Compact Bandpass Filter Research Articles

Compact coplanar waveguide bandpass filter based on coupled S‐shaped split ring resonators

ABSTRACTThis letter is focused on the application of coupled single‐layer S‐shaped split ring resonators (S‐SRRs) to the design of highly compact bandpass filters in coplanar waveguide (CPW) technology. S‐SRRs have been previously demonstrated as miniaturized resonators, particularly suited for applications in conjunction with coplanar line geometries. However, size reduction of CPW filters based on impedance inverters and S‐SRRs is limited by the inverters. Therefore, this letter proposes an alternative geometry of CPW bandpass filters employing S‐SRRs in a configuration based on the theory of coupled resonators. A highly compact third‐order bandpass filter is designed using this principle, and the proposed approach is validated through experiment, demonstrating competitive filter performance achieved in an extremely small area. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1113–1116, 2015

Ku‐band compact bandpass filter with wide upper stopband using multilayer liquid crystal polymer technology

ABSTRACTAn improved compact bandpass filter (BPF) with ultrawide upper stopband on three‐layer liquid crystal polymer substrate is presented. In this work, a broadside‐coupled H‐shape resonator and open circuited with radial stub are used to realize compact BPF. The first BPF is designed with three broadside‐coupled H‐shape resonators, which are placed on the top layer and middle layer, respectively. To improve the selectivity and reduce the size while not widen the bandwidth, an improved filter based on the first filter is proposed, which adds two open circuited with radial stubs and removing two H‐shape resonators. The measured results show that the second filter has better selectivity and much more compact size of 6 mm × 6 mm (about 0.52λg × 0.52λg) while keeping wide upper stopband and high rejection, comparing with the first filter, which size is 7 mm × 8 mm (about 0.61λg × 0.7λg). © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1121–1125, 2015

A compact dual-band bandpass filter based on porous silicon dual-microcavity of one-dimensional photonic crystal

We propose a compact dual-band bandpass filter (BPF) based on one-dimensional porous silicon (PS) photonic crystal by electrochemical etching. By inserting three periods of high and low reflective index layers in the center of porous silicon microcavity (PSM), two sharp resonant peaks appear in the high reflectivity stop band on both sides of the resonance wavelength. Through simulation and experiment, the physical mechanisms of the two resonance peaks and the resonance wavelength are also studied. It is found that the resonance wavelength can be tuned only by adjusting the effective optical thickness (EOT) of each PS layer, in which different resonance wavelengths have different widths between the two sharp resonance peaks. Besides, the analysis indicates that oxidization makes the blue shift become larger for high wavelength than that for low wavelength. Such a fabricated BPF based on PS dual-microcavity is easy to be fabricated and low cost, which benefits the application of integrated optical devices.

A chip-on-board packaged bandpass filter using cross-coupled topological optimised hairpin resonators for X-band radar application

Devices that are compact in design and fabrication continue to draw attention for specific applications that require high performance. A compact elliptic bandpass filter using a cross-coupled topological structure with a hairpin resonator optimised for radar applications is presented in this paper. This work presents the design theory and corresponding semiconductor fabrication processes and describes the chip-on-board packaging method in detail. The proposed design of the bandpass filter can not only reduce the size of the device and result in good RF performance, but the accurate semiconductor fabrication process can also ensure high performance further. In addition, the presented chip-on-board packaging method can greatly enhance the reliability and long-term stability of a microwave device, which rarely introduces RF characteristic interference. The simulated, bare-chip measured and final chip-on-board measured results agreed well, which validated the correctness of the proposed approach.

Compact dual-band bandpass filter using complementary hook-shaped resonators for WLAN applications

Based on the double resonant properties of the complementary hook-shaped resonator (CHSR), a novel miniaturized dual-band microstrip filter is proposed for WLAN operations. The filter, which is only 0.067 λ0 × 0.084 λ0 in overall dimen- sions, is composed of two opposite CHSRs and modified T-shaped feed-lines. Two hook-shaped strips generate two respective passbands, independently. The proposed filter is found to have two transmission zeros around the high resonances for improved selectivity. To verify the proposed method, a dual-band filter is implemented and measured, and the measurement results agree well with the simulated data.

