Showing papers on "Stopband published in 2001"

Attenuation and localization of wave propagation in rods with periodic shunted piezoelectric patches

Abstract: Shunted piezoelectric patches are periodically placed along rods to control the longitudinal wave propagation in these rods. The resulting periodic structure is capable of filtering the propagation of waves over specified frequency bands called stop bands. The location and width of the stop bands can be tuned, using the shunting capabilities of the piezoelectric materials, in response to external excitations and to compensate for any structural uncertainty. A mathematical model is developed to predict the response of a rod with periodic shunted piezoelectric patches and to identify its stop band characteristics. The model accounts for the aperiodicity, introduced by proper tuning of the shunted electrical impedance distribution along the rod. Disorder in the periodicity typically extends the stop bands into adjacent propagation zones and, more importantly, produces the localization of the vibration energy near the excitation source. The conditions for achieving localized vibration are established and the localization factors are evaluated for different levels of disorder on the shunting parameters. The numerical predictions demonstrate the effectiveness and potentials of the proposed treatment that requires no control energy and combines the damping characteristics of shunted piezoelectric films, the attenuation potentials of periodic structures, and the localization capabilities of aperiodic structures. The theoretical investigations presented in this paper provide the guidelines for designing tunable periodic structures with high control flexibility where propagating waves can be attenuated and localized.

Uniplanar one-dimensional photonic-bandgap structures and resonators

Abstract: This paper presents uniplanar one-dimensional (1-D) periodical structures, so-called photonic-bandgap (PBG) structures, and defect high-Q resonators for coplanar waveguide, coplanar strip line, and slot line. Proposed uniplanar PBG structures consist of 1-D periodically etched slots along a transmission line or alternating characteristic impedance series with wide band-stop filter characteristics. A stop bandwidth obtained is 2.8 GHz with a stopband rejection of 36.5 dB. This PBG performance can be easily improved if the number of cells or the filling factor is modified in a parametric analysis. Using uniplanar 1-D PBG structures, we demonstrate new high-Q defect resonators with full-wave simulation and measured results. These structures based on defect cavity or Fabry-Perot resonators consist of a center resonant line with two sides of PBG reflectors. They achieve a loaded Q of 247.3 and unloaded Q of 299.1. The proposed circuits should have many applications in monolithic and hybrid microwave integrated circuits.

Balanced filter structure utilizing bulk acoustic wave resonators having different areas

Abstract: The invention relates to resonator structures of radio communication apparatus, especially bulk acoustic wave filter structures. According to the invention, a bulk acoustic filter structure is constructed with a lattice configuration, in which two of the filters have a different area than other two for creating very steep passband edges in the frequency response of the filter. Preferably, the filter structure further comprises a second lattice structure for increasing the stopband rejection ratio of the filter structure, and for allowing the use of a simple mechanical structure. The cascaded configuration allows the construction of the filter structure in such a way, that the electrodes of the input and output port are at the same layer, thereby removing the need to make vias in the piezoelectric layer, which results in considerable simplification of the manufacturing process. Preferably, an acoustical mirror structure is used as the acoustical isolation in order to further simplify the mechanical structure of the filter structure.

Attenuation and localization of wave propagation in rods with periodic shunted piezoelectric patches

Abstract: Shunted piezoelectric patches are periodically placed along rods to control the longitudinal wave propagation in these rods. The resulting periodic structure is capable of filtering the propagation of waves over specified frequency bands called stop bands. The location and width of the stop bands can be tuned, using the shunting capabilities of the piezoelectric materials, in response to external excitations and to compensate for any structural uncertainty. A mathematical model is developed to predict the response of a rod with periodic shunted piezoelectric patches and to identify its stop band characteristics. The model accounts for the aperiodicity, introduced by proper tuning of the shunted electrical impedance distribution along the rod. Disorder in the periodicity typically extends the stop-bands into adjacent propagation zones and more importantly, produces the localization of the vibration energy near the excitation source. The conditions for achieving localized vibration are established and the localization factors are evaluated for different levels of disorder on the shunting parameters. The numerical predictions demonstrated the effectiveness and potentials of the proposed treatment that requires no control energy and combines the damping characteristics of shunted piezoelectric films, the attenuation potentials of periodic structures, and the localization capabilities of aperiodic structures. The theoretical investigations presented in this work provide the guidelines for designing tunable periodic structures with high control flexibility where propagating waves can be attenuated and localized.

