Attenuation characteristics of coplanar waveguides

Some preliminary Q measurement results obtained on coplanar waveguides are reported. The novel surface strip transmission lines have loss characteristics similar to those of microstrip lines of the same width and characteristic impedance.     

Single-mode operation of coplanar waveguides

A grounded coplanar waveguide structure with finite-size ground planes is analysed as three coupled microstrip lines. The three normal propagation modes of this structure are examined for various geometries, and some physical layout guidelines are established.     

Modal dispersion relations for rectangular corrugated waveguides with corner filled corrugations

A simplified model is developed for the determination of the dispersion diagram and modal fields in rectangular corrugated waveguides with corner filled corrugations. The model, although relying on numerical methods, provides a computationally efficient technique.<>     

Optical control of microwaves by LED-induced DBR structures in silicon coplanar waveguides

An analysis of a periodically photoexcited structure (PPS) in a silicon coplanar waveguide is presented. The numerical results confirm the potential of PPSs to work as optically CW- or pulse-induced tunable filters and reflectors.<>     

Dispersion in shielded coupled coplanar waveguides

A full-wave solution is developed to investigate the dispersion in shielded coupled coplanar waveguides. This study shows that the quasi-TEM data available in the literature for the coupled coplanar waveguide cannot accurately predict the performance of this structure at high frequencies.     

Dispersion and leakage characteristics of coplanar waveguides

The dispersion and leakage characteristics of coplanar waveguides are treated using the spectral-domain approach together with the complex residue technique. To handle the complex propagation constant of the coplanar waveguide, the Fourier transform and Parseval's theorem in the complex plane are extended. A number of numerical results, such as the effective dielectric constant and normalized attenuation constant, are presented to illustrate the characteristics of the coplanar waveguide. Sharp peaks just after leakage together with broad peaks are two interesting phenomena observed in the attenuation characteristics. The physical mechanism of these peaks and the details of transition in the ϵ_eff and α/k₀ curves are still unclear     

Dispersion characteristics of cylindrical coplanar waveguides

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     

Characteristic impedance of surface-strip coplanar waveguides

The dependence of the characteristic impedance of a coplanar waveguide is measured as a function of slotwidth and substrate thickness. For alumina substrates (?r= 9.2), it is shown that the substrate thickness should be at least twice the slotwidth for an accurate determination of this impedance.     

Si-micromachined coplanar waveguides for use in high-frequencycircuits

This paper describes the development and characterization of a new class of Si-micromachined lines and circuit components for operation between 2-110 GHz. In these lines, which are a finite-ground coplanar-waveguide (FGC) type, Si micromachining is used to remove the dielectric material from the aperture regions in an effort to reduce dispersion and minimize propagation loss. Measured results have shown a considerable loss reduction to levels that compare favorably with those of membrane lines and rectangular waveguides. Micromachined FGC lines have been used to develop V- and W-band bandpass filters. The W-band micromachined FGC filter has shown a 0.8-dB improvement in insertion loss at 94 GHz over a conventional FGC line. This approach offers an excellent alternative to the membrane technology, exhibiting very low loss, no dispersion, and mode-free operation without using membranes to support the interconnect structure     

Optically CW-induced losses in semiconductor coplanar waveguides

The authors present a quasi-static analysis of photoinduced wave attenuation in a continuously illuminated coplanar waveguide transmission line on a semiconductor substrate, using a conformal mapping technique. The relevant effects of charge carrier diffusion and surface recombination on photoconductivity and plasma penetration depth have been incorporated into the theory. This allows a quantitative estimate of optically induced losses as a function of the various light-source and substrate parameters by means of numerically calculated diagrams. In the particular case of small-plasma-depth excitation, an appropriate, analytical expression for the light-controlled attenuation constant is presented. Initial experimental results are in relatively good agreement with the theory     

Birefringence control and dispersion characteristics of silicon oxynitride optical waveguides

The design, fabrication and characterisation of birefringent silicon oxynitride planar optical waveguides are described for applications at the wavelength of 1.54 mu m. Form birefringence is attained by interposing a thin silicon nitride film in the waveguide stack, and can be controlled by adjusting the nitride layer thickness. Dispersion characteristics of the oxynitride waveguides have been measured and compared with theory.<>     

Microwave performance of SOI n-MOSFETs and coplanar waveguides

The microwave performance of 1-μm gate-length n-MOSFETs fabricated on both SIMOX and BESOI substrates was measured. The process included a self-aligned silicide in an otherwise conventional MOS sequence. Initial optimization yielded devices with an f_max of 14 GHz on BESOI and 11 GHz on SIMOX. Coplanar waveguides (CPWs) were fabricated on substrates with resistivities from 4 to 4000 Ω-cm. A loss of 1.8 dB/cm at 2 GHz was demonstrated on the 4000-Ω-cm float-zone substrate     

