Surface-wave delay lines with near-octave bandwidth

Efficient operation of lithium-niobate delay lines over bandwidths approaching one octave is reported. The transducers are of a 3-electrode (N = 1) interdigital design. Broad bandwidth to the series-resonant transducer is obtained by the use of a lumped-element impedance invertor coupling network. A 9.1 ¿s delay line is described, which gives 55% 3 dB bandwidth centred at 235 MHz with 25 dB minimum loss and over 50 dB minimum triple-transit suppression.