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

Guided‐wave characteristics of planar periodic microstrip lines with inductive loading are investigated by resorting to the unit‐length transmission parameters of an equivalent transmission line. By applying the SOC de‐embedding technique, the above two quantities are effectively extracted from the full‐wave MoM modeling of a microstrip line with finite periodic cells. Extensive results at first confirm the slow‐wave behavior such that both real parts of such two quantities rise up slowly and then rapidly with frequency. Further, they demonstrate, for the first time, the guided‐wave bandstop characteristic with non‐zero attenuation constant and imaginary characteristic impedance. Five‐cell periodic microstrip circuits are then designed and fabricated for theoretical and experimental verification. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 77–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20052

Two general discrete time-domain transient analysis algorithms for the modeling of lossy and dispersive transmission lines are reviewed and compared. The first is based on the generalized method of characteristics through recursive convolution while the second is based on the more recent Pade macromodeling approach using synthesized lumped networks. The different approximations made in these two algorithms are compared and computational evidence is presented to show that these two methods complement rather than compete with each other.

In this paper, an explicit -non iterative- method for modeling lossy and dispersive transmission lines, allowing the inclusion of skin-effect parameters is described. This method, based on multipoint Pade approximation, allows direct implementation to obtain models for existing simulation program -such as SPICE-without the need of making use of optimization algorithms at any stage. Examples are given to show that the described procedure yields the same accuracy as other existing techniques that do require this iterative approach.

This study presents the accurate characterisation and detailed experimental study of the effect of ground-plane width and suppression of higher-order parasitic modes extending the frequency of operation up to 110 GHz for multilayer conductor-backed coplanar waveguide lines, fabricated in cost-effective thick-film multichip module (MCM) technology. The coplanar waveguides (CPWs) and components have been realised on multiple layers of dielectric onto a ceramic substrate using straightforward and cost-effective photoimageable thick-film process, demonstrating a very low loss of <0.2 dB/mm at 80 GHz for a finite ground CPW and extremely low loss of <0.1 dB at 76 GHz for CPW layer transitions, which are better than many reported results for MCM technologies. Further, the effective dielectric constant (ɛeff) and characteristic impedance (Zch) are extracted from two-port S-parameters measured on a single-line and by conversion to ABCD parameters, to investigate the practical effect of ground-plane width on CPWs on a multilayer ceramic substrate and to facilitate realisation of a cost-effective millimetre-wave MCM.

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.

We investigated the propagation losses and the characteristic impedances Z/sub L/ of coplanar waveguides (CPWs) and microstrip lines (MSLs) on a planar lightwave circuit (PLC)-platform formed on a silica/silicon substrate. The loss of the CPWs was 2.7 dB/cm at 10 GHz on the PLC-platform with 30 /spl mu/m thick silica layer. Thus, a cm-order circuit of this CPW is difficult to fabricate in the 10 Gb/s module. This is because the silicon substrate has a large loss tangent (tan /spl delta/). On the other hand, the loss of the MSLs, where a ground plane shielded the high loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz with 30 /spl mu/m thick polyimide. These lower loss MSLs on a PLC-platform can be applied to module operation at 10 Gb/s. Furthermore they have the advantage that they are suitable for application to array device circuits or circuits in a module where several devices are integrated because unlike CPWs the ground planes are not divided by signal lines or DC bias lines. The structure of CPWs and MSLs on a PLC-platform with a Z/sub L/ of 50 /spl Omega/ was also studied in detail.

The development of very small antennas significantly influences the miniaturization of handheld devices. A planar and symmetric antenna is built up. A capacitive loading for this planar inverted F antenna (IFA) is presented. For a further size reduction, an inductive loading is investigated. The method of moments (MoM) is used to model the antenna and measurements are carried out for verification.

We present a computationally efficient method to stimulate lossy transmission lines using iterative linear least square fitting (ILLSF) model synthesis and piecewise recursive convolution (PRC). Based on the generalized method of characteristics, transmission lines are modeled with characteristic impedances and waveform generators. Thus the first major task involves network synthesis. The second is efficient computation of the synthesized waveform generators which requires computationally expensive convolution integral evaluation during transient simulation of transmission lines. The superior performance of ILLSF and the efficiency of PRC are demonstrated for the transient simulation of coupled lossy transmission lines.

