Programmable delay line for radar testing

Abstract

We have fabricated a programmable fiber optic delay line operating in the 1550 nm band capable of providing a total delay of 1 ms in increments of 83.6 ns for RF signals up to 2.5 GHz. Electromechanical switches with 6 ms switching time are employed for programming the delay line. To overcome the switching speed limitation, we used a dual parallel delay line. Signal selection is via a high speed RF switch. For radar test application, the approach enables continuous tracking (to within a range cell of 42 ft) of a moving target with negligible loss of data. Three erbium-doped fiber optical amplifiers excited by a single 1480 nm pump laser are used to compensate for losses in each of the delay lines.