Method and apparatus for attaining higher amplifier efficiencies at lower power levels

• US 20020019219A1
• Filed: 10/05/2001
• Published: 02/14/2002
• Est. Priority Date: 12/15/1998
• Status: Active Grant

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Doherty, Peter J.
• Granted Patent: US 6,625,430 B2
• Time in Patent Office: Days
• US Class Current: 455/127.1
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 3/24 of transmitter output stages
• 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 2001/045 with means for improving efficiency

Abstract

Apparatus and method for providing a radio frequency output to promote higher amplifier efficiencies is described herein. The apparatus includes driver means having a driver output for providing an amplified radio frequency signal and switching means in communication with the driver output of the driver means. The switching means directs the amplified radio frequency signal to a first or a second circuit path connectable to the driver output of the driver means. The first circuit path provides a low power level output of the radio frequency signal, and the second circuit path provides a high power level output of the radio frequency signal. In the low power level mode, the power amplifier in the output stage is switched out of the circuit path. The method includes the steps of supplying a modulated signal from a driver stage which includes at least one radio frequency amplifier, determining the transmission power requirements of the modulated signal, selecting one of a plurality of output stages in accordance with the transmission power requirements, and switching the modulated signal to the selected output stage to supply the output of the selected output stage to an antenna.

Claims

1. An apparatus for providing a radio frequency output from a radio frequency drive to an antenna, said apparatus comprising:

a driver amplifier having an input connected to said radio frequency drive and an output;

a first circuit path comprising an input connected to the output of the driver amplifier and an output connectable to said antenna;

a second circuit path comprising an input connected to the driver amplifier, an output connectable to said antenna, and a power amplifier connected between the input and output of the second circuit path and comprising a bias lead; and

a switch device having;

a first state wherein the output of the first circuit path is connected to the antenna to provide a radio frequency output thereto, the output of the second circuit path is disconnected from said antenna, and the bias lead of the power amplifier is disconnected from a bias, and

a second state wherein the output of the second circuit path is connected to the antenna to provide a radio frequency output thereto, the output of the first circuit path is disconnected from said antenna, and the bias lead of the power amplifier is connected to a bias.

2. The apparatus, as set forth in claim 1, wherein said first circuit path further comprises a first matching network.

3. The apparatus, as set forth in claim 1, wherein said second circuit path further comprises a second matching network.

4. The apparatus, as set forth in claim 1, wherein said first circuit path further comprises a first matching network and wherein said second circuit path further comprises a second matching network.

5. The apparatus, as set forth in claim 1, further comprising an RF detector.

6. The apparatus, as set forth in claim 5, further comprising a hysteresis circuit in communication with said RF detector for controlling operation of said switching means.

7. The apparatus, as set forth in claim 6, further comprising a second switch device coupled to said driver amplifier.

8. The apparatus, as set forth in claim 7, wherein said second switch device has a first state for coupling said driver amplifier to said power amplifier.

9. The apparatus, as set forth in claim 8, wherein said second switch device has a second state for coupling said power amplifier to said antenna.

10. An apparatus for providing a radio frequency output from a radio frequency drive to an antenna, said apparatus comprising:

a first circuit path comprising an input connectable to said radio frequency drive, an output connectable to said antenna, and a driver amplifier having a first bias lead;

a second circuit path comprising an input connected to said radio frequency drive, an output connectable to said antenna, a second driver amplifier having a second bias lead, and a power amplifier having a third bias lead; and

a switch device having;

a first state wherein the output of the first circuit path is connected to the antenna to provide a radio frequency output thereto, the output of the second circuit path is disconnected from the antenna, a bias is connected to the first bias lead, and the second and third bias leads are disconnected from a bias, and

a second state wherein the output of the second circuit path is connected to the antenna to provide a radio frequency output thereto, the second and third bias leads are connected to a bias, and the first bias lead is disconnected from a bias.

11. The apparatus, as set forth in claim 10, wherein said first circuit path further comprises a first matching network.

12. The apparatus, as set forth in claim 10, wherein said second circuit path further comprises a second matching network.

13. The apparatus, as set forth in claim 10, wherein said first circuit path further comprises a first matching network and wherein said second circuit path further comprises a second matching network.

14. The apparatus, as set forth in claim 10, further comprising an RF detector.

15. The apparatus, as set forth in claim 14, further comprising a hysteresis circuit in communication with said RF detector for controlling operation of said switching device.

17. The method of, as set forth in claim 16, further comprising a step of providing a driver amplifier in said first path.

18. The method of, as set forth in claim 17, further comprising a step of biasing said driver amplifier in said first path when said first path is coupled to said antenna.

19. The method of, as set forth in claim 16, further comprising a step of providing a driver amplifier in said second path.

20. The method of, as set forth in claim 19, further comprising a step of biasing said driver amplifier in said first path when said first path is coupled to said antenna.

16. A method of providing a radio frequency output from a radio frequency drive to an antenna, said method comprising the steps of:

providing a first path to an antenna;

providing a second path to said antenna, said second path having a power amplifier;

coupling said second path to said antenna in response to a high power request; and

providing a first bias to said power amplifier when said second path is connected to said antenna.