Power Amplifier Temperature Correction Circuit for Dynamic EVM Control
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Solution Overview
Problem
Traditional static Error Vector Magnitude (EVM) calculations for power amplifiers do not account for dynamic thermal behavior, which is crucial in Time Division Duplex (TDD) systems and flip chip packages, especially in wide temperature range bipolar power amplifiers aiming for low DEVM levels.
Innovation Solution
A temperature correction circuit that generates a reference current (Iref) using first and second correction currents proportional to absolute and changing temperatures of the semiconductor die, respectively, to maintain the power amplifier transistor in a linear operating region, incorporating current mirrors and sub-circuits to produce and adjust the reference current based on temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional static EVM calculations are used for power amplifiers, then the calculation is simple and based mainly on amplitude-to-amplitude and amplitude-to-phase modulations, but it does not capture the dynamic thermal behaviour which is important in TDD systems and flip chip packages
Solution Approach 1:
The temperature correction circuit is segmented into multiple independent current sources: a first current source for static temperature correction, a second current source for dynamic temperature correction, and a third current source for gain selection. Each current source independently generates correction currents that are combined to form the reference current, allowing modular implementation and maintenance of calculation simplicity while improving measurement precision through comprehensive thermal behavior capture
Solution Approach 2:
The patent introduces temperature correction current as an intermediary element that mediates between the temperature sensor outputs and the power amplifier bias. The correction currents from multiple current sources are combined and applied to adjust the reference current, serving as an intermediate correction mechanism that captures dynamic thermal behavior without requiring direct complex control of the power amplifier, thus improving EVM calculation accuracy while managing circuit complexity
2Reliability
If power gain stabilization is implemented in wide temperature range bipolar power amplifiers to target low DEVM levels, then DEVM levels are reduced, but the circuit complexity increases with multiple current sources and temperature correction mechanisms
Solution Approach 1:
The gain compensation circuit is divided into three separate current sources, each responsible for a specific correction function. The first current source handles static temperature effects, the second handles dynamic temperature effects, and the third handles gain selection. This segmentation allows the circuit to achieve power gain stability across wide temperature ranges while keeping each individual current source relatively simple, thus improving reliability without excessive complexity
Solution Approach 2:
The temperature correction circuit is designed with multi-functional current sources that can operate under different conditions. The same current mirror structure and correction mechanism are used for both static and dynamic temperature compensation, as well as for gain selection. This universal approach allows the circuit to maintain power gain stability across various temperature ranges and operating conditions while avoiding the need for completely separate correction circuits for each function, thereby improving reliability while controlling overall circuit complexity
Data Source
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AI summary
A temperature correction circuit and method for maintaining a transistor of a power amplifier in a linear operating region of the transistor. The temperature correction circuit includes a first current source circuit operable to provide a first correction current proportional to an absolute temperature of a semiconductor die including the transistor. The temperature correction circuit also includes a second current source circuit operable to provide a second correction current proportional to a change in temperature of a part of the semiconductor die in which the transistor is located during operation of the transistor. The temperature correction circuit further includes a third current source circuit operable to provide a gain selection current. The temperature correction circuit also includes circuitry for producing a reference current from the first and second correction currents and the gain current. The temperature correction circuit further includes an output for providing the reference current to the transistor.