Justin Henrie

Electronic color charts for dielectric films on silicon

This paper presents the calculation of the perceived color of dielectric films on silicon. A procedure is shown for computing the perceived color for an arbitrary light source, light incident angle, and film thickness. The calculated color is converted into RGB parameters that can be displayed on a color monitor, resulting in the generation of electronic color charts for dielectric films. This paper shows generated electronic color charts for both silicon dioxide and silicon nitride films on silicon.

Prediction of Passive Intermodulation From Coaxial Connectors in Microwave Networks

Coaxial connectors are frequently the dominant contributors to passive intermodulation (PIM) distortion in high-frequency networks. This paper reports on a circuit model enabling estimation of PIM distortion by coaxial connectors in the design of high-frequency networks. A method of modeling the effect of multiple point sources of PIM is applied to coaxial connectors, allowing the prediction of the PIM of networks with several connectors. Typical ranges of PIM produced by common connectors in a two-tone test are reported. The stability and repeatability of PIM produced by a single connector is examined. Nonlinear current-voltage curves for coaxial connectors are given that predict the PIM distortion output by coaxial connectors over a broad range of input powers. An experimental verification is given showing that PIM of a system can be predicted if the characteristics of the individual components are known.

Engineered Passive Nonlinearities for Broadband Passive Intermodulation Distortion Mitigation

By adding controlled thicknesses of nickel and gold plating to the conductors of a coaxial transmission line, the magnitude of passive intermodulation produced by the transmission line can be controlled with precision. Theoretical predictions of distortion magnitude as a function of plating thicknesses are presented, along with an experimental validation. These adjustable-magnitude passive intermodulation sources are used to give a fourfold improvement in the bandwidth of techniques presented previously, demonstrating that cancellation can for the first time be achieved in bandwidths needed for cellular systems.

Higher Order Intermodulation Product Measurement of Passive Components

The concept of using high-order intermodulation (IM) products beyond the third order for the analysis of passive intermodulation (PIM) sources is introduced. Current PIM characterization techniques focus on measurements of the third-order IM product. An advantage of observing higher order IM is demonstrated by showing that two simulated models, which predict an identical level of third-order IM, exhibit clear qualitative differences in the higher order IM products. A low residual PIM measurement system is able to measure up to the 29th-order IM product. A full discussion of uncertainties in the measurement technique used is given. The measured high-order IM products of a coaxial connector are used to fit and verify a model for its current-voltage characteristic. This fit model, a hyperbolic tangent function, accurately predicts the behavior of the higher orders as a function of input power and matches the third order over the 21-dB input power range with a root mean squared error of 3.5 dB. For another device, a microwave circulator, higher order IM products are used to deduce a model, which is then confirmed using a traditional measurement of third-order IM. High-order IM products are measured and analyzed in order to aid investigations of the physical processes causing PIM.

Improvement to reflective dielectric film color pictures

This paper presents methods used to improve reflective dielectric film color pictures. These changes include improvements in color purity, increased brightness, and elimination of any light absorption within the film layers. The color picture is fabricated by varying the silicon dioxide film thicknesses across a silicon wafer and coating the entire wafer with a thin layer of silicon nitride. In addition to the demonstration of fabricated color pictures, we also present more detailed calculation of basis colors and provide details of the fabrication process.

Linear–Nonlinear Interaction and Passive Intermodulation Distortion

This paper describes several consequences of a linear-nonlinear interaction that was recently found to be of importance in microwave circuits that produce passive intermodulation (PIM) distortion. This paper briefly discusses how this linear-nonlinear interaction operates in an example system. It then discusses how an understanding of the linear-nonlinear interaction allows us to distinguish between different types of nonlinearities from the power dependence of the third-order intermodulation distortion product. Next, an example uses a multiphysics simulator to demonstrate that electrothermal nonlinearities behave as expected from the linear-nonlinear interaction model. Lastly, it illustrates how simple nonlinear models characterized with one circuit can accurately predict distortion levels when the nonlinearity is placed within a very different circuit, showing that knowledge of the interaction gives the ability to accurately predict the behavior of PIM-producing components in a variety of circuits such as resonators, filters, and matching networks.

Linear-nonlinear interaction's effect on the power dependence of nonlinear distortion products

An unusual power dependence of the nonlinear distortion produced by a two-tone test has been observed in several different physical systems. We show that the interaction between the nonlinear and linear elements of a system can dramatically transform the overall nonlinear behavior of the system from that of the nonlinear component in isolation. In particular, we show that when interaction with the linear elements of an electric circuit is appropriately accounted for, rather simple models of nonlinearity display the unusual power dependence of nonlinear distortion products observed in a variety of physical systems.

Cancellation of Passive Intermodulation Distortion in Microwave Networks

Passive nonlinearities in high-power transmit/receive wireless systems cause undesirable transfer of power from high-power transmit carriers to the receive band, causing levels of interference and distortion that can severely limit or debilitate the system. This paper proposes a method of cancellation that allows for reduction of nonlinear distortion due to passive nonlinearities in high-power wireless systems. We verify the method by experiment, resulting in almost 40 dB of cancellation of nonlinear distortion in a high-power radio frequency system, effectively eliminating the reflected passive intermodulation from the system.

Matching network design for passive intermodulation distortion reduction

A method for designing matching networks to reduce the distortion created by nonlinear passive components interfacing with antennas is presented. Coaxial connectors produce passive intermodulation distortion based on the amount of current flowing through them. By increasing the input impedance at the connector using impedance transformations, current, and thereby passive intermodulation distortion, can be reduced. A model is developed which allows designers to understand the relationship between impedance and distortion. Experimentally a reduction greater than 20 dB in passive intermodulation distortion is shown using a λ/4 matching network to transform the input impedance at the passive intermodulation source from 50Ω to 285Ω, while minimally affecting the linear transmission properties of the connection.

Thin film thickness determination using reflected spectrum sampling

This paper discusses an innovation in reflectometry that presents cost and implementation advantages over configurations currently in use. We demonstrate that the semi-continuous wavelength spectrum used by a spectroscopic reflectometer can be replaced with a small set of fixed wavelength optical sources with only a small loss in measurement accuracy. The resulting instrumentation is called a spectrum sampling reflectometer (SSR). Spectrum sampling can be achieved using inexpensive LEDs and/or lasers as the optical sources. Theoretical calculations for instrument accuracy are shown for both LEDs and lasers along with experimental data from a prototype system using LEDs.