Doherty Amplifier Bias Control for Variable PAPR Efficiency
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Solution Overview
Problem
Doherty amplifiers face sub-optimal performance due to being designed for specific peak-to-average power ratios (PAPRs), leading to degraded efficiency when actual deployments encounter different PAPRs, resulting in inefficient operation in communications networks.
Innovation Solution
A Doherty amplifier system with a programmable bias controller that adjusts carrier and peak amplifier bias levels based on dynamic PAPR data, using software-controllable bias voltages to optimize efficiency between 30% and 78.5%, allowing adaptation to varying PAPR conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the Doherty amplifier is designed for a specific PAPR, then the amplifier efficiency is optimized for that specific PAPR, but the amplifier performance degrades when deployed with different PAPR signals
Solution Approach 1:
The patent implements dynamic bias adjustment by making the bias levels of the carrier and peak amplifiers variable rather than fixed. The bias controller continuously adjusts the bias voltages based on real-time PAPR measurements, allowing the amplifier to adapt its operating point dynamically. This transforms the static amplifier design into a dynamic system that maintains optimal efficiency across varying PAPR conditions.
Solution Approach 2:
The patent changes the bias parameters (Vbias_carrier and Vbias_peak) based on the measured PAPR value. By establishing a relationship between PAPR and optimal bias levels, the system adjusts these parameters in real-time to match the current operating conditions. This parameter adaptation allows the amplifier to maintain peak efficiency regardless of whether the input signal has low, medium, or high PAPR.
2Reliability
If the Doherty amplifier is designed for high PAPR signals, then high PAPR performance is improved, but low PAPR performance suffers due to lower efficiency tents
Solution Approach 1:
The patent implements a feedback mechanism where the PAPR of the input signal is measured and used to control the bias levels. The PAPR measurement unit continuously monitors the signal characteristics, and this information feeds back to the bias controller which adjusts the bias voltages accordingly. This closed-loop feedback ensures that whether the signal is high PAPR or low PAPR, the amplifier operates at its optimal efficiency point for that specific condition.
3Device complexity
If the Doherty amplifier uses fixed bias levels, then the device complexity is reduced, but the ability to handle dynamic PAPR variations is lost
Solution Approach 1:
The patent introduces a PAPR measurement unit and bias controller as intermediary components between the input signal and the amplifier stages. These intermediaries measure the PAPR characteristic and translate it into appropriate bias control signals. While this adds some complexity, it enables the amplifier to automatically adapt to dynamic PAPR variations without requiring manual reconfiguration or complex hardware modifications to the core amplifier architecture.
Data Source
AI summary
A Doherty amplifier system (10) is disclosed having a carrier amplifier (12) with a carrier drain bias input (14), and a peak amplifier (24) having a peak drain bias input (26), and a peak gate bias input (28). Also included is a programmable bias controller (40) having a data interface configured to receive peak-to-average power ratio (PAPR) data associated with a basestation. The programmable bias controller (40) further includes a processor (46) coupled to the data interface and configured, in response to the PAPR data, to determine and apply bias levels to the carrier drain bias input (14), the peak drain bias input (26), and the peak gate bias input (28) to provide an amplifier efficiency between 30% and 78.5%.