Showing papers on "Coplanar waveguide published in 2003"

Compact linear lead/lag metamaterial phase shifters for broadband applications

Abstract: A compact one-dimensional phase shifter is proposed using alternating sections of negative refractive index (NRI) metamaterials and printed transmission lines (TL). The NRI metamaterial sections consist of lumped element capacitors and inductors, arranged in a dual TL (high-pass) configuration. By adjusting the NRI-medium lumped element values, the phase shift can be tailored to a given specification. Periodic analysis is applied to the structure and design equations are presented for the determination of the lumped element parameters for any arbitrary phase shift. To validate the design, various phase shifters are simulated and tested in coplanar waveguide (CPW) technology. It is demonstrated that small variations in the NRI-medium lumped element values can produce positive, negative or 0/spl deg/ phase shifts while maintaining the same short overall length. Thus, the new phase shifter offers some significant advantages over conventional delay lines: it is more compact in size, it exhibits a linear phase response around the design frequency, it can incur a phase lead or lag which is independent of the length of the structure and it exhibits shorter group delays.

Broadband CPW-fed square slot antennas with a widened tuning stub

Abstract: By using a coplanar waveguide (CPW) feed with a widened tuning stub, a square slot antenna for broadband operation is presented. Experimental results show that the impedance matching for the proposed antenna strongly depends on the location of the tuning stub in the square slot, and the impedance bandwidth is mainly determined by the width and length of the tuning stub. By properly choosing the location and the size of the tuning stub, a wide impedance bandwidth of 60% can be obtained, which is about 1.9 times that of a conventional CPW-fed square slot antenna with a simple tuning stub. Details of the experimental results are presented and discussed.

Split ring resonator-based left-handed coplanar waveguide

Abstract: In this letter, a planar left-handed propagating medium consisting of a coplanar waveguide (CPW) inductively coupled to split ring resonators (SRR) and periodically loaded with narrow metallic wires is proposed. The wires make the structure behave as a microwave plasma with a negative effective permittivity which covers a broad frequency range. The negative permeability required to achieve left-handed wave propagation is provided by the rings in the vicinity of their resonant frequency. The result is a structure which allows negative wave propagation in a narrow frequency band. The transmission coefficient measured in a fabricated prototype device exhibits very low insertion losses in the pass band and high-frequency selectivity. Since rings are much smaller than signal wavelength at resonance and can be easily tuned, SRR-CPW-based structures are of interest for the design of very compact microwave circuits based on left handedness.

Periodically loaded transmission line with effective negative refractive index and negative group velocity

Abstract: We present the design and implementation of a periodically loaded transmission line, which simultaneously exhibits negative refractive index (NRI) and negative group delay (and, hence, negative group velocity). This is achieved by loading the transmission line in series with capacitors and RLC resonators and in shunt with inductors. We discuss the dispersion characteristics of such a medium and identify the frequency bands of NRI and negative group delay. The structures are theoretically studied using S-parameters simulations on truncated loaded transmission lines of different lengths, and the predicted results are compared to the measured scattering parameters of such lines printed on circuit boards using coplanar waveguide technology.

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.

Wideband coplanar waveguide RF probe pad to microstrip transitions without via holes

Abstract: A novel via-less coplanar waveguide (CPW) to microstrip transition is discussed and design rules based on simulations and experimental results are presented. This transition demonstrates a maximum insertion loss of 1 dB over the frequency range from 10 GHz to 40 GHz with a value of 0.4 dB at 20 GHz. This transition could find a variety of applications due to its compatibility with RF systems-on-a chip, low loss performance, low cost and its ease of fabrication.

Variable capacitance element

Abstract: A variable capacitance element includes a coplanar line or signal conduction and a movable body, which are vertically displaced through a supporting bar and which are provided on a substrate. A movable electrode is provided between a first driving electrode and second and third driving electrodes which are movable electrodes. Voltage is applied between the movable electrodes, such that one of the movable electrodes is pressed against the coplanar line through a dielectric film. Thus, high frequency signals conducting through the coplanar line are shut off. When voltage is applied between the other electrodes, the movable electrode and the dielectric film are moved apart from the coplanar line. Thus, high frequency signals are conducted through the coplanar line.

