Improved Stopband Characteristics Research Articles

Compact multiple electromagnetic band gap (EBG) cells based ultra wide band (UWB) filter with improved stop-band characteristics

PurposeThe purpose of the study is – in Microwave filter design, the performances of passive components are deteriorated by parasitics at gigahertz (GHz) frequency range. A compact and multi-stack electromagnetic band gap (EBG) structure is proposed with improved stop band characteristics at GHz frequency range in this work. This paper proposes a new design for ultra wide band pass filter (resonator BPF) with periodically loaded one-dimensional EBG to achieve the harmonic suppression. This basic EBG structure is developed with combination of a signal strip and ground plane in the slotted section. The resonator BPF is loaded with one EBG, two EBG and three EBGs to improve the stop-band rejection.Design/methodology/approachThe proposed filter is with multi-stack EBG cell for achieving good pass band and stop bands performance. Circuit model is analyzed in Section 2. Section 3 discuses band pass filter loaded with one EBG. In Sections 4 and 5, filter with two and three EBG loaded resonators are discussed, respectively. Section 6 is concluded with comparison of simulation and measured results.FindingsThe stop-band rejection is 20 dB, 40 dB and 50 dB, respectively, in the frequency range of 6 GHz to 20 GHz. The simulation analysis is carried out with advanced system design software. To validate the simulation results, proposed structure is fabricated, and results are found to be in good agreement.Originality/valueThis paper accounts for designing resonator BPF, which has slow wave pass band and stop band characteristics. Second and third harmonics are suppressed using multi-stack EBG. Various stacks with basic designs are proposed and improved results have been demonstrated which is open for future research.

Design and characterization of millimeter-wave micromachined polymer-based cavity filter with resonant cylinders

This paper presents a Ka-band cavity bandpass filter using SU-8 polymer UV lithography technology. The filter has a folded structure with six cavity resonators having resonant cylinders, enabling compact design and improved stopband characteristics. The fabrication of the millimeter- wave filter with a complicated multi-height and high aspect- ratio structure is realized using the proposed methods. A coaxial-rectangular waveguide transition is designed for the measurement process. The measured results of the filter are in good agreement with the simulated ones, with a center frequency of 38 GHz, insertion loss of 0.7 dB, and fractional bandwidth of 4.4%. The stopband rejection reaches 70 dB at 35.5 and 40.5 GHz. The experimental results are discussed and force and thermal stress analysis is conducted to confirm the feasibility of the design and fabrication methods of the cavity filter.

Design of a compact symmetricalc-Band Micro Strip Band Pass Filter with Periodic Saw tooth Grooves

Design of a miniaturized symmetrical band pass filter (BPF) using parallel-coupled half-wavelength micro strip resonators with improved stop band characteristics and 2nd harmonic suppression is presented. The proposed filter is designed at a center frequency of 5.25 GHz with a stop band insertion loss greater than-10dB at 5.15 GHz and fractional bandwidth of 20% (4.74–5.80GHz). The conventional parallel-coupled line band pass filter structure has been folded symmetrically about the horizontal plane and consecutive saw tooth periodic grooves are introduced to the parallel lines. Thus there has been a significant improvement in 2ndharmonic suppression to almost-34.51dB. Size reduction of 46.73% is accomplished with respect to the conventional filter.

Design of a wide-stopband bandpass filter using stepped impedance resonators

In this paper, a compact bandpass filter (BPF) with improved stopband characteristics using stepped impedance resonators (SIRs) is proposed. The filter consists of two quarter-wavelength SIRs with radial stubs and a PI-network of capacitance, which is used to suppress the upper frequency spurious signals. An odd- and even-mode analysis is adopted considering the structure’s symmetry. A new BPF centered at 1.57 GHz has been designed and fabricated to verify the validity of the proposed method. Measured results are in good agreement with the electromagnetic simulation. The frequency selectivity was enhanced via introducing two finite transmission zeros (TZs) near the passband, located at 1.21 GHz with 43.5 dB rejection and 3.10 GHz with 62.3 dB rejection, respectively. The spurious frequencies of the upper stopband are suppressed better than 20 dB from 2.07 to 16.25 GHz. And the circuit only occupies 0.09 λg × 0.09 λg.