GA-Optimized Compact Broadband CRLH Band-Pass Filter Using Stub-Inserted Interdigital Coupled Lines

The design of a new compact band-pass filter is proposed, which is based on the microstrip composite right- and left-handed transmission-line (CRLH-TL) structure. Particularly, the interdigital coupled (IDC) lines of the CRLH geometry are proposed to be parted by inserting open stubs to meet the specifications on the passband. In addition, there is another pair of stubs to complete the design in a limited space. These are considered in the TL-based analysis and the design parameters are calculated by genetic algorithm optimization. The measurement is shown to be acceptable and agreeable with the circuit and electromagnetic field simulations. In addition, the zerothorder resonance (ZOR) phenomenon is verified.

Compact Dual-Band Bandpass Filter Using Quarter-Wave Stepped-Impedance Resonators

A compact dual-band bandpass filter based on a modified stepped-impedance resonator is presented in this article. The conventional low-impedance stub of stepped-impedance resonator is replaced by a closed rectangular loop. The proposed filter consists of two pairs of proposed novel stepped-impedance resonators, one of which is embedded in the other one to obtain two passbands. Five transmission zeros can be generated near the passbands for enhanced frequency selectivity and band-to-band isolation. The center frequencies and bandwidths of the two passbands can be controlled by adjusting the geometric dimensions of the proposed stepped-impedance resonator. To demonstrate the proposed method, a 2.4-/5.2-GHz dual-band bandpass filter for Wireless Local Area Networks (WLAN) application has been designed, fabricated, and measured. The circuit only occupies 0.07λg × 0.09λg.

Compact Quad-Band BPF Using Quad-Mode Stub Loaded Resonators

AbstractA compact quad-band microstrip band-pass filter (BPF) using quad-mode stub loaded resonators (SLRs) is presented in this paper. The proposed SLR can achieve quad-band responses analyzed by the odd-even-mode method and have great flexibility to adjust the resonant frequencies. Based on the analysis, a quad-band filter centred at 1.57, 2.5, 3.5 and 5.2 GHz is designed and fabricated. The predicted results on S parameters are compared with the measured ones and good agreement is observed.

A Novel Compact UWB Bandpass Filter with Quad-Notched Bands Based on S-SCRLHs Resonator

AbstractA novel compact ultra-wideband (UWB) bandpass filter (BPF) with a quad band-notched function using S-SCRLHs (splitted simplified composite right/left-handed) resonator is presented. The S-SCRLHs resonator, which exhibits quadruple resonance, is realized by coupling double S-SCRLH resonator. The S-SCRLHs resonator is integrated into a conventional UWB BPF. The notched frequencies can be adjusted according to specification by altering the S-SCRLHs resonator. Band-rejected filtering properties around the C-band satellite communication band, 5.2 GHz WLAN band and the X-band satellite communication band are generated. The notching frequencies are located at 4.2/5.2/6.3/7.8 GHz. Both simulated and measured results are provided with good agreement. Compared with other BPFs, the proposed BPF has the advantages of compact size, multi-stopband and good selectivity.

DESIGN OF RADIAL MICROSTRIP BAND PASS FILTER WITH WIDE STOP-BAND CHARACTERISTICS FOR GPS APPLICATION

In this paper, a novel compact band pass filter (BPF) is proposed for Global Positioning System (GPS) receivers. The proposed BPF configuration is composed of a low pass filter (LPF) section formed by the coupled line transformer connected with a radial stub and two short circuited stubs embedded within the 50 Ω microstrip line connecting the input/output (I/O) port of LPF. The lumped equivalent model of proposed BPF is also presented and analyzed. Simulation as well as experimental results shows very good in-band (pass-band) and out-of-band (≈ 7fc (centre frequency)) characteristics. The 3 dB fractional bandwidth (FBW) is 3.2% of fc, thus satisfying the GPS receiver requirement and the minimum insertion loss (IL) in pass-band is 1.28 dB.