Guided-wave characteristics of periodic coplanar waveguides with inductive loading - unit-length transmission parameters

Abstract: Periodic coplanar waveguides (CPWs) with inductive loading are thoroughly studied by resorting to unit-length transmission parameters, i.e., propagation constant and characteristic impedance, of an equivalent dispersive and/or lossy transmission line. The admittance-type method of moments (MoM) is at first formulated to full-wave modeling of a finite-cell periodic CPW with the two feeding lines and then the short-open-calibration procedure is carried out to deembed the two-port ABCD matrix of the core periodic CPW section. Thus, the above two parameters can be extracted from the MoM simulation to exhibit their guided-wave characteristics, i.e., slow-wave and bandstop behaviors. It is demonstrated for the first time that, within the bandstop or bandgap, the propagation constant must become complex with a nonzero attenuation constant, while the characteristic impedance appears purely imaginary. Three periodic CPW circuits with six finite cells are then characterized on a basis of the transmission-line theorem and the derived S-parameters are validated by Momentum simulation and RF measurement.

Periodically loaded transmission line with effective negative refractive index and negative group velocity

Abstract: Media with negative refractive index (NRI) are expected to exhibit properties that are unusual compared to materials with a positive index of refraction. However, until recently, these properties were not experimentally observed, since no NRI material occurs naturally. Periodic structures with NRI have been constructed. Our group created artificial NRI materials by loading a cellular network of transmission lines with series capacitors and shunt inductors (Eleftheriades, G.V. et al., IEEE Trans. Microwave Theory and Techniques, vol.50, no.12, p.2702-12, 2002; Microwave and Wireless Component Lett., 2003). We have extended that work to design a medium that exhibits negative group velocity (NGV) in addition to NRI. To achieve the NGV, a resonant circuit is embedded within each loaded transmission line (LTL) unit cell. The resonance produces a region of anomalous dispersion in which the group delay, and thus the group velocity, is negative. The NGV means that the peak of the output pulse emerges from the LTL prior to the peak of the input pulse, though much reduced in magnitude. Note that the front of the output pulse does not precede the front of the input pulse; that is, the output pulse front suffers the usual positive delay. The proposed transmission line is fabricated using coplanar waveguide technology. Scattering matrix measurements verify the theoretical predictions.

Modeling dispersion and radiation characteristics of conductor-backed CPW with finite ground width

Abstract: Dispersion and radiation properties of the conductor-backed coplanar waveguide (CPW) with finite ground planes are analyzed and modeled. A frequency-domain finite-difference method using the perfectly matched layer absorbing boundary condition is used as reference. Based on these results, a closed-form description is derived and implemented into an existing quasi-static CPW model. This leads to a comprehensive and efficient CPW description accounting for all relevant effects from conductor loss to high-frequency dispersion. Additionally, design rules to avoid parasitic radiation effects are given.

Ultra-broadband car antennas for communications and navigation applications

Abstract: This paper presents two different ultra-broadband antenna designs for mobile communications and navigation, which can be integrated conformally into the bodywork of a car. Both antennas are based on the frequency-independent spiral structure. One antenna, which is intended to be integrated into the car's window, is an externally fed spiral antenna in order to obtain a flat structure. The second spiral antenna consists of four arms which are fed by a coplanar waveguide transmission line. This enables the excitation of two different radiation patterns for terrestrial and satellite services. With a low cost feed network both radiation modes can be excited simultaneously and independently of each other. Measurement results are presented within and beyond the specifications.

Dual-polarized dielectric resonator antennas

Abstract: Two high input-isolation dual-polarized dielectric resonator (DR) antennas are presented in this communication. First, a slot-coupled feed technique with two narrow slots forming a "T" configuration is employed to design a dual-polarized DR antenna. Input isolation exceeding 35 dB has been obtained in the band for this design. Secondly, a hybrid feed mechanism with a coplanar waveguide (CPW) feed and a slot feed is used to achieve a dual-polarized DR antenna. A vertical strip is added at the center strip of the CPW feed to improve the coupling to the DR antenna. Also, input isolation exceeding 35 dB has been obtained in the band. Good cross-polarization levels less than -20 dB in the broadside direction are attained. The measured far-field radiation patterns are stable in the passband and the measured gains are around 5.5 dBi for the two feed ports of both cases.

W-band CPW RF MEMS circuits on quartz substrates

Abstract: This paper presents W-band coplanar waveguide RF microelectromechanical system (MEMS) capacitive shunt switches with very low insertion loss (-0.2 to -0.5 dB) and high-isolation (/spl les/ -30 dB) over the entire W-band frequency range. It is shown that full-wave electromagnetic modeling using Sonnet can predict the performance of RF MEMS switches up to 120 GHz. Also presented are W-band 0/spl deg//90/spl deg/ and 0/spl deg//180/spl deg/ switched-line phase shifters with very good insertion loss (1.75 dB/bit at 90 GHz) and a wide bandwidth of operation (75-100 GHz). These circuits are the first demonstration of RF MEMS digital-type phase shifters at W-band frequencies and they outperform their solid-state counterparts by a large margin.

