Apparatus and method for a switched capacitor architecture for multi-band doherty power amplifiers

1. An apparatus for amplifying Radio Frequency (RF) signals, the apparatus comprising:

a multi-band Power Amplifier (PA) comprising:

a plurality of input matching circuits including switchable capacitors; and

a plurality of output matching circuits including the switchable capacitors,

wherein the multi-band PA is tunable to more than one RF frequency band, and

wherein the output matching circuits comprise a plurality of output combiner branches that are selectively actuated via the switchable capacitors to tune the multi-band PA to each band of the more than one RF frequency band.

2. The apparatus of claim 1 , wherein the multi-band PA operates on RF signals having an RF power of at least 50 watts.

3. The apparatus of claim 1 , wherein the switchable capacitors are switchable between a plurality of RF bands corresponding to RF bands designated for a transmission of Long Term Evolution (LTE) RF signals.

4. The apparatus of claim 3 , wherein one switch setting of the switchable capacitors corresponds to more than one of the designated RF bands.

5. The apparatus of claim 1 , wherein the switchable capacitors switch between an ON position corresponding to a capacitor state and an OFF position corresponding to an open circuit state.

6. The apparatus of claim 1 , wherein the multi-band PA is a circuit having a Doherty Power Amplifier circuit design.

7. The apparatus of claim 1 , wherein the switchable capacitors comprise at least one of a varactor diode, a Barium Strontium Titanate (BST) device, a Micro-Electro-Mechanical Systems (MEMS) device, a Laminated MEMS (LMEMS) device, and a RF switch including a fixed capacitor.

8. The apparatus of claim 1 , wherein a number of the output combiner branches corresponds to a number of the more than one RF frequency band.

9. The apparatus of claim 8 , wherein each one of the output combiner branches corresponds to a respective one of the number of possible RF frequency bands.

10. The apparatus of claim 8 , further comprising:

a hybrid coupler for dividing an input RF signal into a first RF signal and a second RF signal;

a carrier transistor for receiving one of the first or second RF signals and connected between respective ones of the input matching circuits and the output matching circuits; and

a peaking transistor for receiving the other of the first and second RF signals and connected between respective ones of the input matching circuits and the output matching circuits.

11. A method for tuning a multi-band Power Amplifier (PA), the method comprising:

switching switchable capacitors of input matching circuits of the multi-band PA to select a Radio Frequency (RF) band of a plurality of RF bands;

switching switchable capacitors of output matching circuits of the multi-band PA to select a RF band of a plurality of RF bands; and

activating switchable capacitors of amplifiers to amplify a RF signal corresponding to the selected RF band,

wherein the switchable capacitors of the amplifiers can be tuned to more than one of the plurality of the RF bands,

wherein the output matching circuits comprise a plurality of output combiner branches that are selectively actuated via the switchable capacitors to select each one of the plurality of bands that the amplifiers can be tuned to.

12. The method of claim 11 , wherein the multi-band PA operates on RF signals having an RF power of at least 50 watts.

13. The method of claim 11 , wherein the switchable capacitors are switchable between a plurality of RF bands corresponding to RF bands designated for a transmission of Long Term Evolution (LTE) RF signals.

14. The method of claim 13 , wherein one switch setting of the switchable capacitors corresponds to more than one of the designated RF bands.

15. The method of claim 11 , wherein the switchable capacitors switch between an ON position corresponding to a capacitor state and an OFF position corresponding to an open circuit state.

16. The method of claim 11 , wherein the multi-band PA is a circuit having a Doherty Power Amplifier circuit design.

17. The method of claim 11 , wherein the multi-switchable capacitors comprise at least one of a varactor diode, a Barium Strontium Titanate (BST) device, a Micro-Electro-Mechanical Systems (MEMS) device, a Laminated MEMS (LMEMS) device, and a RF switch including a fixed capacitor.

18. The method of claim 11 , wherein a number of the output combiner branches corresponds to a number of the more than one RF frequency band.

19. The method of claim 18 , wherein each one of the output combiner branches corresponds to a respective one of the more than one RF frequency bands.