Patent ID: 7230510

Claim:
An electronic device, comprising a band separating unit for separating a transmission band and a receive band comprising: a first port, a second port and an antenna port; a first band-pass filter connecting the first port and the antenna port; and a series arrangement connecting the second port and the antenna port, the series arrangement comprising: a second band-pass filter that includes a ladder circuit with shunt and series elements, of which series elements at least a first element comprises a film bulk acoustic wave resonator (FBAR), the first element of the second band-pass filter having a parallel inductor; and a frequency tuning element coupled between the antenna port and the second band-pass filter: wherein the first element and the parallel inductor together form an antiresonant circuit that blocks the transmission band at the entrance of the second band-pass filter ( 6 ), as its antiresonant frequency corresponds to the center frequency f Tx of the transmission band, and the first element together with the frequency tuning element form a resonant circuit that allows the receive band to pass, as its resonant frequency corresponds to the center frequency f Rx of the receive band.