Microwave Double‐Sweep Method for Analysis of Time‐Dependent Cavity Characteristics

The impedance of a microwave cavity whose characteristics are time‐dependent, as caused for example by a contained gaseous discharge afterglow, can be examined by means of a frequency‐modulated search signal and a swept receiver. The intersection of the search‐signal frequency and the acceptance frequency of the receiver results in a pulse whose shape is sensitive to cavity resonance. The time of occurrence of the pulse depends upon signal‐to‐receiver phase. This in combination with the measured receiver dispersion allows measurement of reflection coefficient and frequency shifts smaller than the readability of a precision wavemeter at 10 kMc. Problems of oscillator tuning are mitigated and special stabilization procedures are eliminated. Only standard components are used.