Showing papers on "Stopband published in 2003"

Microstrip stepped impedance resonator bandpass filter with an extended optimal rejection bandwidth

Abstract: Bandpass filters with an optimal rejection bandwidth are designed using parallel-coupled stepped impedance resonators (SIRs). The fundamental (f/sub o/) and higher order resonant harmonics of an SIR are analyzed against the length ratio of the high-Z and low-Z segments. It is found that an optimal length ratio can be obtained for each high-Z to low-Z impedance ratio to maximize the upper rejection bandwidth. A tapped-line input/output structure is exploited to create two extra transmission zeros in the stopband. The singly loaded Q(Q/sub si/) of a tapped SIR is derived. With the aid of Q/sub si/, the two zeros can be independently tuned over a wide frequency range. When the positions of the two zeros are purposely located at the two leading higher order harmonics, the upper rejection band can be greatly extended. Chebyshev bandpass filters with spurious resonances up to 4.4f/sub o/, 6.5f/sub o/, and 8.2f/sub o/ are fabricated and measured to demonstrate the idea.

Miniaturized coplanar waveguide stop band filters based on multiple tuned split ring resonators

Abstract: A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology.

Parallel-coupled microstrip filters with over-coupled end stages for suppression of spurious responses

Abstract: In a parallel-coupled microstrip filter, end stages with over-coupling are designed to suppress the unwanted responses at twice the passband frequency (2f/sub 0/). The inherent transmission zero of an over-coupled input/output stage is shown tunable. It is found that increasing the image impedance of the filter sections can further enhance the suppression. The designed bandpass filters thus have a wide upper stopband and improved passband response symmetry. Measured results of fabricated circuits show that the idea works very well.

On the design of novel compact broad-band planar filters

Abstract: On the basis of impedance steps and coupled-line sections as inverter circuits, novel wide-band and very compact filters are presented. The application of alternately high- and low-impedance lines presented to the connected transmission-line resonators partly reduces their lengths to a quarter-wavelength only. In addition, effective techniques are demonstrated to reduce spurious stopband resonance resulting from a remaining half-wavelength resonator. Both suspended stripline (SSL) and microstrip filters were designed, fabricated, and tested, proving this concept in an excellent way. For the prototype filters, center frequencies around 6 GHz were selected. Bandwidths are between 2.5-3.25 GHz, and insertion-loss amounts to around 0.25 dB for the microstrip filters and 0.5 dB (including the transitions to coaxial line) for the SSL filters, respectively. For the selected center frequency and on a substrate with a dielectric constant of 10.8, the smallest microstrip filter is only 15 mm/spl times/5 mm in size.

Investigations into nonuniform photonic-bandgap microstripline low-pass filters

Abstract: With the advent of planar photonic bandgap (PBG) materials, different PBG topologies have been proposed to improve bandgap performances of microwave signals. Conventional circular-patterned PBGs have constraints in the wide stopband performance due to high passband ripples. In this paper, we suggest two novel configurations with nonuniform dimensions of circular-patterned PBGs to improve the stop bandwidth and passband ripples. The dimensions of PBG units are varied proportionally to the coefficients of binomial and Chebyshev polynomials. The simulated and measured responses of the proposed PBG units are presented. It is seen that Chebyshev distribution produces excellent performance by suppressing passband ripples and producing distinct stopband. These performances of passband ripples and stop bandwidth are further improved with Chebyshev distributed annular-ring PBG units with their unique feature of aspect ratio control.

Three-dimensional cone filter banks

Abstract: Three dimensional (3-D) narrow cone-shaped filter passbands are ideally required for the selective filtering of sampled broad-band 3-D plane waves on the basis of their directions of arrival. A method is proposed for approximating narrow 3-D cone-shaped passbands using a 3-D cone-filter-bank structure in which the subbands consist of band limited 3-D narrow-band infinite impulse response (IIR) beam filters having 3-D uniform bandwidths that are approximately proportional to their distance from the origin in the 3-D frequency space. The 3-D beam filters may be realized from a cascade of 3-D IIR frequency-planar filters. It is shown that the proposed 3-D cone filter bank achieves low distortion of broad-band passband 3-D plane waves, and significant attenuation of broad stopband plane waves.

