Showing papers on "Coplanar waveguide published in 2001"

Coplanar waveguide circuits, components, and systems

Abstract: Preface Introduction Conventional Coplanar Waveguide Conductor-Backed Coplanar Waveguide Coplanar Waveguide with Finite-Width Ground Planes Coplanar Waveguide Suspended Inside A Conducting Enclosure Coplanar Striplines Microshield Lines and Coupled Coplanar Waveguide Attenuation Characteristics of Conventional, Micromachined, and Superconducting Coplanar Waveguides Coplanar Waveguide Discontinuities and Circuit Elements Coplanar Waveguide Transitions Directional Couplers, Hybrids, and Magic-Ts Coplanar Waveguide Applications References Index

Waveguide to microstrip transition

Abstract: A waveguide to microstrip T-junction includes a microstrip transmission line structure having a ground plane separated from a strip conductor by a dielectric layer, the ground plane defining an aperture; a waveguide channel having a conductive periphery being electrically coupled to the ground plane to provide a waveguide short circuit wall located at the end of the waveguide channel; at least one conducting ridge inside the waveguide channel; and an end of the ridge being electrically coupled with the ground plane.

Mechanical design and optimization of capacitive micromachined switch

Abstract: Design and optimization of a shunt capacitive micromachined switch is presented. The micromachined switch consists of a thin metal membrane called the “bridge” suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static electromechanical model considering the residual stress effects is developed to predict the effective stiffness constant and the critical collapse voltage of the bridge for several typical bridge geometries. The deformation of the bridge and its contact behavior with the dielectric layer are analyzed using the finite element method (FEM) in order to explore a good contact field with different bridge geometries. Furthermore, a nonlinear dynamic model that captures the effects of electrostatic forces, elastic deformation, residual stress, inertia, and squeeze film damping is developed, and is used for predicting the switching speed (including the switching-down and the switching-up time) and the Q -factor. The effects of variation of important parameters on the mechanical performance have been studied in detail, and the results are expected to be useful in the design of optimum shunt capacitive micromachined switch. The results may also be useful in the design of actuators with membranes or bridges.

Integrated transition of coplanar to rectangular waveguides

Abstract: Usual transitions between planar circuit and rectangular waveguide make use of 3-D complex mounting structures. Such an integration requires costly high precision mechanical alignment, In this paper, a new planar platform is developed in which a coplanar waveguide (CPW) and a rectangular waveguide are fully integrated on the same substrate, and they are interconnected via a simple transition. They can be built with a standard PCB process. Our experiments at 28 GHz show that an effective bandwidth of 7% at 15 dB return loss can easily be achieved. The CPW-to-waveguide transition allows for a complete integration of waveguide components on substrate with active components such as MMIC.

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.

Dielectric spectroscopy for bioanalysis: From 40 Hz to 26.5 GHz in a microfabricated wave guide

Abstract: We report developing coplanar waveguide devices which can perform dielectric spectroscopy on biological samples within a microfluidic channel or well. Since coupling to the fluid sample is capacitive, no surface functionalization or chemical sample preparation are required. Data on cell suspensions and solutions of proteins and nucleic acids spanning the frequency range from 40 Hz to 26.5 GHz are presented. Low-frequency data are well explained using a simple dispersion model. At microwave frequencies, the devices yield reproducible and distinguishable spectral responses for hemoglobin solution and live E. coli.

Tunable lumped components with applications to reconfigurable MEMS filters

Abstract: This paper presents a novel design scheme for tunable coplanar waveguide components with applications to compact lumped-element MEMS reconfigurable filters. Shunt MEMS switches are employed for tuning the values of lumped components frequently encountered in microwave integrated circuits. In particular, shunt capacitors, series inductors and shunt inductive stubs are the main tunable circuit elements utilized in this work. Furthermore, accurate equivalent circuits that include the most important parasitics introduced by the tuning mechanism are provided. Finally, the proposed method is applied to the design and implementation of very compact low-pass and bandpass tunable filters. The very high tunability range, the compactness of the resulting networks and their very wideband response constitute the main advantages of this technique.

Miniature low-loss CPW periodic structures for filter applications

Abstract: Several novel periodic structures for coplanar waveguides are presented. The proposed structures exhibit low insertion loss in the passband, simple fabrication, and slow-wave characteristics. These structures are applied to realize miniature low-pass filters one-tenth the size of conventional filters, with spurious-free response and deep attenuation levels using only three cells.

