Envelope Tracking Power Supply Modulation for RF Linear Amplifiers
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Solution Overview
Problem
Wireless communication devices require RF circuitry that is low cost, small, simple, and efficient to accommodate various wireless communication protocols while minimizing size, cost, and power consumption, and to efficiently handle amplitude-modulated RF signals through envelope tracking.
Innovation Solution
The implementation of a linear amplifier and power supply system that selects optimal supply voltages based on the desired envelope power supply signal, allowing the voltage to track the envelope of the RF transmit signal, reducing voltage drop in the linear amplifier, and toggling between DC power source and linear amplifier power supply voltages to maintain efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage of the envelope power supply signal is increased to accommodate the envelope of the RF transmit signal, then proper operation of the RF PA is ensured, but power consumption increases
Solution Approach 1:
The linear amplifier supply voltage is dynamically selected from multiple available voltages based on the instantaneous envelope amplitude. The voltage selection circuit monitors the envelope signal and switches between different supply voltages to match the instantaneous power requirements, ensuring the RF PA operates reliably only when needed while minimizing power consumption during low-envelope periods.
Solution Approach 2:
The system changes the supply voltage parameter of the linear amplifier according to the envelope amplitude. By adjusting the supply voltage to match the instantaneous envelope level, the system ensures sufficient voltage headroom for proper RF PA operation during high-power periods while reducing voltage and power consumption during low-power periods.
2Use of energy by moving object
If the voltage of the envelope power supply signal tracks the envelope of the RF transmit signal to increase efficiency, then power consumption is reduced, but the voltage may be insufficient to accommodate the envelope
Solution Approach 1:
The system dynamically switches between multiple discrete supply voltage levels rather than using continuous tracking. This dynamic voltage selection ensures that at any instantaneous moment, the selected voltage is sufficient for the current envelope amplitude, preventing operation failures while still reducing power consumption by selecting lower voltages when the envelope amplitude is low.
Solution Approach 2:
The system uses a set of discrete voltage levels that may slightly exceed the minimum required voltage for each envelope amplitude level. This partial over-provisioning ensures reliable operation even with voltage transitions and ripple, while the discrete nature of the voltage levels prevents continuous excessive voltage application, balancing reliability and efficiency.
3Device complexity
If a single DC power source provides all linear amplifier supply voltages, then system simplicity is maintained, but the ability to reduce voltage drop and improve efficiency is limited
Solution Approach 1:
The power supply system is segmented into multiple independent voltage sources instead of using a single DC source. This segmentation allows the system to select the most appropriate voltage source for each operating condition, minimizing voltage drop by choosing sources that can deliver the required voltage without excessive current draw, thereby reducing energy loss.
Solution Approach 2:
Multiple power sources are provided, each capable of supplying linear amplifier supply voltages under different operating conditions. This multi-functionality allows the system to switch between sources based on efficiency requirements, with some sources optimized for low-voltage operation and others for high-voltage operation, reducing overall energy loss.
Data Source
AI summary
Circuitry, which includes a linear amplifier and a linear amplifier power supply, is disclosed. The linear amplifier at least partially provides an envelope power supply signal to a radio frequency (RF) power amplifier (PA) using a selected one of a group of linear amplifier supply voltages. The linear amplifier power supply provides at least one of the group of linear amplifier supply voltages. Selection of the selected one of the group of linear amplifier supply voltages is based on a desired voltage of the envelope power supply signal.