Dispersion characteristics of multilayer coplanar waveguide using Single Layer Reduction (SLR) technique

High performance coplanar waveguides (CPWs) on GaN membrane technology for AlGaN/GaN high electron mobility transistors (HEMTs) grown on low-resistivity (LR) Si substrates have been demonstrated in this work. The developed CPW technology shows a remarkable improvement in RF losses when the lossy Si beneath CPW structures is removed, resulting in comparable RF performance to that of CPW realized on high-resistivity (HR) Si and semi-insulating (SI) SiC substrates, with similar AlGaN/GaN top epitaxial layers. Experimental results, first to be reported, demonstrate transmission losses ( $S_{21}$ ) of 0.47 dB and $Q$ -factor of 20.77 for the CPW on GaN membrane technology, compared to $S_{21}$ of 2.95 dB and $Q$ -factor of 4.51 for the CPW on GaN-on-LR Si, at 40 GHz. Furthermore, the influence of substrate parasitics on RF performance of CPW on GaN-based HEMTs grown on various substrates was studied and analyzed by the extraction of transmission line parameters for frequencies up to 40 GHz. These findings offer viable integrated GaN-based HEMTs on LR Si technology suitable for high-power and high-temperature system applications at RF and millimeter-wave frequencies, when used in conjunction with high thermal coefficient materials such as diamond and AIN.

This paper presents the characteristics of coplanar waveguides (CPW) on silicon substrates fabricated through the MCM-D process. The propagation constant and characteristic impedance are measured at frequencies from 0.05 GHz to 10.05 GHz, using a vector analyzer, and with LRRM on-wafer calibration techniques followed with a de-embedding procedure. Two quasi-TEM models are developed to account for the EM affects in the CPW structure: the distributed equivalent elements RLGC were modeled by both closed-form approximation and fully lumped-equivalent circuits. The calculated characteristics show good agreement with the measured ones. The proposed models should be useful for the analysis and design of RFIC on silicon.

Simplified computation of coplanar waveguide with finite conductor thickness

A single layer, low profile, compact metamaterial zeroth-order resonator (ZOR) antenna has been proposed in this paper. A composite right/left-handed (CRLH) transmission line structure that is comprised of a single unit cell makes up the complete antenna. The design complexity of the proposed antenna is very low, since it does not involve any vias. A symmetric coplanar waveguide (CPW) structure is chosen to have design flexibility and to satisfy the design constraints. The main aim of incorporating the left handed behaviour into the design is to achieve compactness. The resonant frequency of zeroth-order mode is around 5.8GHz. A prototype of the proposed antenna has been fabricated and it has the dimensions of 0.348λo × 0.309λo × 0.033λo. The simulated peak gain of the antenna is found to be 0.65dBi. A significant amount of size reduction is observed in the patch area of proposed structure when compared to a regular patch antenna operating at the same frequency. The metamaterial behaviour has been verified with the help of dispersion diagram and vector electric field plot. Simulation is done so as to plot the reflection coefficient of the presented CPW ZOR antenna and it is also observed on the vector network analyzer (VNA). Simulation results show that the proposed ZOR antenna achieves −10dB impedance bandwidth of 7.76% and has a radiation efficiency of about 81.27% at the ZOR mode.

This paper describes an antenna design for wideband high directivity operation using an aperture coupled patch antenna as the feeding source and an FSS (frequency selective surface) based structure as the superstrate for high directivity. The new antenna device combines the wideband characteristic of the aperture coupled antenna and the desirable characteristics of the FSS structure as a superstrate for high performance operation. A coplanar waveguide (CPW) feed design is used to obtain wideband performance for the feeding antenna. Both single layer and double layer based FSS designs are studied for improvement of directivity. The performance is further enhanced by using an air gap between the patch on a thin film substrate and the CPW and aperture structures on an FR4 substrate and also between the layers of a double layer FSS design. The air gaps can be produced using micromachined PMMA rims for low cost construction. An impedance bandwidth in excess of 50% has been obtained for a centre frequency of 10 GHz. The antenna device exhibits a directivity of about 13.6 dBi. A 1-dBi ripple radiation bandwidth as high as ∼42% has been achieved.

We have studied the tuning properties of a high-temperature superconducting (HTS) half-wavelength coplanar waveguide (CPW) resonator operating at 5 GHz. The tuning schemes are based on flip-chip bonding of an electrically tunable ferroelectric (FE) thin film and a mechanically movable low-loss single crystal on top of the resonator. Using the conformal mapping method, closed-form analytical expressions have been derived for a flip-chip bonded conductor-backed and top-shielded CPW transmission line. The obtained expressions are used to analyse the volume effect of the FE thin film and the gap between the flip-chip and the CPW resonator on the tuning properties of the device. It has been found that large frequency modulation of the resonator produces impedance mismatch, which can considerably enhance the insertion loss of high-performance HTS microwave devices. Analysis also suggests that, for electrically tunable devices, flip-chip bonded FE thin films on HTS CPW devices provide a relatively higher performance compared to bilayer HTS/FE tunable devices.

Using the method of lines and the separation of even/odd mode, the dispersion characteristics of broadside-coupled coplanar waveguides (CPW) are analyzed. It is found that the structure has a very weak dispersion in a wide frequency band. The theoretical basis is laid for the application of broadside-coupled CPW in three dimensional microwave integrated circuits, and using the quasi-static TEM approach to analyze and design the circuit in wide frequency band.

