HIGH-EFFICIENCY MODULATING RF AMPLIFIER

• US 20010014593A1
• Filed: 02/09/1999
• Published: 08/16/2001
• Est. Priority Date: 02/09/1999
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Tropian, Inc. (Panasonic Holdings Corporation)
• Inventors: MCCUNE, EARL
• Granted Patent: US 6,377,784 B2
• Time in Patent Office: Days
• US Class Current: 455/127.1
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H03C 1/36 by means of semiconductor device having at least three electrodes H03C1/34, H03C1/50, H03C1/52, H03C1/62 take precedence
• 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 1/0205 in transistor amplifiers
• CPC Class Codes: H03F 1/0211 with control of the supply voltage or current
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0244 Stepped control
• CPC Class Codes: H03F 1/0277 Selecting one or more amplifiers from a plurality of amplifiers
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03F 3/2178 using more than one switch or switching amplifier in parallel or in series H03F3/2173, H03F3/2175 take precedence
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03G 3/004 Control by varying the supply voltage
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals
• CPC Class Codes: H04B 2001/0408 with power amplifiers
• CPC Class Codes: H04B 2001/045 with means for improving efficiency

Abstract

The present invention, generally speaking, provides for high-efficiency power control of a high-efficiency (e.g., hard-limiting or switch-mode) power amplifier in such a manner as to achieve a desired modulation. In one embodiment, the spread between a maximum frequency of the desired modulation and the operating frequency of a switch-mode DC-DC converter is reduced by following the switch-mode converter with an active linear regulator. The linear regulator is designed so as to control the operating voltage of the power amplifier with sufficient bandwidth to faithfully reproduce the desired amplitude modulation waveform. The linear regulator is further designed to reject variations on its input voltage even while the output voltage is changed in response to an applied control signal. This rejection will occur even though the variations on the input voltage are of commensurate or even lower frequency than that of the controlled output variation. Amplitude modulation may be achieved by directly or effectively varying the operating voltage on the power amplifier while simultaneously achieving high efficiency in the conversion of primary DC power to the amplitude modulated output signal. High efficiency is enhanced by allowing the switch-mode DC-to-DC converter to also vary its output voltage such that the voltage drop across the linear regulator is kept at a low and relatively constant level. Time-division multiple access (TDMA) bursting capability may be combined with efficient amplitude modulation, with control of these functions being combined. In addition, the variation of average output power level in accordance with commands from a communications system may also be combined within the same structure.

Claims

1. Apparatus for generating an RF signal modulated in accordance with a modulation scheme, the apparatus comprising:

a switch mode converter having a power input, a power output and a control input;

a regulator having a power input, a power output and a control input, the power input of the regulator being coupled to the power output of the switch-mode converter; and

a magnitude driver responsive to a modulation signal for producing a first control signal coupled to the control input of the switch mode converter and a second control signal coupled to the control input of the regulator.

2. The apparatus of

claim 1

, further comprising an RF power amplifier having a non-linear operational mode, a power output of the regulator supplying a operating voltage of the RF power amplifier.

3. The apparatus of

claim 2

, wherein the modulation signal is a magnitude control signal.

4. The apparatus of

claim 3

, wherein the modulation scheme is amplitude modulation.

5. The apparatus of

claim 2

, further comprising means responsive to a phase control signal for generating a carrier signal having a phase modulation characteristic, the carrier signal being applied to the RF power amplifier.

6. The apparatus of

claim 5

, further comprising a modulation encoder responsive to a data signal for generating the magnitude control signal and the phase control signal.

7. The apparatus of

claim 6

, wherein the modulation encoder operates in a polar coordinate system.

8. The apparatus of

claim 2

, further comprising:

a plurality of amplifier modules, each amplifier module comprising;

a switch mode converter having a power input, a power output and a control input;

a regulator having a power input, a power output and a control input, the power input of the regulator being coupled to the power output of the switch-mode converter;

a magnitude driver responsive to a modulation signal for producing a first control signal coupled to the control input of the switch mode converter and a second control signal coupled to the control input of the regulator; and

an RF power amplifier having a non-linear operational mode, a power output of the regulator supplying a operating voltage of the RF power amplifier;

an RF signal applied in common to all of the RF power amplifiers; and

a magnitude driver responsive to an overall magnitude signal for generating one or more magnitude drive signals, a magnitude drive signal being applied to each of the RF power amplifiers.

9. The apparatus of

claim 8

, wherein a separate respective magnitude drive signals are generated for each of the RF power amplifiers.

10. The apparatus of

claim 8

, wherein a single magnitude drive signal is applied in common to all of the RF power amplifiers.

11. A method of generating a modulated RF signal, comprising:

generating first and second control signals in response to a modulation signal;

in response to the first control signal, performing switch-mode conversion of a supply voltage to an intermediate voltage, the intermediate voltage exceeding a desired voltage; and

in response to the second control signal, regulating the intermediate voltage to produce the desired voltage.

12. The method of

claim 11

, further comprising applying the desired voltage as an operating voltage to an RF amplifier, and applying an RF input signal to the RF amplifier.

13. The method of

claim 12

, wherein the RF input signal is phase modulated.

14. The method of

claim 13

, further comprising;

encoding data in polar coordinates to produce a magnitude signal and a phase signal; and

generating the RF input signal in accordance with the phase signal;

wherein said modulation signal is derived from said magnitude signal.

15. A method of generating a high-power RF signal, comprising:

coupling in parallel multiple RF amplifiers and adding output signals of the multiple RF amplifiers to produce a resultant high-power RF output signal;

applying an RF input signal in common to all of the RF amplifiers; and

in response to an overall magnitude signal, generating one or more magnitude drive signals, a magnitude drive signal being applied to each of the RF power amplifiers.

16. The method of

claim 15

, wherein a sum of magnitude drive signals applied to the RF power amplifiers substantially equals the overall magnitude signal.