An intermodulation phenomenon in the ring modulator

Analysis of intermodulation distortion effects in diode modulators by `modulating function¿ techniqueshas, for some time, been recognized to be applicable where the diodes can be represented by a bi-linear d.c. characteristic in which the change of state from blocking to conduction takes place at zero bias. Experiments on ring modulators have shown, however, that predictions based on this diode model give unduly pessimistic results under some conditions. It is shown that theuse of a modified diode model incorporating a suitable offset voltage in the d.c. characteristic permits prediction of thehitherto anomalous results with greatly improved accuracy.