Abstract: A one-dimension longitudinal model microwave transducer made with high quality piezoele otric aluminium nitride thin films is reported in this paper. These films are deposited by d. o. planar magnetron sputtering on a z-LiNbO₃ propagation medium. With these films, a microwave bulk acoustic wave delay line is fabricated which has a time delay of 1.83 μs, insertion loss of 22 dB, and bandwidth (3 dB) of 13% under the central frequency of 2.21 GHz. For such piezoelectric films used in the microwave frequency, the electromechanical coupling coefficient (kt) of 0.13 is obtained by the comparison of theoretical input admittance values of the transducer with the measured values. This kt is smaller than that of the bulk material which may be mainly caused by the derivation and inversion of c-axis orientation in crystallites. The experimental results also show that there is an equivalent series resistance in the, transducer that may illustrate why the tuned and matched transducer has losses.

Key words: transducer, aluminium nitride, thin film