Bulk Acoustic Wave Diplexer for Medium Wave Application Based on Lead Zirconate Titanate Piezoelectric Material

In this brief, a bulk acoustic wave (BAW) filter is designed for medium wave (MW) communication systems application. Based on this BAW filter, a diplexer is also designed. A passband within the desired frequency is achieved by connecting BAW resonators with different resonant frequencies in series and parallel. Meanwhile, transmission zeros at lower and upper-stopband are produced to realize a good out-of-band rejection, which improves the overall filtering selectivity. The overall size of the device is about 10 cm, which can effectively reduce the size of filters and diplexers in medium-wave communication systems when compared with other traditional filters. The insertion loss in the passband is up to 2.6 dB and 2.5 dB, while the out-of-band rejection is up to 14 dB. The proposed BAW filter and diplexer use Lead (Pb) Zirconate Titanate Piezoelectric (PZT) as the piezoelectric material, which is cost and size effective.