Bulk-Biased Power Amplifier for Linearity and Compression Point
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Solution Overview
Problem
Power amplifiers in wireless communication systems face challenges in achieving high linearity and compression points due to nonlinear transfer functions, which result in intermodulation products and harmonic distortion, and existing linearization methods are not always effective.
Innovation Solution
A power amplifier design that drives the bulk node of a field-effect transistor with a dynamic bias voltage as a nonlinear function of the input signal's envelope, using a bias-voltage generation circuit that can be digital or analog, to improve the amplifier's linearity and compression point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional linearization methods (negative feedback, error feed forward, predistortion) are used, then linearity is improved, but device complexity increases and compression point remains limited
Solution Approach 1:
The patent changes the biasing parameter of the transistor from a static value to a dynamic value that varies with the input signal envelope. The bulk terminal bias voltage is modulated according to the envelope detection of the input signal, transforming the transistor's transfer characteristic in real-time to maintain linearity across different signal levels without requiring complex feedback or predistortion circuits
Solution Approach 2:
The patent uses envelope detection to create a copy of the input signal's amplitude information, which is then used to modulate the bulk terminal bias. This copied envelope information allows the system to anticipate and compensate for nonlinearities without requiring complex real-time processing or feedback mechanisms
2Manufacturing precision
If static bias is used, then device complexity is low, but compression point is limited and linearity deteriorates at higher input powers
Solution Approach 1:
The patent transitions from a static bias configuration to a dynamic bias configuration where the bulk terminal voltage changes continuously with the input signal envelope. This dynamic adaptation allows the transistor to operate in different regions of its transfer characteristic, pushing the compression point to higher input power levels while maintaining simplicity through direct envelope modulation
3Manufacturing precision
If dynamic bias voltage is applied to bulk terminal, then linearity is improved and compression point increases, but use of energy increases
Solution Approach 1:
The system uses the input signal itself to generate the bias modulation through envelope detection, rather than requiring an external control signal or complex processing circuitry. The envelope detector extracts amplitude information from the input signal, which is then directly used to modulate the bulk terminal, making the system self-sufficient and energy-efficient
Data Source
AI summary
A power amplifier, for a transmitter circuit is disclosed, which comprises at least one field-effect transistor having a gate terminal and a bulk terminal. The at least one field-effect transistor is configured to receive an input voltage at the gate terminal and a dynamic bias voltage at the bulk terminal. The power amplifier comprises a bias-voltage generation circuit configured to generate the dynamic bias voltage as a nonlinear function of an envelope of input signal. The input voltage is a linear function of the input signal. The bias-voltage generation circuit comprises a rectifier circuit configured to generate a rectified input voltage and an amplifier circuit, operatively connected to the rectifier circuit, configured to generate the dynamic bias voltage based on the rectified input voltage. The amplifier circuit is a variable-gain amplifier circuit and the power amplifier comprises a control circuit configured to tune the gain of the amplifier circuit.