Circuit theory of video delay lines

Electromagnetic slow waves guided by single-layer coils and video delay lines are studied from the point of view of circuit theory. The main idea is to introduce into the model the mutual inductance that exists between nearby coil turns. This concept leads to finite-difference, finite-sum equations which pass in the limit into a partial differential equation and an integro-differential equation. The capacitance between adjacent wire turns is taken into account. The decrease of inductance at high frequencies, as computed from the integro-differential equations, is compared with prior computations based on electromagnetic field theory. In this respect agreement between the two theories is complete. A comparison with experiment is made, from which a novel parameter of the coil, termed the series capacitance parameter and measured in Fm, is determined.