The Application of Low-Frequency Circuit Analysis to the Problem of Distributed Coupling in Ultra-High-Frequency Circuits

The general problem of coupling between circuits which extend beyond the near zone is investigated theoretically. Integrals defining generalized coefficients of inductance are displayed and discussed for the case of the near zone and in general. As an application, the specific problem of determining the current distribution in two coupled circuits which extend beyond the near zone is examined, and solved for the special case of two loosely coupled sections of parallel line. It is proved that the electromotive force induced in the secondary by the primary oscillator may be treated as though concentrated at a point opposite the center of the oscillator provided the current distribution in the oscillator is symmetrical with respect to this center. The conclusions are generalized to include other circuits than the parallel line, in particular an antenna coupled to a symmetrical oscillator. Experimental curves are shown which verify the general theory.