The application of an electrooptic sampling technique for the characterization of propagating modes of uniplanar guiding structures on GaAs is described. The characteristics of slotline and even and odd modes of coplanar waveguides (CPW) on semi-insulating GaAs substrate are investigated. The potential distribution over the cross section of each was measured. The guide wavelength for each guide was directly obtained from standing-wave measurements by electrooptic sampling, and the dispersion characteristics of CPW modes and slotline were measured from 15 to 40 GHz. >

This paper deals with the field of passive microwave components. Coming from the requirements of mobile communication devices, miniaturization of microwave components is needed. The DIOM laboratory is using the RF sputtering to realize magnetic thin films. The use of these magnetic thin films for a circulator design enables to develop a new manufacturing technique compatible with the miniaturization of these devices. These components are devoted to future wireless applications in the 8–12 GHz frequency range. The advantages of these components lie in using YIG thin film and in the fact that accesses to the device are coplanar waveguide (CPW). The CPW structure has a signal line and a ground in the same plane. Therefore, the circulator with a CPW structure will be easily fabricated using low cost lithography. Moreover, connections with other devices will be easier.

We report the effective complex permittivity and permeability of 1D planar left‐handed transmission‐line metamaterials. These metamaterials are formed on coplanar waveguide (CPW) with simultaneous load of series‐capacitive and shunt‐inductive elements in periodic intervals. By employing our self‐calibrated method of moments (MoM), the effective permittivity and permeability of these 1D metamaterials are numerically derived to illustrate the propagating and evanescent guided‐wave behaviors over a microwave frequency range. We demonstrate that, in a certain frequency band, the permittivity and permeability simultaneously become negative with zero imaginary parts, and the transmission phase of a finite‐extent CPW metamaterial becomes negative, as exhibited by both simulation and measurement. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1050–1052, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21597

The design and development of novel microelectromechanical systems’ (MEMS) coplanar waveguide (CPW) transmission lines, using microshield and groove, are presented in the paper to operate between 5–60 GHz. The quasi-static capacitances of CPW are calculated using the conformal mapping technique to express the propagation properties, i.e., the characteristic impedance and effective permittivity. Simulation results have shown a considerable loss reduction to levels that compare favorably with the conventional CPW. These transmission lines can be widely used in the development of phase shifters, filters, and antennas, because of their advantages in loss reduction and improvement in the performance.

Due to their major advantage of conformability to curved surfaces, many studies of printed circuits and antennas on a cylindrical substrate have been reported. We extend the study of conformal printed circuits to two novel types of cylindrical coplanar waveguides (CPWs). The configurations of the outside and inside cylindrical CPWs, which can be applied in the design of conformal microstrip circuits or in feeding cylindrical printed antennas, are shown. For the study a full-wave approach is applied, and accurate expressions of the dyadic Green's functions for the two different structures shown are derived and used in a Galerkin's moment-method calculation. Theoretical results of the frequency-dependent effective dielectric constant of the cylindrical CPW with various curvatures are calculated and analyzed, and the curvature effect on the effective dielectric constant is discussed. To verify the accuracy of the theoretical results, several cylindrical CPWs were fabricated and measured.

A planar circularly-polarized (CP) small antenna is proposed. To obtain a low profile configuration, a co-planar waveguide (CPW) structure is employed. Circular polarization is achieved using a curved stub that generates current distribution in a direction orthogonal to the current distribution from the patch. Using meander lines and a series gap capacitance, a 70% size reduction is achieved compared to a half-wavelength resonant antenna. To the best of the authors' knowledge, the proposed antenna is the smallest CP antenna using CPW technology. The measured 3dB axial ratio bandwidth is 8.3% from 3.83GHz to 4.16GHz, and a 1.6dBic gain and 89% efficiency are achieved.

A novel ultra-wideband (UWB) bandpass filter (BPF) with dual notched bands using the hybrid microstrip and coplanar waveguide (CPW) structure is proposed, to prevent interference problems between the UWB radio system and existing radio systems. A multiple-mode resonator on a CPW is formed to allocate its first three resonant modes around the lower-end, centre and upper-end of the 3.1 to 10.6 GHz UWB passband. Its two sides are fed by two microstrip-to-CPW transitions with enhanced frequency-dispersive coupling degree. The dual narrow notched bands are introduced by embedding a open stub in the CPW line and etching two U-shaped slots on the ground plane to form defected ground structures (DGSs) in each side of the microstrip structure. Then, dual-band rejected filtering properties in the C-band (3.7–4.2 GHz) and WLAN (5.15–5.825 GHz) are achieved. The UWB bandpass filter with notched bands has been carried out by designs and related simulations to demonstrate the notch-band-included and upper-stopband-improved performances.

A modified transverse resonance method is presented for analyzing generalized multilayered, multiconductor quasiplanar structures with practical parameters such as finite conductor thickness and mounting grooves. Recurrence relations are obtained by using network theory for obtaining the overall transverse equivalent network. while the discontinuity involving the finite-thickness metal sheet and mounting groove is carried out by a field-theory-based multimodal variational formulation. The frequency behaviors of propagating, evanescent, and complex modes are obtained for several commonly used quasiplanar lines, showing good agreement with published results. Furthermore, a leaky-wave study is carried out for open structures, since the open condition can be included in this formulation without difficulties.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>