Showing papers on "Coplanar waveguide published in 1996"

Flared conductor-backed coplanar waveguide traveling wave antenna

Abstract: A conductor-backed coplanar waveguide traveling wave antenna including a dielectric substrate, a coplanar waveguide structure disposed on the substrate, a plate separated from the substrate for concentrating energy radiated by the antenna generally in a half-space adjacent the exterior of the coplanar waveguide structure, and a feed electrically coupled to the coplanar waveguide for transmitting electromagnetic energy to and from the antenna. Preferably, the plate includes a conductive surface facing the substrate. The aforementioned substrate and plate are separated by a structure which has electromagnetic wave absorbing properties. This antenna is flush-mountable because the separation between the plate and substrate can be made very small, and has broadband capabilities due to its traveling wave producing structure. In addition, the antenna produces significant gain patterns in the forward field of view in a plane parallel to the radiating surface of the coplanar waveguide, and E field polarization perpendicular to this plane of the radiating surface.

Tunable and adaptive bandpass filter using a nonlinear dielectric thin film of SrTiO3

Abstract: We have prepared an electrically tunable and adaptive 3‐pole half‐wave bandpass coplanar waveguide filter incorporating a 1.2‐μm‐thick paraelectric SrTiO3 bottom layer and a 0.4‐μm‐thick superconducting YBa2Cu3O7−x top electrode layer on a LaAlO3 substrate. By applying a separate bias voltage on each pole and also on each coupling capacitance of the device at 4 and 76 K, the filter response is not only fine tuned to achieve symmetric and optimized filter characteristics with less than 2% bandwidth centered around 2.5 GHz, but also broadband tuned to shift the passband by more than 15%.

Methods of suppression or avoidance of parallel-plate power leakage from conductor-backed transmission lines

Abstract: Four useful methods are presented to suppress and/or avoid parallel-plate leakage from conductor-backed printed transmission lines. These include: 1) the use of shorting-pins; 2) the use of a dielectric-guide-coupled configuration; 3) using a two-layered conductor-backing configuration; and 4) dielectric loading on top. New analyses to model the leakage suppression due to the shorting-strips and the dielectric-guide-coupled geometries are presented, with selected demonstrative results and critical discussions. It is concluded that the unwanted leakage in many printed transmission lines, that are otherwise attractive for integrated circuits and phased array applications, can be successfully avoided and/or significantly suppressed using the proposed techniques.

Window mounted mobile antenna system using annular ring aperture coupling

Abstract: A low cost window-mounted antenna system for mobile communication systems operating at frequencies in and above the 1.5 GHz band includes an annular ring aperture coupler fabricated on printed circuit boards on each side of the window, with a microstrip line etched on each of the printed circuit boards. A collinear array-type whip antenna with a 1/2-wavelength lower section is used with the coupler. A coplanar waveguide trace is printed on the outside coupling unit to form an impedance matching network for the active element. The RF signal is thus electro-magnetically coupled through the window.

A coaxial 0.5-18 GHz near electric field measurement system for planar microwave circuits using integrated probes

Abstract: This paper reports on the basic theory of operation and experimental results obtained from an electric field imaging system for planar microwave circuits that employs the method of modulated scattering with monolithically integrated probes. The low-cost system is capable of mapping the normal and tangential electric field intensities and electrical phase delays above reciprocal microwave circuits in the frequency range of 0.5-18 GHz with a spatial electric field resolution of better than 100 /spl mu/m. Monolithic probes incorporating silicon Schottky diodes integrated with electrically small dipole and monopole antenna scatterers on a 40-/spl mu/m-thick high-resistivity silicon substrate are used. Electric field intensity and electrical phase delay images are presented for a 55-/spl Omega/ coplanar waveguide line (CPW), a three-turn microstrip meander line at 8.8, 11.7, and 13.4 GHz, a microstrip coupled-line directional coupler at 10 GHz, and a microstrip patch antenna at 12.85 GHz. The results demonstrate that the modulated scattering technique is a valuable low-cost tool for microwave circuit diagnostics.

GaAs monolithic integrated microwave power sensor in coplanar waveguide technology

Abstract: We present the fabrication technology, theoretical and experimental results of a novel MMIC compatible broadband power sensor. With a 50 /spl Omega/ coplanar waveguide design, integrated AlGaAs thermoelectric sensor and GaAs bulk micromachined membrane for increased sensitivity, this sensor is capable of detecting RF power with a sensitivity of 1.1 V/W without any waveguide coupling structure.

