Design Of Coplanar Waveguide Research Articles

Design Methodology and Optimization of Distributed MEMS Matching Networks for Low-Microwave-Frequency Applications

A design methodology for the distributed microelectromechanical system (MEMS) impedance matching networks based on the optimization of the uniformity of the Smith chart coverage has been developed. The proposed approach was validated through a comparison between a traditional coplanar waveguide (CPW) design and an improved design based on a slow-wave (SW) structure. The enhanced reconfigurable impedance matching network has been developed for low-frequency applications. The network is based on a distributed MEMS transmission line (DMTL) coupled with the SW structure to reduce the total physical length of the network by 25% in comparison with a traditional DMTL. An extensive analysis was performed to identify the impact of each design parameter in order to optimize the structure and reduce the required size for relatively low-frequency applications. Several parameters are extracted from the electromagnetic simulation results and are used to design the proposed impedance matching network. Measurement results confirm the efficiency of the proposed design methodology in improving the impedance coverage and also miniaturization of the DMTL impedance matching networks.

Multiple band-stop bow-tie slot antennas for multiband wireless systems

A novel and simple design of wideband coplanar waveguide (CPW)-fed bow-tie slot antennas with multiple band-stop characteristics featuring multi-network applications is presented. A frequency stop band can be created by embedding the slot with a pair of stubs, which causes the resultant magnetic fields almost counterbalance in the slot and to be non-responsive at the desire stop band. The effects of the dimensions of the stub on the stop band are also analysed. Dual band-stop characteristic is also accomplished by embedding two pairs of stubs in the slot. Details of the proposed designs and experimental results of the constructed prototypes are presented.

An integrated microelectromechanical microwave switch based on piezoelectric actuation

In the field of microwave applications, microelectromechanical systems (MEMS) are attractive devices in order to force miniaturization by on chip integration. Here, we describe the design, fabrication and testing of a silicon based micromachined switch using piezo-electrically actuated elements. The microwave circuit consists of a coplanar waveguide (CPW) design with two piezoelectric activated beams integrated between the middle line and the ground planes. During operation the beams short the CPW by two overhanging bridge contacts and therefore the transmission characteristics of the microwave circuit change. The CPW is realized by 3 µm thick electroplated copper to yield good transmission characteristics, whereas the clamped—clamped beams benefit from a 250 nm thin PZT film between 100 nm thin Pt electrodes on top of a SiO2 layer. By the use of double side clamped beams awkward stress compensation of the piezoelectric stack is omitted. Instead the system relies on some initial mechanical stress. Measurements prove deflections of more than 13 µm for a 1400 µm long beam with operation voltages below 10 V. This is in good agreement with finite element simulations. The novel RF-MEMS is predicted to reach an isolation (in “on” state) of more than 20 dB up to 15 GHz.

Voltage tunable Ba 0.6Sr 0.4TiO 3 thin films and coplanar phase shifters

Not only the ferroelectric properties of Ba 0.6Sr 0.4TiO 3 thin films but also the design, fabrication and microwave properties of coplanar waveguide (CPW) phase shifter were investigated. When the applied voltage changes from zero to 20 V range at a frequency of 1 kHz, the dielectric constant, tunability, remanent polarization (2P r) and coercive electric field (Ec) of the BST films are 1266, 29.5%, 2.29 μC/cm 2 and 22.27 kV/cm, respectively. The structure of CPW phase shifter was designed by ANSOFT High Frequency Structure Simulator (HFSS) and Agilent Advanced Design System (ADS). The designed phase shifter consists of 56 same sections. It is observed from the photograph of the fabricated device that the lines of electrodes are regular and the widths of bottom electrodes overlapped by top electrodes are about 5 μm. It was found that the phase shift gradually increases as the voltage increases from 0 V to 20 V, which may be due to the tunability of BST films varies with external dc field. About 168° phase shift was achieved at 28 GHz with a bias voltage of 20 V.