Photonics-based interference mitigation filters

Abstract: New photonic filter structures for interference mitigation of microwave signals are presented. These fiber filters have a parallel topology, and comprise a grating based photonic bandpass filter, or a dual offset cavity structure based on a new noncommensurate delay-line approach. The new topologies overcome the problem of synthesizing both a narrow stopband and a very-wide and flat passband, to simultaneously excise interference with minimal impact on the wanted signal over a wide microwave range. Results demonstrate stopbands of around 1% of center frequency, wide-band flat transmission, and a shape factor of 10.5 that is the lowest reported for a photonic notch filter, in excellent agreement with predictions.

Acoustic loss mechanisms in leaky SAW resonators on lithium tantalate

Abstract: Discusses acoustic losses in synchronous leaky surface acoustic wave (LSAW) resonators on rotated Y-cut lithium tantalate (LiTaO/sub 3/) substrates. Laser probe measurements and theoretical models are employed to identify and characterize the radiation of leaky waves into the busbars of the resonator and the excitation of bulk acoustic waves. Escaping LSAWs lead to a significant increase in the conductance, typically occurring in the vicinity of the resonance and in the stopband, but they do not explain the experimentally observed deterioration of the electrical response at the antiresonance. At frequencies above the stopband, the generation of fast shear bulk acoustic waves is the dominant loss mechanism.

A new micromachined overlay CPW structure with low attenuation over wide impedance ranges and its application to low-pass filters

Abstract: In this paper, a new micromachined overlay-coplanar-waveguide (OCPW) structure has been developed and its characteristics are studied in detail as a function of the line parameters. In OCPW, the edges of the center conductors are lifted by micromachining techniques and partially overlapped with the ground plane to facilitate low-impedance lines. The elevated center conductors help to reduce the conductor loss by redistributing the current over a broad area. Comparative experiments on low-loss and lossy substrates also confirm the screening effect from the substrate losses by confining the electric field in the air between the overlapped conductor plates. Compared with the coplanar-waveguide (CPW) lines, the OCPW lines show wider impedance range (25-80 /spl Omega/) and lower loss (<0.95 dB/cm at 50 GHz). The advantages of OCPW for low-Z/sub 0/ lines are utilized to realize a high-performance stepped-impedance low-pass filter at X-band. The OCPW filter shows distinct advantages over the conventional CPW filter in terms of size, loss, skirt, and stopband characteristics.

A novel periodic electromagnetic bandgap structure for finite-width conductor-backed coplanar waveguides

Abstract: The one-dimensional (1-D) periodic electromagnetic bandgap (EBG) structure for the finite-width conductor-backed coplanar waveguide (FW-CBCPW) is proposed. Unlike the conventional EBG structures for the microstrip line and the coplanar waveguide (CPW), which are typically placed on one of the signal strips and the ground plane, this EBG cell is etched on both the signal strip and the upper ground plane of FW-CBCPW resulting in a novel circuit element. The equivalent circuit is also used to model the EBG cell. Measured and full-wave simulated results show that the cell exhibits remarkable stopband effect. The low-pass filter with lower cutoff frequency and wider rejection bandwidth is constructed from a serial connection of the EBG cells. The effect of back metallization on the guiding characteristic is also discussed. Compared to the published EBG cells, the proposed structure has the advantages of relative flexibility, higher compactness, lower radiation loss, and easier integration with the uniplanar circuits.

Submicron three-dimensional infrared GaAs/AlxOy-based photonic crystal using single-step epitaxial growth

Abstract: A relatively simple technique is demonstrated to fabricate three-dimensional face-centered-cubic infrared photonic crystals with submicron feature sizes using GaAs-based technology, single-step epitaxial growth, and lateral wet oxidation. The photonic crystals were fabricated with feature sizes (a) of 1.5 and 0.5 μm. Transmission measurements reveal a stopband centered at 1.0 μm with a maximum attenuation of 10 dB for the submicron (a=0.5 μm) photonic crystal. This technique is scalable to small photonic crystal periodicity and hence to shorter wavelengths.

