Temperature compensated bias for AM/PM improvement
First Claim
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1. A polar modulation system comprising:
- a polar modulator adapted to receive data to be transmitted and to provide a phase signal and an amplitude signal of a polar modulated signal;
a power amplifier adapted to provide an amplified polar modulated signal and comprising a transistor, which comprises;
a base providing a base input, which is adapted to receive the phase signal;
a collector providing a supply input, which is adapted to receive the amplitude signal; and
an emitter, the transistor having a base-emitter voltage drop that is dependent on the operating temperature of the power amplifier; and
bias circuitry adapted to provide a bias signal, which is a function of an operating temperature of the power amplifier, to the base input,wherein the bias signal compensates for the base-emitter voltage drop as the operating temperature of the power amplifier changes and varies with the operating temperature of the power amplifier to maintain a consistent operating point as the operating temperature of the power amplifier changes.
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Abstract
A system and method are provided for maintaining a consistent operating condition of a power amplifier power amplifier across a range of operating temperatures. The power amplifier is provided with an input bias voltage (Vbias) that adjusts with temperature to compensate for the temperature dependent change of the power amplifier'"'"'s base-emitter voltage drop Vbe. This maintains a consistent operating condition in the power amplifier, which reduces temperature-dependent changes in the amplifier'"'"'s gain.
158 Citations
13 Claims
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1. A polar modulation system comprising:
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a polar modulator adapted to receive data to be transmitted and to provide a phase signal and an amplitude signal of a polar modulated signal; a power amplifier adapted to provide an amplified polar modulated signal and comprising a transistor, which comprises; a base providing a base input, which is adapted to receive the phase signal; a collector providing a supply input, which is adapted to receive the amplitude signal; and an emitter, the transistor having a base-emitter voltage drop that is dependent on the operating temperature of the power amplifier; and bias circuitry adapted to provide a bias signal, which is a function of an operating temperature of the power amplifier, to the base input, wherein the bias signal compensates for the base-emitter voltage drop as the operating temperature of the power amplifier changes and varies with the operating temperature of the power amplifier to maintain a consistent operating point as the operating temperature of the power amplifier changes. - View Dependent Claims (2, 3, 4)
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5. A polar modulation system comprising:
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a polar modulator adapted to receive data to be transmitted and to provide a phase signal and an amplitude signal of a polar modulated signal; a power amplifier adapted to receive the phase signal at a base input and the amplitude signal at a supply input, and provide an amplified polar modulated signal; and bias circuitry comprising; a band-gap voltage generator adapted to provide a temperature-dependent voltage reference; and a bias voltage generator adapted to receive the temperature-dependent voltage reference and provide a bias signal, which is a function of an operating temperature of the power amplifier and has a temperature-dependent bias voltage, to the base input, wherein the bias signal provided to the base input of the power amplifier varies with the operating temperature of the power amplifier to maintain a consistent operating point as the operating temperature of the power amplifier changes. - View Dependent Claims (6, 7, 8)
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- 9. A method for maintaining a consistent operating point across a range of operating temperatures of a transmitter operating according to a polar modulation scheme comprising providing a temperature-dependent bias voltage to a bias input of a power amplifier, varying the bias voltage to compensate for temperature dependent characteristics of the power amplifier, and varying the bias voltage to compensate for a base-emitter voltage drop of a heterojunction bipolar transistor power amplifier that is dependent upon the operating temperature of the power amplifier, wherein the bias voltage varies with an operating temperature of the power amplifier to maintain a consistent operating point of the power amplifier as the operating temperature of the power amplifier changes.
Specification