Balanced RF Power Amplifier Current Detection Under VSWR Mismatch
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Solution Overview
Problem
Conventional RF power amplifiers face challenges in maintaining linearity and power control, especially under voltage standing wave ratio (VSWR) mismatch conditions, leading to signal distortion and power loss in high peak-to-average ratio linear transmitter systems.
Innovation Solution
A balanced RF power amplifier system with a phase splitter, in-phase and out-of-phase power amplifier branches, and a phase combiner, along with in-phase and out-of-phase branch current detectors and detection circuitry that combine current indications to accurately detect output power, enabling effective power control and maintaining constant current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If forward power detection using a coupler and detector is implemented, then output power can be detected, but signal compression occurs in high peak-to-average ratio linear transmitter systems under high impedance load phases
Solution Approach 1:
The patent introduces an intermediary current detection mechanism that measures current through the amplifying transistor rather than directly detecting forward power. This intermediary approach (detecting collector current) avoids the signal compression issue that occurs with conventional forward power detection in high peak-to-average ratio systems, while still enabling accurate output power detection through the relationship between current and power.
2Stability of the object's composition
If collector voltage detection is used to maintain constant voltage, then phase shift from VSWR matching circuitry is compensated, but output power drops significantly under mismatch conditions
Solution Approach 1:
The patent changes the detection parameter from voltage (collector voltage) to current (collector current). By detecting current instead of voltage, the system avoids the energy loss and output power drop that occur when trying to maintain constant voltage under VSWR mismatch conditions. The current detection approach naturally compensates for impedance variations without causing significant power loss.
3Device complexity
If conventional current mirror detection is used, then simple current detection is achieved, but linearity performance degrades under VSWR mismatch conditions
Solution Approach 1:
The patent implements a feedback mechanism where the detected current signal is fed back to control the power amplifier operation. This feedback loop ensures that linearity performance is maintained under VSWR mismatch conditions while still using a relatively simple current detection approach. The feedback compensates for the limitations of the current mirror detection method.
Data Source
AI summary
A radio frequency (RF) power amplifier system having a power detection feature includes a balanced power amplifier, an in-phase branch current detector, an out-of-phase branch current detector, and detection circuitry. The balanced power amplifier includes a phase splitter, an in-phase power amplifier branch, an out-of-phase power amplifier branch, and a phase combiner. The in-phase branch current detector provides an indication of current in the in-phase power amplifier branch. The out-of-phase branch current detector provides an indication of current in the out-of-phase power amplifier branch. The detection circuitry combines the indications of current in the in-phase and out-of-phase power amplifier branches to produce an indication of current in the balanced power amplifier.