Andreas Weisshaar

Bio: Andreas Weisshaar is an academic researcher from Oregon State University. The author has contributed to research in topics: Equivalent circuit & Microstrip. The author has an hindex of 20, co-authored 93 publications receiving 1575 citations. Previous affiliations of Andreas Weisshaar include University of Stuttgart.

CAD-oriented equivalent-circuit modeling of on-chip interconnects on lossy silicon substrate

Abstract: A new, comprehensive CAD-oriented modeling methodology for single and coupled interconnects on an Si-SiO/sub 2/ substrate is presented. The modeling technique uses a modified quasi-static spectral domain electromagnetic analysis which takes into account the skin effect in the semiconducting substrate. Equivalent-circuit models with only ideal lumped elements, representing the broadband characteristics of the interconnects, are extracted. The response of the proposed SPICE compatible equivalent-circuit models is shown to be in good agreement with the frequency-dependent transmission line characteristics of single and general coupled on-chip interconnects.

A comprehensive compact-modeling methodology for spiral inductors in silicon-based RFICs

Abstract: A new comprehensive wide-band compact-modeling methodology for on-chip spiral inductors is presented. The new modeling methodology creates an equivalent-circuit model consisting of frequency-independent circuit elements. A fast automated extraction procedure is developed for determining the circuit element values from two-port S-parameter measurement data. The methodology is extremely flexible in allowing for accurate modeling of general classes of spiral inductors on high- or low-resistivity substrate and for large spirals exhibiting distributed trends. The new modeling methodology is applied to general classes of spirals with various sizes and substrate parameters. The extracted models show excellent agreement with the measured data sets over the frequency range of 0.1-10 GHz.

Compact folded line rat-race hybrid couplers

Abstract: A new, compact folded line configuration for rat-race hybrid couplers is proposed. Simple design equations are presented for the single and double C-section folded line structures. The new configuration exhibits a four- to fivefold reduction in footprint as compared to the conventional rat-race configuration. The design is validated both by using the full-wave electromagnetic simulator and with measurement.

Analysis and modeling of quantum waveguide structures and devices

Abstract: A complete description of the numerical analysis of quantum waveguide structures and devices is given. Modal expansions of the wave function together with a mode‐matching technique are utilized to calculate the generalized scattering matrices (GSMs) of junctions or discontinuities and uniform waveguide sections. The different GSMs are combined via an extended generalized scattering‐matrix technique to obtain the scattering parameters of composite quantum waveguide structures. Results for cascaded right‐angle bends and periodic multiwaveguide structures in a split‐gate configuration are presented. A sharp transition to a plateau of zero conductance is observed for the double‐bend configuration. For the periodic multiwaveguide structures, strong resonant behavior similar to that in resonant tunneling diodes is found. Calculated current‐voltage characteristics for the special case of a double constriction are shown, exhibiting a region of negative‐differential resistance (NDR) for temperatures up to approximately 10 K with a peak‐to‐valley ratio of about 2.5:1 at zero temperature. Using a simple design procedure, the temperature range with achievable NDR is extended to up to approximately 60 K with a peak‐to‐valley ratio of over 80:1 at zero temperature.

Accurate closed-form expressions for the frequency-dependent line parameters of on-chip interconnects on lossy silicon substrate

Abstract: Accurate closed-form expressions for the complete frequency-dependent R, L, G, C line parameters of microstrip lines on lossy silicon substrate are presented. The closed-form expressions for the frequency-dependent series impedance parameters are obtained using a complex image method. The frequency-dependent shunt admittance parameters are expressed in closed form in terms of the shunt capacitances obtained in the low and high frequency limits. The proposed closed-form solutions are shown to be in good agreement with the electromagnetic solutions.

Transport in Nanostructures

Abstract: 1. Introduction 2. Quantum confined systems 3. Transmission in nanostructures 4. Quantum dots and single electron phenomena 5. Interference in diffusive transport 6. Temperature decay of fluctuations 7. Non-equilibrium transport and nanodevices.

Transport in nanostructures

Abstract: 1 Introduction 2 Quantum confined systems 3 Transmission in nanostructures 4 Quantum dots and single electron phenomena 5 Interference in diffusive transport 6 Temperature decay of fluctuations 7 Non-equilibrium transport and nanodevices

Physical modeling of spiral inductors on silicon

Abstract: This paper presents a physical model for planar spiral inductors on silicon, which accounts for eddy current effect in the conductor, crossover capacitance between the spiral and center-tap, capacitance between the spiral and substrate, substrate ohmic loss, and substrate capacitance. The model has been confirmed with measured results of inductors having a wide range of layout and process parameters. This scalable inductor model enables the prediction and optimization of inductor performance.

Carbon Nanomaterials for Next-Generation Interconnects and Passives: Physics, Status, and Prospects

Abstract: This paper reviews the current state of research in carbon-based nanomaterials, particularly the one-dimensional (1-D) forms, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs), whose promising electrical, thermal, and mechanical properties make them attractive candidates for next-generation integrated circuit (IC) applications. After summarizing the basic physics of these materials, the state of the art of their interconnect-related fabrication and modeling efforts is reviewed. Both electrical and thermal modeling and performance analysis for various CNT- and GNR-based interconnects are presented and compared with conventional interconnect materials to provide guidelines for their prospective applications. It is shown that single-walled, double-walled, and multiwalled CNTs can provide better performance than that of Cu. However, in order to make GNR interconnects comparable with Cu or CNT interconnects, both intercalation doping and high edge-specularity must be achieved. Thermal analysis of CNTs shows significant advantages in tall vias, indicating their promising application as through-silicon vias in 3-D ICs. In addition to on-chip interconnects, various applications exploiting the low-dimensional properties of these nanomaterials are discussed. These include chip-to-packaging interconnects as well as passive devices for future generations of IC technology. Specifically, the small form factor of CNTs and reduced skin effect in CNT interconnects have significant implications for the design of on-chip capacitors and inductors, respectively.