Duplexer

1. A duplexer, comprising:

2N band pass filters, N being an integer greater than 1, the 2N band pass filters each having an input and an output and each having a characteristic impedance of Z 0 ohms, the 2N band pass filters being in an electrically parallel configuration;

a first adaptation circuit configured to couple a transmit signal received from a transmitter to each one of the 2N band pass filters, the first adaptation circuit including:

a first 90° hybrid coupler having at least one input and at least two outputs and configured to couple the transmit signal toward the 2N band pass filters, the first 90° hybrid coupler having an impedance of Z 0 /N ohms;

a first quarter-wave transmission line coupled to the at least one input of the first 90° hybrid coupler, the first quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z o )/N)} ohms, where Z in is an input impedance of the transmitter; and

a second adaptation circuit configured to couple outputs of the 2N band pass filters to an antenna, the second adaptation circuit providing a reflective path between the antenna and a receiver.

2. The duplexer of claim 1 , wherein the first adaptation circuit further includes a splitter circuit configured to direct an output of the 90° hybrid coupler to each of a plurality of the 2N band pass filters.

3. The duplexer of claim 2 , wherein the splitter circuit includes a first splitter having N output ports and a second splitter having N output ports, each splitter receiving as an input an output of the first 90° hybrid coupler.

4. The duplexer of claim 1 , wherein the second adaptation circuit includes a second 90° hybrid coupler configured to receive outputs of the 2N band pass filters, and to couple the received outputs to the antenna.

5. The duplexer of claim 4 , wherein the second adaptation circuit includes a combiner circuit having a plurality of input ports, each input port receiving an output of one of a plurality of the 2N band pass filters.

6. The duplexer of claim 5 , wherein the first combiner circuit includes a first combiner having N input ports coupled to a first set of N output ports of the 2N band pass filters.

7. The duplexer of claim 6 , wherein the first combiner circuit includes a second combiner having N input ports coupled to a second set of N output ports of the 2N band pass filter.

8. The duplexer of claim 1 , wherein the band pass filters are acoustic wave band pass filters.

9. The duplexer of claim 1 , wherein the band pass filters are low temperature co-fired ceramic, LTCC, filters.

10. A duplexer configured to couple a transmitter to an antenna, and to couple the antenna to a receiver, the duplexer comprising:

2N band pass filters, N being an integer greater than 1, the 2N band pass filters each having an input and an output and each having a characteristic impedance of Z 0 , the 2N band pass filters being in an electrically parallel configuration;

a first adaptation circuit configured to couple the transmitter to each one of the 2N band pass filters, the first adaptation circuit comprising:

a first 90° hybrid coupler having at least one input and at least two outputs, the first 90° hybrid coupler having an impedance of Z 0 /N;

a first quarter-wave transmission line coupled to the at least one input of the first 90° hybrid coupler, the first quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z 0 )/N)}, where Z in is an input impedance of the transmitter;

a first splitter having an input and N outputs, the input of the first splitter being coupled to a first one of the at least two outputs of the first 90° hybrid coupler, and the N outputs of the first splitter being coupled to the inputs of a first set of N of the 2N band pass filters; and

a second splitter having an input and N outputs, the input of the second splitter being coupled to a second one of the at least two outputs of the first 90° hybrid coupler, and the N outputs of the second splitter being coupled to the inputs of a second set of N of the 2N band pass filters; and

a second adaptation circuit configured to couple each one the 2N band pass filters to the antenna, the second adaptation circuit configured to provide a reflective path between the antenna and the receiver, the second adaptation circuit comprising:

a second 90° hybrid coupler having at least two inputs and at least two outputs, the second 90° hybrid coupler having an impedance of Z 0 /N;

a second quarter-wave transmission line coupled to a first one of the at least two outputs of the second 90° hybrid coupler, the second quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z l1 )/N)}, where Z l1 is a load impedance of the antenna;

a third quarter-wave transmission line coupled to a second one of the at least two outputs of the second 90° hybrid coupler, the third quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z l2 )/N)}, where Z l2 is a load impedance of the receiver;

a first combiner having N inputs and an output, the N inputs of the first combiner being coupled to the outputs of the first set of N of the 2N band pass filters, and the output of the first combiner being coupled to a first one of the at least two inputs of the second 90° hybrid coupler; and

a second combiner having N inputs and an output, the N inputs of the second combiner being coupled to the outputs of the second set of N of the 2N band pass filters, and the output of the second combiner being coupled to a second one of the at least two inputs of the second 90° hybrid coupler.

11. The duplexer of claim 10 , wherein the band pass filters are acoustic wave band pass filters.

12. The duplexer of claim 10 , wherein the band pass filters are low temperature co-fired ceramic, LTCC, filters.