A 60-GHz-band planar dielectric waveguide filter for flip-chip modules

Abstract: A planar dielectric waveguide filter with coplanar waveguide (CPW) I/O ports suitable for flip-chip bonding is proposed and is demonstrated for 60-GHz-band applications. The filter is formed incorporating metallized through holes in an alumina substrate. In order to improve stopband rejection, short-circuited CPW resonators with a half-wavelength are added to waveguide-to-CPW transitions. A fabricated four-resonator filter exhibits an insertion loss of 3.2 dB with a 3-dB bandwidth of 3.0 GHz and rejection of 35 dB at 3-GHz lower separation from a center frequency of 59.5 GHz. The filter is mounted by using flip-chip bonding in a multilayer ceramic package with structures to suppress parasitically propagating electromagnetic waves. No degradation of the stopband rejection is observed from 50 to 80 GHz.

Stop-band improvement of rectangular waveguide filters using different width resonators: selection of resonator widths

Abstract: Rectangular waveguide resonators having different widths can be mixed in order to improve the stopband performance of band-pass filters. Two effective procedures for the choice of the resonator widths are presented and implemented to realise X-band 6-cavity filters which hold 30 dB of attenuation over a frequency range 40% wider than a standard filter. Theoretical and experimental results are shown and commented on.

High-temperature superconductor low-pass filter for suppressing broadband harmonics

Abstract: Disclosed is a high-temperature superconductor low-pass filter for removing broadband harmonics in a wireless communication system. The high-temperature superconductor low-pass filter includes a coupled line section and a transmission line section, in which the coupled line section is connected in parallel with the transmission line section. The coupled line section has two microstrip open-stub type parallel stripe lines stacked on a high-temperature superconductor, and the transmission line section has one stripe line. Since the high-temperature superconductor low-pass filter has attenuation poles at a stopband, it has stopband characteristics to 7-8 times wider than a cutoff frequency. The high-temperature superconductor low-pass filter can easily remove sub-harmonics which are inevitably occurred in the wireless communication system.

Packaging using microelectromechanical technologies and planar components

Abstract: A novel millimeter-wave packaging structure was developed in which a micromachined low-loss planar component and flip-chip devices were integrated on a silicon substrate. A low-loss planar filter was achieved on a 7-mm-square silicon substrate employing an inverted microstrip line and a unique resonator. High attenuation in the stopband was also obtained by introducing a pole control technique. Fabrication of a compact K-band receiver front-end incorporating a built-in filter was realized using multilayered benzocyclobutene (BCB) and flip-chip bonding techniques. Furthermore, we propose an alternative BCB suspended structure and demonstrate a planar antenna for Ka-band applications. These technologies bring to reality high-performance compact packaged systems in millimeter-wave region applications.

New class of microstrip miniaturised filter using triangular stub

Abstract: A new class of compact microstrip filter loaded with a low-characteristic impedance triangular stub is introduced. The respective filter upper stopband selectivity is improved. Without the presence of cross-coupling between non-adjacent resonators, one transmission zero is observed. Frequency tuning can easily be achieved by adjusting the reactance of the stub.

Nonlinear coaxial photonic crystal

Abstract: We demonstrate that large-scale photonic crystals can be used to simulate nonlinear optical effects occurring in real photonic crystals. A crystal made of coaxial segments with periodic impedance is used to create a stop band in transmission near 10 MHz. When a semiconductor rectifying diode is added to the crystal, a nonlinear mode of propagation appears within the forbidden band gap. It originates from a breaking of symmetry and an intensity-dependent attenuation similar to that encountered in saturable absorbers. Experimental results agree well with a theory based on a simple coupled-mass model with nonlinear resistive force.

