| Abstract: A microwave bandpass filter with a large ratio between the output and the input impedance has been designed and fabricated. Consequently, it functions both as a voltage transformer and a bandpass filter or transfilter for brevity. It represents a two-port micro-acoustic resonator employing Lamb waves in a thin piezoelectric AlN film grown onto a Si carrier substrate with a center frequency of around 887 MHz. The transfilter has a transformer ratio of 10 and a voltage efficiency over 80%. The component has a small size (<0.5 mm2) and is shown to sustain power levels of 250 mW. It can be used in a variety of cases where both voltage amplification and frequency filtering are required. Examples include: charge pumps in RFID tags, energy scavenging, remotely triggered switches, wake-up radios in wireless networks, stand-by units in home electronics, etc. |
| References: [1] Dickson, J.F. (1976) On-chip high-voltage generation in NMOS integrated circuits using an improved voltage multiplier technique. IEEE Journal of Solid-State Circuits, vol. SSC-11, 3, 374–378.
[2] Gu, L. & Stankovic, J.A. (2005) Radio triggered wake-up in wireless sensor networks. Real-Time Systems, 29, 157–182 [DOI: 10.1007/s11241-005-6883-z].
[3] Bjurström, J., Katardjiev, I. & Yantchev, V. (2005) Lateral-field-excited thinfilm Lamb wave resonator. Applied Physics Letters, 86 [DOI: 10.1063/1.1900312].
[4] Kaajakari, V. (2009). Practical MEMS. Small Gear Publishing: Las Vegas, ISBN: 978-0-9822991-0-4.
[5] Moreira, M., Bjurström, J., Katardjev, I. & Yantchev, V. (2011) Aluminum scandium nitride thin-film bulk acoustic resonators for wide band applications. Vacuum, 86, 23–26 [DOI: 10.1016/j.vacuum.2011.03.026]. |
Author Rights 