Method and apparatus for dielectric spectroscopy of biological solutions

Abstract: A coplanar waveguide for use in dielectric spectroscopy of biological solution is described. The waveguide's inner conductor can have a small gap and a sample containing space is laid over the gap. The sample containing space holds a small volume, ranging from a few picoliters to a few microliters of a biological solution. The waveguide is then driven with electrical signals across an extremely wide frequency range from 40 Hz to 40 GHz. The waveguide is coupled to a network or impedance analyzer by means of appropriate connectors and the response of the biological solution to the input signals is recorded. One-port and two-port measurements can be made without any modifications. The simple geometry of the waveguide makes it easy to integrate with microfluidic systems.

Low-loss CPW on low-resistivity Si substrates with a micromachined polyimide interface layer for RFIC interconnects

Abstract: The measured and calculated propagation constant of coplanar waveguide (CPW) on low-resistivity silicon (1 /spl Omega//spl middot/cm) with a micromachined polyimide interface layer is presented in this paper. With this new structure, the attenuation (decibels per centimeter) of narrow CPW lines on low-resistivity silicon is comparable to the attenuation of narrow CPW lines on high-resistivity silicon. To achieve these results, a 20-/spl mu/m-thick polyimide interface layer is used between the CPW and the Si substrate with the polyimide etched from the CPW slots. Only a single thin-film metal layer is used in this paper, but the technology supports multiple thick metal layers that will further lower the attenuation. These new micromachined CPW lines have a measured effective permittivity of 1.3. Design rules are presented from measured characteristics and finite-element method analysis to estimate the required polyimide thickness for a given CPW geometry.

Distributed MEMS transmission lines for tunable filter applications

Abstract: This paper describes the design and fabrication of a distributed MEMS () transmission line DMTL , used to realize a transmission-line with a voltage-variable electrical length for microwave circuits. The DMTL is a coplanar waveguide periodically loaded with continuously-variable MEMS capacitors. A tunable bandpass filter was de- signed and fabricated on 700 m thick glass substrates using three capacitively coupled DMTL sections as variable shunt resonators. The measured results demonstrate a 3.8% tuning range at 20 GHz with 3.6 dB minimum insertion loss. Issues for future improvement are discussed. 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 254260, 2001.

Millimeter wave module and radio apparatus

Abstract: A millimeter wave module includes a silicon substrate with first and second cavityes formed by anisotropic etching on the silicon substrate, and a glass substrate having a microstrip filter pattern and microbumps for connecting the glass substrate to the silicon substrate. A filter is provided using an air layer as a dielectric disposed in the first cavity. An MMIC is mounted by the flip chip method over the second air layer. A coplanar waveguide is on the silicon substrate for connecting the filter and MMIC. The filter having low loss is achieved because it has the microstrip structure using air as an insulating layer. Also change in characteristics of the MMIC during mounting is eliminated because the MMIC is protected by contacting air. Accordingly, the millimeter wave module has excellent characteristics and is made using a simple method.

Film bulk acoustic resonator filters with a coplanar waveguide

Abstract: Multiple thin film bulk acoustic resonators (10, 11) configured in series (10) and parallel (11) within a coplanar waveguide line structure provides a compact ladder filter. The resonators (10, 11) are formed over an opening (28) in a substrate (20) and connected to associated circuitry by one or more transmission lines formed on the substrate (20). The arrangement of the resonators (10, 11) between the ground and signal lines of a coplanar line structure provides a means of minimising the area of the filter. Embedding a ladder filter within the coplanar transmission line structure eliminates the need for wire bonds, thus simplifying fabrication. Embodiments for 2×2, and hither order filters are described.

Uniplanar picosecond pulse generator using step-recovery diode

Abstract: A simple, compact, low-cost picosecond pulse generator has been developed using a coplanar waveguide and step-recovery diode. This pulse generator generates pulses of 154 ps pulsewidth and 3.5 V amplitude from an input square wave of 10 MHz repetition rate. The generated pulses have low ringing level and good symmetry. The simplicity, compactness, low cost, and good performance of the developed pulse generator make it attractive for low-cost time-domain microwave systems.

Novel reduced-size coplanar-waveguide bandpass filters

Abstract: Two novel reduced-size coplanar-waveguide (CPW) bandpass filters are proposed. Specifically, the bended short-end parallel stubs together with the folded open-end series stubs are utilized to design a broadband filter, and the slow-wave structures are adopted to implement a narrowband filter. In this study, the proposed filters are examined, theoretically and experimentally.

