Design of a bulk acoustic wave filter for wi-fi band

In order to ensure the normal operation of mobile devices in the Wi-Fi band without interference from adjacent frequency bands, a BAW filter for the Wi-Fi 802.11b band (2402-2482 MHz) is designed. An initial structure ladder filter based on a one-dimensional Mason equivalent circuit model of thin-film bulk acoustic resonator (FBAR) is designed. The resonance area value of series FBARs and the ratio of resonance area value of parallel FBARs to series FBARs are made into two types of optimization parameters reasonably. According to the required insertion loss and out of band rejection of filter as the optimization objective, the optimized values are obtained by the algorithm based on gradient and genetic in ADS software. In order to make the simulation results more accurate, the combined acoustic-electromagnetic method is used to simulate and compare with the simulation results of the Mason equivalent circuit model in the filter design process. The results show that the performance of the filter is decreased, insertion loss increased 1.6 dB, ripple increased 1.1 dB, out of band rejection is basically the same. The design of Wi-Fi band BAW filter has low insertion loss (less than 3 dB) and high out of band rejection (more than 40 dB) performance.