抄録
It has been a difficult task for analog electronic circuits to delay signals by a few milliseconds or more. Theoretically a ladder circuit consisting of numbers of lumped inductors and capacitors might act as a good approximation of delay cable if the signal fre-quency is limited below a certain bound, but unfortunately the characteristics of such a circuit cannot really be satisfied because of the imcomplete performance of conventional large inductance coils.
In this paper the authors propose a method for forming a delay line using resistors and active elements instead of classical inductors and capacitors. The admittance across one active element is proportional to the minus of the square of the frequency. Each active element consists of several transistors and a few additional capacitors and resistors, and the “active delay line” requeres no more coils than an active filter does. This is just the reason why the active delay line could be almost as ideal as a theoretical one.
Two active delay lines are actually manufactured, one of which is now used as the delay element of a correlation flow velocity meter. Satisfactory results are obtained in experiments on these delay lines, which imply practical applicability of the active delay line.
