Showing papers on "Stopband published in 2008"

A Compact Open-Loop Filter With Mixed Electric and Magnetic Coupling

Abstract: A novel cascaded microstrip open-loop resonator filter with controllable electric and magnetic mixed coupling is presented to have one or more transmission zeros. For two coupled resonators, the coupled sides with the maximum magnetic field are combined with their open gaps with the maximum electric field, creating the electric and magnetic mixed coupling. By adjusting the distances between resonators and the positions of open gaps in a mixed coupled filter, the coupling coefficients can be changed, and controllable transmission zeros can be produced in the lower stopband, upper stopband, or both. Design and fabrication of the proposed second-and fourth-order filters show the advantages: such as a smaller number of resonators, higher rejection level, as well as asymmetrical response; moreover, the location of the transmission zeros can be precisely controlled.

An Embedded Common-Mode Suppression Filter for GHz Differential Signals Using Periodic Defected Ground Plane

Abstract: A novel low-cost filter design for common-mode noise suppression in high-speed differential signals is proposed. It is realized by periodically etching the dumbbell-shape defected ground structure (DGS) to perturb the return current of the common- mode noise. A transmission-line model for the proposed structure is also developed with good agreement to the full-wave simulation and measurement result. It is found that over 20 dB suppression of common-mode noise can be achieved over a wide frequency range from 3.3 to 5.7 GHz with 3 cascaded DGS cells, while the differential signals still keep good signal integrity in eye-pattern observation. The common-mode current, which generally results in common-mode EMI, on the attached input/output cable is also proved to be efficiently suppressed (15 dB in average) within the stopband by the proposed filter.

Hybrid optoelectronics: A polymer laser pumped by a nitride light-emitting diode

Abstract: We demonstrate indirect electrically pumped lasing in a hybrid polymer laser. The lasers comprise a corrugated fluorene copolymer waveguide on an InGaN light-emitting diode and were driven under nanosecond pulsed operation. We observe the onset of distributed feedback lasing at 568nm for peak drive currents above 144A. Angle-resolved photoluminescence measurements identify the lasing mechanism as band edge feedback from a photonic stopband in the TE0 waveguide mode.

Small Ultra-Wideband (UWB) Bandpass Filter With Notched Band

Abstract: A compact ultra-wideband (UWB) bandpass filter (BPF) with notched band has been proposed and implemented in this letter. H-shaped slot is studied and adopted to tighten the coupling of inter-digital capacitor in order to improve the BPF's performance. Three pairs of tapered defected ground structures (DGS) are formed to assign their transmission zeros towards the out of band signal, thereby suppressing the spurious passband. Combining these two structures we obtain a small sized UWB BPF. Meander line slot is developed to reject the undesired wireless local-area network (WLAN) radio signals. An experimental UWB filter with notched band was fabricated with 35% less length as compared to an embedded open-circuited stub. The measured BPF insertion loss is less than 1.0 dB throughout the pass band of 2.8 to 10.8 GHz, the variation of group delay less than 0.20 ns in this band except for the notched band, and a wide stopband bandwidth with 20 dB attenuation up to at least 20.0 GHz.

Stopband-Expanded Low-Pass Filters Using Microstrip Coupled-Line Hairpin Units

Abstract: In this letter, a class of stopband-expanded low-pass filters (LPFs) is proposed via attenuation poles of microstrip coupled-line hairpin unit. By centrally tap-connecting this coupled-line unit and adjusting its coupling strength, three attenuation poles can be excited above the desired low passband. A coupled-line-oriented closed-form model is then constructed to provide a physical insight into the excitation of these poles and to execute an efficient synthesis design of this LPF. Two prototype filters with single and two units are finally designed with the specified cutoff frequency at 2.5 GHz. Measured results of the fabricated filters evidently demonstrate good LPF performance, sharp roll-off skirt, and a wide upper-stopband of 3.2 to 11.8 GHz with the insertion loss higher than 20.0 dB.

Electrically Tunable Polypyrrole Inverse Opals with Switchable Stopband, Conductivity, and Wettability

Abstract: An electrically tunable Ppy inverse opal was fabricated by electropolymerization. The stopband, conductivity, and wettablity of the inverse opal could be reversibly modulated by electroredox. These properties endowed the material with promising applications in multifunctional optoelectronic devices.

