Suppression of multiple pass signals from microwave acoustic delay lines

Microwave acoustic delay lines normally exhibit an output that shows a series of delayed pulses corresponding to a succession of passes through the delay medium. Such a train of multiple pass pulses can be used to advantage in many test equipment applications. In some applications, however, they are highly undesirable. In cw applications they are, of course, prohibited. While complete suppression of multiple passes is practically impossible, effective suppression of multiple pass signals, 30 db suppression, can be achieved in a number of ways.