Modal dispersion and attenuation measurements of silicon nitrideand silicon oxynitride waveguides using a streak camera

By measuring short pulse propagation in silicon nitride and oxynitride waveguides fabricated on silicon, it has been possible to characterize both attenuation and group velocity dispersion accurately for the different modes that propagate. The method is self-calibrating, using the ratio between scattered light from forward and backward traveling pulses at a particular point on the waveguide. In principle, the group velocity data can be used to calculate the phase velocities for the different modes using known dispersion relations. The phase velocities were measured independently using a prism coupling technique, and the group velocities that could be derived from them matched the experimental data within a few percent. The resolution of the technique is limited mainly by amplitude fluctuations of the laser. The full-width-half-maximum resolution was at best about 12 ps but should be extendable to better than 5 ps     

Equivalent circuit representation of lossy coplanar waveguides

The study of the dispersion properties of planar transmission lines including metallic losses with the generalized transverse resonance method is formalized in building an equivalent network of the cross-section which specifies the relationships between the tangential components of the fields on each side of the interfaces. Virtual sources represent the trial quantities chosen to describe the problem. With twoport type boundary conditions, the trial quantities are not easily defined from physical considerations, but the virtual sources obey to specific rules. This purpose is illustrated in studying the attenuation in lossy suspended coplanar transmission lines.     

Broadside-coupled coplanar waveguides and their end-coupledband-pass filter applications

Broadside-coupled coplanar waveguides, suitable for applications requiring wide bandwidths, tight couplings, and large mode effective-dielectric-constant ratios, are presented, and their analysis and investigation are described. Simple equations relating the per-unit-length capacitances of the c- and π-modes and the per-unit-length capacitance matrices of the coupled structures to those obtained when applying even- and odd-symmetric voltages are also derived. Broadside end-coupled bandpass filters have been developed at X-band (8-12 GHz) with less than 1.5 and 1.0 dB passband insertion losses using the proposed four-ground-plane and two-ground-plane coplanar waveguide structures, respectively. Good agreement between the experimental results and those predicted theoretically was observed     

Modal analysis of multi-connected waveguides

A general analysis for the modal characterization of multiconnected uniform, hollow, conducting waveguides is presented. It is relevant to waveguides with an `outer' conductor for which analytical Green's functions are known and `inner' conductors described by integral equations. The transverse electromagnetic (TEM)-mode space is analyzed, and singularities of the integral equations are studied to determine the higher-order modes. The cases of parallel wires into rectangular waveguides and above a ground plane are addressed in detail; experimental results about a complex multiwire line are reported. Mixed coaxial and circular offset coaxial waveguides are also analyzed. Spurious solutions arise due to the structure of the integral equations for multiconnected waveguides. Criteria to discard such modes are presented     

Modal attenuation in multilayered coated waveguides

Propagation and attenuation constants of low-order normal modes in a circular waveguide lined with lossy coating layers are calculated using a generalized dispersion equation. It is found that the use of multilayered coating can significantly enhance modal attenuations over a broader frequency range compared to that for a single-layer coated structure. For a cylinder with radius a=2λ, the attenuation constants for the dominant modes are shown to increase by 20 dB per a by adding a lossless padding layer to a lossy magnetic coating. Application of this result in radar cross-section (RCS) reduction is discussed     

Time-domain response of MIS coplanar waveguides for MMICs

An MIS coplanar waveguide propagating a slow-wave mode has been characterised in the time domain. The theoretical analysis proposed to obtain the time-domain response of the line gives results in good agreement with measurements. The circuit analysis used is suitable for the determination of spurious propagation effects, inherent to the use of miniature waveguides encountered in MMICs, such as Schottky contact coplanar lines and coupled microstrip lines laid on MIS substrates.     

Parameters of coplanar waveguides with lower ground plane

A new analytical expression for the impedance and the permittivity of coplanar waveguides with lower ground plane is presented. Although approximate in principle, this expression shows very good agreement with the upper or lower bounds of the parameters, computed via a spectral-domain variational approach.     

Attenuation characteristics of coplanar waveguides at subterahertz frequencies

We present experimental and simulation data of subterahertz attenuation of coplanar waveguides (CPWs) with wide and narrow ground planes. Experimental data are obtained by using a subpicosecond measurement technique based on electrooptic sampling. While time-domain data qualitatively describe the attenuation characteristics, they are converted to the frequency domain by a Fourier transform to give a quantitative interpretation. Simulation data are obtained by full-wave analysis and compared with the experimental results. It is shown that the simulation results consistently agree with experimental results. Furthermore, in the case of CPWs with wide ground planes, both of them are consistent with analytical theory. While CPWs with narrow ground planes have not been analytically studied, our results show that they suffer considerably lower attenuation, which we attribute to a reduced coupling between the CPW mode and substrate modes. The effects of ground-plane width and line dimensions on the attenuation characteristics are discussed in detail.