Power control of a power amplifier
First Claim
1. A method of providing power control of a power amplifier used to amplify input signals modulated in accordance with a variable envelope modulation scheme, the power control being effective to control the output power of signals amplified by the power amplifier to be within a predetermined power control range, the method comprising:
- providing a power amplifier having a gain which reduces as the supply voltage to the power amplifier reduces, the change in gain over the voltage supply range of the power amplifier being at least the change in output power over the predetermined power control range; and
during operation of said power amplifier to amplify input signals modulated in accordance with the variable envelope modulation scheme, controlling the output power of the power amplifier by regulation of the supply voltage to the power amplifier over a voltage control range, the power amplifier being arranged to provide that at each respective value of the supply voltage in the voltage control range the output power of the power amplifier is less than the saturation output power of the power amplifier.
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Accused Products
Abstract
To effect power control of a power amplifier 2 having three amplifier stages 3, 4 and 5 used to amplify input signals modulated in accordance with a variable envelope modulation scheme, there is used a power amplifier 2 having a gain which reduces as the supply voltage to the power amplifier 2 reduces, and the output power POUT of the power amplifier 2 is controlled by regulation of the supply voltage VS. Taking advantage of the reduction in gain of the power amplifier 2, it is ensured that, in respect of each respective amplifier stage 3, 4 and 5 and at each respective value of the supply voltage in the voltage control range, the output power POUT of the respective amplifier stage 3, 4 and 5 is less than the saturation output power PSAT of the respective amplifier stage 3, 4 and 5. As a result, distortion of the signal is reduced. The power control technique improves efficiency over known techniques of backing off the output power and using a variable gain amplifier stage to control the output power.
44 Citations
29 Claims
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1. A method of providing power control of a power amplifier used to amplify input signals modulated in accordance with a variable envelope modulation scheme, the power control being effective to control the output power of signals amplified by the power amplifier to be within a predetermined power control range,
the method comprising: -
providing a power amplifier having a gain which reduces as the supply voltage to the power amplifier reduces, the change in gain over the voltage supply range of the power amplifier being at least the change in output power over the predetermined power control range; and
during operation of said power amplifier to amplify input signals modulated in accordance with the variable envelope modulation scheme, controlling the output power of the power amplifier by regulation of the supply voltage to the power amplifier over a voltage control range, the power amplifier being arranged to provide that at each respective value of the supply voltage in the voltage control range the output power of the power amplifier is less than the saturation output power of the power amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A power amplifier power control circuit of a power amplifier operable to amplify signals modulated in accordance with a variable envelope modulation scheme, the power amplifier control system being capable of controlling the output power of signals amplified by the power amplifier to be within a predetermined power control range, wherein:
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the power amplifier has a gain which reduces as the supply voltage to the power amplifier reduces, the change in gain over the voltage supply range of the power amplifier being at least the change in output power over the predetermined power control range;
the power amplifier control system comprises a supply regulation circuit operable, during operation of said power amplifier to amplify input signals modulated in accordance with the variable envelope modulation scheme, to regulate the supply voltage to the power amplifier and thereby control the output power of the power amplifier, the power amplifier being arranged to provide that the output voltage is below the saturation output voltage of the power amplifier across the entire predetermined power control range. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification