Hybrid-coupler-based radio frequency multiplexers

1. A radio frequency multiplexer, comprising:

a plurality of ports including a common port, a first port for a first frequency band, a second port for a second frequency band, and a third port for a third frequency band;

a plurality of quadrature hybrid couplers (QHCs) including a first QHC, a second QHC, and a third QHC; and

a plurality of pairs of filters including a first pair of filters and a second pair of filters, wherein:

the first pair of filters is coupled between the first QHC and the second QHC, and is configured to pass the second frequency band and not pass the first frequency band and the third frequency band,

the second pair of filters is coupled between the first QHC and the third QHC, and is configured to pass the third frequency band and not pass the first frequency band and the second frequency band,

the first QHC, the first pair of filters, and the second QHC are configured to separate the first frequency band from the common port to the first port, and separate the second frequency band from the common port to the second port, and

the first QHC, the second pair of filters, and the third QHC are configured to separate the first frequency band from the common port to the first port, and separate the third frequency band from the common port to the third port.

2. The radio frequency multiplexer of claim 1 , comprising an additional filter coupled to the first port and configured to pass the first frequency band.

3. The radio frequency multiplexer of claim 1 , comprising:

circuitry coupled to the first port, wherein:

the circuitry is configured to pass the first frequency band, but not pass the second frequency band, and not pass the third frequency band,

the circuitry includes a first filter tuned at the first frequency band, a fourth QHC, a second filter tuned at the second frequency band, and a third filter tuned at the third frequency band, and

the second filter and the third filter are coupled in parallel between two ports of the fourth QHC to generate band-stop responses at the second frequency band and the third frequency band.

4. The radio frequency multiplexer of claim 1 , wherein more frequency bands are supported in a configuration that includes an additional QHC and an additional pair of filters for an additional frequency band, wherein:

the additional pair of filters is coupled to the same two ports of the first QHC to which the first pair of filters and the second pair of filters are coupled,

the additional pair of filters is configured to pass the additional frequency band, but do not pass remaining frequency bands, and

the first QHC, the additional pair of filters, and the additional QHC are configured to separate the first frequency band from the common port to the first port, and separate the additional frequency band from the common port to the additional port.

5. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer includes one or more pairs of equalizers coupled to one or more of the pairs of filters.

6. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer includes one or more pairs of impedance matching networks coupled to one or more of the pairs of filters.

7. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer includes one or more tunable or variable impedances coupled to one or more of the QHCs.

8. The radio frequency multiplexer of claim 1 , wherein one or more of the pairs of filters are tunable or reconfigurable.

9. The radio frequency multiplexer of claim 1 , wherein one or more of the QHCs are tunable or reconfigurable.

10. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is configured to provide a cascade connection with one or more other radio frequency multiplexers to form a radio frequency multiplexer configuration.

11. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a front-end of a wireless communication system that supports carrier aggregation.

12. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a front-end of a wireless communication system that supports frequency division duplexing.

13. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a front-end of a multiband communication system.

14. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a hand portable device supporting wireless communication.

15. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a base station supporting a wireless communication infrastructure.

16. The radio frequency multiplexer of claim 1 , wherein the radio frequency multiplexer is included in a repeater supporting a wireless communication infrastructure.

17. The radio frequency multiplexer of claim 1 , wherein one or more of the filters include one or more of surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters.

18. The radio frequency multiplexer of claim 1 , wherein the first pair of filters and the second pair of filters are coupled to the same two ports of the first QHC.

19. The radio frequency multiplexer of claim 1 , wherein one or more of the plurality of QHCs is realized in an integrated passive device (IPD) technology, or in a low temperature co-fired ceramic (LTCC) technology, or in a printed circuit board (PCB).

20. The radio frequency multiplexer of claim 1 , wherein one or more filters of the plurality of pairs of filters are stacked over one or more QHCs of the plurality of QHCs.