Design and Measurement of Self-Matched Dual-Frequency Coplanar Waveguide-Fed-Slot Antennas

Two new designs of dual frequency coplanar waveguide (CPW)-fed double folded slot antennas are presented. An important advantage of these antennas is that they are self-matched to the feeding CPW without the need for external matching circuit. This reduces the antenna size and simplifies its design. To verify the designs, the return loss and radiation patterns are measured and compared to those obtained using available commercial software with good agreement

Design of Composite Right/Left-Handed Coplanar-Waveguide Bandpass and Dual-Passband Filters

The design and implementation of novel coplanar-waveguide (CPW) bandpass and dual-passband filters that consist of the composite right/left-handed short-circuited stubs are proposed. In contrast to the conventional short-circuited stub, whose input impedance repeats every half-wavelength, the composite right/left-handed CPW stub combines the phase-lead composite right/left-handed CPW and the phase-lag uniform CPW to achieve the arbitrary resonant frequencies with compact size. The equivalent bandpass and dual-passband LC resonators are established by investigating the frequency responses of the composite right/left-handed CPW stubs. The composite right/left-handed CPW bandpass filter is 62.5% more compact than the conventional quarter-wavelength shunt-stub CPW bandpass filter. The composite right/left-handed CPW dual-passband filter, which possesses the sharp rejection between the two asymmetric passbands, is also developed. The synthesis procedures of the composite right/left-handed CPW bandpass and dual-passband filters are successfully validated by measurement and full-wave simulation

A crossed coplanar waveguide design for ultrafast magnetization switching utilizing polymer insulation layers

A crossed coplanar waveguide design using polymer insulation layers is developed as a tool to experimentally investigate fast, precessional switching phenomena in view of applications in magnetic random access memory. The photosensitive polymer Cyclotene 4024™ (benzocyclobutene) is used as an electric insulation layer to realize a multilayer sample consisting of several different conducting and insulating layers. We report on the processing of Cyclotene 4024™ multilayers with optimized surface and electric insulating properties after hard cure. The micropatterned impedance matched coplanar waveguides have a bandwidth of 8.5GHz according to −2dB criterion, and for the −3dB criterion the bandwidth exceeds the measurement range of up to 15GHz. These values allow for short rise and fall times of the pulse for ultrafast magnetization dynamics measurements.

Studies of CPW-fed equilateral triangular-ring slot antennas and triangular-ring slot coupled patch antennas

Designs of coplanar waveguide (CPW)-fed equilateral triangular-ring slot antennas with tuning-stub and triangular-ring slot coupled patch antennas are proposed and experimentally investigated. The impedance matching of the resonant frequency can be obtained only by adjusting the tuning-stub length for the proposed triangular-ring slot antenna with tuning-stub. For the design of ring-slot coupled patch antenna, slightly changing the patch size causes the tunable frequency-ratio f/sub 2//f/sub 1/ between the first two operating frequencies to fall in the range of about 1.1-1.42. Details of the proposed designs are investigated by experimental as well as theoretical studies.

Balanced distributed-element phase shifter

We present a balanced distributed-element phase shifter based on a nonlinear transmission line (NLTL) structure. Results show the second harmonic is more than 13dB lower at 0-V bias than a conventional single-ended NLTL phase shifter. We fabricated both balanced and conventional NLTL phase shifters with the same coplanar waveguide (CPW) design and diodes, and observed that phase shifting and insertion loss for both structures were quite similar, yet harmonic distortion was greatly improved in the balanced structure.

Compact asymmetric coplanar waveguide filter

The design and implementation of a novel asymmetric coplanar waveguide (ACPW) band rejection filter using defected ground structure (DGS) is presented. The proposed ACPW DGS technology provides bandgap characteristics with only one cell in the lateral ground plane. The equivalent circuit model of the proposed DGS unit section is described. Measurements of ACPW DGS showed good agreement with simulation and the proposed model.

