Then: Parametric Diode Q Measurements

The measurements of microwave impedance and the Q of solid-state diodes has become increasingly important since the advent of the parametric amplifier. A new method of measuring the Q of such a diode, Q_d, has recently come into rather general use; the purpose of this paper is to explain it and to show its validity.

Recent publications^1,2 have dealt with methods of measuring parametric diode impedance. The semiconductor diode with its cartridge is usually embedded in a transmission line which may be preceded by a microwave impedance transformer and followed by a short circuit or a matched load. Normalized impedances are measured by standard slotted line techniques. The problem is to find the absolute value of the impedance of the semi-conductor material itself, taking into account various impedance transformations occurring in the rest of the cartridge and connecting transmission line system. In order to establish an absolute impedance level, it is necessary to utilize resistive standards or TEM waveguides of known characteristic impedance. In the measurement of diode Q_d to be treated, the problems and equipment are similar except that it is not necessary to establish an impedance level. Since Q_d is essentially a ratio of reactance to resistance, it can be related to normalized impedance measurements made with a slotted line.