High-efficiency modulating RF amplifier
First Claim
1. A variable output RF power amplifier comprising:
- voltage regulator means for producing a specified voltage within a range of voltages in accordance with a control signal for performing at least one of level control, burst control, and modulation; and
a power amplifier including a final amplification stage having the specified voltage as a supply voltage and having a drive signal causing the final amplification stage to be driven repeatedly between two states, a hard-on state and a hard-off state, without operating the amplifier in a linear operating region for an appreciable percentage of time;
wherein the amplifier is controlled without continuous or frequent feedback adjustment.
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Abstract
The present invention, generally speaking, provides for high-efficiency power control of a high-efficiency (e.g., bard-limiting or switch-mode) power amplifier in such a manner as to achieve a desired control or modulation. Unlike the prior art, feedback is not required. That is, the amplifier may be controlled without continuous or frequent feedback adjustment. 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.
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Citations
21 Claims
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1. A variable output RF power amplifier comprising:
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voltage regulator means for producing a specified voltage within a range of voltages in accordance with a control signal for performing at least one of level control, burst control, and modulation; and
a power amplifier including a final amplification stage having the specified voltage as a supply voltage and having a drive signal causing the final amplification stage to be driven repeatedly between two states, a hard-on state and a hard-off state, without operating the amplifier in a linear operating region for an appreciable percentage of time;
wherein the amplifier is controlled without continuous or frequent feedback adjustment.
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- 2. The apparatus of claim 2, wherein the voltage regulator means comprises a first switch-mode converter stage and a second linear regulator stage.
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19. A method of controlling a power amplifier, comprising:
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generating a specified voltage in accordance with a control signal for performing at least one of level control, burst control, and modulation;
applying the specified voltage to a power amplifier as a supply voltage of a final amplification stage of the power amplifier; and
repeatedly driving the final amplification stage between two states, a hard-on state and a hard-off state, without operating the amplifier in a linear operating region for an appreciable percentage of time;
wherein the amplifier is controlled without continuous or frequent feedback adjustment. - View Dependent Claims (20, 21)
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Specification