Amplitude Error De-glitching Circuit for RF Power Amplifier
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Solution Overview
Problem
Conventional RF power amplifier (PA) systems face inefficiencies due to wide spectral occupancy and amplitude-to-phase modulation (AM-to-PM) distortion, especially in high peak to average modulation techniques, leading to significant power consumption and compromised spectral occupancy performance.
Innovation Solution
A power amplifier controller circuit with an amplitude control loop and phase control loop that adjusts the supply voltage and phase of the RF signal to minimize AM-to-PM distortion, using a switched mode power supply and variable gain amplifier to optimize efficiency and spectral occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the output transistor is biased to remain linear at peak power transmitted, then spectral occupancy is improved, but power consumption increases significantly during off-peak periods
Solution Approach 1:
The patent implements dynamic biasing control where the output transistor's bias point is continuously adjusted based on the instantaneous amplitude of the RF input signal. During peak power periods, the transistor is biased to maintain linearity and acceptable spectral occupancy. During off-peak periods, the bias is reduced to minimize power consumption. This dynamic adaptation resolves the contradiction by allowing the system to optimize for spectral occupancy when needed and for power efficiency when the signal amplitude is low.
2Manufacturing precision
If fixed biasing is used to maintain linearity at peak power, then distortion is reduced, but efficiency drops to below 30% during off-peak amplitude periods
Solution Approach 1:
The system dynamically adjusts the biasing condition of the output transistor based on the RF signal amplitude. When the input signal is at peak power, the transistor is biased to operate in the linear region to minimize distortion. When the signal amplitude decreases during off-peak periods, the bias is reduced to allow the transistor to operate more efficiently, accepting some non-linearity that is corrected by the feedback loop. This dynamic biasing strategy resolves the contradiction between maintaining linearity and preserving energy efficiency.
Solution Approach 2:
The patent employs a feedback control mechanism where the actual output signal is monitored and compared with the desired output. The error signal generated by this comparison is used to adjust the biasing and operating conditions of the output transistor in real-time. This feedback enables the system to maintain acceptable linearity and spectral occupancy while dynamically optimizing power efficiency, resolving the contradiction between distortion reduction and energy loss.
3Loss of energy
If EER technique is used to vary supply voltage based on amplitude signal, then efficiency gains are attempted, but the technique fails to provide significant efficiency improvement due to difficulty in realizing fast accurate voltage converter
Solution Approach 1:
The patent extracts and addresses only the critical portion of the EER technique by focusing on dynamic biasing control of the output transistor rather than attempting to implement the complete EER architecture with its complex voltage converter. By taking out the essential function of amplitude-based efficiency optimization and implementing it through a simplified biasing control mechanism, the system achieves efficiency improvement without the complexity of a fast accurate voltage converter.
Data Source
AI summary
A power amplifier controller circuit controls a power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the input signal and an attenuated amplitude of the output signal. The power amplifier controller circuit comprises an amplitude control loop and a phase control loop. The amplitude control loop adjusts the supply voltage to the power amplifier based upon the amplitude correction signal. The RF power amplifier system may reduce the corrective action of the amplitude loop during periods of relatively rapid changes in amplitude, and thus distortion can be further reduced.