RF Power Amplifier Bias-Tuned MOSCAP Circuit for AMPM Distortion
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Solution Overview
Problem
Designing a satisfactory power amplifier for electronic devices with wireless communications capabilities is challenging due to amplitude modulation to phase modulation (AMPM) distortion caused by non-linear input capacitance.
Innovation Solution
Incorporating an amplitude modulation to phase modulation (AMPM) distortion compensation circuit with n-type metal-oxide-semiconductor capacitors (MOSCAPs) configured to receive a bias voltage, which can be coupled to the input or output terminals of the power amplifier to mitigate AMPM distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power amplifier design is used, then the device can transmit radio-frequency signals, but AMPM distortion occurs due to non-linear input capacitance
Solution Approach 1:
The patent introduces an intermediary compensation circuit between the input signal and the power amplifier's input capacitance. This circuit includes a first capacitor coupled to the input terminal and a second capacitor coupled to the gate terminal of the input transistor, acting as a mediator to counteract the non-linear effects of the input capacitance and reduce AMPM distortion.
Solution Approach 2:
The patent changes the electrical parameters of the compensation circuit based on the operating conditions. The capacitors in the compensation circuit are designed with specific capacitance values that vary to counteract the non-linear input capacitance of the power amplifier across different signal amplitudes, thereby reducing AMPM distortion while maintaining signal transmission reliability.
2Measurement precision
If compensation circuit is added to reduce AMPM distortion, then EVM and phase response improve, but device complexity increases
Solution Approach 1:
The patent segments the compensation function into distinct circuit elements: a first capacitor coupled to the input terminal and a second capacitor coupled to the gate terminal. This segmentation allows each capacitor to perform a specific compensation function, improving EVM and phase response while keeping the overall circuit complexity manageable through modular design.
Solution Approach 2:
The compensation circuit serves multiple functions simultaneously: it reduces AMPM distortion, improves error vector magnitude, enhances phase response, and maintains signal transmission reliability. By designing the compensation circuit to perform multiple functions, the patent achieves significant performance improvements without proportionally increasing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces undesired AMPM distortion, improving the error vector magnitude (EVM) and phase response of the power amplifier, leading to enhanced wireless transmission performance.
Implementation Method 1
The compensation circuit may include one or more n-type metal-oxide-semiconductor capacitors (MOSCAPs). The n-type MOSCAPs may be configured to receive a bias voltage at their gate terminals or may be configured to receive a bias voltage at their body terminals.
Data Source
AI summary
An electronic device may include wireless circuitry with a processor, a transceiver, an antenna, and a front-end module coupled between the transceiver and the antenna. The front-end module may include one or more power amplifiers for amplifying a signal for transmission through the antenna. A power amplifier may include a phase distortion compensation circuit. The phase distortion compensation circuit may include one or more n-type metal-oxide-semiconductor capacitors configured to receive a bias voltage. The bias voltage may be set to provide the proper amount of phase distortion compensation.