Wide bandwidth measurement of complex permittivity of liquids using coplanar lines

Abstract: A technique for measurement of complex permittivity of dielectric materials, using coplanar waveguide cells is presented. A complete solution of the forward and inverse problems, based on a quasi-TEM propagation model, is given. Unlike other methods, our method allows solution of the inverse problem without the use of iterative or graphical techniques. The model accounts for the various discontinuities along the line. Several advantages result from this approach. Measurement over a broad frequency range is possible, limited only by dispersive effects. It is suitable for solids not amenable to machining for cavity measurements, and there need not be any contact.

Micromachined filters for 38 and 77 GHz supported on thin membranes

Abstract: This paper presents the fabrication processes for micromachined millimetre-wave devices, on two different types of semiconductor substrates. The first process uses micromachining on high-resistivity oriented silicon. A three-layer dielectric membrane, with a total thickness of 1.5 µm is used as support for the millimetre-wave structures. This process was used for the manufacturing of two coupled line filters, with central operating frequencies of 38 and 77 GHz, respectively. The second process is based on GaAs micromachining. For the first time, a 2.2 µm thin GaAs/AlGaAs membrane, obtained by molecular beam epitaxy growth and micromachining of semi-insulating GaAs, is used as a support for millimetre-wave filter structures. Cascaded coplanar waveguide open-end series stubs filter type structures, with central frequencies of 38 and 77 GHz, respectively, were designed and manufactured on a GaAs micromachined substrate. `On wafer' measurements for the filter structures were performed. Losses of less than 1.5 dB at 38 GHz and less than 2 dB at 77 GHz have been obtained for both the silicon as well as for the GaAs-based micromachined filters.

Novel design for coplanar waveguide to microstrip transition

Abstract: A new design of a coplanar waveguide (CPW) to microstrip transition is presented. Simulation using the high frequency simulator software (HFSS) shows that a bandwidth of 13 GHz with less than -25 dB return loss can be achieved. The transition was fabricated and characterized. Experimentally, the S/sub 11/ of two back to back conductor backed CPW to microstrip transitions on InP substrate is better than -12 dB up to 14 GHz. For alumina substrate the S/sub 11/ was less than -15 dB up to 25 GHz.

A general conformal-mapping approach to the optimum electrode design of coplanar waveguides with arbitrary cross section

Abstract: The Schwarz-Christoffel toolbox, a free MATLAB package for the computation of conformal maps, is applied to the quasi-static analysis of coplanar waveguides (CPWs) of arbitrary cross section in order to provide computationally efficient and very accurate estimates of their capacitance, inductance, characteristic impedance, and skin-effect attenuation. A few examples of many-sided polygonal waveguides are discussed, and the trapezoidal CPW, important, for example, for electrooptic modulators, is described in full detail, providing general guidelines for the electrode geometry optimization. The technique is validated through a comparison with the results of a full-wave finite-element method, and excellent agreement is demonstrated both in vacuo and with two-layer dielectric substrates.

1.55-/spl mu/m wavelength periodic traveling-wave photodetector fabricated using unitraveling-carrier photodiode structures

Abstract: We report the first periodic traveling-wave photodetector fabricated by using unitraveling-carrier photodiodes (UTC-PDs). The photodetector comprises three UTC-PDs with a 0.06-/spl mu/m absorption layer that is periodically arranged along a coplanar waveguide transmission line. The photoresponse of the photodetector is three times larger than that of a single UTC-PD. A photodetector with terminal resistors at the input end achieves a 3-dB bandwidth of 115 GHz at 1.55 /spl mu/m. This is almost the same value as that for a single UTC-PD. For one without terminal resistors, the 3-dB bandwidth degrades to 56 GHz as a result of the backward-propagating microwave being reflected at the input end. These results suggest that the photodetector is well designed with both velocity and impedance matchings.

Planar antenna for wireless communications

Abstract: Embodiments of a planar antenna suitable for use with a portable device for wireless communications are described. One such embodiment includes a microstrip line coupled to a radiating poise on one side of a circuit board, and a ground plane coupled to a structure on the other side of the circuit board that functions as a coplanar waveguide having an effective length of one quarter-wavelength. A further implementation includes a transformer portion configured and arranged to match the impedance of an RF signal source to the antenna driving impedance.

Application of on-wafer TRL calibration on the measurement of microwave properties of Ba/sub 0.5/Sr/sub 0.5/TiO/sub 3/ films

Abstract: A series of Al/Ba/sub 0.5/Sr/sub 0.5/TiO/sub 3/ (BST) /sapphire multi-layered coplanar waveguide (CPW) transmission lines of different geometries and thin-film configurations was fabricated. We employed an accurate on-wafer Through-Line-Reflect (TRL) calibration technique and quasi-TEM analysis to measure the dielectric constant, loss tangent, and tunability of BST thin films using this CPW structure. Experimental results show that the overall insertion loss is less than 3 dB/cm even at frequencies as high as 20 GHz, which is the lowest obtained to date for metal/BST CPW devices. This result indicates that, with optimized impedance matching, normal conductors are also possibly suitable for fabricating low-loss tunable phase-shifter devices.

