Temperature-Dependent PA Biasing for Dynamic EVM Control
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Solution Overview
Problem
Power amplifiers (PAs) experience gain and phase variance during transitions from idle to steady-state conditions, leading to increased dynamic error vector magnitude (EVM) due to temperature fluctuations, which current solutions like waiting for thermal settling or using external passive networks cannot effectively mitigate without introducing delays or requiring extensive tuning.
Innovation Solution
A method and circuit for power amplifiers that utilize a temperature sensor proximate to the amplifier circuitry to generate a temperature-dependent bias signal, adjusting the biasing to maintain desired gain and phase responses, thereby reducing dynamic EVM by providing real-time temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the PA waits for thermal settling before amplifying signals, then gain and phase stability is improved, but transmission delay increases
Solution Approach 1:
The bias circuit applies a speed-up bias current to the amplifier circuitry before the RF input signal arrives, pre-heating the circuitry and reducing the thermal settling time. This preliminary action allows the PA to reach its operating temperature faster, thereby reducing transmission delay while maintaining gain and phase stability.
Solution Approach 2:
The bias circuit changes the bias current parameter dynamically - applying a higher speed-up bias current during the transient period and then transitioning to a standard bias current under steady-state conditions. This parameter change enables the PA to quickly reach operational temperature without compromising the stability of gain and phase response.
2Speed
If external passive networks (resistor and capacitor) are used to reduce settling time, then thermal settling speed is improved, but device complexity and tuning requirements increase
Solution Approach 1:
The invention extracts the thermal management function from external passive components and implements it within the bias circuit itself. The bias circuit directly controls the heating rate of the amplifier circuitry through electronic bias current adjustment, eliminating the need for external resistors and capacitors, thereby reducing device complexity and tuning requirements.
Solution Approach 2:
The bias circuit provides self-service by internally generating and applying the speed-up bias current to its own amplifier circuitry. This self-contained approach eliminates dependence on external passive networks and reduces the overall system complexity while achieving fast thermal settling.
3Duration of action of stationary object
If the speed-up capacitor is used to provide forward current, then settling time is reduced, but dynamic EVM at signal onset remains elevated
Solution Approach 1:
The bias circuit applies the speed-up bias current in advance, before the RF input signal arrives. This preliminary heating action ensures that the amplifier circuitry is already at its operational temperature when the signal begins, eliminating the transient gain and phase variations that cause elevated dynamic EVM at signal onset.
Solution Approach 2:
The speed-up bias current performs a preliminary anti-action by pre-heating the amplifier circuitry to counteract the inevitable temperature rise that would occur during signal transmission. This prevents the thermal transients from affecting the gain and phase response, thereby maintaining low dynamic EVM performance from the very beginning of signal transmission.
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
This approach reduces dynamic EVM by ensuring accurate and timely biasing, allowing power amplifiers to operate without undesirable delays and minimizing the need for external components or extensive fine-tuning, while maintaining consistent gain and phase responses during RF signal transmission.
Implementation Method 1
sensing circuitry for sensing a temperature of amplifier circuitry and for generating a temperature signal in dependence upon the temperature
Implementation Method 2
bias circuitry connected to the temperature sensing circuitry and for generating a temperature dependent bias signal in dependence upon the temperature signal
Data Source
AI summary
A circuit and method are provided for reducing dynamic EVM of a power amplifier (PA) used for RF communication. A temperature dependent boost bias signal is applied to the bias input port of amplifier circuitry of the PA in dependence upon a temperature of the amplifier circuitry to compensate for transience in the gain or phase response of the PA while components of the PA is differentially warming-up, advantageously taking into account an actual temperature of the amplifier circuitry.