Duplexer
A duplexer includes an antenna terminal, a transmit filter, and a receive filter. The receive filter includes a first sub-filter that includes one or more resonators, and a second sub-filter including a double mode surface acoustic wave (DMS) filter. The second sub-filter is downstream of the first sub-filter relative to the antenna.
1 . A duplexer comprising:
an antenna terminal;
a transmit filter; and
a receive filter comprising:
a first sub-filter comprising one or more resonators; and
a second sub-filter comprising a double mode surface acoustic wave (DMS) filter, the second sub-filter being downstream of the first sub-filter relative to the antenna.
2 . The duplexer of claim 1 , wherein at least one resonator comprises a series resonator.
3 . The duplexer of claim 1 , wherein at least one resonator comprises a parallel resonator.
4 . The duplexer of claim 1 , wherein at least one resonator comprises a series resonator and at least one resonator comprises a parallel resonator.
5 . The duplexer of claim 1 , wherein at least one resonator comprises cascaded transducers.
6 . The duplexer of claim 1 , wherein the second sub-filter has an output side; and
wherein the second sub-filter is balanced on the output side.
7 . The duplexer of claim 6 , wherein the second sub-filter comprises sub-transducers connected in series, the sub-transducers being formed from a V-split balanced output transducer.
8 . The duplexer of claim 1 , wherein the DMS filter comprises more than one acoustic track; and
wherein different acoustic tracks of the DMS filter are interconnected electroacoustically via coupling resonators.
9 . The duplexer of claim 1 , wherein an output impedance of the second sub-filter differs from an input impedance of the second sub-filter.
10 . The duplexer of claim 1 , further comprising:
a phase shifter between the antenna terminal and the receive filter.
11 . The duplexer of claim 1 , wherein the transmit filter comprises at least one surface acoustic wave resonator.
12 . The duplexer of claim 1 , wherein the transmit filter comprises at least one bulk acoustic wave resonator.
13 . The duplexer of claim 1 , further comprising:
a piezoelectric substrate on which component structures of the transmit filter and component structures of the receive filter are formed.
14 . The duplexer of claim 13 , further comprising:
a base plate having a buried electrical element, the piezoelectric substrate being electrically connected to the base plate.
15 . The duplexer of claim 14 , wherein the piezoelectric substrate is mechanically connected to the base plate.
16 . The duplexer of claim 1 , wherein at least one resonator comprises a bulk acoustic wave resonator.
17 . The duplexer of claim 1 , further comprising:
one or more additional resonators downstream of the second sub-filter relative to the antenna.
18 . The duplexer of claim 8 , wherein an output impedance of the second sub-filter differs from an input impedance of the second sub-filter.
19 . The duplexer of claim 8 , further comprising:
a phase shifter between the antenna terminal and the receive filter.
20 . The duplexer of claim 8 , wherein the transmit filter comprises at least one surface acoustic wave resonator.
21 . The duplexer of claim 17 , wherein the second sub-filter comprises a balanced output port, and wherein at least one resonator is electrically connected in series to each one of two terminals of the balanced output port.
22 . The duplexer of claim 1 , wherein the first sub-filter comprises two resonators electrically connected in series to each other, wherein the two resonators are part of a multi-port resonator and acoustically coupled to each other, and wherein at least one additional resonator is electrically connected in parallel to the two resonators.