L-band internally matched Si-MMIC front-end

Abstract: A 1.9 GHz-band internally matched Si-MMIC front-end, fabricated in standard 0.8 /spl mu/m BiCMOS process, was developed. This IC front-end contains a MOSFET T/R switch, a two-stage BJT low noise amplifier (LNA), and a down converter BJT mixer. Since the circuits are monolithically integrated on a low resistivity Si substrate, the coplanar waveguide (CPW) type spiral inductors are used to reduce the dielectric loss of on-chip matching circuits. The T/R switch has measured insertion loss of 2.5 dB and isolation of 25.5 dB at 0/3 V control voltage. The two-stage LNA has gain of 17.1 dB and noise figure (NF) of 2.9 dB at 2 V, 4 mA dc supply. The mixer has conversion gain of 5.9 dB and NF of 15 dB at 2 V, 1.7 mA dc supply. The measured performance of the fabricated Si-MMIC front-end indicates the possibility of application to mobile communication handset terminals.

Electrooptic sampling of low temperature GaAs pulse generators for oscilloscope calibration

Abstract: Optoelectronic generation of well characterized ultrashort electrical pulses plays an important role in the calibration of fast-sampling oscilloscopes. In this paper the authors describe the National Physical Laboratory (NPL) pulse generator, comprising a femtosecond laser and an ultrafast photoconductive switch which can generate electrical pulses as short as 650 fs. The photoconductive switch consists of a GaAs substrate with a top GaAs layer grown under low temperature conditions to ensure a subpicosecond recombination rate. The technique of electrooptic sampling is used to measure pulses on planar transmission lines, such as coplanar waveguide and coplanar stripline. Good agreement is shown between electrooptic sampling measurement and the modelling of pulse propagation along a coplanar waveguide, enabling one to optimize a design of a calibration test source. The use of a pulse generator to calibrate a 50 GHz sampling oscilloscope is described.

Coplanar millimeter-wave ICs for W-band applications using 0.15 /spl mu/m pseudomorphic MODFETs

Abstract: A small signal S-parameter and noise model for the cascode MODFET has been validated up to 120 GHz, allowing predictable monolithic microwave integrated circuit (MMIC) design up to W-band. The potential of coplanar waveguide technology to build compact, high performance system modules is demonstrated by means of passive and active MMIC components. The realized passive structures comprise a Wilkinson combiner/divider and a capacitively loaded ultra miniature branch line coupler. For both building blocks, very good agreement between the measured and modeled data is achieved up to 120 GHz. Based on the accurate design database, two versions of compact integrated amplifiers utilizing cascode devices for application in the 90-120 GHz frequency range were designed and fabricated. The MMICs have 26.3 dB and 20 dB gain at 91 GHz and 110 GHz, respectively. A noise figure of 6.4 dB was measured at 110 GHz. The 90-100 GHz amplifier was integrated with an MMIC tunable oscillator resulting in a W-band source delivering more than 6 dBm output power from 94 to 98 GHz.

Uniplanar power dividers using coupled CPW and asymmetrical CPS for MICs and MMICs

Abstract: Uniplanar coplanar waveguide (CPW), coplanar strip (CPS), and slotline on dielectric substrates have many applications in microwave integrated circuit (MIC) and monolithic microwave/millimeter wave integrated circuit (MMIC) designs. New power dividers using one-section and two-section coupled CPW have been developed. These circuits provide substantially improved performance over a wider bandwidth than conventional microstrip power dividers. Measured results show that the one-section CPW power divider has greater than 20-dB isolation, less than 0.3-dB insertion loss, a 0.2-dB power dividing imbalance, and a 20 phase imbalance over a bandwidth of more than 30% centered at 3 GHz. The two-section CPW power divider has greater than 24-dB isolation, less than 0.5-dB insertion loss, a 0.1 dB power dividing imbalance, and a 1.6/spl deg/ phase imbalance over a bandwidth of more than 66% centered at 3 GHz. Experimental results agree well with calculated ones. In-phase and 180/spl deg/ out-of-phase power dividers constructed by the circuit configuration method are described in this paper. The even-odd mode excited method is used to analyze the power dividers. Also two other power dividers using asymmetrical coplanar strip (ACPS) have been developed with good performance. A 180/spl deg/ out-of-phase power divider is demonstrated with an amplitude imbalance of 0.4 dB and a phase difference of 180/spl deg//spl plusmn/1/spl deg/ over a wide bandwidth.

