Jifu Huang

Comparing coax launcher and wafer probe excitation for 10 mil conductor backed CPW with via holes and airbridges

An experimental comparison of coax launchers versus wafer probe excitation of a 10-mil conductor backed CPW (coplanar waveguide) is presented. It was found that conductor backing of a CPW can cause a serious moding problem when a coax launcher is used. Introducing via holes can eliminate this problem to some degree. In comparison, wafer probe excitation generally shows a better response but the back metallization causes some moding problems. The transition effect from the coax launcher onto the CPW was modeled numerically, and good agreement with measured data was found.<<ETX>>

Rigorous analysis of mixed transmission line interconnects using the frequency-domain TLM method

A rigorous analysis of mixed transmission line interconnects is presented using an improved version of the frequency-domain TLM method. Direct via hole through connections and indirect coupling effects between layered microstrip and coplanar waveguides are investigated as well as the effect of bonding wire transitions between MMIC modules and the microstrip substrate carrier. This investigation is extended to include the abrupt transition from a GaAs-based microstrip line to a rib-type microstrip line, which has not been analyzed before. In the context of this work new developments of the frequency-domain TLM method are discussed. In particular, it is shown that the transmission line nodes used in the FDTLM can be obtained either by modifying the existing time-domain TLM nodes or directly in the frequency domain. The latter approach leads to a faster algorithm. >

Rigorous field theory analysis of flip-chip interconnections in MMICs using the FDTLM method

This paper presents a rigorous 3-D field theory analysis of the flip-chip assembly by using the frequency-domain TLM method. The scattering parameters of the bump discontinuities are calculated in the cases of CPW and microstrip. Simulation results show that the flip-chip packaging using solder bump connecting the mother board and the chip provides better electrical performance in comparison with the conventional wire bonding approach. With the dimensions used in this paper, the reflections at the bump discontinuities are found to be better than -40 dB and -20 dB, respectively, for CPW and microstrip over the frequency spectrum from 1 GHz to 40 GHz.<<ETX>>

Microstrip discontinuities on cylindrical surfaces

S-parameter analysis of microstrip discontinuities on cylindrical dielectric surfaces using the full-wave frequency-domain TLM (transmission line matrix) method is presented. Microstep step and gap discontinuities on the same side of the substrate as well as overlay coupling of two microstrip lines on opposite sides of the substrate are investigated. The finite conductor thickness as well as the interaction of higher order modes between cascaded discontinuities is taken into account. The present algorithm is based on a 12-port symbolic S-matrix.<<ETX>>

Rigorous analysis of mode propagation and field scattering in silicon-based coplanar MIS slow wave structures with abrupt transitions to transmission lines on normal substrate

This paper presents a rigorous field theoretical analysis of slow wave mode propagation in coplanar waveguide (CPW) metal-insulator-semiconductor (MIS) transmission lines with a laterally confined doping profile. Two types of transmission line structures are investigated-bulk silicon and semiconductor-on-insulator (SOI). In both cases a Gaussian profile of the doping depth is assumed. It was found that an optimum lateral width of the doping region exists for which both structures exhibit a much better slow wave factor at lower losses than traditional thin-film MIS transmission lines. The abrupt transition between MIS, CPW, and CPW on a normal insulating substrate was investigated as well. It was found that the reflection coefficient increases significantly with frequency and when the lateral width of the doping region is extended over the whole cross section of the CPW. The investigation was carried out using the frequency-domain transmission line modeling (TLM) (FDTLM) method.

Full-wave analysis of discontinuities in uniplanar and multiplanar transmission lines using the frequency-domain TLM method

The authors introduce a rigorous analysis of a variety of transmission line transition discontinuities and module interconnect assemblies in MMIC (monolithic microwave integrated circuit) and miniature MIC circuits using the frequency-domain TLM (transmission line matrix) method. Numerical results on frequency-dependent S-parameters are presented which include the effect of finite thickness and conductivity of the metallization as well as mode interaction between cascaded discontinuities. The effect of inserting an intermediate section of transmission line between two different transmission media is analyzed, and it is found that CPW transitions can be made more broadband. The effects of the bonding wire for module assemblies are investigated. Itis found that the properties of the interconnect largely depend on the total length of the wire and are quite insensitive to the shape of the wire. This is in good agreement with experimental observations.<<ETX>>

Frequency-domain TLM analysis of the transition from rectangular to circular waveguides

This paper presents a rigorous analysis and design of various transitions between rectangular and circular waveguides. Three types of transitions are presented: An abrupt transition, a tapered transition consisting of cascaded sections of circular waveguide with increasing (decreasing) radii, and a ridged waveguide transition. The latter one has never been analyzed in the literature before, but is potentially the most effective transition because for its ease of manufacturing. The numerical analysis is based on the frequency-domain TLM (FDTLM) method using a graded rectangular mesh arrangement. A comparison with other techniques and measurements validates the approach taken. The typical return loss values achieved without optimizing the structures ranges, for most of the transitions investigated, between 15 to 25 dB.<<ETX>>

Computer-aided design of circular ridged waveguide evanescent-mode bandpass filters using the FDTLM method

The analysis and design of a circular ridged waveguide evanescent mode bandpass filter are described. Two and three resonators filters are presented for the 30 GHz range. Insertion loss is typically below 1 dB and return loss is better than 20 dB, on the average. The full-wave FDTLM (frequency-domain transmission line matrix) method is used to compute the generalized S-parameters of the overall filter structures including the effect of finite metalization thickness and model interaction between filter discontinuities. A comparison to other filter structures in circular waveguides shows excellent agreement between measured and computed results.<<ETX>>

Direct derivation of the TLM symmetrical condensed node from Maxwell's equations using centered differencing and averaging

This paper presents a direct derivation of the TLM symmetrical condensed node (SCN) model from Maxwells equations by using centered differencing and averaging. Direct correspondence between the TLM and finite difference method is established. The node scattering matrix and field expressions are given for the general case with graded mesh and anisotropic materials including both electric and magnetic losses. It is found that the TLM SCN method always has 2nd-order accuracy regardless of a uniform or graded mesh discretization of the space.<<ETX>>

A new frequency-domain TLM algorithm using a decoupled symmetrical condensed node

This paper describes a new algorithm for the frequency-domain TLM (FDTLM) method. The conventional 12-port symmetrical condensed node (SCN) utilized in the past to construct the FDTLM algorithm is decoupled into a pair of independent 6-port nodes. Based upon the properties of decoupled nodes, a new decoupled algorithm for the entire FDTLM network is derived. As a result of this, the memory space requirements of the FDTLM is reduced significantly and the savings in CPU-time is more than 50 per cent.<<ETX>>