Band3 Duplexer using ZERO TCF Love wave device

In this paper, a novel Love wave device which has Al
₂
O
₃
under layer structure is proposed. Al
₂
O
₃
under layer structure enables us to adjust the electromechanical coupling factor k
²
of Love wave. As a result, a suitable k
²
for Band3 Duplexer of about 10% was realized using 0°YX-LiNbO
₃
substrate, Cu electrodes and thick SiO
₂
film. In addition, the temperature coefficient of frequency (TCF) was improved especially at resonant frequency of 1-port resonator with Al
₂
O
₃
under layer structure. Using this novel Love wave device with Al
₂
O
₃
under layer structure a Band3 Duplexer was realized with excellent temperature characteristics. The TCF of the higher frequency side of pass band in Tx filter was -3.6 ppm/°C, that of the lower frequency side of pass band in Rx filter was -7.3 ppm/°C.