Compact Ultra-Wide Band Bandpass Filter Design Employing Multiple-Mode Resonator and Defected Ground Structure

A compact bandpass filter (BPF) for ultra wideband (UWB) applications is proposed in this paper. The filter is consisting of two symmetrical multiple-mode resonators (MMRs) connected to quarter-wavelength parallel coupled lines in the input and output ports on the top, and a rectangular shaped defected ground structure (DGS) on the bottom of the filter. This filter provides in the passband an insertion loss of 0.2 dB and a return loss greater than 17 dB. Furthermore, the filter occupies an area of 10.42 x 2 mm2. The simulation results are in satisfactory agreement with the measurement ones reported elsewhere. The proposed UWB-BPF presents good performances in terms of insertion loss, return loss, fractional bandwidth and compact size than those reported in the literature.

Compact Tunable Filters for Broadband Applications

Microwave filters are essential components of modern communication systems. Miniaturization of microwave filters is of much demand in today's rapidly changing communication world with ever more growing wireless applications. The paper presents compact tunable band pass filters to provide multiple bands of operation. The filter employs tunable/chip inductors along with an inter-digital coupled line for introducing transmission zeros on both band edges. Tunability is achieved by varying the inductor values. The stop band attenuation is improved by etching Complementary Split Ring Resonators (CSRR's) and Defected Ground Structures (DGS) in the ground plane.

New design of compact dual band‐notch ultra‐wideband bandpass filter based on coupled wave canceller inverted T‐shaped stubs

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.

Compact stub‐loaded open‐loop BPF with enhanced stopband by introducing extra transmission zeros

Open-loop resonators (OLRs) are loaded with one or two stubs to design a compact bandpass filter (BPF) with a wide stopband by creating extra transmission zeros. By properly selecting the length of the stubs and their positions, extra transmission zeros are created in the stopband before the spurious passband, thus giving wide stopbands. Mathematical analyses are performed to show the effect of open stubs on the OLR. A two-stub-loaded BPF is designed and fabricated, which shows a harmonic suppression of up to 3.2fo by creating five transmission zeros and 44% size reduction as compared with a simple OLR-based filter without stubs. Measured results are in good agreement with the theoretical analysis and simulation results.

Miniaturized Close Dual-Band Bandpass Filter Based on Short Stub-Loaded Stepped-Impedance Resonators

Based on a short stub-loaded stepped-impedance resonator, a novel compact microstrip bandpass filter with controllable passband center frequencies is presented. To obtain dual-passband characteristics, dual-mode short stub-loaded stepped-impedance resonator and novel quad-pole-splitting techniques are investigated. The single passband is split into two with a notch when two resonators are employed, and dual passbands of a close band could be realized. It was found that the filter exhibits two desirable close passbands, an adjustable fractional bandwidth, and wide upper-stopband response. Moreover, the compact size of the proposed structure can be achieved. Good agreement between the measured and simulated results is shown.

Ultra-compact UHF Band-pass Filter Designed by Archimedes Spiral Capacitor and Shorted-loaded Stubs

Abstract UHF microstrip band-pass filters (BPFs) that much smaller than the referred BPFs are proposed in this communication. For the designing purpose of compactness, archimedes spiral capacitor and ground-loaded stubs are utilized to enhance capacitances and inductance of a filter. Two compact BPFs denoted as BPF 1 and BPF 2 are designed by applying these techniques. The size of BPF 1 and BPF 2 are 0.062 λg × 0.056 λg and 0.047 λg × 0.043 λg, respectively, where λg are guided wavelengths of the centre frequencies of the corresponding filters. The proposed filters were constructed and measured, and the measured results are in good agreement with the simulated ones.