Models of coplanar lines and elements over the frequency range 0-120 GHz

Abstract: The electrical properties of uniform coplanar lines on GaAs have been investigated, using a finite element simulator. Experimental results, extracted from on-wafer measurements to 120 GHz, are in good agreement with the simulated results. Frequency dependent models were developed for all characteristic parameters of the coplanar lines, such as impedance, effective relative dielectric constant and attenuation, describing the behavior of coplanar lines of different geometries over the entire frequency range from 0-120 GHz. Similarly, exact models applicable over the same frequency range have been developed for a number of coplanar elements, such as air bridges, 90 degree corners and probing pads. These models have been implemented in our HP-MDS data base, resulting in accurate designs of a number of millimeter wave circuits.

High resistivity Si as a microwave substrate

Abstract: Silicon has many advantages as a system substrate material including low cost and a mature technology. However, Si has not been demonstrated as a good microwave substrate compared to semi-insulating GaAs or quartz. The aim of this paper is to evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study. Coplanar waveguides fabricated on Si, GaAs and quartz substrates are tested and their characteristics are compared. Microwave spiral inductors and meander lines are also fabricated on various substrates, and their performance is also analyzed. The results demonstrate that the losses of a coplanar transmission line (CPW) realized on high-resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate covered with insulator. Furthermore, measured unloaded Q's of microwave inductive structures on high-resistivity silicon substrates are comparable to the measured unloaded Q's of the same structures on GaAs and on quartz. The measured results are explained using both microwave and semiconductor physics theory. This paper demonstrates that high-resistivity Si can be used as a microwave substrate.

Microwave vertical interconnect through circuit with compressible conductor

Abstract: A microwave frequency transmission line (20') provides the capability of solderless interconnections between stacked microwave hybrid and printed wiring board (PWB) assemblies. A wire-like transmission like is embedded in a dielectric (26') and placed in an open square trough. A compressible center conductor (28A', 28C') is realized by densely packing thin wire into an opening (30) in the supporting dielectric (26') to form the compressible center conductor (28A, 28C). A vertical right angle bend transition uses the transmission line (20') to interconnect between grounded coplanar waveguide (CPWG) transmission lines (60, 80).

Novel directional couplers using broadside-coupled coplanar waveguides for double-sided printed antennas

Abstract: Two types of tight-coupling, broadband directional couplers employing open broadside-coupled coplanar waveguides (BC CPWs) are proposed which can easily be integrated with printed strip antennas. The first type uses the BC CPWs with dielectric overlays above and below the center substrate, while the second type uses the nonuniform BC CPWs. The scattering parameters of these directional couplers are derived with the even-odd mode analysis method based on the quasi-TEM wave approximation. Two 3-dB directional couplers, one for each type, are designed and measured characteristics are compared with theoretical results.

Low-voltage and broadband Ti:LiNbO/sub 3/ modulators operating in the millimeter wavelength region

Abstract: Summary form only given. In conclusion we have developed ridged Ti:LiNbO/sub 3/ optical modulators with thin buffer layers and thick coplanar waveguide (CPW) electrodes. We demonstrated that a low-voltage-type-module has a drive voltage of 3.3 V with bandwidth of 45 GHz and a broadband type-module has a bandwidth of >100 GHz with drive voltage of 5.1 V.

Impedance mismatch effects on propagation constant measurements

Abstract: By measuring propagation constants of coplanar waveguide transmission lines, we show the significant systematic errors of common measurement techniques when the characteristic impedance of the lines does not match the reference impedance of the instrument.

Extending the bandwidth performance of heterojunction bipolar transistor-based distributed amplifiers

Abstract: An InAlAs-InGaAs-InP HBT CPW distributed amplifier (DA) with a 2-30 GHz 1-dB bandwidth has been demonstrated which benchmarks the widest bandwidth reported for an HBT DA. The DA combines a 100 GHz fmax and 60 GHz fT HBT technology with a cascode coplanar waveguide DA topology to achieve this record bandwidth. The cascode gain cell offers 5-7 dB more available gain (MAG) than a common-emitter, and is used to extend the amplifier's upper frequency performance. A coplanar waveguide design environment is used to simplify the modeling and fabrication, as well as to reduce the size of the amplifier. Novel active load terminations for extending the DA's lower frequency response were separately demonstrated. The active loads are capable of extending the lower bandwidth performance by two decades resulting in performance below 45 MHz. This work explores both design techniques and technology capability which can be applied to other distributively matched HBT circuits such as active baluns for mixers, active combiners/dividers, and low DC power-broadband amplifiers.

