Balanced Power Amplifier Impedance Adaptation
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Solution Overview
Problem
Variations in antenna impedance cause mismatched impedances between power amplifiers and antennas, leading to decreased linearity, power efficiency, and potential damage to power amplifiers due to reflected power.
Innovation Solution
A balanced power amplifier adjusts its operating conditions based on measurements of the antenna's impedance, using three measurements to determine the magnitude and sign of the reflection coefficient, allowing for dynamic adjustments to maintain efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power amplifier operates with fixed impedance matching, then the design is simple and stable, but the performance degrades when antenna impedance varies due to beamforming or user proximity
Solution Approach 1:
The patent implements dynamic impedance adjustment by continuously monitoring the antenna impedance through measurements at the isolated port and adjusting the power amplifier's operating conditions in real-time. This transforms the static impedance matching into a dynamic system that adapts to varying antenna impedance caused by beamforming operations or user proximity, thereby maintaining reliability without requiring complex pre-configured impedance matching networks
Solution Approach 2:
The patent employs feedback mechanisms by measuring the impedance at the isolated port of the quadrature combiner and using this information to adjust the operating conditions of the power amplifiers. This closed-loop feedback system enables the power amplifier to automatically compensate for impedance variations, resolving the contradiction between maintaining simple fixed-matching design and adapting to variable antenna impedance conditions
2Measurement precision
If three measurements are performed to determine reflection coefficient magnitude and sign, then the impedance detection precision is improved, but the measurement complexity and processing time increase
Solution Approach 1:
The patent uses the isolated port of the quadrature combiner, which is already part of the standard power amplifier architecture, to perform impedance measurements. This existing component serves multiple functions: combining the quadrature signals and simultaneously providing a measurement point for impedance detection. By reusing this existing structure for measurement purposes, the patent achieves precise reflection coefficient measurement without adding separate dedicated measurement hardware, thus avoiding increased device complexity
3Use of energy by moving object
If the operating conditions are dynamically adjusted based on antenna impedance, then the power efficiency and linearity are improved, but the control system complexity increases
Solution Approach 1:
The patent adjusts operating parameters such as bias voltages and supply voltages of the power amplifiers based on the measured antenna impedance. By dynamically changing these electrical parameters in response to impedance variations, the system maintains optimal power efficiency and linearity performance without requiring complex structural modifications or additional control hardware beyond basic voltage adjustment capabilities
Data Source
AI summary
In an example aspect, an apparatus includes a balanced power amplifier, which performs amplification in the presence of a variable antenna impedance. The balanced power amplifier includes a quadrature output power combiner coupled to a first power amplifying path and a second power amplifying path, detection circuitry, and control circuitry. The detection circuitry includes at least one power detector coupled to an isolated port of the quadrature output power combiner and a resistor coupled between the isolated port and a ground. The at least one power detector is configured to measure power at the isolated port, which is based on a resistance of the resistor. The control circuitry is configured to adjust operating conditions of a first power amplifier of the first power amplifying path and the second power amplifier of the second power amplifying path based on the power that is measured at the isolated port.