Tunability of Bulk Acoustic Wave filters using CMOS transistors: concept, design and implementation
Résumé
This paper presents the feasibility of a new method to reconfigure the Bulk Acoustic Wave (BAW) filters by adding capacitors to the shunt resonators and by controlling these capacitors with CMOS transistors that act as switches. The reconfigurable BAW-SMR filter is realized in a ladder topology. It is used for the 802.11b/g standard (2.40 - 2.48 GHz). Mainly, the filter fulfills the requirements for the WLAN 802.11 b/g standard, presenting a measured -3.3 dB of insertion loss, -12.7 dB of return loss and selectivity higher than 33 dB @ 30 MHz of the bandwidth. Moreover, a measured shift of 0.5% of the centre frequency (2.44 GHz) towards higher frequencies is obtained. This reconfigurable BAW-SMR filter has reduced dimensions (1035*1075 μm²).