W-band finite ground coplanar (FGC) line circuit elements

Abstract: This paper describes the modeling and experimental evaluation of Finite Ground Coplanar (FGC) lines, stubs, and filters between 2 and 110 GHz. These lines provide a very low loss alternative to microstrip or coplanar waveguide for millimeter- and submillimeter-wave applications without the use of vias. Their mode free operation allows excellent agreement between measured data and LIBRA modeling to 110 GHz. The lines have very low loss at W-band and filters have a loss comparable with the best membrane filters reported recently. The paper includes details of analytic and FDTD investigations of the lines, a description of the fabrication and measurement calibration and measured data on lines, tuning stubs, and a variety of low-pass filters.

High-impedance coplanar waveguides with low attenuation

Abstract: The conventional MMIC coplanar line covers an impedance range from about 30-80 /spl Omega/. Values outside this range cannot be fabricated reliably or cause excessive losses, For several applications, however, it is desirable to use high-impedance lines (e,g., for reduced-size couplers and nonlinear transmission lines). This letter reports results from experiment and electromagnetic simulation for a coplanar waveguide (CPW) structure with an elevated center conductor realized by an air-bridge technique. We achieve wave impedances of about 100 /spl Omega/ at a lower attenuation level as conventional 50-/spl Omega/ CPW's of comparable size.

K/Ka-band coplanar waveguide directional couplers using a three-metal-level MMIC process

Abstract: Two novel types of coupled line structures have been realized on GaAs monolithic microwave integrated circuits to obtain 90° couplers operating at a center frequency of 24 GHz. Both of the couplers are made up of either two or three conductive layers to improve the coupling. The aim is to achieve compact couplers with smaller aspect ratios and to decrease the losses due to field crowding on the edges. Both couplers have achieved good matching and coupling. The simulation is carried out on the electromagnetic simulator em (a trademark of Sonnet Software Inc.).

Push-pull power amplifier

Abstract: A means of connecting a plurality of essentially identical active devices (Q1, Q2, Q3, Q4) is presented for the purpose of multifunction and multiple function operation. These devices (Q1, Q2, Q3, Q4), mounted on a chip (66), are flip-mounted to a circuit motherboard having large passive elements. A push-pull amplifier (50) is presented as an example in which the multiple function operation is the combining of amplifiers (56, 58) whose active devices (Q1, Q2, Q3, Q4) are on a single chip (66). The electromagnetic coupling, impedance matching and signal transmission are variously provided by the use of striplines (82, 88), slotlines (94, 100), coplanar waveguides (116, 130), and a slotline (180) converted into a coplanar waveguide (176, 178).

Direct three-wire to stripline connection

Abstract: A transition for providing connection between a stripline transmission line which is buried in a substrate and the surface of the substrate where components are mounted. A three-wire line disposed orthogonally to the stripline is directly connected to the stripline. The center wire of the three-wire line is connected to the stripline center conductor strip, and the two ground wires are connected to the upper and lower ground planes of the stripline. The center wire of the three-wire line passes through an open area formed in the upper stripline ground plane. To improve the performance of the transition, mode conversion between the electric field configuration of stripline and the electric field configuration of three-wire line is provided, by terminating one ground wire at the upper stripline ground plane. The transition can be used to connect to a conductor-backed coplanar waveguide transmission line circuit formed on the substrate surface.

Fabrication and microwave characterisation of multilayer circuits for MMIC applications

Abstract: A technique to fabricate novel multilayer monolithic microwave integrated circuit (MMIC) structures using polyimide as insulating dielectric layer is described. The polyimide layer formation, curing and dry etching processes are investigated in an attempt to obtain high quality dielectric layers suitable for MMIC applications. By employing this technique, MMIC design and circuit routings become much easier and conventional microstrip transmission lines and lumped passive components can be realised with effective use of the substrate material. In the paper it is shown that a V-shaped MMIC coplanar waveguide (CPW) transmission lines with low characteristic impedance and edge offset broadside directional couplers can easily be designed using the multilayer technique. This implementation can avoid the well known current crowding effects on the conductor edges. Within the Ku and K band frequency range, circuits have been characterised and show good performances. By using the same technique, miniaturisation of a lumped-distributed CPW ring-resonator bandpass filter can be achieved with built-in shunt capacitors. Two transmission poles and two transmission zeros could be implemented by introducing two discontinuities. The measured results show a 3 dB bandwidth of 3.7 GHz at 13.7 GHz.