New π –T generalised metamaterial negative refractive index transmission line for a compact coplanar waveguide triple band pass filter applications

This study presents, for the first time, a novel π − T generalised negative refractive index (NRI) transmission line (TL) configuration. It is innovated for increasing the possible passbands in designing microwave components. It is proved that the proposed transmission line can introduce up to seven passbands for completely unbalanced transmission line condition. The detailed mathematical analysis of that configuration based on the periodic network analysis and equivalent circuit model is introduced. As an application for the novel π − T generalised NRI TL configuration, a new compact triple band coplanar waveguide (CPW) metamaterial filter is introduced. The proposed triple bands CPW filter design steps are introduced and its performance is validated using equivalent circuit model simulation, electromagnetic full wave simulation and experimental measurements. Good agreements between the circuit modelling, electromagnetic full wave simulation and practical measurement results are achieved. All the results confirm that the proposed filter has triple passbands from 900 to 960 MHz, 1.4 to 1.48 GHz and 2.4 to 2.45 GHz. Moreover the filter size is compact whose length is only 12.1% λg at first passbands, 18.2 λg % at second passbands and 31.7 λg % at third passbands.

A systematic study on electrical properties of the BaTiO3–epoxy composite with different sized BaTiO3 as fillers

The epoxy composites consisting of BaTiO3 fillers with size of 100nm and 200nm were prepared, respectively. The thermo-mechanical and electrical properties of BaTiO3–epoxy composites were investigated using complex permittivity, electric modulus and ac electrical conductivity. The effects of filler size on the structure, filler–matrix interface and properties were discussed. The Havriliak–Negami model was used to analyze the dielectric relaxation of composites. The results show that larger filler tends to exhibit enhanced dynamic modulus and higher Tg because of the increase of effective volume fraction. The tetragonal phase formation in the BaTiO3 is important to achieve enhanced permittivity of the composite. The relaxation responses of composites revealed by electric modulus and complex permittivity show that the Maxwell–Wagner–Sillars (MWS) polarization and tetragonal phase transition of BaTiO3 affect the dielectric responses of composites. The conduction process is not only related with the barrier hopping but also tunneling effect of electrons. Based on the electrical properties of BaTiO3–epoxy composite with 100nm BaTiO3 at GHz, a compact band-pass filter with significant area reduction was designed and fabricated. The measured results show that the BaTiO3–epoxy composite is promising for advanced wireless device applications.

Millimeter-wave reconfigurable bandpass filters

Millimeter-wave reconfigurable bandpass filters with the ability to operate between 60 GHz and the E-band, capable of providing good channel isolation, are presented. A fully integrated filter with all reconfigurable elements embedded for compactness and a switchable filter that uses radio frequency micro-electro-mechanical system (RF MEMS) single-pole double-throw switches are designed. A new method that increases fractional bandwidths is introduced. It uses inductively coupled inverters without requiring their tuning. New circuit models are offered for inverters, reconfigurable resonators, and reconfigurable bandstop stubs. Our compact bandpass filter achieved a footprint of only 4.75 mm × 3.75 mm. Measurements for our filters show good agreement with the results of simulations.

Internally loaded cross‐coupled open‐loop resonators for a miniaturized bandpass filter using integrated passive device technology

ABSTRACTIn this article, an open‐loop resonator with internally loaded side‐coupled double open‐loops is proposed for use in the design of a compact bandpass filter with high selectivity and improved out‐of‐band rejection characteristics. The outer main open‐loop resonators are designed to operate at the center frequency of 7.7 GHz. In addition, side‐coupled double open‐loops are used to enhance electromagnetic coupling to provide high selectivity response and suppressed harmonics with an additional transmission zero at the bandstop region. The operating frequency shifting is performed by tuning the electromagnetic coupling strength without changing the configuration of the outer main open‐loops. To achieve a miniature size with high selectivity, the integrated passive devices semiconductor fabrication technology is implemented to achieve a compact size of 2.2 × 4.98 mm2, which is a compact size for X‐band downlink satellite communication applications. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2737–2740, 2014