Envelope Tracking PA Gain Shaping for PAE and Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power amplifiers in RF communication systems face challenges in achieving high peak power added efficiency (PAE) while maintaining linearity, particularly when using envelope tracking, as gain boosting circuits often degrade performance at low and high supply voltage levels.
Innovation Solution
Implementing a gain shaping circuit that adjusts gain shaping current based on the supply voltage level, using a combination of current steering circuits and a regulator to generate reference voltages, allowing for flexible gain expansion and reduction, thereby enhancing PAE by up to 2% while maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If gain boosting circuits are used to enhance PAE, then peak power added efficiency is improved, but linearity performance degrades at low and high supply voltage levels
Solution Approach 1:
The gain shaping circuit dynamically adjusts the gain shaping current based on the supply voltage level, transitioning between different gain expansion characteristics as voltage changes. This dynamic adaptation allows the circuit to maintain optimal performance across varying operating conditions, resolving the contradiction between PAE enhancement and linearity maintenance.
Solution Approach 2:
The circuit changes the gain expansion parameter based on supply voltage level. At moderate voltage levels, higher gain expansion is applied to boost PAE, while at low and high voltage levels, the gain expansion is reduced to preserve linearity. This parameter adaptation resolves the contradiction by adjusting the operating characteristics according to the supply voltage condition.
2Use of energy by moving object
If gain shaping current is increased to provide gain expansion, then PAE is enhanced, but memory effects increase
Solution Approach 1:
The gain shaping current parameter is dynamically changed based on supply voltage level. By reducing the gain shaping current at extreme voltage levels (low and high), the circuit minimizes memory effects while still providing PAE enhancement at moderate voltage levels where the current is optimized.
3Use of energy by moving object
If envelope tracking is used to control supply voltage, then power efficiency is improved, but gain linearity control becomes more difficult
Solution Approach 1:
The gain shaping circuit uses feedback from the supply voltage level to automatically adjust the gain shaping current. This feedback mechanism simplifies the overall control by allowing the circuit to self-adjust according to the envelope tracking voltage variations, reducing the complexity of manual gain control while maintaining linearity.
Solution Approach 2:
The gain shaping circuit acts as an intermediary between the envelope tracker and the power amplifier gain control. It translates the supply voltage level into appropriate gain adjustments, simplifying the control architecture by decoupling the envelope tracking function from direct gain control.
Data Source
AI summary
Envelope tracking power amplifiers with advanced gain shaping are provided. In certain implementations, a power amplifier system includes a power amplifier that amplifies a radio frequency (RF) signal and an envelope tracker that controls a voltage level of a supply voltage of the power amplifier based on an envelope of the RF signal. The power amplifier system further includes a gain shaping circuit that generates a gain shaping current that changes with the voltage level of the supply voltage from the envelope tracker. For example, the gain shaping circuit can include an analog look-up table (LUT) mapping a particular voltage level of the supply voltage to a particular current level of gain shaping current. Additionally, the gain shaping circuit biases the power amplifier based on the gain shaping current.