Effectively balanced dipole microstrip antenna

Abstract: A effectively balanced dipole antenna is provided comprising an unbalanced microstrip antenna having a transmission line interface and a planar balun connected to the transmission line interface of the antenna. The balun can be coplanar or multi-planar. For example, a coplanar balun includes an unbalanced coplanar transmission line, with a signal line interposed between a pair of coplanar grounds, and a pair of planar stubs plan-wise adjacent the coplanar grounds. The coplanar grounds are connected to the plane stubs with conductive lines proximate to the antenna transmission line interface. A microstrip planar balun includes an unbalanced microstrip signal line, a microstrip ground formed on the dielectric layer underlying the signal line, and a pair of planar stubs, plan-wise adjacent the microstrip ground. The planar stubs can be located on the same dielectric layer as the signal line or the ground. A stripline planar balun is also provided.

Dual electromagnetic bandgap CPW structures for filter applications

Abstract: A novel coplanar waveguide (CPW) low pass filter based on electromagnetic bandgaps (EBG) with double periodicity has been designed and fabricated. The device consists on a CPW with T-shaped loading capacitances at periodic positions and slot width modulation. By properly choosing the ratio between the two periods of the structure, a huge band gap (more than five times the bandwidth) is obtained through the suppression of spurious frequencies. The fabricated prototypes also exhibit very sharp cutoff, very low insertion loss in the passband and slow wave effect.

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.

Fabrication, assembly, and testing of RF MEMS capacitive switches using flexible printed circuit technology

Abstract: A novel approach for cost effective fabrication, assembly, and packaging of radio-frequency microelectromechanical systems (RF MEMS) capacitive switches using flexible circuit processing techniques is reported. The key feature of this approach is the use of most commonly used flexible circuit film, Kapton-E polyimide film, as the movable switch membrane. The physical dimensions of these switches are in the mesoscale range. For example, electrode area and gap height of a capacitive shunt switch on coplanar waveguide are 2 /spl times/ 1 mm/sup 2/ and 43 /spl mu/m, respectively. Pull-down voltage is in the range of 90-100 V. In the ON state (up-position), the insertion loss is less than 0.3-0.4 dB up to 30 GHz. In OFF state (down-position), the isolation value is about 15 dB at 12 GHz and increases to 36 dB at 30 GHz. These switches are uniquely suitable for batch integration with printed circuits and antennas on laminate substrates.

Embedded shielded stripline (ESS) structure using air channels within the ESS structure

Abstract: A technique for facilitating signal transmission at high signal frequencies in a multi-layer substrate is disclosed. In one embodiment a multi-layer substrate comprises a conductor or pair of conductors, a first dielectric layer on a first side of the conductor or pair of conductors and a second dielectric layer on a second side of the conductor or pair of conductors. An air channel is provided in the first dielectric layer, the air channel formed to be substantially coextensive with the conductor or pair of conductors. A conductive shield surrounds the conductor or pair of conductors, the first dielectric layer, and the second dielectric layer in order to eliminate crosstalk. The conductor or pair of conductors may have discrete spaced edges and the width of the conductor or pair of conductors may be increased in order to adjust the impedance because of the low dielectric constant of air. Furthermore, additional air channels and a supporting layer may be included in the structure.

Revisiting the partial-capacitance approach to the analysis of coplanar transmission lines on multilayered substrates

Abstract: A theoretical justification is presented of the partial-capacitance (PC) approach, widely exploited in the modeling of coplanar waveguides on finite-thickness and multilayered substrates. The analysis is based on the static spectral-domain approach to the computation of the capacitance of a set of planar conductors embedded into a multilayered substrate. It is shown that the PC method can be derived from approximating the static Green's function of a multilayered dielectric as the sum of partial contributions; such a decomposition can be applied to the Green's function either in parallel (admittance) or series (impedance) form. The resulting (parallel or series) PC approaches are shown to be accurate with substrates having layers of decreasing or increasing permittivity, respectively. Lines backed by magnetic or electric walls are introduced as limiting cases of multilayered structures.

