Frequency Conversion by Means of a Nonlinear Admittance

Point contact rectifiers using either silicon or germanium are used as the nonlinear element in microwave modulators to change an intermediate frequency signal to an outgoing microwave signal and in receiving converters to change an incoming microwave signal to a lower intermediate frequency. Most point contact rectifiers now in use behave as pure nonlinear resistors as evidenced by the fact that in either of the above uses the conversion loss is the same. In recent experiments with heterodyne conversion transducers* using point contact rectifiers made with ion bombarded silicon this was found to be no longer true. The conversion loss of the modulator was found to be unusually low and * This term is defined in American Standard Definitions of Electrical Terms -- ASA C42 -- as "a conversion transducer in which the useful output frequency is the sum or difference of the input frequency and an integral multiple of the frequency of another w a v e " . 1403 1404 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1 9 5 6