Flat-top interleavers using two Gires-Tournois etalons as phase-dispersive mirrors in a Michelson interferometer

Abstract: We present our experimental investigations of a flat-top 50-GHz optical interleaver using two Gires-Tournois etalons (GTEs) as phase dispersive mirrors in a Michelson interferometer. The spectral characteristics of the interleaver in a 50-GHz channel spacing application exhibit a 0.5-dB passband larger than 43.8 GHz (88% of the spacing), a 25-dB stopband greater than 40 GHz (80% of the spacing), and a channel isolation higher than 30 dB. The result shows that the interleaver interferometer with novel GTE technique can simultaneously produce a 0.5-dB passband and a 25-dB stopband wider than other interferometer techniques.

Uniplanar compact wideband bandstop filter

Abstract: A uniplanar wideband bandstop filter is proposed using two bent open-end stubs. The proposed filter consists of the bent connecting line of /spl lambda//sub g//2 between two bent /spl lambda//sub g//4 stubs, which results in wideband design with a rejection bandwidth of 90% at 2.05 GHz. Further, the connecting line and stubs have the same characteristic impedance. The proposed filter compared to the conventional one is also more compact. The area of the novel filter is (/spl lambda//sub g//4)/sup 2/ at the center frequency of the stopband, while the area of the filter realized using the nonbent stubs and connecting line is 2(/spl lambda//sub g//4)/sup 2/ for the same stopband characteristics.

Photonic band gap effect in layer-by-layer metallic photonic crystals

Abstract: Theoretical models have been developed to investigate the reflection and transmission spectra, and photonic band structure for a midinfrared layer-by-layer metallic photonic crystal. It is found that photonic band gap effects due to global coupling between different unit cells in different layers play a key role in the formation of the lowest stop band gap extending to zero frequency and a high transmission passband adjacent to the stop band gap. Excellent agreement of theoretical results with experimental measurements is achieved.

Analysis and Applications of Uniplanar Compact Photonic Bandgap Structures

Abstract: This paper reviews recent advancements in the research and development of Uniplanar Compact Photonic Bandgap (UCPBG) structures for microwave and millimeter-wave applications. These planar periodic structures are particularly attractive and have been intensively investigated due to their easy fabrication, low cost, and compatibility with standard planar circuit technology. In this paper, basic properties of UC-PBG will be studied such as the slowwave effect, distinct stopband and passband, leakage suppression of surface waves, and realization of a magnetic surface. Owing to the different features of UC-PBG, these structures have been applied to microwave circuits to improve microstrip filters and patch antennas, to perform harmonic tuning in power amplifiers, to suppress leakage in conductor-backed coplanar waveguide, to realize TEM waveguides, and to implement low-profile cavity-backed slot antennas.

Electromagnetic band gap microwave filter

Abstract: A microwave filter is formed from an electromagnetic band gap structure. The electromagnetic band gap structure includes a periodic array of metal features (16, 42, 44, 50) formed within a dielectric matrix (14, 52). A defect feature (17, 48) is formed within the periodic array of metal features (16, 42, 44, 50) in order to create a pass band within a stop band region.

Wideband and compact bandstop filter structure using double-plane superposition

Abstract: 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.

Optimal design of multichannel transmultiplexers with stopband energy and passband magnitude constraints

Abstract: Optimal design incorporating filter stopband energy and passband magnitude constraints is studied for multichannel, uniform, and nonuniform transmultiplexers. Central to the development is a reformulation of the design problem as a quadratic programming problem with quadratic constraints and semi-infinite constraints while the composite distortion measure for reconstruction is minimized. An iterative optimal design procedure for finite-impulse-response synthesis and analysis filters is developed and applied to two design examples, one for the uniform case and another for the nonuniform case based on general building blocks.

