Long Delay Lines Employing Surface Acoustic Wave Guidance

Folded-path guided surface wave delay lines offer a significant potential advantage over single-propagation path delay lines for obtaining very long delay times. Measurements are reported here for a spiral folded-path delay line employing a gold strip on fused quartz as the guidance structure. A 260 μsec delay was obtained at 20 MHz. The spurious signal was ≥35 dB down and the differential propagation loss was 0.03 dB/μsec. These favorable results indicate that practical long delay lines based on surface acoustic wave guidance techniques are quite feasible and that delay times into the millisecond range are attainable at higher frequencies.