The way printed circuit board interconnects for high-speed digital signals are designed ultimately determines the performance that can be achieved for a certain interface, thus having a profound impact on whether the complete communication channel will comply with the desired standard specification or not. Good understanding and methods for anticipating and verifying this behaviour through computer simulations and practical measurements are therefore essential. Characterization of an interconnect can be performed either in the time domain or in the frequency domain. Regardless of the domain chosen, a method for unobstrusively connecting to the test object is required. After various different attempts it could be concluded that frequency domain measurements using a vector network analyzer together with microwave probes will provide the best measurement fidelity and ease of use. In turn, this method requires the test object to be prepared for the measurement. Advanced computer simulation software is available, but comes with the drawback of dramatically increasing the requirements on computational resources for improved accuracy. In general, these simulators can be configured to show good agreement with measurements at frequencies as high as ten gigahertz. For ideal interconnects, the simplest and, thus, fastest methods will provide good enough accuracy. These simple methods should be complemented with the results from more accurate simulations in cases where the physical structure is complex or in other ways deviates from the ideal. Several practical routing situations were found to introduce severe signal integrity issues. Through appropriate use of the methods developed in this thesis, these can be identified in the design process and thereby avoided.

Electron densities and collision frequencies were obtained on a number of gases in a dc discharge at low pressures (0.70-2mm of Hg). These measurements were performed by microwave probing of a filament of the dc discharge placed coaxially in a resonant cavity operating in a TM₀₁₀ mode. The equipment and techniques for making the microwave measurements employing the resonant cavity are described. One of the main features of this investigation is the technique of differentiating the resonance signal of the loaded cavity in order to make accurate measurements of the resonant frequency and half-power point frequencies.