The design of a precision video delay line

The paper reviews briefly the very stringent conditions which must be fulfilled by video delay lines connected in a television programme chain. The most suitable method of construction is found to be a cascade of delay sections of the same image impedance, and three types, onebelieved to be novel, are examined in detail with respect to their suitability for long delays inserted in main signal-handling paths. It is concluded that the advantage lies with low-pass sections combining pairs of complex conjugate m values in an appropriate configuration. These offer a markedly improved performance compared with conventional methods of construction, together with a substantial reduction in the number of inductors for a given delay over the video band. Guide lines for the design of video delay networks are laid down, and methods of compensationfor component dissipation are discussed in some detail. The performance of a prototype 1 ¿s delay line built on these principles has fully confirmed the theoretical findings.