Spiral microstrip resonators for narrow-stopband filters

Abstract: A rectangular spiral microstrip resonator is proposed for use in planar narrow-stopband filters. A full-wave electromagnetic simulator is used to show that this small-size resonator is suitable for realising compact narrow-stopband microstrip filters. Simulated and measured results indicate that minimal coupling between adjacent resonators exists, with the effect that the microstrip filter response corresponds very closely to that of the equivalent network response of the filter. As a comparison, results are also shown for a similar filter realised with microstrip open-loop resonators.

Multiperiod EBG structure for wide stopband circuits

Abstract: A multiperiod electromagnetic band-gap (EBG) structure is proposed and studied. The stopbands of single-period and multiperiod EBG structures are assessed using finite-difference time-domain (FDTD) simulation and experimental measurements. Simulated and measured results show that the multiperiodic EBG structure can achieve a wider stopband compared to a single period EBG structure.

Cavity formation and light propagation in partially ordered and completely random one-dimensional systems

Abstract: We study light transport in ordered, partially ordered, and completely random one-dimensional (1-D) systems. In a periodic structure, there are three types of passbands with different origins. When disorder is introduced to a periodic system, the passbands change differently, depending on their origins. The transmissivity and decay length in the passbands near the band edges decrease drastically. The stopbands are widened. The introduction of randomness to a periodic structure enhances light localization in frequency regions in which it is delocalized in a periodic structure. In a completely random system, a resonant cavity is formed by two stacks of multiple layers which serve as two highly reflective broadband mirrors. We calculate the size and the quality factor of 1-D random cavities. With an increase in the degree of disorder, the lasing threshold in such a cavity first decreases, then increases. The lasing frequency spreads from the band edge toward the stopband center.

Examining by the Rayleigh-Fourier method the cylindrical waveguide with axially rippled wall

Abstract: Axially corrugated cylindrical waveguides with wall radius described by R/sub 0/(1+/spl epsi/cos2/spl pi/z/L), where R/sub 0/ is the average radius of the periodically rippled wall with period L and amplitude /spl epsi/, have been largely used as slow-wave structures in high-power microwave generators operating in axisymmetric transverse magnetic (TM) modes. On the basis of a wave formulation whereby the TM eigenmodes are represented by a Fourier-Bessel expansion of space harmonics, this paper investigates the electrodynamic properties of such structures by deriving a dispersion equation through which the relationship between eigenfrequencies and corrugation geometry is explored. Accordingly, it is found that for L/R/sub 0//spl ges/1 a stopband always exists at any value of /spl epsi/; the condition L/R/sub 0/=1 gives the widest first stopband with the band narrowing as the ratio L/R/sub 0/ increases. For L/R/sub 0/=0.5 the stopband sharply reduces and becomes vanishingly small when /spl epsi/<0.10. Illustrative example of such properties is given on considering a corrugated structure with L/R/sub 0/=1,R/sub 0/=2.2 cm, and /spl epsi/=0.1, which yields a stopband of 1.5-GHz width with the central frequency at 8.4 GHz; it is shown that in a ten-period corrugated guide, the attenuation coefficient reaches 165 dB/m, which makes such structures useful as an RF filter or a Bragg reflector. It is also discussed that by varying L/R/sub 0/ and /spl epsi/ we can find a variety of mode patterns that arise from the combination of surface and volume modes; this fact can be used for obtaining a particular electromagnetic field configuration to favor energy extraction from a resonant cavity.

An equivalent circuit and modeling method for defected ground structure and its application to the design of microwave circuits

Abstract: In this article, the equivalent circuit and modeling method for a defected ground structure (DGS) is proposed, to be used in the design of a microwave circuit. Using the proposed equivalent circuit permits the optimization of the DGS circuits. Simulation and measurements on a fabricated DGS low pass filter show its optimized passband and stopband performance. Furthermore, this article describes a novel design method to improve the performance of a class-AB power amplifier, using the proposed DGS structure. The equivalent circuit of DGS has been used to optimize the output matching circuit of the power amplifier. The design method for a power amplifier presented in this article can provide accurate design results to simultaneously satisfy the optimum load condition and desirable harmonic rejection. As another example, a microwave DGS oscillator was designed by the suggested method. Measured results on the fabricated DGS circuits show the validity of this approach.

