model. To validate theoretical predictions, a prototype dual-band BSF operating at 900 MHz and 2,100 MHz with fractional bandwidths of 72% and 36% respectively, is implemented in microstrip.

A Novel and Compact Bandstop Filter with Folded Microstrip/CPW Hybrid Structure

A novel and compact circuit configuration for narrowband bandstop filter (BSF) is proposed. The distinct filtering characteristics of this new type of transmission line filter are investigated theoretically and experimentally. The presented filter consists of hybrid microstrip/coplanar waveguide (CPW) transmission-line units with a pair of uniformly shunt microstrip stubs. At the bottom of substrate material, two identical CPW short-circuited resonators and an open-circuited CPW resonator are broadside-coupled to the top microstrip main transmission lines, respectively. To reduce the size of the filter, the folded microstrip/CPW composite elements and parallel stubs have been applied to layout. A demonstrator with approximately 16.7% fractional bandwidth at a mid-stopband frequency of 6 GHz is developed and presented. The proposed filter is successfully realized in theory and verified by full-wave electromagnetic simulation and experiment. Simulated and measured results are in excellent agreement.

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

Design of Band-Notched UWB BPF with Very Wide Upper Stopband Using Combined λ/4 TSSIR

In this paper, a new band-notched UWB BPF with a very wide upper stopband is designed using a λ/4-type multi-mode resonator (MMR). The proposed MMR, being formed by combining two identical λ/4 tri-section stepped-impedance resonators (TSSIRs) in a structure-shared fashion, exhibits both λ/4 and embedded λ/2 types of resonance with a relatively smaller circuit size. By properly locating the first four resonant modes of the MMR and the coupling peaks of the input/output parallel-coupled lines, a five-transmission-pole UWB BPF is realized with a favorable uniform in-band UWB response. Besides the good UWB performance, a 5-GHz notched band is created by embedding in the output feed line a T-shape lumped-element bandstop structure to reject the influence from WLAN signals. Also, a very wide upper stopband is achieved by implementing a compact bandstop filter structure in the input feed line together with the properly located transmission zeros generated by the input/output interdigital-coupled lines and the second harmonic of the T-shape bandstop structure. A prototype of the proposed UWB BPF was fabricated and measured for performance verification. The measured results show a return loss of higher than 10 dB, a minimum insertion loss of 0.41 dB, and a group delay variation of less than 0.11 ns in the UWB passband except the notch. The notched band has a 3-dB bandwidth of 18%. The measured upper-end –20-dB stopband ranges from 11.94 to 30.56 GHz, with a bandwidth of 18.62 GHz.

Design of compact, wide‐band bandstop filters with sharp‐rejection characteristics

AbstractIn this study, a novel transmission line configuration has been proposed to design a sharp‐rejecting, compact bandstop filter with wide rejection‐bandwidth. Signal interference technique is used to obtain transmission zeros, which provide the sharp rejection characteristic. Rejection bandwidth is controlled by the characteristic impedances of transmission lines. Filter is analyzed using transmission line model. Theoretical predictions have been verified by the measurements of two compact filters fabricated in microstrip line. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1244–1248, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23335

Compact Bandstop Filters with Extended Upper Passbands

This paper presents new compact bandstop filters (BSFs) with extended upper passbands. In the basic proposed filter configuration, the conventional quarter-wavelength open-stub resonators are replaced with equivalent two-section stepped impedance resonators. Transmission line analysis is used to determine the dimensions of the equivalent stepped impedance sections. The filter structure is analyzed using a full wave electromagnetic (EM) simulator and then realized at 2.3 GHz band. Experiments have also been done to validate the performance of the design concept. Compared with the conventional quarter-wavelength-based bandstop filter, significant extensions of the upper passband beyond 9 GHz and 40% size reduction are achieved. Two other variations of the proposed basic BSF with further size reduction (more than 60%) are implemented and their measured performances are verified.

Compact Dual-Band Bandstop Filters Using Stepped-Impedance Resonators

This work presents a compact dual-band bandstop filter (DBBSF) that features two controllable stopbands at desired frequencies. Stepped-impedance resonators are utilized to realize the dual-stopband characteristics, and reduce size. The synthesis method is developed. An experimental circuit is fabricated and evaluated to validate the design concept. Measurements correlate well with the simulation results, and the size is 12.6% less than that of a standard DBBSF.

Compact bandstop filter using signal interference technique

A signal interference technique is proposed to design a compact wideband bandstop filter (BSF). Two parallel transmission lines of different lengths and characteristic impedances are used. The signal propagates through these two paths and interferes at the other end with different phases and magnitudes. By varying these phases and magnitudes two finite transmission zeros can be obtained. To improve the stopband rejection level another zero is obtained using an open-circuited quarter-wavelength stub at the stopband centre frequency (fc). One single section prototype fabricated BSF of fc=0.449 GHz has 3 and 40 dB fractional bandwidths of 50.6 and 22.3%, respectively. The filter implementation area is 0.116λg×0.163λg, λg being the guided wavelength at fc.

Wideband and compact bandstop filter structure using double-plane superposition

A novel bandstop filter (BSF) structure is proposed and measured for wideband and compact circuit applications. The proposed BSF realizes the wide stopband (2-octave) characteristics by superposing two different photonic bandgap (PBG) structures into a coupled double-plane configuration. Only three cells of the proposed structure are enough for the measured 10 dB stopband from 4.3 to 16.2 GHz. We expect this novel BSF structure is widely used for compact and wideband circuit applications, such as compact high-efficiency power amplitiers using harmonic tuning techniques.

Folded-Line and Hybrid Folded-Line Bandstop Filters (Short Papers)

The feasibility of a compact bandstop-filter geometry is demonstrated. The filter geometry is particularly suited for stripline and microwave-integrated-circuit (MIC) fabrications in that grounding is not required for any part of the filter. Hybrid geometries allow the filter designer increased flexibility in choosing a suitable shape factor without significantly affecting the filter's electrical characteristics. Folded-line filter geometries are suitable for narrow bandwidths (provided capacitive-coupled stubs are used) to wide-bandwidth applications. Experimental confirmation is presented.