Modeling and design for electrical performance of wideband flip-chip transition

Abstract: A locally matching technique is proposed in this paper to improve the wideband performance of the flip-chip transition. The gap width of the coplanar waveguide (CPW) line in the bump pad region of both the chip and board is enlarged for achieving larger inductance to compensate the capacitance at the transition, making the approximate impedance close to 50 /spl Omega/. An equivalent circuit is derived from the frequency response of the transition simulated by Sonnet and is used to control the zero frequency of the structure. With a properly chosen value of the enlarged width, the zero frequency can be controlled to achieve an optimal transition performance over an as wide as possible bandwidth. A systematic design procedure is established and employed to design a transition over a band from dc to 60 GHz. The design and simulation results are also compared with the measured data of a scaled structure as well as a realization of an optimized flip-chip transition design ranging from dc to Ka band. The measured data show a good agreement with the simulation results, if under a careful calibration procedure. Both demonstrate that the present transition design can achieve better than 25 dB in return loss and 0.2 dB in insertion loss over dc to 35 GHz.

Tunable bandpass filter using distributed MEMS transmission lines

Abstract: This paper presents a two-state tunable RF MEMS bandpass filter operating at 16.5 and 22 GHz. The topology consists of coplanar waveguide sections that are periodically loaded with MEMS capacitors. The passband insertion loss and bandwidth are 2.3 dB and 11.5% at 16.5 GHz, and 3.3 dB and 16.5% at 22 GHz. The typical switching voltage is 45-50 V.

Design of a superconducting MEM shunt switch for RF applications

Abstract: We have designed, simulated and optimized a capacitively shunted RF MicroElectroMechanical (MEM) superconducting switch. The switch consists of a High Temperature Superconducting (HTS) YBa/sub 2/Cu/sub 3/O/sub 7/ coplanar waveguide (CPW) structure with a gold membrane bridge suspended above the center conductor and anchored at the ground planes (air gap 3 /spl mu/m). A thin layer of BaTiO/sub 3/, in the shape of a patch, lies on top of the center conductor and underneath the suspended gold membrane. Under an applied voltage, the gold bridge membrane actuates downwards and collapses on top of the dielectric layer of BaTiO/sub 3/ thereby capacitively shunting the RF signal to ground. Using Sonnet, simulations were conducted to optimize the switch design. An analysis of these results revealed interesting relationships between the switch mechanical and electrical parameters; this paper discusses and analyzes these results, along with measured data.

Reduction of backward radiation for CPW fed aperture stacked patch antennas on small ground planes

Abstract: A coplanar waveguide fed aperture coupled patch antenna mounted on a finite sized ground plane that incorporates a reflector element to reduce backward radiated fields is investigated. By altering the reflector element parameters, the rear field pattern can be adjusted to provide field cancellation in arbitrary directions.

A self-attenuating superconducting transmission line for use as a microwave power limiter

Abstract: We have designed, fabricated, and tested microwave power limiter based on high-temperature superconductor thin-film technology. The power limiter takes the form of a 50 /spl Omega/ coplanar waveguide transmission line that is reversibly driven from the low-loss superconducting state to the high-loss normal state when the microwave currents within the device exceed a critical value. When operated at 70 K, the power limiter displays very low insertion loss in the nonlimiting state ( 40 GHz), with constant impedance over the entire microwave range. The maximum power transmitted by the device can be engineered by varying the transmission-line dimensions, and can be further tuned once the device has been fabricated by varying the operating temperature. In the over-power state the device continues to pass a portion of the incident signal, although with reduced linearity. Switching times for the power limiter are estimated to be on the order of microseconds or less, based on both pulsed rf measurements and on measurements using a periodic amplitude-modulated drive signal. We expect this device to be useful for protecting high-performance receiver circuits from over-power conditions without limiting the dynamic range or bandwidth of receiver systems.

Mechanical characterization of micromachined capacitive switches: design consideration and experimental verification

Abstract: The mechanical modeling and experimental study of radio frequency (RF) micromachined capacitive switches is presented in this paper. The micromachined capacitive switch, fabricated using bulk and surface micromachining techniques, consists of a thin metal membrane suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static mechanical model considering complicated geometry and the residual stress effect of the bridge is established to demonstrate the pull-in instability phenomenon of the micromachined capacitive switch, and to predict the effective stiffness constant and critical collapse voltage of the bridge for several typical bridge geometries. An optoelectronic laser interferometric system, based on a modified Michelson interferometer incorporated with optoelectronic devices is developed to evaluate the membrane deformation characteristics of the micromachined capacitive switch with different applied dc bias voltages. It is illustrated that the analytical solution is well agreed with the numerical simulation and experiment.