Simulation of an elevated coplanar waveguide using 2-D FDTD

Abstract: Nonlinear transmission lines (NLTLs) are commonly used together with sampling circuits for millimeter-wave instruments. Recently, the use of an elevated coplanar waveguide (CPW) has been proposed to increase the bandwidth of sampling circuits. A full-wave analysis between 10 and 500 GHz of such an elevated CPW using 2-D FDTD is presented. The influence of the elevation heights on the capacitance and the loss behavior of the transmission line is discussed. The analysis shows that the distributed capacitance of the elevated CPW is four times lower and, the losses are at least divided by two in comparison to a normal CPW at 300 GHz.

Dispersion characteristics of cylindrical coplanar waveguides

Abstract: A full-wave analysis of the coplanar waveguide (CPW) printed on a cylindrical substrate is presented, and the dispersion characteristics of the cylindrical CPW are studied. Numerical results of the effective relative permittivity are calculated using a Galerkin's moment-method calculation. Experiment is also conducted, and the measured data are in good agreement with the theory.

CAD Model of a Gap in a Coplanar Waveguide

Abstract: The partial capacitance approach and conformal mapping techniques are used to evaluate simple closed-form models for parallel and series capacitances of equivalent π-network of a symmetric gap in a CPW. Models are compared with experimental data and full wave analysis. They are useful for a wide range of CPW parameters and frequencies.

Design and analysis of transitions from rectangular waveguide to layered ridge dielectric waveguide

Abstract: Transitions from rectangular waveguide to layered ridge dielectric waveguide are studied both experimentally and theoretically. In addition, a design procedure is given for each transition. The analysis and design procedures are valid for transitions between rectangular waveguide and other open dielectric waveguides such as image guide, insulated image guide, dielectric ridge guide, and inverted strip dielectric waveguide. It is shown that for small dielectric waveguides such as layered ridge dielectric waveguide, a transition which is comprised of a tapered ridge waveguide reduces the radiation loss by at least 1 dB.

Thick metal integrated transmission line fabrication

Abstract: A method for fabricating thick metal integrated transmission lines and circuit topologies for microwave integrated circuits. Microstrip or coplanar waveguide (CPW) transmission line and circuit topologies may be fabricated on semiconductor or dielectric substrates. For microstrip transmission line topologies, a metal ground plane is applied to the opposite side of the substrate from the thick metal transmission line conductor structures. To fabricate a thick metal transmission line topology, a metal plating base is applied to a substrate surface. A photoresist layer, which may include a preformed photoresist sheet, is then applied over the plating base layer. The photoresist layer is exposed to X-rays, such as from a synchrotron, through a mask having an X-ray absorber pattern that defines the desired transmission line or circuit topology. The photoresist layer is then developed to remove sections of the photoresist layer corresponding to the mask pattern and to expose portions of the plating base layer. Thick metal transmission line circuit structures are then electroplated onto the plating base, into the wells formed by the developed photoresist layer. Transmission line thicknesses of approximately 5 μm-1 mm, may thereby be formed, having highly vertical side walls. The method may be used to fabricate various microstrip and CWT transmission line and tightly coupled circuit topologies, including couplers, low-pass and band-pass filters, and resonators.

Millimetre-wave coplanar waveguide slow wave transmission lines on InP

Abstract: Millimetre-wave slow wave electrodes on InP are realised by capacitively loading of coplanar waveguide (CPW) transmission lines using interdigitated metal-semiconductor-metal (MSM) structures. The slow wave structures are designed for velocity matching with InP-based optical waveguides and a 50 /spl Omega/ line impedance. Their dispersion, loss and impedance characteristics are measured up to 40 GHz, and they demonstrate the suitability of the lines for use in distributed MSM photodetectors.

Vertical grounded coplanar waveguide H-bend interconnection apparatus

Abstract: An interconnection apparatus (50) providing a right angle H-plane bend in grounded coplanar waveguide GCPW transmission line media is disclosed. Respective first and second GCPW lines (60, 80) each include a dielectric substrate (62, 82), on which is formed on a bottom surface (62B, 82B) a bottom conductive ground plane (64, 84), and on a top surface (62A, 82A) is formed a center conductor strip (68, 88) sandwiched between first and second top ground plane strips (66A, 66B, 86A, 86B). The two GCPW lines (60, 80) are disposed orthogonally, forming a corner junction (100) at which corresponding bottom and top ground planes (66A, 86A, 64, 84), and the center conductor strips (68, 88) of the lines (60, 80) are electrically connected. The gaps (70A, 70B, 90A, 90B) between the top ground plane strips (66A, 66B, 86A, 86B) and the center conductor strips (68, 88) have regions (76A, 76B, 96A, 96B) of increased width at the corner junction (100) to compensate for the capacitance resulting from the junction (100).