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.

Coplanar waveguide (CPW) transmission lines periodically coupled to split‐ring resonators (SRRs) are analyzed, designed, and characterized. Due to inductive coupling between the lines and SRRs, signal propagation is inhibited in the vicinity of the resonant frequency of the rings. The result is a stop‐band behavior that can be of interest for the elimination of frequency parasitics in CPW‐based devices. Two different approaches are envisaged: a uniplanar structure, where CPW and rings share the same metal level; and a bimetal structure with SRRs etched on the back side of the substrate. It has been found that the latter exhibits almost negligible insertion losses in the pass band, and sharp cutoff and a high level of rejection in the stop band, with few unit cells. Since ring dimensions are small compared to the signal wavelength at resonance, the proposed SRR‐CPWs are very promising for the design of miniaturized microwave circuits. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 3–6, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11269

The paper deals with the numerical analysis of the effects of septum thickness and positions on the characteristic impedance and the electric field distribution in an asymmetric transverse electromagnetic (TEM) cell by using the method of moments (MOM). The distribution of the electric charge on the periphery of the conductors is determined using a quasi-static approximation for operation of the cell at frequencies well below its cut off frequency and by finding the Green's function for the structure. The impedance results are compared with those available in the literature and found to be in very good agreement. An investigation has also been carried out on the effects of the dimensions of the septum on the electric field distributions in the cross-section. The method has the advantage over others that no assumption is needed for the specific choice of the electric charge distribution on the conductors and the analysis considering the effects of the thickness of an offset septum becomes simpler and is most universal.

An algorithm based on an extended scattering matrix formulation is presented for time-domain simulation of lossy dispersive multiconductor transmission lines with arbitrary linear or nonlinear terminations. At each point in time, both sides of the transmission line structure are represented by an extended Thevenin equivalent. This general transmission line model was implemented in a SPICE-like simulation program, and the results are presented. >

In order to obtain low-driving-voltage band-operation optical modulators, we investigated a reflection-type Mach-Zehnder LiNbO/sub 3/ optical modulator with double-stub structure. The double-stub structure consists of a modulating electrode and two stubs. The modulating electrode has two arms of the same length, and is an asymmetric coplanar waveguide (ACPW). A feeding line, which is a coplanar waveguide (CPW), is connected at the center of the modulating electrode. Two stubs, which are also CPWs of the same length, are also connected at the junction of the modulating electrode and the feeding line, so that we call it a double-stub structure.

A structure consisting of dielectric-loaded feed lines (such as surface-wave lines similar to Goubau lines) and below-cutoff air-filled cavities can be used to form essentially L-C sections. The capacitance is due to electric-field coupling from the feed-line dielectric medium into the below-cutoff section. The inductance results from combining the inductors in the inductive tee equivalent circuit for such below-cutoff sections. Dielectric loading is used to shorten the guide wavelength at the input to the evanescent section, increasing the effective input inductance. The dielectrically loaded feed lines can comprise microstrip, coplanar waveguide (CPW), coplanar stripline (CPS), Goubau lines (surface-wave structures), waveguide, etc. The resulting resonant elements are usable at frequencies below 1 GHz, with small dimensions. If connected to the common ground plane, these L-C sections act as a transmission zero. If "floated," i.e., connected in the "hot" line rather than to the ground plane, the sections form bandpass circuits (transmission poles). The air-filled below-cutoff sections (evanescent mode) are placed in a supporting low dielectric-constant medium (air, Teflon, or similar) with the open end in proximity to the dielectric portion of the feed line and are, thus, termed "suspended." The individual L-C sections can be coupled together using microstrip, surface-wave line, CPW, CPS, finline, waveguide, or lumped elements. Such combinations can be chosen to implement Chebychev, Butterworth, quasi-elliptic, etc. responses.

The method of lines (MoL) has been used to analyze the characteristics of various structures of coplanar waveguide widely. However, a large number of literatures do not study the efiects of the ground-plane width on the propagation characteristics, especially characteristic impedance. In this paper, the characteristics (efiective dielectric constant and especially char- acteristic impedance) of shielding coplanar waveguide with flnite ground-planes are analyzed by MoL and the computation results are shown.