Iron and Permalloy based magnetic monolithic tunable microwave devices

Abstract: We fabricated a series of magnetic monolithic tunable microwave notch-filters and phase shifters. In contrast to previous work with molecular beam epitaxy grown metallic ferromagnets, our devices were created by magnetron sputtering. Single crystal GaAs (001) was used as a substrate. Iron and Permalloy were used as magnetic materials in a coplanar waveguide geometry. The transmission characteristics of the filters were observed to depend on substrate quality, film deposition parameters (Argon pressure, growth rate, power, etc.), and grain size. In addition we observed a substantial increase in the resonance frequency for the Fe based notch-filters. This increase in the resonance frequency is due to a growth-induced uniaxial anisotropy field of 40 kA/m in the Fe films. This is an unexpected and important result especially because the observed anisotropy is growth and not field induced. The resonance frequency shifted from 9.3 GHz at zero applied magnetic field to 15 GHz for an applied static magnetic field...

W-band characterization of finite ground coplanar transmission lines on liquid crystal polymer (LCP) substrates

Abstract: Liquid Crystal Polymer (LCP) is a material with properties that suit it well as both a substrate and packaging material. LCP's multi-layer lamination capabilities, excellent electrical properties, and near hermetic nature suit it to a wide range of RF applications. Several frequency bands of interest. such as evolving applications in the 60 GHz band and military use at 94 GHz, could potentially benefit from the use of LCP system on package (SOP) devices. To test the viability of LCP at these frequencies, a conductor-hacked coplanar waveguide (CBCPW) on a 50 micron LCP substrate was fabricated and measured from 2 - 110 GHz. For measurement accuracy and substrate characterization, a through, reflect, line, (TRL) calibration was performed according to the National Institute of Standards and Technology (NIST) guidelimes. For the first time, LCP is characterized as a nun-wave circuit substrate up to 110 GHz.

Design and Performance of High Tc Superconducting Coplanar Waveguide Matching Circuit for RF-CMOS LNA

Abstract: SUMMARY As an RF high Tc superconducting (HTS) front end for a microwave receiver, we propose a new design method for the broadband matching circuit composed of coplanar waveguide (CPW) meanderline resonators connecting a slot antenna with CMOS low noise amplifier (LNA). The parameters of the antenna sections with matching circuit are calculated and simulated with the circuit simulator and electromagnetic field simulator. CMOS LNA was designed and its input and output impedances and noise figure were obtained by SPICE simulation.

Study on low voltage actuated MEMS rf capacitive switches

Abstract: We report the study on the MEMS rf switches with low actuated voltage. The switch structure has been optimized by the calculation on the dependence of actuated voltage on the Young’s modulus of membrane materials and geometrical sizes. Compared with gold material, AlSi0.04 is a good movable film material having lower actuated voltage (5 V). The switches array is made on the coplanar waveguide (CPW) transmission lines, which were fabricated on quartz, high resistivity (>2 kΩ cm) silicon and porous silicon substrates respectively. The pull-in voltage of the variable capacitor was below 20 V. Furthermore, the 21 bridges MEMS switch array had 372°/3.5 mm phase shift operating at 35 GHz. The chip is compacted into a size of 3.5 mm ×0.5 mm .

Input/output coupling structure for dielectric waveguide

Abstract: Disclosed is an input/output coupling structure for coupling a printed circuit board with a dielectric waveguide having a dielectric body and a conductive film covering the dielectric body. The coupling structure comprises a first conductive pattern formed on the bottom surface of the dielectric waveguide to serve as an input/output electrode, in such a manner as to be surrounded directly by an exposed portion of the dielectric body and further by the conductive film formed around the outer periphery of the exposed portion, a spacer having a surface made substantially entirely of a conductive material and a portion for defining a given space, and a second conductive pattern formed on a principal surface of the printed circuit board and electrically connected to the microstrip line. The bottom surface of the dielectric waveguide is joined to the principal surface of the printed circuit board through the spacer, to allow the first and second conductive patterns to be located in opposed relation to one another and define the space therebetween in cooperation with the spacer. The present invention can provide a simplified structure for mounting a dielectric waveguide on a printed circuit-wiring board to couple the dielectric waveguide with a microstrip line of the dielectric waveguide, and achieve a mode conversion mechanism operable in a wide frequency band and less subject to the influence of the possible displacement between the microstrip line and the dielectric waveguide.