Envelope Tracking Amplifier Control for Bandwidth-Stable Gain
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Solution Overview
Problem
In envelope tracking controlled amplifiers, power supplies used in transmitters show a dependency on signal characteristics, leading to a decrease in supply voltage with increasing bandwidth, causing deviations from desired gain trajectories and increased Adjacent Channel Leakage Rate (ACLR).
Innovation Solution
A circuit and method that generate a control signal based on the bandwidth of the baseband signal to compensate for variations in the supply voltage, using an envelope tracking circuit to adjust the power supply voltage, ensuring the amplifier operates on a desired gain trajectory independent of bandwidth, thereby maintaining constant signal gain across wide power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to adjust supply voltage based on instantaneous power demand, then amplifier efficiency is improved, but supply voltage becomes dependent on signal bandwidth causing gain trajectory deviations
Solution Approach 1:
The system measures the actual supply voltage at the amplifier input and uses this feedback to dynamically adjust the control signal to the power supply. This closed-loop feedback mechanism compensates for bandwidth-dependent voltage drops, ensuring the amplifier receives the correct supply voltage regardless of signal characteristics, thus maintaining accurate gain trajectory while preserving efficiency benefits
Solution Approach 2:
The system dynamically changes the control voltage parameter supplied to the power supply based on measured supply voltage conditions and signal bandwidth. By adjusting this control parameter in real-time, the system compensates for power supply gain variations caused by different signal bandwidths, ensuring consistent amplifier performance across varying operating conditions
2Power
If DC-to-DC converter gain decreases with increasing input signal bandwidth, then supply voltage becomes insufficient, but increasing supply voltage without compensation causes gain trajectory deviation
Solution Approach 1:
The system continuously monitors the actual supply voltage at the amplifier input and uses this feedback information to adjust the control signal to the power supply. This ensures that regardless of bandwidth-induced gain variations in the DC-to-DC converter, the amplifier receives the precise supply voltage needed to maintain the desired gain trajectory
Solution Approach 2:
The system performs preliminary measurement of the supply voltage before it reaches the amplifier and proactively adjusts the power supply control signal in advance. This preliminary action compensates for upcoming bandwidth-related voltage drops, ensuring the amplifier always receives the correct supply voltage level before any performance degradation occurs
Data Source
AI summary
A circuit for generating a radio frequency signal is provided. The circuit includes an amplifier configured to generate a radio frequency signal based on a baseband signal. Further, the circuit includes a power supply configured to generate a variable supply voltage based on a control signal indicating a desired supply voltage, and to supply the variable supply voltage to the amplifier. The circuit further includes an envelope tracking circuit configured to generate the control signal based on a bandwidth of the baseband signal, and to supply the control signal to the power supply.