Stable single-mode operation of distributed feedback lasers with wirelike active regions

Abstract: A stable single-mode operation mechanism in distributed feedback (DFB) lasers with wirelike active regions was theoretically investigated by taking into account "gain matching" between standing wave profiles of each resonant mode and periodic active regions. As a result, it was clarified that the resonant modes at the longer wavelength side of the stopband have higher modal gain than those at the shorter wavelength side and that the oscillation takes place at the longer wavelength side resonant mode nearest to the stopband. The influence of the cleaved facet with respect to the grating phase was also analyzed. The measured spectral properties of buried heterostructure GaInAsP/InP DFB lasers consisting of wirelike active regions, such as a subthreshold gain spectrum and the lasing wavelength with respect to the stop band, agreed well with theoretical results. Finally, it was confirmed that a stable single-mode operation was preserved even after a room temperature continuous wave aging of 7300 h at bias current of around 10/spl times/ the threshold.

Tunable duplexer having multilayer structure using LTCC

Abstract: A tunable duplexer has been designed for GSM1800/1900 digital cellular system. The tunable duplexer has been fabricated with LTCC (Low Temperature Co-fired Ceramics) multilayer technologies assisted by varactor diodes. To accomplish higher attenuation for each system, multi-tuning method, which enables to control the passband and the stopband independently, is applied. Size is designed as 5.7/spl times/5.7/spl times/1.8mm. Insertion losses are less than 3.5dB. Attenuation is more than 25dB at Fo+200MHz in Tx, and is more than 10dB at F0-150MHz in Rx.

Micromachined FBAR RF filters for advanced handset applications

Abstract: In this paper, fully integrated FBAR (Film Bulk Acoustic Wave Resonator) RF BPFs (Band Pass Filters) and a duplexer have been designed, fabricated, and characterized for advanced mobile/wireless communication systems by using silicon bulk micromachining technology. Two different RF band pass filters are realized by combining 6 to 7 resonators in series and parallel connection for two chip FBAR duplexer for CDMA PCS applications. AlN, Mo, and silicon nitride are utilized for realizing the proposed FBAR BPFs and duplexer as a piezoelectric material, electrodes, and a supporting membrane, respectively. The fabricated FBAR filters have insertion loss of -1.46 dB and -1.86 dB, return loss of -13 dB and -10 dB, and stop band rejection of -14 dB, and -33 dB, center frequency of 1.88 GHz and 1.96 GHz, and size of 1.3 mm /spl times/ 1.5 mm, respectively. The demonstrated FBAR duplexer for CDMA PCS applications has insertion loss of -1.3 dB (Min.) and absolute attenuation of -42 dB (Min.) at Tx to Antenna port, while it has insertion loss of -2.3 dB (Min.) and absolute attenuation of -52 dB (Min.) at Antenna to Rx port.

Novel periodically loaded E-plane filters

Abstract: Novel E-plane waveguide filters with periodically loaded resonators are proposed. The proposed filters make use of the slow wave effect in order to achieve improved stopband performance and size reduction of roughly 50% without introducing any complexity in the fabrication process. Numerical and experimental results are presented to validate the argument.

A design for a high finesse parallel‐coupled microring resonator filter

Abstract: Interaction between the circulating waves in microrings and the connecting busbars provides two parallel-coupled microrings with filter characteristics that feature a stopband with uniformly large rejection and high finesse. Performance degradation due to waveguide and coupler loss and facet discontinuities have also been computed and found to be moderate. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 125–129, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10992

Compact ridged waveguide filters with improved stopband performance

Abstract: A novel ridged waveguide bandpass filter configuration is proposed. The proposed filter has comparable size to standard E-plane filters while having suppressed spurious resonance. Compactness is achieved by taking advantage of the properties of slow waves in half wavelength resonators, while spurious behaviour suppression is achieved by means of an integrated lowpass structure. Periodicity is readily imposed by cascading ridge waveguides with rectangular waveguides. The structure is simple and compatible with E-plane technology. Numerical and experimental results are presented to validate the argument.

