Design of 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 bulk acoustic wave (BAW) filter for the Wi-Fi 802.11b band (2401-2482 MHz) is designed. An initial structure ladder filter based on a one-dimensional Mason equivalent circuit model using thin-film bulk acoustic resonators (FBARs) is designed. The resonance area value of series FBARs and the ratio of resonance area value of parallel FBARs to series FBARs were made into two types of optimization parameters reasonably. Using the required insertion loss and out of band rejection of filter as the optimization objectives, the optimized values were obtained by the algorithm based on gradient and genetics 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, with 1.6 dB insertion loss increase and 1.1 dB ripple increase, while out of band rejection is basically the same. The designed Wi-Fi band BAW filter has low insertion loss (less than 3 dB) and high out of band rejection (more than 40 dB) performance.