RF Power Amplifier Circuit Balancing Efficiency and Bandwidth
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Solution Overview
Problem
RF amplifiers in mobile communication terminals face reduced average power efficiency when handling RF signals with variable signal envelopes, as the output stage is driven at below optimal levels due to varying power levels, leading to bandwidth widening issues that can compromise power efficiency.
Innovation Solution
A power amplifier circuit comprising a main amplifier, an auxiliary amplifier, and a signal processing circuit with a non-linear processing section that dynamically adjusts the degree of non-linearity based on the rate of change of the input signal's amplitude characteristic, restricting bandwidth expansion and optimizing power efficiency by varying the non-linear dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single amplifier device is used to provide RF output signal with variable signal envelope, then the device complexity is reduced, but the average power efficiency deteriorates because the amplifier is driven at variable power levels below optimal efficiency points
Solution Approach 1:
The amplifier is divided into a main amplifier device and one or more auxiliary amplifier devices. The main amplifier operates continuously at its optimal efficiency point, while auxiliary amplifiers are activated only when additional power is needed. This segmentation allows the system to maintain high average power efficiency by keeping at least one amplifier operating at its peak efficiency point regardless of the overall power level required.
2Use of energy by moving object
If auxiliary amplifier is driven with strongly non-linear functional dependency from signal envelope, then the power efficiency is improved, but the bandwidth of driving signal widens which may exceed component bandwidth limits
Solution Approach 1:
The patent introduces dynamic control of the auxiliary amplifier's drive signal envelope based on the instantaneous power level requirements. The control circuit dynamically adjusts the auxiliary amplifier's contribution by modulating its drive signal envelope according to the main amplifier's output power level and the desired total output power, thereby optimizing efficiency while controlling bandwidth expansion.
Solution Approach 2:
The patent changes the parameter of non-linearity degree dynamically. Instead of using a fixed strong non-linear function for the auxiliary amplifier drive, the system adjusts the degree of non-linearity based on the rate of change of the signal envelope. When the signal envelope changes slowly, a higher degree of non-linearity is applied for maximum efficiency. When the signal envelope changes rapidly, the degree of non-linearity is reduced to control bandwidth expansion.
3Use of energy by moving object
If the degree of non-linearity is increased for auxiliary amplifier driving, then the average power efficiency is improved, but the bandwidth expansion increases which may compromise efficiency at higher signal bandwidths
Solution Approach 1:
The system dynamically adapts the degree of non-linearity in the auxiliary amplifier drive signal based on the instantaneous rate of change of the signal envelope. This dynamic adjustment allows the amplifier to maintain high efficiency for slowly varying signals while controlling bandwidth expansion for rapidly varying signals, thus adapting to different signal conditions in real-time.
Solution Approach 2:
The patent changes the parameter of non-linearity degree as a function of the signal envelope's rate of change. For slowly varying signal envelopes, a higher degree of non-linearity is applied to maximize power efficiency. For rapidly varying signal envelopes, the degree of non-linearity is reduced to limit bandwidth expansion, thereby maintaining both efficiency and bandwidth adaptability across different operating conditions.
Data Source
AI summary
An amplifier circuit is disclosed for providing a radio frequency output signal having a variable signal envelope, comprising a main amplifier device and an auxiliary amplifier and a combiner network for combining an output signal from said first amplifier device and a second output signal from said second amplifier device to provide a combined output signal of variable signal envelope to a load, and a signal processing circuit comprising an input and a non-linear processing section to provide at least said second radio frequency output signal with a signal envelope that has a non-linear dependency from an amplitude characteristic of the input signal such that the degree of non-linearity of the non-linear dependency varies dependent on the amount of change per time unit of the amplitude characteristic of the input signal. Further, a method of power amplifying a radio frequency signal having a variable signal envelope is disclosed.