Abstract: An S band narrowband bandpass filter bulk acoustic wave(BAW)with center frequency 2.460 GHz, bandwidth 41 MHz, band insertion loss -1.154 dB, passband ripple 0.9 dB, out of band rejection about -42.5 dB@2.385 GHz and -45.5 dB@2.506 GHz was designed for potential UAV measurement and control applications. According to the design specifications, each FBAR stack was designed in BAW filter by using Mason model, each FBARs shape was designed with the method of apodizied electrode. The acoustic-electromagnetic co-simulation model was built to validate the performance of the designed BAW filter. The presented design procedure is a common one, and it has two characteristics: (1) an acoustic-electromagnetic(AEM) co-simulation method is used for the final BAW filter performance validation in the design stage, thus ensures over-optimistic designs by the bare 1D Mason model are found and rejected in time;(2) An in-house developed auto-layout method is used to get compact BAW filter layout, which simplifies iterative error-and-try work here and outputs necessary in-plane geometry information to the AEM co-simulation model.