The generation of a selected harmonic or sub-harmonic by means of a single externally-driven switch

It is shown that it is possible to generate a selected harmonic with high efficiency using a circuit containing a single externally-operated switch driven by the signal source. Higher efficiencies are obtainable at the cost of less convenient circuit impedances if the switch is operated in quadrature rather than in phase with the controlling input. The circuit cannot function with ideal switches, and the efficiencies quoted are for practical switches. For simplification, however, ideal tuning is assumed. A circuit in which the switch is controlled from both input and output is also considered, and shown to give good results although it is not self-starting. Finally, applications of the circuits to sub-harmonic generators are mentioned.