Semiconductor delay line tuner

The drift of minority carriers in an electric field can be used to provide a voltage variable signal delay. In the semi-conductor delay line tuner, minority carriers are injected into a germanium bar subjected to an electric field. A series of equally spaced collectors, placed down stream from the point of injection, provide delayed versions of the injected signal with delays of , etc. When these signals are brought to a summing junction, the summer exhibits peak response for injected signals whose period is Δτ. For a sine wave, sine , the output will be maximum when . Since the delay increment Δτis inversely proportional to the electric field, the frequency of maximum response may be varied by changing the voltage across the germanium bar.