Dylan F. Williams

Accurate transmission line characterization

A method for the characterization of transmission lines fabricated on lossy or dispersive dielectrics is introduced. The method, which is more accurate than conventional techniques, is used to examine the resistance, inductance, capacitance, and conductance per unit length of coplanar waveguide transmission lines fabricated on lossy silicon substrates.<<ETX>>

An optimal vector-network-analyzer calibration algorithm

We present an iterative algorithm for calibrating vector network analyzers based on orthogonal distance regression. The algorithm features a robust, yet efficient, search algorithm, an error analysis that includes both random and systematic errors, a full covariance matrix relating calibration and measurement errors, 95% coverage factors, and an easy-to-use user interface that supports a wide variety of calibration standards. We also discuss evidence that the algorithm outperforms the MultiCal software package in the presence of measurement errors and accurately estimates the uncertainty of its results.

Calibration of sampling oscilloscopes with high-speed photodiodes

We calibrate the magnitude and phase response of equivalent-time sampling oscilloscopes to 110 GHz. We use a photodiode that has been calibrated with our electrooptic sampling system as a reference input pulse source to the sampling oscilloscope. We account for the impedance of the oscilloscope and the reference photodiode and correct for electrical reflections and distortions due to impedance mismatch. We also correct for time-base imperfections such as drift, time-base distortion, and jitter. We have performed a rigorous uncertainty analysis, which includes a Monte Carlo simulation of time-domain error sources combined with error sources from the deconvolution of the photodiode pulse, from the mismatch correction, and from the jitter correction

Permittivity characterization of low-k thin films from transmission-line measurements

Developed a broad-band technique for measuring the relative permittivity of low-k thin films using microstrip transmission-line measurements. From measurements of the complex microstrip propagation constant and the characteristic impedance, we determined the relative permittivity of thin films incorporated in microstrip lines. We present measurement results to 40 GHz for both an oxide and a bisbenzocyclobutene low-k thin film and show a variability of permittivity of approximately /spl plusmn/5% over the entire frequency range.

Calibrated measurement of optoelectronic frequency response

Describes the most straightforward method for accurately measuring the frequency response of optoelectronic devices. The method uses a calibrated optical reference receiver, a modulated optical source, and a calibrated electrical vector network analyzer.

An optimal multiline TRL calibration algorithm

We examine the performance of two on-wafer multiline Thru-Reflect-Line (TRL) calibration algorithms: the popular multiline TRL algorithm implemented in the MultiCal/spl reg/ software package, and a newly implemented iterative algorithm designed to give optimal results in the presence of measurement noise. We show that the iterative algorithm outperforms the MultiCal software in the presence of measurement noise, and verify its uncertainty estimates.

Compensation of Random and Systematic Timing Errors in Sampling Oscilloscopes

In this paper, a method of correcting both random and systematic timebase errors using measurements of only two quadrature sinusoids made simultaneously with a waveform of interest is described. The authors estimate the fundamental limits to the procedure due to additive noise and sampler jitter and demonstrate the procedure with some actual measurements

LRM probe-tip calibrations using nonideal standards

The line-reflect-match (LRM) calibration is enhanced to accommodate imperfect match standards and lossy lines typical of monolithic microwave integrated circuits. We characterize the match and line standards using an additional line standard of moderate length. The new method provides a practical means of obtaining accurate, wideband calibrations with compact standard sets. Without the enhancement, calibration errors due to imperfections in typical standards can be severe. >

Linearization of large-signal scattering functions

We describe a linearization of large-signal scattering functions describing weakly nonlinear device behavior. The linearization takes on a convenient form similar to scattering parameters that clearly illustrates the role of phase-conjugated mixing products in the theory. We develop rules for the evolution of the linearization with time. We illustrate the theory with transistor measurements and apply the theory to the characterization of the reflection coefficients of a microwave source in its large-signal operating state.

Metal-insulator-semiconductor transmission lines

This paper investigates the one-dimensional metal-insulator-semiconductor transmission line. It develops closed-form expressions for equivalent-circuit parameters, compares them to exact calculations, and explores their limitations. It also investigates the usual assumption of single-mode propagation and shows that, in certain fairly common circumstances, the fundamental mode of propagation becomes so lossy that it can no longer be considered to be the dominant propagating mode.