Dispersion-free fibre Bragg gratings

Abstract: Fibre Bragg gratings with reduced/eliminated in-band dispersion are presented. When tested in add-drop configurations at 10 Gbit/s both 25 GHz and 50 GHz bandwidth gratings are shown to exhibit superior performance with no dispersion-induced penalties in the stopband. Furthermore, the demonstrated linear-phase Bragg gratings have >70% channel filling factor values and reflectivities in excess of 99.9%.

Fundamental frequency response bounds of direct-form recursive switched-capacitor filters with capacitance mismatch

Abstract: A theoretical statistical analysis is developed to investigate the effects of random capacitance matching errors in the frequency response of recursive switched-capacitor filters implemented in direct form. As a result, with appropriate approximations, closed-form solutions for the mean and the standard deviation of the frequency response error are derived. The obtained expressions provide insight into the quantitative influence of capacitance ratio tolerance, numerator and denominator orders, passband and stopband ripples, and edge frequencies, and reveal existing tradeoffs among these parameters, so that the most efficient filter design can be found. The main theoretical results are extensively verified by simulation through Monte Carlo analysis to show the effectiveness of the proposed formulas.

Adaptive-passive control of vibration transmission in beams using electro/magnetorheological fluid filled inserts

Abstract: A method for the control of the transmission of bending vibrations in beams is described. A composite beam (a structural insert) is inserted into a part of the structure to affect the transmission there. The insert comprises two elastic face plates and a central core of tunable fluid such as an electrorheological (ER) or magnetorheological (MR) fluid. By adjusting the applied electric or magnetic field the theological properties of the fluid can be controlled and so can the vibration transmission properties of the insert. Theoretical results concerning the transmission of vibrations in beam-like structures are reviewed. Numerical results are presented for the transmission through ER and MR fluid filled inserts, with experimental results for an ER case. The transmission is seen to show a pass/stopband structure with the stopbands being tunable.

Micromachined filters on synthesized substrates

Abstract: Effective high-frequency spectrum usage requires high-performance filters to have a sharp cutoff frequency and high stopband attenuation. Stepped-impedance low-pass designs achieve this function best with large ratios of high-to-low-impedance values. In high-index materials, such as Si (11.7) and GaAs (12.9), however these high-to-low-impedance ratios are around five, thereby significantly limiting optimum filter performance. This paper characterizes the use of Si micromachining for the development of synthesized substrates, which, when utilized appropriately, can further reduce the low-impedance value or increase the high-impedance value. Both designs have demonstrated high-to-low-impedance ratios that are 1.5-2 times larger than conventional techniques.

ZnO based thin film bulk acoustic wave filters for EGSM band

Abstract: We present results for a ZnO based filters for the mobile Extended GSM (EGSM) Rx band centered at 942.5 MHz. Our devices are of the SMR type. The acoustical isolation from the glass substrate is achieved by a tungsten-silicon dioxide quarter wavelength mirror. Resonators with an effective coupling coefficient of 0.236 and Q/spl sim/800 have been achieved. The filters are realized as either 3-section ladder or 2-section lattice connected FBARs without any external components. The ladder filters achieve a 3.5 dB absolute bandwidth of 39 MHz with minimum insertion loss of 1.3 dB, stop band rejection at 23 dB and VSWR of 2.2 in the pass band. The balanced filter design has a slightly larger bandwidth of 46 MHz and improved stop band behavior characteristic for this type of device.

A compact distributed low-pass filter with wide stopband

Abstract: A distributed parallel resonance circuit is used to design a very compact low-pass filter with cutoff frequency 0.5 GHz. The circuit has a section of transmission line shunt with an interdigital capacitor connecting with two low-impedance lines at both of its terminals. A finite transmission zero can be generated near the passband edge so that. the filter has a sharp transition response. In addition, the stopband can be extended to more than 6 GHz by properly choosing the structural parameters of the circuit. The measured responses match with the simulation quite well.

Meander microstrip photonic bandgap filter using a Kaiser tapering window

Abstract: Compact photonic bandgap structures in microstrip technology with reasonable physical sizes have recently been proposed as efficient frequency-band reflectors. Here, it is shown how the application of a Kaiser tapering window to the periodic pattern etched in the ground plane of the structure provides appreciable performance improvement, reducing both passband ripple and stopband attenuation and increasing bandwidth.

