RF Power Amplifier Constant Gain Using a Reference Amplifier
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Solution Overview
Problem
RF power amplifiers experience significant gain variations due to changes in supply voltage, leading to fluctuations that degrade signal quality and are difficult to accurately compensate for using existing techniques.
Innovation Solution
A system comprising a main amplifier and a reference amplifier, both operating on a variable supply voltage, with a gain control loop that produces a gain control signal to compensate for variations in the reference amplifier, which is then applied to the main amplifier to maintain constant gain, utilizing a constant-envelope signal for stable and accurate gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a variable supply voltage is applied to the power amplifier to improve efficiency, then energy efficiency is improved, but gain stability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the output of the reference amplifier is fed back to control the gain of both the reference and main amplifiers. The gain control loop continuously monitors the reference amplifier output and adjusts the gain control signal to compensate for gain variations caused by supply voltage changes, thereby maintaining stable gain while operating with variable supply voltage for improved efficiency.
Solution Approach 2:
The patent uses a reference amplifier that replicates the gain characteristics of the main power amplifier. By creating this copy and controlling it separately with a constant supply voltage, the system can measure and compensate for gain variations without affecting the main amplifier's efficiency-optimized variable supply voltage operation.
2Ease of operation
If existing ALC techniques are used to compensate for gain variations, then gain control is achieved, but compensation accuracy deteriorates due to difficulty in accurately tracking gain variations
Solution Approach 1:
The reference amplifier creates an accurate copy of the main amplifier's gain characteristics by operating with the same variable supply voltage. This copying approach allows direct measurement of gain variations without the complexity and inaccuracies of trying to track and model gain variations through separate sensing and calculation circuits.
Solution Approach 2:
The reference amplifier acts as an intermediary that translates the main amplifier's gain variations into a measurable signal. Instead of directly measuring the main amplifier's gain variations, the system uses the reference amplifier as a mediator to convert these variations into a control signal that can be used for accurate compensation.
Data Source
AI summary
A method includes amplifying a non-constant-envelope input signal using a main amplifier having a first gain that varies depending on a supply voltage of the main amplifier. A constant-envelope signal is amplified using a reference amplifier having a second gain that varies depending on the supply voltage of the reference amplifier. Both the main amplifier and the reference amplifier are operated using a same variable supply voltage whose amplitude varies over time. A gain control signal is produced so as to compensate for changes in the second gain of the reference amplifier that are caused by the variable supply voltage. The gain control signal is applied in compensating for variations in the first gain of the main amplifier.