Miniaturized mixed-cross coupling bandpass filter with source–load coupling

A miniaturized trisection bandpass filter (BPF) with improved stopband characteristics is presented. The proposed BPF consists of three stepped impedance resonators (SIRs), where the nonadjacent SIRs share a common shorted stub, and the other SIR is embedded inside the nonadjacent SIRs. To improve frequency selectivity, mixed-cross (M-C) coupling and source–load (S–L) coupling were introduced in the nonadjacent resonators and source/load ports, respectively. Owing to the M-C and S–L couplings, multiple transmission zeros (TZs) can be employed for high skirt selectivity and upper wide stopband. A new BPF centered at 2.45 GHz with 17.6% fractional bandwidth has been designed and fabricated to verify the validity of the proposed method. The measurement result shows four finite TZs in the stopband, located at 2.09, 2.98, 4.64, and 12.47 GHz, respectively. The circuit only occupies 6.70 × 8.60 mm2

Compact dual-band bandpass filter with improved stopband characteristics

A compact dual-band bandpass filter with an improved stopband using short-circuit centred stepped impedance resonators (SCSIRs) is presented. The proposed filter consists of two SCSIRs, one of which is embedded in the other one to obtain two passbands. Multiple transmission zeros can be generated by the proposed SCSIR for high passband selectivity and upper wide stopband bandwidth. The centre frequencies and bandwidths of the two passbands can be controlled by adjusting the geometric dimensions of the SCSIRs, respectively. A 2.4/5.2 GHz dual-band experimental BPF has been designed and fabricated to demonstrate the proposed method.

A Method for Improving Stopband Characteristics of a Dual-Band Filter

This paper presents a simple and effective method for improving stopband rejection characteristics of previously studied dual-band filters. Small electric couplings were applied to the symmetrically positioned shunt resonators, which di-vided each transmission zero into two transmission zeros without any effect on passbands. We were able to achieve improved stopband rejection characteristics by these additional transmission zeros. For the filter application, we de-signed a dual-band filter with improved stopband characteristics using microstrip quasi-lumped elements. The electric couplings that control the location of transmission zeros are controlled by the distance between symmetric open stubs of the filter. The filter was fabricated with a relative dielectric constant of 3.5 and a thickness of 0.76 mm. The fabri-cated filter has a small size (14.6×13.2×0.76 mm) and a low insertion loss when compared with conventional filters. Key words: Dual-Band Filter, Electric-Coupling, Quasi-Lumped Elements, Transmission Zero.

A Novel Low-Pass Filter With an Embedded Band-Stop Structure for Improved Stop-Band Characteristics

This letter presents a novel design of a microstrip low- pass filter (LPF) with an embedded band-stop structure, which is constructed from a simple two transmission line band-stop filter. The band-stop structure is ingeniously embedded into a classical step-impedance microstrip LPF. The stop-band of the proposed LPF is more than two times broader than the original design, while its cut-off frequency remains at 1.8 GHz. The embedded structure does not increase the physical dimension of the LPF, but improves the performance significantly. Measured results agree with simuAcircnot lation well, and validate the dual-frequency design method.

A slow wave structure and its application in bandpass filter design

This paper presents a new slow wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of different kind of coupling in this structure is demonstrated. Two and four resonator band pass filters at center frequency 2.15 and 2.30 GHz with different bandwidth are designed. The simulated results are verified with the help of two different software packages (IE3D and Sonnet Lite).

A compact dual‐band bandpass filter using stub‐loaded two‐mode resonators and direct source‐load coupling to obtain improved stopband characteristics

AbstractIn this article, a dual‐band bandpass filter is designed by using microstrip stub‐loaded two‐mode resonators. Because the resonant frequencies of the odd‐mode and even‐mode of the stub‐loaded resonator can be varied individually, the midband frequencies of the dual‐bands of filter can be controlled separately. Direct coupling between the source and load of the filter is introduced, and four transmission zeros in the stopband of the filter are produced. As a consequence, excellent performance of the filter with sharp passband skirts and wide stopbands is realized. For example, dual‐band filter has midband frequencies of 2.4 GHz and 3.6 GHz, respectively, with fractional bandwidths of 11.35% and 5.21%, correspondingly. The measured frequency response of the filter agrees excellently with the predicted result. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 618–621, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24129

A microstrip dual‐band bandpass filter with reduced size and improved stopband characteristics

AbstractA novel compact microstrip dual‐band bandpass filter (BPF) is developed with remarkably improved stopband characteristics. Two‐square open‐loop resonators are embedded in a U‐shaped resonator to achieve a significant size reduction of the filter. Meanwhile, a cross‐coupling between nonadjacent resonators is exploited to produce multiple transmission zeros in the stopbands of the filter. As a consequence, wide stopbands with sharp and large attenuations are obtained. Theoretical and measured frequency responses of the designed filter show a good agreement.© 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 618–620, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23154

