Tunability of Bulk Acoustic Wave Solidly Mounted Resonators Using Passive Elements: Concept, Design and Implementation

摘要

This paper presents the impedance behavior of the bulk acoustic wave solidly mounted resonators (BAW-SMR). Also, it shows the effects of the addition of passive elements (L, C) to this type of resonators. In addition, this article presents a tunable BAW-SMR filter realized in a ladder topology 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 at ±30 MHz of the bandwidth. This tunable BAW-SMR filter has reduced dimensions (1035 × 1075 μm~2). Moreover, we show how to shift the center frequency of this tunable filter toward higher and lower frequencies by adding passive elements. Measured shifts of -1.3% of the center frequency (2.44 GHz) toward lower frequency and +0.6% of the center frequency toward higher frequencies are obtained.