Ultra-Wideband Bandpass Filter Using Multilayer Liquid-Crystal-Polymer Technology

Abstract: Novel ultra-wideband (UWB) bandpass filters are proposed based on quasi-lumped-element prototypes and implemented with multilayer liquid-crystal-polymer (LCP) technology. In this study, the broadside-coupled microstrip radial stubs and high-impedance microstrip lines are adopted as quasi-lumped elements for realizing compact UWB bandpass filters. By introducing a short-circuited high-impedance microstrip line as a shunt inductor and suitably designing quasi-lumped-element capacitors, a compact six-pole bandpass filter is implemented with the Federal Communications Commission (FCC) defined UWB specifications. To further improve the selectivity and wideband performance, an eight-pole filter of this type is developed by adding two shunt short-circuited microstrip stubs, which introduce a transmission zero at the upper passband edge. The proposed filters are fabricated using multilayer LCP technology. Good agreement between simulated and measured results of these filters are observed. The measured results show that the fabricated six-pole filter has good specifications for the FCC-defined UWB system. The fabricated eight-pole filter has an ultra-wide fractional bandwidth (139%) and a good stopband rejection level, which is higher than 38.1 dB from 10.57 to 18.0 GHz. The proposed filters are attractive for UWB communications and radar systems.

The tunable acoustic band gaps of two-dimensional phononic crystals with a dielectric elastomer cylindrical actuator

Abstract: By calculating the transmission coefficients by finite-element software, the study of the tunable acoustic band gap for two-dimensional (2D) phononic crystals composed of a square array of hollow cylinders in an air background is considered. The inclusions are a dielectric elastomer cylindrical actuator, which is made of a hollow cylinder sandwiched between two compliant electrodes. By applying a voltage between the compliant electrodes, the radial strain of the silicone-made actuator is investigated. The acoustic band gaps are changed due to the radial strain of the dielectric elastomer. The frequency range of the dielectric elastomer composite can be extended by increasing the applied voltage. A tunable acoustic band gap of the phononic crystal is realized via the unique character of dielectric elastomer. The calculations also demonstrate that there exists a local stop band within the pass band. With a local stop band gap, 2D phononic crystals may thus serve as an acoustic filter or switch.

Power divider with microstrip electromagnetic bandgap element for miniaturisation and harmonic rejection

Abstract: A novel technique for harmonic suppression and size reduction in planar Wilkinson power divider is presented. The proposed technique served by a microstrip electromagnetic bandgap element (MEBE) is used to reject the unwanted harmonics by employing its stopband effect and to reduce the length of microstrip by utilising its slow-wave effect. The whole size of the proposed divider has been reduced by 39% compared to the conventional power divider. Higher harmonics are effectively suppressed.

Compact Elliptic-Function Low-Pass Filter Using Defected Ground Structure

Abstract: A novel elliptic-function low-pass filter (LPF) is presented, which consists of a dumb-bell-shaped defected ground structure (DB-DGS), a spiral-shaped defected ground structure (SP-DGS) and a broadened microstrip line. The DB-DGS provides the required wideband attenuation in stopband, while the SP-DGS provides steep transition from passband to stopband. A 2.4 GHz five-pole LPF is developed and experimental results show that it has a sharp cutoff frequency response. The measured passband insertion-loss is below 0.3 dB, and the rejection band over 20 dB is from 2.95 to 8.25 GHz.

Wideband Smaller Unit-Cell Planar EBG Structures and Their Application

Abstract: A new low-cost smaller unit-cell planar electromagnetic bandgap (EBG) structure operating at the lower GHz frequencies (below 6 GHz) is proposed. EBG structures based on this new geometry are designed on a number of commonly available substrates. Characteristics of such structures, such as bandgap and reflection phase profile are analyzed. A simple empirical model is proposed to predict the surface wave stopband frequency of the proposed EBG structure. Finally, a low-profile dipole antenna is designed and tested for operation on the EBG structure.

Compact ultra-wideband antenna with dual bandstop characteristic

Abstract: A simple and compact ultra-wideband microstrip-fed planar antenna with dual bandstop characteristic is presented. By using a U-slot defected ground structure (DGS) in the feedline, a stopband of 600 MHz (from 5.45 to 6.05 GHz) for band rejection of WLAN is achieved. To obtain another stopband, an arched slot is etched on the radiating patch. Experimental results show that the designed antenna, with a compact size of 30 times 24.5 mm, has an impedance bandwidth of 2.8-11 GHz for voltage standing wave ratio (VSWR) less than 2, except two frequency stop-bands of 3.5-4.25 GHz and 5.45- 6.05 GHz. Moreover, the antenna has good omnidirectional radiation patterns in the H-plane.

