Power amplifier with switched output matching for multi-mode operation

• US 8,750,810 B2
• Filed: 11/20/2009
• Issued: 06/10/2014
• Est. Priority Date: 07/24/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Pletcher, Nathan, Hadjichristos, Aristotele, Zhao, Yu, Nejati, Babak
• Primary Examiner(s): Nguyen, Simon
• Application Number:
  US12/623,248
• Publication Number:
  US 20110018632A1
• Time in Patent Office: 1,663 Days
• Field of Search: 455/91, 455/107, 4551142-1143, 455121-125, 4551271-1275, 455/129, 330/51, 330/144, 330/295
• US Class Current: 455/91
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

Exemplary embodiments are directed to a transmitter with a power amplifier and a switched output matching circuit implementing a plurality of output paths for a plurality of operating modes is described. The power amplifier receives an input RF signal and provides an amplified RF signal. An output matching network performs impedance transformation from low impedance at the power amplifier output to higher impedance at the matching network output. The plurality of output paths are coupled to the output matching network. Each output path provides a different target output impedance for the power amplifier and routes the amplified RF signal from the power amplifier to an antenna when that output path is selected. Each output path may include a matching network coupled in series with a switch. The matching network provides the target output impedance for the power amplifier when the output path is selected. The switch couples or decouples the output path to/from the power amplifier.

Claims

1. An apparatus for wireless communication, comprising:

a power amplifier to receive an input radio frequency (RF) signal and provide an amplified RF signal;

an output matching network configured to receive the amplified RF signal; and

a plurality of output paths coupled by switches to the output matching network, each output path provides a different target output impedance for the power amplifier and routes the amplified RF signal from the power amplifier to an antenna when the output path is selected, wherein an output impedance of the output matching network is greater than each different target output impedance for the power amplifier for each output path.

2. The apparatus of claim 1, further comprising:

a matching network coupled between the power amplifier and the plurality of output paths, the matching network performs impedance transformation from a first impedance at an output of the power amplifier to a second impedance at an output of the matching network.

3. The apparatus of claim 2, the first impedance is determined based on target output impedances for the power amplifier for the plurality of output paths, and the second impedance is determined by a target impedance for the antenna.

4. The apparatus of claim 1, each output path comprising:

a matching network to provide the target output impedance for the power amplifier when the output path is selected; and

a switch coupled in series with the matching network, the switch couples the output path to the power amplifier when the output path is selected and decouples the output path from the power amplifier when the output path is not selected.

5. The apparatus of claim 4, the plurality of output paths include an output path comprising a matching network implemented with a short.

6. The apparatus of claim 4, the tunable matching network comprising a a tunable capacitor.

7. The apparatus of claim 1, the plurality of output paths support a plurality of operating modes, each operating mode is associated with different operating characteristics for the power amplifier.

8. The apparatus of claim 7, the plurality of operating modes include first and second operating modes, the first operating mode supports higher maximum output power than the second operating mode, and the second operating mode provides higher linearity than the first operating mode.

9. The apparatus of claim 7, the plurality of operating modes include first and second operating modes, the power amplifier operates in a saturation region for higher efficiency in the first operating mode and operates outside the saturation region for higher linearity in the second operating mode.

10. The apparatus of claim 1, the plurality of output paths support a plurality of radio technologies, each output path supports a different set of at least one radio technology.

11. The apparatus of claim 1, the plurality of output paths include first and second output paths, the first output path supports a first radio technology with an output RF signal having a constant envelope, and the second output path supports a second radio technology with an output RF signal having a variable envelope.

12. The apparatus of claim 11, the first radio technology is Global System for Mobile Communications (GSM), and the second radio technology is Code Division Multiple Access (CDMA).

13. The apparatus of claim 1, further comprising:

a switchplexer comprising a plurality of switches coupled to the plurality of output paths, each switch routing the amplified RF signal from the power amplifier via an associated output path to the antenna when the switch is selected.

14. A wireless device comprising:

a power amplifier to receive an input radio frequency (RF) signal and provide an amplified RF signal;

a switched output matching circuit coupled to the power amplifier and to support a plurality of operating modes, the switched output matching circuit provides different target output impedances for the power amplifier for the plurality of operating modes, wherein an output impedance of the switched output matching circuit is greater than each different target output impedance for the power amplifier for each operating mode

a switchplexer coupled to the switched output matching circuit and to route the amplified RF signal from the power amplifier via the switched output matching circuit; and

an antenna coupled to the switchplexer and to transmit the amplified RF signal received from the switchplexer.

15. The wireless device of claim 14, the switched output matching circuit comprising

an output matching network coupled to an output of the power amplifier, the output matching network performs impedance transformation from a first impedance at the output of the power amplifier to a second impedance at an output of the output matching network, and

a plurality of output paths coupled to the output matching network, each output path provides a different target output impedance for the power amplifier.

16. The wireless device of claim 14, the switched output matching circuit comprising a plurality of output paths, each output path comprising:

a matching network to provide a target output impedance for the power amplifier when the output path is selected; and

a switch coupled in series with the matching network, the switch couples the output path to the power amplifier when the output path is selected and decouples the output path from the power amplifier when the output path is not selected.

17. The wireless device of claim 14, the plurality of operating modes include first and second operating modes, the first operating mode supports higher maximum output power than the second operating mode, and the second operating mode provides higher linearity than the first operating mode.

18. A method of signal transmission, comprising:

amplifying an input radio frequency (RF) signal with a power amplifier to obtain an amplified RF signal;

providing different target output impedances for the power amplifier for a plurality of output paths with a matching circuit;

selecting by switches an output path among the plurality of output paths providing different target output impedances for the power amplifier, wherein an output impedance of the matching circuit is greater than each different target output impedance for the power amplifier for each output path; and

routing the amplified RF signal from the power amplifier via the selected output path to an antenna.

19. The method of claim 18, further comprising:

performing impedance transformation from a first impedance at an output of the power amplifier to a second impedance at a common node for the plurality of output paths.

20. The method of claim 18, the routing the amplified RF signal comprising:

passing the amplified RF signal via a switch in the selected output path; and

passing the amplified RF signal via a matching network providing a target output impedance for the power amplifier for the selected output path.

21. The method of claim 18, the plurality of output paths support a plurality of operating modes, each operating mode is associated with different operating characteristics for the power amplifier.

22. An apparatus for signal transmission, comprising:

means for amplifying an input radio frequency (RF) signal to obtain an amplified RF signal;

means for providing different target output impedances for the means for amplifying for a plurality of output paths;

means for selecting by switches an output path among the plurality of output paths, wherein an output impedance of the means for providing different target output impedances is greater than each different target output impedance for the means for amplifying for each output path; and

means for routing the amplified RF signal from the means for amplifying via the selected output path to an antenna.

23. The apparatus of claim 22, further comprising:

means for performing impedance transformation from a first impedance at an output of the means for amplifying to a second impedance at a common node for the plurality of output paths.

24. The apparatus of claim 22, the means for routing the amplified RF signal comprising:

means for passing the amplified RF signal via a switch in the selected output path; and

means for passing the amplified RF signal via a matching network providing a target output impedance for the means for amplifying for the selected output path.

25. The apparatus of claim 22, the plurality of output paths support a plurality of operating modes, each operating mode is associated with different operating characteristics for the means for amplifying.