High-resolution photonics-based interference suppression filter with wide passband

Abstract: A new topology for a photonic signal processor, which overcomes the basic recursive frequency response problem that limits the passband range, is presented. The structure is based on a new multiple-wavelength offset-cavity structure that is cascaded with a series of unbalanced delay line structures. This not only can synthesize a very narrow notch response with good shape factor but also permits a multifold extension of the free spectral range (FSR) and passband width. Results on the interference mitigation filter demonstrate a stopband of 1% of center frequency and a fourfold increase in the FSR and passband width, while also having a very small shape factor, in excellent agreement with predictions.

Band elimination filter, filter device, antenna duplexer and communication apparatus

Abstract: It has been difficult to provide a band elimination filter having characteristics of a high attenuation within a desired stop band and a low loss over wide frequency bands higher and lower than the stop band. A band elimination filter includes: a plurality of acoustic wave resonators as an acoustic resonator each having one end grounded; and a transmission line to which the other end of each of the plurality of acoustic wave resonators as an acoustic resonator is connected, in which at least some of the other ends are coupled to the transmission line at predetermined intervals, and at least one inductor is provided on transmission line in all or some of the predetermined intervals.

Wide bandgap composite EBG substrates

Abstract: High-K ceramics are embedded into a polymer host to create an electromagnetic bandgap (EBG) substrate that possess superior properties to previous bandgap implementations in terms of stopband width, attenuation per layer, and practicality. Ceramics are periodically spaced in a commercially-available, Teflon-based host to create a bandgap that spans from 12.1 to 24.1 GHz. Miniature dielectric rods were created in a separate extrusion process, and then placed in a square lattice in a substrate to create the periodic composite. As an application of the material, a defect resonator was created at 20.41 GHz and a Q of 760 was measured.

Fundamental mode 5 GHz surface-acoustic-wave filters using optical lithography

Abstract: Resonators and bandpass filters have been implemented in the 5 GHz frequency range, based on “longitudinal leaky” surface-acoustic waves on standard YZ-cut lithium niobate substrate. The synchronous one-port resonators constituting a ladder filter operate in the fundamental mode. The electrode width in the resonators is above 0.25 μm, thus making them readily accessible for fabrication with optical lithography. Test resonators are fabricated to study the effects of the metallization ratio and aperture on the resonator behavior. For the prototype filter, a center frequency of 5.20 GHz, a wide fractional 3 dB bandwidth of 6.3%, a minimum insertion loss of 3.3 dB and a high stopband suppression of 25 dB have been achieved.

Tapered photonic bandgap microstrip lowpass filters: design and realisation

Abstract: The application of tapering techniques to two-dimensional photonic bandgap (2D-PBG) microstrip structures allows great improvement in the sidelobe level of the S11 scattering parameter and, consequently, a very flat passband. In this paper, many tapering windows are proposed for 2D-PBG canonical (straight microstrip line) stopband filters. By suitably designing three rows of tapered periodic structures which are characterised by different centre frequency of the stopband, a novel photonic bandgap lowpass filter was realised and characterised. Numerical simulations show satisfactory agreement with experiments.

Coplanar waveguide periodic structures with resonant elements and their application in microwave filters

Abstract: Coplanar waveguide (CPW) periodic structures with resonant elements on the ground plane have been investigated for lowpass and bandstop filter applications. The resonator is constructed by etching out radial shapes on the ground plane. The use of resonant elements allows larger attenuation in the stop band to be obtained with less number of periodic structures as compared with conventional photonic bandgap (PBG) structures. A theoretical study of this type of periodic structure has revealed some useful information for designing filters. Two filters of this type, one for lowpass application and the other for bandstop application have been designed, fabricated and tested. The results are presented.