Constant-resistance modulators

It is shown how Zobel´s constant-resistance networks may be interpreted in terms of constancy with time when the elements of the network are time-variable, but that the original conception of constancy with frequency when the elements are frequency-variable may be simultaneously realized in the same network. The application to rectifier modulators is examined, and it is shown that for the whole class of networks, the simplest condition for the realization of constant input resistance coincides with that for the elimination of even-order modulation products provided the carrier waveform contains only odd-order harmonics. In symmetrical networks, it also coincides with the condition for minimum conversion loss. It is shown how a constant-resistance network can be made to give a frequency-response (or output spectrum) corresponding to a specified frequency-dependent series or shunt modulator.