Compact ultra-wideband bandpass filter with defected ground structure

Abstract: A compact planar microstrip ultra-wideband (UWB) bandpass filter is presented in this paper. The proposed UWB filter is realized by cascading a high pass filter (HPF) and a lowpass filter (LPF). HPF with short-circuited stubs is used to realize the lower stopband and a lowpass filter based on a defected ground array in the ground plane employed to attenuate the upper stopband. One such a bandpass filter is designed and simulated.

High Isolation Proximity Coupled Multilayer Patch Antenna for Dual-Frequency Operation

Abstract: A new method to enhance the isolation between two ports in a dual-frequency proximity coupled patch antenna is presented. The dual-polarized patch antenna has a multilayer substrate configuration to achieve a compact design. In addition, two periodic structures have been included under the two feeding lines to have stopband behavior in the other frequency port. These electromagnetic bandgap (EBG) filters have been realized by introducing mushroom type resonators underneath the antenna feeding lines. Measurements show how the isolation between the feeding ports can be improved by selecting a suitable size for the resonators. The proposed antenna design achieves an isolation higher than 55 dB in the first frequency band (2.1 GHz) and better than 40 dB in the second one (2.45 GHz). Radiation patterns are not affected by the proposed structures showing low cross-polarization levels in both planes at the two frequency bands.

A Novel Power/Ground Layer Using Artificial Substrate EBG for Simultaneously Switching Noise Suppression

Abstract: A novel power/ground plane for eliminating the power noise in the high-speed digital circuits using an artificial substrate electromagnetic bandgap (AS-EBG) structure is proposed. The AS-EBG is designed by embedding the air rods and high dielectric constant (DK) rods between the coplanar EBG power/ground planes to enhance the stopband bandwidth. A 2-D transmission-line model of the AS-EBG power planes is also developed with experimental verification to explain the mode perturbation and predict the bandgap of the AS-EBG. It is found that over 60% enhancement of bandwidth (from 1.5 to 2.4 GHz) can be achieved for a 3 times 3 AS-EBG power plane compared to the coplanar-EBG power planes by proper design of the high DK rod with DK of 92. Based on SPICE-based modeling, the excellent power/signal integrity performance of the AS-EBG structure is also presented by the chip-package co-simulation in the time domain. It is found over 70% reduction of the simultaneously switching noise can be obtained with good signal eye-diagram improvement.

Novel design of dual-mode bandpass filter using rectangle structure

Abstract: A compact dual-mode filter is proposed by using rectangle structure. The filter has the characteristics of compact structure, low insertion loss and so on. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The experimented results were in good agreement with simulated results.

Synthesis of ultra-wideband bandpass filter employing parallel-coupled stepped-impedance resonators

Abstract: To design an ultra-wideband (UWB) bandpass filter with the fractional bandwidth (FBW) up to 110% (31%106%GHz), a new filter prototype consisting of multi-stage parallel-coupled stepped-impedance resonators (SIRs) is synthesised based on the transmission-line theory rather than the conventional multi-mode property Asymmetrical SIRs are employed instead of the conventional symmetrical/quasi-symmetrical ones, so that an extra degree of freedom is introduced in circuit parameter selection As a result, the minimum dimension of the coupling gaps between the adjacent SIRs is successfully enlarged to be more than 01%mm, which alleviates the requirement on fabrication precision A simple equivalent circuit for this filter prototype is represented in the form of distributed parameters and the corresponding Chebyshev filtering function is derived as well The relation between the number of poles in passband, N p , and the stage of the filter, n , is summarised to be N p =3 n +2 To validate the newly derived synthesis theory, a one-stage UWB filter is first synthesised to compare with the previously published results obtained by the electromagnetic (EM) simulator Furthermore, a two-stage filter is synthesised to successfully meet the Federal Communications Commission (FCC)+s indoor/outdoor spectrum specifications The fabricated UWB filter exhibits a compact size of 2658+mm in total length, low insertion loss (09+dB at 685+GHz), flat group delay (05+01+ns), good stopband characteristics (+S21+++40+dB at 1+2+GHz) and steep skirt property (+28+dB/GHz) as well It should be noted that the proposed filter prototype can be also used to realise aUWB filter with an FBW even greater than 110+

Sharp-Rejection Wideband Bandstop Filters

Abstract: In this letter, a novel transmission line configuration has been proposed to design a sharp-rejection, bandstop filter (BSF) with wide rejection bandwidth. The rejection bandwidth and the level of rejection are controlled by the characteristic impedances of the transmission lines. Design equations are obtained by using a lossless transmission line model. The proposed design has been verified in microstrip line by fabricating a prototype BSF of -20 dB fractional bandwidth of 100% at a stopband center frequency f0 = 1.5 GHz. The filter structure is simple and easy to fabricate.

