Single- and Coupled-Circuit Systems

This article discusses networks based upon singly-tuned circuits, and upon coupled circuits with primary and secondary both resonant to the same frequency. Transmission equations are developed and it is shown that for a desired possible transmission-curve shape, the sum of all decrement coefficients must be a certain amount, readily computable for coupled circuits as well as for single circuits. Coupled circuit transmission-curve shapes may be developed from single-circuit curves by a multiplication process as in staggered-cascade amplification, or by a vector difference process, employing two staggered single circuits with opposite couplings from a power source. A special case of the vector difference method is the coupled circuit itself, with primary current the vector sum and secondary current the vector difference of two single-circuit currents. This property permits a suitable coupled system to be used for radiating energy of two closely adjacent channels from a single antenna without cross reactions on the power sources. Complex networks are handled by transfer equations by which a branch consisting of a voltage source and resistor in series coupled to a network by a transformer device is replaced by an equivalent voltage and impedance within the network. Application is made to computation of interstage amplifying transformers, and of single-and two-circuit filters with resistance loading. A brief treatment is given of the impedance and power-factor loading of generator circuits which is of especial importance when tuned networks are output devices of power tubes operating at high plate efficiency.