Study and design of a broadband coplanar waveguide–fed modified folded slot antenna

This paper presents the study and design of a coplanar waveguide–fed broadband modified folded slot antenna, including new techniques to achieve broad impedance bandwidth when the antenna size is small. Antenna impedance and bandwidth are investigated as functions of slot parameters, substrate dielectric constant, and substrate thickness. Prototypes of broadband antennas are fabricated on RO4003 (ɛr = 3.38) and are measured. Two types of antennas are proposed with respective bandwidths of 44.4 and 80% with less than 2:1 VSWR.

Design and performance of bilateral interdigital coplanar waveguide phase shifter for rf communication applications

A new design of a bilateral interdigital coplanar waveguide (BI-CPW) phase shifter using tunable barium strontium titanate thin film is presented and analyzed. This new design has shown a phase shift of 203°/cm at 25 GHz. Compared to a normal coplanar waveguide (CPW) type, a two-thirds size BI-CPW phase shifter is realized by interdigital capacitive loading. The phase shifter is fabricated with processes fully compatible with current SiGe technology. In addition, it is shown that operating voltages can be reduced significantly within a practical range by the inclusion of a polysilicon layer as a control electrode.

A CPW-Fed Dual-Frequency Monopole Antenna

A new dual-frequency design of coplanar waveguide (CPW)-fed monopole antenna is proposed and experimentally studied. The proposed antenna utilizes the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, thereby making easier the integration with the microwave integrated circuits. The two operating modes of the proposed antenna are associated with various lengths of two monopoles, in which the longer monopole works for the first resonant mode and the shorter monopole works for the second mode. Moreover, by increasing the width of the longer monopole, a broadband dual-frequency operation is demonstrated. Experimental results show that the impedance bandwidth, determined from 10-dB return loss, of the two operating frequencies can both be greater than 14%. Details of the experimental results are presented and discussed.

HTS Coplanar Meander-Line Resonator Filters With a Suppressed Slot-Line Mode

The design and experimental results of a four-pole coplanar waveguide (CPW) quasi-elliptic filter using high-temperature superconductor (HTS) films are presented. Quarter-wavelength meander-line resonators are used in the filter topology. Although the resonators are aligned in two lines, no bond-wire bridges are required to balance the ground planes in the design and measurement. The slot-line mode of the filter was shifted to be higher than its third harmonic. The filter is highly miniaturized and the performance is significantly improved by the use of superconductors. The main circuit of the filter only has an area of about 6.6 mm /spl times/ 2.4 mm on a magnesium oxide substrate, coated with 600-nm-thick YBCO HTS thin film on single side of the substrate. The 3-dB bandwidth is about 1.6% centered at 2.95 GHz. The performance measured at 30 K, without any tuning, gives an insertion loss of better than 0.4 dB and a return loss of about 12 dB in the passband. The first spurious mode is about triple the center frequency.

Design and experimental results of bilateral interdigital coplanar delay line for MMICs

AbstractThe design and development of a bilateral interdigital coplanar waveguide (Bi‐CPW) delay line that can be used as a passive device in MMICs is presented in this paper. This Bi‐CPW design is analyzed using the conformal mapping method and realized via an RF‐CMOS‐compatible fabrication process using high‐k dielectric thin film. The Bi‐CPW design shows 180° phase delay at 10 GHz for a 2.8‐mm transmission line. It is shown that a conventional coupler can be implemented in a few mm2 area without any lumped element. The measured results show the potential for monolithic integration of conventional couplers using Bi‐CPW phase delay line. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 127–130, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11305

Dual-band characteristics of annular-ring slot antenna with circular back-patch

The design of coplanar waveguide fed single annular-ring slot antenna for obtaining dual-frequency operation is presented. This is achieved by introducing a back-patch to perturb the slot's electric-field distribution. Details of the proposed designs are described, and experimental and theoretical results are presented and discussed.

