Preserving linearity of a rf power amplifier

• US 20050270105A1
• Filed: 08/04/2003
• Published: 12/08/2005
• Est. Priority Date: 09/17/2002
• Status: Active Grant

• Current Assignee: Ampleon Netherlands B.V. (Ampleon Coöperatief UA)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Bezooijen, Adrianus, Chanlo, Christophe
• Granted Patent: US 7,482,873 B2
• Time in Patent Office: Days
• US Class Current: 330/297
• CPC Class Codes: H03F 1/0238 using supply converters
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• 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: H03G 3/004 Control by varying the supply voltage
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A method and circuit for preserving linearity of a RF power amplifier, the power amplifier including a RF power output unit (4, 24, 62) having a characteristic drive level and fed by a supply voltage, comprising measuring the output voltage of the RF power output unit (4, 24, 62); comparing the measured output voltage to at least one threshold voltage to produce a control signal; and adapting the drive level or the supply voltage of the RF power output (4, 24, 62) unit by means of the control signal to operate the output unit below its saturation level. A method and circuit for stabilizing an antenna circuit comprising a RF power amplifier and a matching circuit by preserving linearity of a RF power amplifier, where the above power amplifier is used.

Claims

1. A method for preserving linearity of a RF power amplifier, the power amplifier including a RF power output unit having a characteristic drive level and fed by a supply voltage, comprising:

measuring the output voltage of the RF power output unit;

comparing the measured output voltage to at least one threshold voltage to produce a control signal; and

adapting the drive level or the supply voltage of the RF power output unit by means of the control signal to operate the output unit below its saturation level.

2. The method of claim 1, wherein the power amplifier includes a variable gain preamplifier supplying the drive voltage to the RF power output unit and wherein the control signal is used to adapt the gain of the preamplifier.

3. The method of claim 2, wherein the control signal is combined with the gain control signal of the preamplifier.

7. The method of claim 1, wherein the output voltage of the RF power output unit is rectified before being compared to the threshold voltage.

8. The method of claim 1, wherein the output voltage of the RF power output unit is compared to the threshold voltage by means of an operational amplifier.

9. The method of claim 8, wherein the output voltage of the RF power output unit is compared in at least two parallel operational amplifiers to threshold voltages to produce at least two control signals, and wherein the at least two control signals are fed to the base-band controller.

10. The method of claim 9, wherein the at least two threshold voltages have different voltage levels.

11. The method of claim 1, wherein the supply voltage is adapted by a programmable DC-DC converter controlled by a base-band controller which is fed by the control signal.

4. A method for controlling an antenna circuit comprising a RF power amplifier and a matching circuit by preserving linearity of a RF power amplifier, the power amplifier comprising a RF power output unit having a characteristic drive level and fed by a supply voltage source, comprising:

measuring the output voltage of the RF power output unit;

comparing the measured output voltage to at least one threshold voltage to produce a control signal; and

adapting the output matching circuit by means of the control signal to operate the output unit below its saturation level.

5. The method of claim 4, wherein the adapting of the output matching circuit is done by changing either the magnitude or the phase of the impedance transform function.

6. The method of claim 4, wherein the adapting of the output matching circuit and the adapting of the supply voltage are combined with a power amplifier efficiency optimization in case of a multiple threshold detection by an analog-to-digital converter.

12. A circuit for preserving linearity of a RF power amplifier wherein the power amplifier includes a RF power output unit having a characteristic drive level, comprising

a measuring unit measuring the output voltage of the RF power output unit;

a comparing unit comparing the measured output voltage of the RF power output unit to a threshold voltage to produce a control signal;

a drive level adaptation unit adapting the drive level of the RF power output unit or a supply voltage adaptation unit adapting a supply voltage of the RF power output unit to operate the output unit below its saturation level for preserving linearity of the RF power amplifier.

13. The circuit of claim 12, wherein the power amplifier includes a variable gain preamplifier supplying the drive voltage to the RF power output unit;

and wherein the control signal is fed from the comparing unit to the preamplifier to adapt the gain of the preamplifier.

14. The circuit of claim 13, comprising a combining circuit between the comparing unit and the preamplifier combining the control signal with the gain control signal of the preamplifier.

17. The circuit of claim 12, comprising a rectifier between the RF power output unit and the comparing unit.

18. The circuit of claim 12, wherein the comparing unit comprises an operational amplifier.

19. The circuit of claim 18, comprising at least two parallel operational amplifiers to produce at least two control sub-signals, and wherein the at least two control sub-signals are fed to a base-band controller to adapt the gain of the RF power output unit to adapt the gain thereof.

20. An apparatus comprising a circuit as claimed in claim 12.

15. A circuit for stabilizing an antenna circuit comprising a RF power amplifier and a matching circuit, wherein the RF power amplifier comprises a RF power output unit having a characteristic drive level, comprising

a measuring unit measuring the output voltage of the RF power output unit;

a comparing unit comparing the measured output voltage of the RF power output unit to a threshold voltage to produce a control signal;

a drive level adaptation unit adapting the output matching circuit by means of the control signal thereby adapting the drive level of the RF power output unit to operate the RF output unit below its saturation level for preserving linearity of the RF power amplifier.

16. The circuit of claim 15, wherein the output matching circuit is configured to be adaptable with respect to either the magnitude or the phase of its impedance transform function.