RF Power Amplifier AM-PM Compensation Using Biased MOSCAPs
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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 distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier is designed to amplify radio-frequency signals, then the signal power is increased, but amplitude modulation to phase modulation (AMPM) distortion is generated due to non-linear input capacitance
Solution Approach 1:
The patent applies AMPM compensation circuits that convert the harmful AMPM distortion into beneficial phase correction. The compensation circuits generate opposite phase shifts that cancel out the distortion caused by non-linear input capacitance, effectively converting the harmful effect into a corrective mechanism that improves signal fidelity while maintaining power amplification
Solution Approach 2:
The patent introduces intermediate compensation circuits as mediators between the power amplifier stages. These circuits include series capacitors and parallel resonant circuits that act as intermediaries to pre-correct the signal phase before amplification, thereby eliminating the need for the amplifier itself to generate distortion in the first place
2Measurement precision
If compensation circuits are added to reduce AMPM distortion, then the error vector magnitude (EVM) is improved, but the device complexity increases
Solution Approach 1:
The patent employs parameter changes by adjusting capacitor values and resonant frequencies to optimize compensation effectiveness. By carefully selecting component parameters, the design achieves effective AMPM distortion cancellation using minimal circuit elements, thereby improving EVM without proportionally increasing device complexity
Solution Approach 2:
The patent applies partial compensation strategies where only the dominant AMPM distortion components are corrected rather than attempting to eliminate all distortion. This selective approach achieves sufficient EVM improvement for practical applications while avoiding the complexity of comprehensive distortion cancellation circuits
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 effectively reduces undesired AMPM distortion, improving the error vector magnitude (EVM) and phase response of radio-frequency signals, thereby enhancing the performance of the power amplifier.
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
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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 (50) for amplifying a signal for transmission through the antenna. A power amplifier (50) may include a phase distortion compensation circuit (58). The phase distortion compensation circuit (58) may include one or more n-type metal-oxide-semiconductor capacitors (N1, N2) configured to receive a bias voltage (Vbias). The bias voltage (Vbias) may be set to provide the proper amount of phase distortion compensation.