Stepped-Impedance Hairpin Resonators with Asymmetric Capacitively Loaded Coupled Lines for Improved Stopband Characteristics

New microstrip bandpass filters with extended stopband bandwidths are proposed by using new asymmetric stepped-impedance hairpin resonators (ASIHRs). The size of the proposed resonators has been reduced around 16%, comparing with the conventional stepped-impedance hairpin resonators (SIHRs) structure. The first bandpass filter is a combination of differ resonators with the same fundamental frequency but differ in harmonic frequencies, resulting in improved suppression spurious responses in stopbands. Furthermore, another bandpass filter uses the ASIHRs periodically loaded on a microstrip line to improve stopband characteristics. The proposed filters not only have compact size of resonators, but also provide improved upper stopband characteristics. The proposed filters provide 20 dB rejection levels in the stopband up to 6f 0 . The measured filters responses agree very well with the simulated expectations.

Microstrip Bandpass Filters with Reduced Size and Improved Stopband Characteristics Using New Stepped-Impedance Resonators

This paper proposes a new microstrip stepped-impedance resonator (SIR) used for bandpass filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends of the resonator with loaded triangular and rectangular microstrips is described. The design concept is demonstrated by two filter examples including four-resonator parallel-coupled Chebyshev bandpass and compact four-resonator cross-coupled elliptic-type filters. These filters are not only compact size due to the slow-wave effect, but also have a wider upper stopband resulting from the resonator bandstop characteristic. The filter designs are described in details. The simulated and experimental results are demonstrated and discussed.

Novel Compact Microstrip Dual-Mode Ring Resonator Wideband Bandpass Filter with Significantly Improved Stopband Property

A novel wideband bandpass filter with improved stopband characteristics is presented in this paper. Dual-mode square ring resonator is used in the proposed filter. New formulas based on the even- and odd-mode analysis are derived to facilitate the design of transmission zeros of the square ring resonator. A short-circuited stub and a piece of aperture-enhanced parallel-coupled lines are introduced to the input and output of the resonator to lower the passband return loss and widen the stopband of the filter significantly. The filter has a 50% fractional bandwidth, is compact in configuration, and shows remarkably improved performance compared with previously reported filters of the same kind. The measured filtering response shows a good agreement with the simulated result.

Microstrip Slow-Wave Open-Loop Resonator Filters with Reduced Size and Improved Stopband Characteristics

This paper presents a new class of microstrip slow-wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends loaded with triangular and rectangular ends is described, leading to the invention of a microstrip slow-wave open-loop resonator. Two-resonator and four-resonator bandpass filters are designed at the operating frequency of about 2 GHz, and a bandwidth of 60 MHz. The size of the slow-wave open-loop resonator is optimized from the standpoint of the unloaded Q-factor. The filters are not only compact in size due to the slow-wave effect, but also have a wider upper stopband resulting from the dispersion effect. The filter designs of this type are described in details. The experimental results are demonstrated and discussed.

A compact open-loop resonator filter with a wide stopband response

This paper presents a new class of microstrip slow-wave open-loop resonator filter with reduced size and improved stopband characteristics. A comprehensive treatment of both resonator ends loaded with triangular and rectangular shapes is described, leading to the invention of a microstrip slow-wave open-loop resonator. A four-resonator bandpass filter is designed at the operating frequency about 2 GHz, bandwidth of 60 MHz. The size of the slow-wave open-loop resonator is optimized from the standpoint of the unloaded Q -factor. The proposed filter is not only compact size due to the slow-wave effect but also has a wider upper stopband resulting from the dispersion effect. The filter design of this type will be described in detail. The experimental results are demonstrated and discussed.

Microstrip Lowpass Filters with Reduced Size and Improved Stopband Characteristics

Novel microstrip lowpass filters are developed with reduced size and significantly improved stopband characteristics. After introducing quarter-wavelength open stubs, we get one or two transmission zeros in the stopband. By folding the high impedance microstrip lines, we reduce the size of the filter. Three-pole and five-pole lowpass filters are designed, and their measured frequency responses agree well with theoretical predictions.

Compact Cross-Coupled Microstrip Bandpass Filter with Improved Stop-Band Characteristics

Compact Cross-Coupled Microstrip Bandpass Filter with Improved Stop-Band Characteristics