Transmitter utilizing a duty cycle envelope reduction and restoration modulator

• US 8,131,234 B2
• Filed: 07/23/2009
• Issued: 03/06/2012
• Est. Priority Date: 07/23/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Liang, Paul Cheng-Po, Takinami, Koji, Matsuura, Toru
• Primary Examiner(s): Nguyen, Duc M
• Application Number:
  US12/508,464
• Publication Number:
  US 20110018640A1
• Time in Patent Office: 957 Days
• Field of Search: 4551271-1275, 455/574, 455/102, 375/295, 375/353
• 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 1/0227 using supply converters
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 2001/045 with means for improving efficiency

Abstract

A broad power band transmitter utilizing a duty cycle modulator achieves 80dB of power range for 3G signals. The present invention greatly improves the efficiency of transmitters used in mobile phones, for example, by using the duty cycle modulator during medium and low power levels of the transmitting power amplifier. The power amplifier operates in three different modes based upon the amplifier power level selected. The power amplifier operates in an EER mode during high power levels, in a DCM ERR mode during medium power levels, and in a DCM mode during low power levels.

Claims

1. A method for conserving power over a wide dynamic range in a power amplifier in response to a power level signal indicating a low, medium, or high power range, the method comprising the steps of:

operating the power amplifier in a duty cycle modulation envelope reduction and restoration (“

DCM ERR”

) mode wherein power output of the power amplifier is selected to be between a first predetermined power threshold and a second predetermined power threshold when the power level signal indicates the medium power range; and

operating the power amplifier in a duty cycle modulation (“

DCM”

) mode wherein power output of the power amplifier is selected to be below the second predetermined power threshold when the power level signal indicates the low power range.

2. The method of claim 1 further comprising the step of:

operating the power amplifier in an envelope elimination and restoration (“

EER”

) mode wherein power output of the power amplifier is selected to be above the first predetermined power threshold when the power level signal indicates the high power range.

3. The method of claim 2 wherein the first predetermined power threshold and the second predetermined power threshold are determined on the basis of adjacent channel leakage ratio (“

ACLR”

) specifications and receive band noise specifications.

4. A system for conserving power in an RF transmitter comprising:

means for generating a power level signal indicating a low, medium, or high power range; and

a power amplifier including a supply port and an RF input port, the power amplifier operating in a DCM ERR mode wherein power output of the power amplifier is selected to be between a first predetermined power threshold and a second predetermined power threshold when the power level signal indicates the medium power range, the power amplifier operating in a DCM mode wherein power output of the power amplifier is selected to be below the second predetermined power threshold when the power level signal indicates the low power range.

5. The system of claim 4 wherein the power amplifier operates in an EER mode when power output of the power amplifier is selected to be above the first predetermined power threshold when the power level signal indicates the high power range.

6. The system of claim 5 wherein the first predetermined power threshold and the second predetermined power threshold are determined on the basis of ACLR specifications, and receive band noise specifications at a 45 MHz offset.

7. A method for conserving power over a wide dynamic range in a power amplifier having an RF input port and a supply port, the method comprising the steps of:

receiving a power level signal indicating a low, medium, or high power range;

preparing a first amplitude component, above a predetermined amplitude threshold, a second amplitude component below the predetermined amplitude threshold, and a phase component, based on an in-phase component and a quadrature component;

modulating the second amplitude component onto a pulse sequence to generate a duty cycle modulated signal when the power level signal indicates the low or medium power range for the power amplifier causing the power output of the power amplifier to be below a first predetermined power threshold;

generating a constant envelope signal from the phase component;

combining the duty cycle modulated signal and the constant envelope signal;

supplying the combined signal to the RF input port of the power amplifier; and

supplying the first amplitude component to the supply port of the power amplifier when the power level signal indicates the medium or high power range for the power amplifier causing the power output of the power amplifier to be above a second predetermined power threshold which is below the first predetermined power threshold.

8. The method of claim 7 further comprising the step of:

amplifying the combined signal before supplying the combined signal to the RF input port.

9. The method of claim 7 further comprising the steps of:

generating a constant level signal when the power level signal indicates the low power range for the power amplifier causing the power output of the power amplifier to be below the second predetermined power threshold; and

supplying the constant level signal to the supply port of the power amplifier in place of the first amplitude component.

10. The method of claim 7 further comprising the step of:

supplying the constant envelope signal to the RF input port of the power amplifier in place of the combined signal when the power level signal indicates the high power range for the power amplifier causing the power output of the power amplifier to be above the first predetermined power threshold.

11. The method of claim 10 further comprising the step of:

amplifying the constant envelope signal before supplying the constant envelope signal to the RF-input port.

12. The method of claim 7 further comprising the step of:

determining the first predetermined power threshold and the second predetermined power threshold on the basis of adjacent channel leakage ratio (“

ACLR) specifications, and receive band noise specifications at a 45 MHz offset.

13. The method of claim 7 wherein the first predetermined power threshold is between a range of 6 dBm to 24 dBm.

14. The method of claim 13 wherein the second predetermined power threshold is between a range of −

50 dBm to 6 dBm.

15. The method of claim 14 wherein the second predetermined power threshold is between a range of −

50 dBm to −

22 dBm.

16. The method of claim 15 wherein the first predetermined power threshold is between a range of 12 dBm to 24 dBm.

17. A system for conserving power in an RF transmitter comprising:

means for generating a power level signal indicating a low, medium, or high power range;

a power amplifier having an RF input port and a supply port;

a signal decomposer preparing a first amplitude component above a predetermined amplitude threshold, a second amplitude component below the predetermined amplitude threshold, and a phase component, based on an in-phase component and a quadrature-phase component;

a duty cycle modulator receiving the second amplitude component and modulating the second amplitude component onto a pulse sequence to generate a duty cycle modulated signal, when the power level signal indicates the low or medium power range for the power amplifier causing the power output of the power amplifier to be below a first predetermined power threshold;

a constant envelop generator receiving the phase component and generating a constant envelope signal;

a combining unit combining the duty cycle modulated signal and the constant envelope signal and supplying the combined signal to the RF input port; and

a supply modulator receiving the first amplitude component from the signal decomposer and supplying the first amplitude component to the supply port when the power level signal indicates the medium or high power range for the power amplifier causing the power output of the power amplifier to be above a second predetermined power threshold, which is below the first predetermined power threshold.

18. The system of claim 17 further comprising a power controller receiving the power level signal and generating a threshold signal which is supplied to the signal decomposer for setting the predetermined amplitude threshold.

19. The system of claim 17 further comprising

an amplifier receiving the combined signal before supplying an amplified combined signal to the RF input port.

20. The system of claim 17 wherein the supply modulator generates a constant level signal and supplies the constant level signal to the supply port in place of the first amplitude component when the power level signal indicates the low power range for the power amplifier causing the power output of the power amplifier to be below the second predetermined power threshold.

21. The system of claim 17 wherein the constant envelope signal generator supplies the constant envelope signal to the RF input port in place of the combined signal when the power level signal indicates the high power range for the power amplifier causing the power output of the power amplifier to be above the first predetermined power threshold.

22. The system of claim 21 further comprising:

an amplifier receiving the constant envelope signal and providing an amplified constant envelope signal to the RF input port of the power amplifier.

23. The system of claim 17 wherein the first predetermined power threshold and the second predetermined power threshold are determined on the basis of adjacent channel leakage ratio (“

ACLR”

) specifications and receive band noise specifications at a 45 MHz offset.

24. The system of claim 17 wherein the first predetermined power threshold is between a range of 6 dBm to 24 dBm and the second predetermined power threshold is between a range of −

50 dBm to 6 dBm.