RF Power Amplifier Bias Circuit for AM-PM Distortion Suppression
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Solution Overview
Problem
Existing radio-frequency power amplification circuits face challenges in suppressing distortion of output characteristics due to the nonlinearity of amplification transistors, particularly in field-effect transistor (FET) circuits, which affects the amplitude modulation-phase modulation (AM-PM) characteristics.
Innovation Solution
The proposed amplification circuit incorporates a field-effect transistor (FET) connected to a radio-frequency input terminal, a power supply circuit, a simulated transistor, a resistor in the bias path, and a detection diode, along with a simulated diode and a difference detection circuit to manage bias voltages and currents, ensuring that the bias voltage increases with signal power and compensates for capacitance variations, thereby reducing AM-PM distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a field-effect transistor is used for radio-frequency power amplification, then amplification capability is improved, but distortion of output characteristics occurs due to nonlinearity
Solution Approach 1:
The patent implements feedback by detecting the radio-frequency signal characteristics through the diode connected to the gate, and using this detection to dynamically adjust the bias voltage applied to the gate of the field-effect transistor. This closed-loop feedback mechanism compensates for nonlinear effects in real-time, maintaining output characteristic linearity while preserving amplification capability.
Solution Approach 2:
The patent dynamically changes the bias voltage parameter applied to the gate of the field-effect transistor based on the detected signal characteristics. By varying the bias voltage in response to signal conditions, the system compensates for nonlinear effects and maintains consistent output characteristics across different operating points.
2Manufacturing precision
If bias voltage is increased to compensate for capacitance variation, then AM-PM characteristics improve, but power consumption increases
Solution Approach 1:
The patent transitions from a static bias voltage approach to a dynamic bias adjustment mechanism. The bias voltage is continuously adjusted based on real-time detection of signal characteristics and capacitance variations, allowing the system to achieve improved AM-PM characteristics only when and where needed, rather than maintaining high bias voltage continuously.
Solution Approach 2:
The system dynamically changes the bias voltage parameter in response to detected signal conditions and capacitance variations. This selective parameter adjustment improves AM-PM characteristics during critical operating conditions while avoiding unnecessary power consumption during conditions where compensation is not required.
Data Source
AI summary
An amplification circuit includes an amplification transistor connected to a signal input terminal, a power supply circuit configured to supply a bias voltage to the amplification transistor, a resistor disposed in series to a bias path connecting the power supply circuit and the amplification transistor, a transistor that is connected to the bias path and the power supply circuit and that is a simulated transistor for the amplification transistor, and a detection diode connected to the signal input terminal and the bias path between the resistor and a gate of the amplification transistor.