Design of the Compact Wideband Bandpass Filter With Low Loss, High Selectivity and Wide Stopband

Abstract: In this letter, a novel compact wideband bandpass filter using the asymmetric stepped-impedance resonator (SIR) with one step discontinuity is designed and implemented to achieve characteristics of low loss, wide stopband and very high passband selectivity, simultaneously. The first two resonant modes of the asymmetric SIR are coupled together and applied to create a wide passband. The design procedure is discussed in detail. The proposed filter at center frequency f0 of 4 GHz has very good measured characteristics including a low insertion loss of 0.5 plusmn 0.3 dB, the bandwidth of 2.9-5.3 GHz, sharp rejection due to two transmission zeros in the passband edge. Experimental results of the fabricated filter show a good agreement with the predict results.

Microstrip Parallel-Coupled Filters With Cascade Trisection and Quadruplet Responses

Abstract: Microstrip parallel-coupled filters with generalized Chebyshev responses are presented. The basic structure of the proposed filter is a conventional parallel-coupled filter of which the physical dimensions can be easily obtained by the well-known analytical method. With the aid of the equivalent circuit corresponding to a conventional parallel-coupled filter, the relative insertion phase from source or load to each open end of resonators can be easily obtained by observing the two-port admittance matrix. Applying the cross coupling from source or load to a proper nonadjacent resonator, a trisection or a quadruplet coupling scheme can be realized with prescribed transmission zeros. More importantly, the proposed trisection can be designed to have a transmission zero on the lower or upper stopband by just adjusting the length of the cross-coupling strip. Using the proposed structure, the conventional time-consuming adjusting procedure to obtain initial physical dimensions of filters is no longer required. In this paper, a fourth-order parallel-coupled filter is used as the basic structure to demonstrate various combinations of transmission zeros. Simulated and measured results are well matched.

Wide-Stopband Microstrip Bandpass Filters Using Quarter-Wavelength Stepped-Impedance Resonators and Bandstop Embedded Resonators

Abstract: Novel compact microstrip bandpass filters (BPFs) with extended stopband are proposed using both quarter-wavelength (lambda/4) stepped-impedance resonators and bandstop embedded resonators. First, by properly designing the impedance and length ratios of the stepped-impedance resonators, the developed filter may be made compact and its spurious harmonics may be pushed to the higher frequency region. Next, by suitably designing the bandstop structure so as to suppress the lower spurious harmonics of stepped-impedance resonators and then embedding the bandstop structure into the lambda/4 resonators, one may realize the BPFs with wideband spurious suppression. In particular, by connecting the bandstop embedded resonators to the input/output ports, a compact fourth-order BPF of dimension 0.089 lambdag times 0.27 lambdag is implemented and its stopband is extended up to 8.25 f 0 with an adequate rejection of greater than 32.49 dB, where f 0 is the passband center frequency and lambdag is the microstrip guided wavelength at f 0.

A novel bandpass filter based on complementary split rings resonators and substrate integrated waveguide

Abstract: One novel bandpass filter implemented with combination of two different structures-complementary split rings resonators (CSRRs) and substrate integrated waveguide (SIW) is proposed in this article. Several CSRRs are etched on the surface of SIW to form the stopband with very sharp rejection. One prototype was fabricated, the measured results indicate 30% passband (at −15 dB return loss), the rejection band ranges from 6.4 GHz to 7.8 GHz, about 20% bandwidth at −20 dB rejection, the maximum rejection even reaches 50 dB. The rejection skirt is very sharp, only 18 MHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 699–701, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23182

Impedance-matched low-pass stripline filters

Abstract: We have constructed several impedance-matched low-pass filters using a stripline geometry with a dissipative dielectric. The filters are compact, simple to construct, and operate in cryogenic environments. The dissipative dielectric consists of magnetically-loaded silicone or epoxy, which is commercially available under the trade name Eccosorb. For a stripline length of 32 mm, the filters have a passband that extends from dc to a 3 dB bandwidth between 0.3 and 0.8 GHz. The 3 dB bandwidth can be adjusted beyond this range by changing the filter length. An extremely broad stopband at higher frequencies, with attenuation exceeding 100 dB, is achieved along with a return loss greater than 10 dB measured up to 40 GHz. This combination of high attenuation and low reflected power across a broad stopband ensures that spurious or unwanted signals outside the passband do not reach or return to the device under test. This type of filter has applications in microwave frequency measurements of sensitive nonlinear devices such as superconducting heterodyne mixers, quantum tunneling devices and quantum computing elements.

Multi-level diffractive optics for single laser exposure fabrication of telecom-band diamond-like 3-dimensional photonic crystals.

