Signals and Telecommunication Journal M. Moreira, J. Bjurström, I. Katardjiev and V. Yantchev 12 1 2023 https://doi.org/10.6025/stj/2023/12/1/21-26 https://www.dline.info/stj/fulltext/v12n1/stjv12n1_4.pdf 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.