Dielectric and patch antenna characteristics of new high- Q (1 − x)(Al 1/2Ta 1/2)O 2− x(Mg 1/3Ta 2/3)O 2 (0 ≤ x ≤ 1.0) microwave ceramics

The microwave dielectric properties of (1− x)(Al 1/2Ta 1/2)O 2− x(Mg 1/3Ta 2/3)O 2 (AMT) (0≤ x≤1.0) ceramics and design of small coplanar waveguide fed antenna (CPWFA) have been investigated. As (Mg 1/3Ta 2/3)O 2 concentration increased, dielectric constant ( ε r) and quality factor ( Q) significantly increased and the temperature coefficient of resonant frequency ( τ f) changed from negative to positive value. The τ f of 0 ppm °C −1 was realized at x=0.65 and the Qf 0 value and ε r for this composition were 112 470 GHz and 26.1, respectively. A newly developed 0.35(Al 1/2Ta 1/2)O 2–0.65(Mg 1/3Ta 2/3)O 2 dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using AMT ceramics with high dielectric constant, insetting slits into patch, and fabricating CPW feed line in the ground plane. The slits play roles in not only lowering a center frequency but also fine-tuning for the proposed CPWFA together with open stub of CPW feed line. The CPWFA with slits has the lower center frequency than the conventional CPWFA, which suggests that an antenna size can reduce as large as 16.3%. Experimental results of the fabricated device were in good agreement with the simulation.

Novel transition between different configurations of planar transmission lines

New designs of coplanar waveguide (CPW)-microstrip, CPW-stripline, conductor backed CPW (CBCPW)-microstrip, and CBCPW-stripline transitions are presented. Simulation using the high frequency structures simulator (HFSS) shows that the return loss of the CPW-microstrip transition is less than -25 dB up to 11 GHz. Similarly is the CPW-stripline transition. In the case of two back to back CBCPW-stripline transitions, the return loss is less than -22 dB up to 9 GHz. Experimentally, the S/sub 11/ of two back to back CBCPW-microstrip transitions on an alumina substrate is less than -15 dB up to 25 GHz.

Computer-aided design of small patch antenna using (Al, Mg)TaO2 ceramics

The microwave dielectric properties of \(\left( {1 - x} \right)\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - x\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) (AMT) \(\left( {0 \leqslant x \leqslant 1.0} \right)\) ceramics and the design of small coplanar waveguide fed antenna (CPWFA) have been investigated. (\(\left( {Al_{1/2} Ta_{1/2} } \right)O_2\) and (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) have orthorhombic and tetragonal structure, respectively. As (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) concentration increased, AMT ceramics transformed into the tetragonal structure. Specimens having tetragonal single phase could be obtained above x=0.6. As (\(\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\) concentration increased, the grain size, dielectric constant \(\varepsilon _r\) and quality factor (Q) significantly increased and the temperature coefficient of resonant frequency \(\tau _f\) changed from negative to positive. The \(\tau _f\) of \(0 ppm ^\circ C^{ - 1}\) was realized at x=0.65 and the Q · fO value and \(\varepsilon _f\) for this composition were 112 470 GHz and 26.1, respectively. Newly developed \(0.35\left( {Al_{1/2} Ta_{1/2} } \right)O_2 - 0.65\left( {Mg_{1/3} Ta_{2/3} } \right)O_2\)dielectric materials were used for 1.5 GHz band CPWFA design and fabrication. The size of the CPWFA can be reduced by using high dielectric constant AMT ceramics, insetting slits into the patch, and fabricating CPW feed line in the ground plane. The slits play a role in not only lowering a center frequency but also fine tuning for the proposed antenna together with the open stub of CPW feed line. The CPWFA with slits has a lower center frequency than the conventional CPWFA, which suggests that the antenna size can be reduced by as much as 16.3%. The structure simulations of the CPWFAs have been performed to obtain impedance matching and to investigate the effects of slits. Experimental results of the fabricated device were in good agreement with the simulation.

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

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.