Abstract: We present a novel multi-level diffractive optical element for diffractive optic near-field lithography based fabrication of large-area diamond-like photonic crystal structure in a single laser exposure step A multi-level single-surface phase element was laser fabricated on a thin polymer film by two-photon polymerization A quarter-period phase shift was designed into the phase elements to generate a 3D periodic intensity distribution of double basis diamond-like structure Finite difference time domain calculation of near-field diffraction patterns and associated isointensity surfaces are corroborated by definitive demonstration of a diamond-like woodpile structure formed inside thick photoresist A large number of layers provided a strong stopband in the telecom band that matched predictions of numerical band calculation SEM and spectral observations indicate good structural uniformity over large exposure area that promises 3D photonic crystal devices with high optical quality for a wide range of motif shapes and symmetries Optical sensing is demonstrated by spectral shifts of the Γ-Z stopband under liquid emersion

Ultra high-speed electro-optically modulated VCSELs: modeling and experimental results

Abstract: We have studied the modulation properties of a vertical cavity surface-emitting laser (VCSEL) coupled to an electrooptical modulator. It is shown that, if the modulator is placed in a resonant cavity, the modulation of the light output power is governed predominantly by electrooptic, or electrorefraction effect rather than by electroabsorption. A novel concept of electrooptically modulated (EOM) VCSEL based on the stopband edge-tunable distributed Bragg reflector (DBR) is proposed which allows overcoming the limitations of the first-generation EOM VCSEL based on resonantly coupled cavities. A new class of electrooptic (EO) media is proposed based on type-II heterostructures, in which the exciton oscillator strength increases from a zero or a small value at zero bias to a large value at an applied bias. A EOM VCSEL based on a stopband-edge tunable DBR including a type-II EO medium is to show the most temperature-robust operation. Modeling of a high-frequency response of a VCSEL light output against large signal modulation of the mirror transmittance has demonstrated the feasibility to reach 40 Gb/s operation at low bit error rate. EOM VCSEL showing 60 GHz electrical and ~35 GHz optical (limited by the photodetector response) bandwidths is realized.

Ultra Wideband Bandpass Filter Using Embedded Stepped Impedance Resonators on Multilayer Liquid Crystal Polymer Substrate

Abstract: This letter proposes an ultra wideband (UWB) bandpass filter (BPF) based on embedded stepped impedance resonators (SIRs). In this study, broad side coupled patches and high impedance microstrip lines are adopted as quasi-lumped elements for realizing the coupling between adjacent SIRs, which are used to suppress stopband harmonic response. An eight-pole UWB BPF is developed from lump-element bandpass prototype and verified by full-wave simulation. The proposed filter is fabricated using multilayer liquid crystal polymer (LCP) process and measured using vector network analyzer. Good agreement between simulated and measured response is observed. The measurement results show that the fabricated filter has a low insertion loss of 0.18 dB at center frequency 6.05 GHz, an ultra wide fractional bandwidth of 127.3% and excellent stopband rejection level higher than 32.01 dB from 10.9 to 18.0 GHz.

Higher Order Cochlea-Like Channelizing Filters

Abstract: A design method is presented for contiguous-channel multiplexing filters with many channels covering a wide bandwidth. The circuit topology extends previous work on cochlea-like channelizers by introducing multiple resonator-channel filter sections. The new design provides increased stopband rejection, lower insertion loss, and improved passband shape compared with the earlier version while retaining a simple design method and a compact layout, and requires no post-fabrication tuning. Results of a three-pole ten-channel channelizer covering from 182 MHz to 1.13 GHz with 17.5% bandwidth channels and 1.1-dB insertion loss are presented, and agree well with theory. A discussion of the power handling of planar channelizers is also presented.

Compact double-mode cross-coupled microstrip bandpass filter with tunable transmission zeros

Abstract: A compact double-mode cross-coupled microstrip bandpass filter with an asymmetric frequency characteristic and three transmission zeros is presented. The bandpass filter consists of a cross-coupled gap and a double-mode resonator of a half-wavelength line with a shunt-stepped-impedance open stub. In comparison to the conventional square loop dual-mode resonator, the proposed double-mode resonator achieves a 59% size reduction. The parametric studies on the electrical length of the open stub and the capacitance of the cross-coupling are provided in order to gain a better insight into the transmission poles and zeros. Then, a bandpass filter is designed, fabricated and tested to validate the design concept. From 2.3 to 2.5 GHz, the return loss is better than 10 dB and the insertion loss is <1.5 dB. There are three transmission zeros in the upper stopband at 2.8, 3.4 and 4.9 GHz.