Computer-aided design of broad band reflection type amplifiers

Microwave negative resistance reflection type amplifiers using stable transferred electron devices (TED's) are optimized by numerical optimization techniques programmed for an interactive graphic datascreen.

The small signal impedance of packaged TED's is measured on an automatic network analyzer. At the same time the impedance of unpackaged devices are obtained by on-line correction for the package parasitics. The microwave circuit chosen is a multiple slug coaxial cavity, that is modelled by sections of lossy transmission lines including step susceptances. The measured small signal impedance of the packaged TED's and the cavity model are used in a direct optimization procedure, in which the calculated minimum gain in the prescribed frequency range is progressively maximized by adjusting the lengths, characteristic impedances and positions of the slugs. The computed results are displayed on a datascreen, which allows for interactive programming.

Comparisons of predicted amplifier performance for packaged and unpackaged devices form a basis for evaluating the possible degrading effect of package parasitics. The predictions of the computer-aided design are in good agreement with experimental results. The design procedure imposes no restraint on the frequency variation of the active device impedance and is therefore useful for any stable broad-banded negative resistance device.