Highly-efficient generation of a specified harmonic or sub-harmonic by means of switches

It is shown that a given harmonic can be generated efficiently by using a circuit in which the tuning is such that only the fundamental current flows in the input and only the desired harmonic voltage can appear at the output, and in which a balanced switching system is operated at the fundamental frequency by an external drive connected to the fundamental source. The switches cannot be replaced by rectifiers controlled by the voltages in the circuit except at the cost of dissipating a very large proportion of the available power in a d.c. load. The same principle of switching can be applied to make an efficient generator of sub-harmonics.