Tunable millimeter-wave filters using a coplanar waveguide and micromachined variable capacitors

Abstract: In this paper, new micromachined tunable bandpass filters for multi-band millimeter-wave telecommunication systems are proposed. Two types of millimeter-wave tunable filters have been fabricated using micromachining technology and the responses of the filters have been measured: one type is a two-pole lumped element filter and the other a two-pole resonator filter. The frequency tunability of the filter has been achieved by changing the gap between a common coplanar waveguide ground plate and a movable cantilever beam connected to the transmission line with a controllable range of 2.5 µm. The deflection of the cantilever beam has been measured with applied dc voltage. With the applied bias voltage from 0 to 50 V, the fabricated filters have shown center frequency shifts of 0.6 GHz (2.3%) at 26.6 GHz and 0.8 GHz (2.5%) at 32 GHz for the lumped element and resonator filters, respectively. The mechanical lifetime of the fabricated gold cantilever structure has been tested by observing the existence of the spring memory phenomenon; there is no memory phenomenon or breakdown until a repeated actuation of 1.6×108 cycles.

Miniaturized HTS coplanar waveguide bandpass filters with highly packed meanderlines

Abstract: Design and performance of miniaturized coplanar waveguide (CPW) bandpass filters (BPFs) using high T/sub c/ superconducting (HTS) films have been studied. In order to realize the miniaturized filters, we coupled highly packed meanderline half-wavelength resonators with interdigital gaps, where admittance inverters (J inverters) were made of interdigital gaps. The exact J values, susceptance slope parameters and the length of the resonators of the meanderline are calculated from the cascade matrix (K-matrix) and scattering matrix (S-matrix) obtained by the 2.5-dimensional electromagnetic field simulator (HP-Momentum). It is shown that the size of the filters can be greatly reduced by introducing CPW with highly packed meanderline geometry (center frequency 2 GHz, fractional band width 15 MHz, ripple 0.1 dB) packed within 10 mm square substrate. Simulated performance was in good agreement with the designed one.

A novel PBG coplanar waveguide

Abstract: A novel coplanar waveguide with photonic bandgap structure is proposed and is implemented by etching holes in the ground plane with an open connected with the gap between strip line and ground plane. Simulation and measurement results show the existence of a bandgap.

Via-free broadband microstrip to CPW transition

Abstract: A broadband microstrip to coplanar waveguide (CPW) transition is proposed. The design is based on vertical resonant coupling between the microstrip and CPW. The transition does not require via holes, wire bonds, or air bridges. The design of the transitions at C band shows good agreement with return loss better than -15 dB over 2.8-7.5 GHz. The new transition has the advantages of broad bandwidth and easy fabrication.

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.

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.

A finite ground coplanar line-to-silicon micromachined waveguide transition

Abstract: Circuits operating in the terahertz frequency range have traditionally been developed using hollow metal waveguides, which, due to the small wavelength at these operating frequencies, must be correspondingly small in cross section. As a result of the high cost of conventional precision machining of such small waveguides, alternate fabrication methods continue to be explored. Silicon micromachining has been suggested as a potential means to produce waveguides in a more cost-effective manner for operation at these frequencies. This paper presents a transition structure that couples the popular finite ground coplanar transmission line to a W-band silicon micromachined waveguide, forming a fully micromachined module. The waveguide is formed via bulk micromachining using a wet etchant, resulting in a diamond cross section. The consequences of utilizing a diamond waveguide in place of the more common rectangular waveguide are considered and potential means of developing rectangular-walled waveguides in silicon are noted. A Ka-band microwave model of a similar transition to a conventional rectangular waveguide is also demonstrated.

Low-loss micromachined inverted overlay CPW lines with wide impedance ranges and inherent airbridge connection capability

Abstract: A new type of overlay coplanar waveguide (CPW) structure, "inverted overlay CPW (IOCPW)" is developed using micromachining techniques to provide easy means of airbridge connection between the ground planes, as well as to achieve low losses over wide impedance ranges. Measured IOCPW showed less than 1 dB/cm loss at 50 GHz over a wide impedance range from 25 to 80 /spl Omega/. It also offered low effective dielectric constant, and insensitivity to the substrate losses. Wide impedance ranges and simple process steps make IOCPW a promising uniplanar transmission line medium for mm-wave monolithic applications.