RF Power Amplifier Bias Adjustment for Reflected Wave Stability
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Solution Overview
Problem
Power amplifier circuits face increased load loss and lack of directivity in responding to load changes, leading to power gain suppression challenges due to the effect of reflected waves.
Innovation Solution
A power amplifier circuit design incorporating a first and second amplifier, bias circuits, and a bias adjustment circuit with a diode connected to ground, which adjusts bias current or voltage based on RF signals to suppress the effect of reflected waves and maintain power gain stability during load changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clamp diodes are connected in output matching and RF signal is detected from an anode of a predetermined diode among the clamp diodes, then the power amplifier circuit can control bias voltage, but it lacks directivity and may be affected by reflected waves
Solution Approach 1:
The patent introduces a coupling circuit as an intermediary between the RF signal and the bias control mechanism. This coupling circuit selectively couples the RF signal while isolating the bias control from reflected waves, thus maintaining reliability without being affected by the harmful reflected waves.
Solution Approach 2:
The patent separates the bias control function from the output matching network by using a dedicated coupling circuit. This segmentation allows the bias voltage control to operate independently without being influenced by reflected waves in the output matching section, resolving the contradiction between reliability and susceptibility to reflected waves.
2Power
If the power amplifier circuit outputs higher power to compensate for increased load loss, then the power output increases, but the power gain becomes unstable when load changes
Solution Approach 1:
The patent employs feedback mechanisms where the coupling circuit continuously monitors the RF signal and provides feedback to adjust the bias voltage dynamically. This feedback control stabilizes the power gain even when output power is increased or load conditions change, resolving the contradiction between high power output and gain stability.
Solution Approach 2:
The patent makes the bias voltage dynamic rather than fixed, allowing it to adjust in response to changing load conditions and RF signal levels. This dynamic adaptation enables the power amplifier to maintain stable power gain across varying operating conditions while delivering high output power.
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 suppresses the impact of reflected waves and maintains power gain stability when load changes occur, preventing transistor damage from excessive RF signals.
Implementation Method 1
a first diode having an anode to which a control signal indicating a signal based on the first RF signal, the second RF signal, or the third RF signal is inputted
Data Source
AI summary
A power amplifier circuit includes a first amplifier that amplifies a first RF signal and outputs a second RF signal, a second amplifier that amplifies the second RF signal and outputs a third RF signal, a bias circuit that supplies a bias current or voltage to the first or second amplifier, and a bias adjustment circuit that adjusts the bias current or voltage on the basis of the first RF signal, the second RF signal, or the third RF signal. The bias adjustment circuit includes a first diode having an anode to which a control signal indicating a signal based on the first, second, or third RF signal is inputted, and a cathode connected to a ground. The bias circuit includes a bias transistor that outputs the bias current or voltage on the basis of a voltage at the anode of the first diode.