Acoustic matrix diplexers and radios using acoustic matrix diplexers

1. A diplexer, comprising:

a common port, a low-band port, and a high-band port;

n low-band sub-filters, where n is an integer greater than one, each low-band sub-filter having a first 1 sub-filter port connected to the common port and a second sub-filter port connected to the low band port;

n high-band sub-filters, each high-band sub-filter having a first h sub-filter port connected to the common port and a second sub-filter port connected to the high band port;

a first acoustic resonator connected between the common port and ground; and

a second acoustic resonator connected between the low-band port and ground, wherein

the first and second acoustic resonators are configured to create respective transmission zeros adjacent to a lower edge of a passband of the diplexer.

2. The diplexer of claim 1 , wherein

the passband of the diplexer is equal to a sum of passbands of the 2n high-band and low-band sub-filters.

3. The diplexer of claim 1 wherein the first and second acoustic resonators are transversely-excited film bulk acoustic resonators (XBARs).

4. The diplexer of claim 1 , further comprising:

a third acoustic resonator connected between the common port and ground; and

a fourth acoustic resonator connected between the high-band port and ground, wherein

the third and fourth acoustic resonators are configured to create transmission zeros adjacent to an upper edge of the passband of the diplexer.

5. The diplexer of claim 4 wherein the third and fourth acoustic resonators are transversely-excited film bulk acoustic resonators (XBARs).

6. The diplexer of claim 1 , each of the 2n low-band and high-band sub-filters comprising:

m acoustic resonators connected in series between the first sub-filter port and the second sub-filter port, where m is an integer greater than one; and

m−1 capacitors, each capacitor connected between ground and a node between a respective pair of acoustic resonators from the in acoustic resonators.

7. The diplexer of claim 6 wherein the in acoustic resonators in each of the 2n low-band and high-band sub-filters are transversely-excited film bulk acoustic resonators (XBARs).

8. The diplexer of claim 6 , wherein

the in acoustic resonators of each of the 2n low-band and high-band sub-filters include a first end acoustic resonator connected to the first sub-filter port, a second end acoustic resonator connected to the second sub-filter port, and one or more middle acoustic resonators connected between the first and second end acoustic resonator, and

each of the 2n low-band and high-band sub-filters further comprises a switch in series with one of the one or more middle resonators.

9. A frequency division duplex (FDD) radio, comprising:

a matrix diplexer, comprising:

a common port configured for connection to an antenna, a low band port, and a high band port;

n low band sub-filters, where n is an integer greater than one, each low band sub-filter having a first sub-filter port connected to the common port and a second sub-filter port connected to the low band port;

n high band sub-filters, each high band sub-filter having a first sub-filter port connected to the common port and a second sub-filter port connected to the high band port;

a first acoustic resonator connected between the common port and ground; and

a second acoustic resonator connected between the low band port and ground, wherein

the first and second acoustic resonators are configured to create respective transmission zeros adjacent to a lower edge of a passband of the diplexer;

a transmitter having an output connected to one of the low band port and the high band port; and

a receiver having an input connected to the one of the low band port and the high band port that is not connected to the transmitter.

10. The radio of claim 9 , wherein

the passband of the diplexer is equal to a sum of passbands of the 2n low-band and high-band sub-filters.

11. The radio of claim 9 wherein the first and second acoustic resonators are transversely-excited film bulk acoustic resonators (XBARs).

12. The radio of claim 9 , further comprising:

a third acoustic resonator connected between the common port and ground; and

a fourth acoustic resonator connected between the high band port and ground, wherein

the third and fourth acoustic resonators are configured to create transmission zeros adjacent to an upper edge of the passband of the diplexer.

13. The radio of claim 12 wherein the third and fourth acoustic resonators are transversely-excited film bulk acoustic resonators (XBARs).

14. The radio of claim 9 , each of the 2n low-band and high-band sub-filters comprising:

m acoustic resonators connected in series between the first sub-filter port and the second sub-filter port, where m is an integer greater than one; and

m−1 capacitors, each capacitor connected between ground and a node between a respective pair of acoustic resonators from the in acoustic resonators.

15. The radio of claim 14 wherein the in acoustic resonators in each of the 2n low-band and high-band sub-filters are transversely-excited film bulk acoustic resonators (XBARs).

16. The radio of claim 14 , wherein

the in acoustic resonators of each of the 2n low-band and high-band sub-filters include a first end acoustic resonator connected to the first sub-filter port, a second end acoustic resonator connected to the second sub-filter port, and one or more middle acoustic resonators connected between the first and second end acoustic resonator, and

each of the 2n low-band and high-band sub-filters further comprises a switch in series with one of the one or more middle resonators.

17. The radio of claim 9 , further comprising the antenna.