Hairpin filters with tunable transmission zeros

Abstract: In the previous work, it was found that filter designed with 0/spl deg/ feed structure could have two extra transmission zeros in the stopband. In this paper, a method for tuning the frequencies of these two transmission zeros using impedance transformers is proposed. These zeros can be tuned to reject unwanted signals near the passband, such as image signals, This new approach has been experimentally verified with three second-order Butterworth filters.

Design of polarization‐preserving circular waveguide filters with attenuation poles

Abstract: Bandpass filters in circular waveguide technology are designed to have enhanced stopband responses. Highly dispersive coupling sections are introduced to replace regular circular irises. The resulting direct-coupled resonator bandpass filters have the advantage of preserving the polarization of the incident excitation while providing sharp cutoff skirts. Attenuation poles at finite frequencies are generated on either side of the passband by using radial stubs, which also perform the role of inverters. In contrast to the pole-extraction technique, or the classical technique of using stubs for the sole purpose of pole generation, the zero-generating elements act as inverters, and are not necessarily the first elements at the input and/or output. A simple approximate design technique which provides adequate starting values for optimization-based design is also introduced. Design examples are presented to show the validity of the approach and the performance of these filters. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 334–336, 2001.

The Simplest Notch and Bandstop Filters Based on the Slotted Strips

Abstract: New configuration of the notch and bandstop filters is proposed and investigated. Here a rejection section is based on a thin slotted H-plane strip that may be considered as a limiting case of a three-slot iris. Such a section forms symmetrical frequency response with very low insertion loss out of the stopband. The results of numerical design and measurement data are given for a 3% notch filter and for 2% three-section bandstop one. In the low-power applications the proposed notch filter is probably the simplest one due to its easy fabrication and a possibility to be incorporated into a waveguide circuit by placing between the waveguide flanges.

Microwave tunable filters and non reciprocal devices using magnetic nanowires

Abstract: This paper proposes two new methods to obtain "multizero" stopband filters, using microstrip lines on nanoporous membranes filled with magnetic materials. The first method consists of electrodeposition of multilayered nanowires in the pores of the membrane. In the second one uniform nanowires are rearranged under the strip to form Photonic Bandgaps (PBG) structures. Next, we show that the ferrimagnetic properties of the nanowired substrate can be used to fabricate a planar circulator topology yielding nonreciprocal effects without applying a DC magnetic field.

12 nm FWHM 20 dB stop-band filter based on cascaded dual concentric core fibre filters

Abstract: A spectral stop-band filter with peak attenuation = 5 dB, full width at half-maximum (FWHM) = 31 nm based on a dual asymmetric concentric core optical fibre is investigated. An efficient 12 nm FWHM 20 dB peak attenuation is demonstrated at 1300 nm by cascading four filters.

Design of lightweight multilayer partitions based on sonic crystals

Abstract: The sound transmission coefficient of different multilayer partitions commonly encountered in buildings has been measured as a function of frequency. Most of the samples studied showed an increase in the sound transmission coefficient over a specific frequency, called the critical frequency, depending on the layer material. However, for partitions built with the same materials, but built with a periodic arrangement of layers, this behavior has not been observed. This kind of periodic multilayer partition can be considered as a sonic crystal, because the stopband corresponding to a one-dimensional sonic crystal with a constant lattice equal to the modulation of the partition is in the same range as the critical frequency of the panel.

Microwave tunable filters and nonreciprocal devices using magnetic nanowires

Abstract: This paper proposes two new methods to obtain "multizero" stopband filters, using microstrip lines on nanoporous membranes filled with magnetic materials. The first method consists of electrodeposition of multilayered nanowires in the pores of the membrane. In the second one uniform nanowires are rearranged under the strip to form Photonic Bandgaps (PBG) structures. Next, we show that the ferrimagnetic properties of the nanowired substrate can be used to fabricate a planar circulator topology yielding nonreciprocal effects without applying a DC magnetic field.