Power Amplifier Temperature Compensation for Burst Gain Stability
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Solution Overview
Problem
WiFi power amplifiers face challenges in maintaining constant gain over long bursts due to thermal effects, leading to increased Error Vector Magnitude (EVM) and dynamic EVM degradation, especially with more aggressive EVM requirements and longer bursts in newer standards like 802.11AC.
Innovation Solution
A temperature compensation circuit adjusts the gain of power amplifiers by generating a compensation signal based on temperature changes, using a temperature coefficient that is dependent on the amplifier's average temperature, allowing for optimal biasing across a range of temperatures, regardless of the thermal environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power amplifier operates over a long burst duration, then the throughput is improved, but the amplifier gain drops due to warming up
Solution Approach 1:
The patent changes the bias current parameter dynamically based on temperature. A temperature sensor monitors the amplifier's temperature, and the bias current is adjusted accordingly to compensate for gain droop. This allows the amplifier to maintain stable gain over long burst durations while achieving high throughput.
2Stability of the object's composition
If PTAT compensation is used to maintain constant gain over temperature, then gain stability is improved, but linearity deteriorates at extreme temperatures
Solution Approach 1:
The patent implements dynamic bias adjustment where the bias current is modified based on real-time temperature feedback. Unlike static PTAT compensation, this dynamic approach adjusts the bias point adaptively to maintain both gain stability and linearity across the full temperature range, preventing the linearity degradation that occurs with fixed PTAT compensation at extreme temperatures.
3Reliability
If the bias current is increased to maintain linearity at high temperatures, then linearity is improved, but power consumption increases
Solution Approach 1:
The patent dynamically adjusts the bias current parameter based on temperature conditions. At high temperatures, the bias current is increased only enough to maintain linearity, rather than using a fixed high bias current. This selective parameter adjustment maintains the necessary linearity while minimizing unnecessary power consumption during normal operating conditions.
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 solution ensures stable amplifier gain over long bursts, reducing EVM and improving performance across various temperatures, including room, low, and high temperatures, while also reducing current consumption and improving DEVM compensation compared to prior approaches.
Implementation Method 1
generating a compensation signal based on a temperature coefficient that is temperature dependent and an indication of temperature change relative to the initial temperature of the power amplifier
Implementation Method 2
a sampling circuit configured to capture an indication of initial temperature of the power amplifier when the power amplifier is energized
Implementation Method 3
the temperature compensation circuit is configured to adjust a reference signal based on the compensation signal to provide a bias signal. In another embodiment, the power amplifier is a multi-stage power amplifier, and a first stage of the power amplifier is configured to receive the bias signal to correct for gain drop over time for the power amplifier
Data Source
AI summary
A temperature compensation circuit comprises a temperature coefficient circuit that generates a temperature coefficient that is temperature dependent and a compensation circuit that generates a compensation signal based on an indication of temperature of an amplifier and the temperature coefficient, and based on the compensation signal, a gain of the amplifier is adjusted to improve amplifier linearity during data bursts.