Load Modulation Amplifier With Dynamic Peak Impedance Control
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Solution Overview
Problem
Traditional Doherty power amplifiers experience efficiency decay at high frequencies due to parasitic capacitance and inductance, and digital pre-distortion techniques are undesirable for non-linear operation at millimeter wave frequencies, limiting output power efficiency and linearity in 5G wireless networks.
Innovation Solution
A load modulation amplifier with a carrier and peak amplifier coupled in parallel, utilizing a matching network and bias current to adjust output impedance monotonically with increasing power, enhancing efficiency and linearity without digital pre-distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional Doherty power amplifier is used, then high power backed off efficiency is improved, but efficiency decays linearly with frequency at millimeter wave frequencies
Solution Approach 1:
The patent changes the operating parameters of the peak amplifier by adjusting bias current and output impedance dynamically. The bias current is set to monotonically increase output impedance as output power increases, which compensates for frequency-dependent efficiency degradation at millimeter wave frequencies, thereby maintaining backed off efficiency across the frequency range.
2Reliability
If digital pre-distortion techniques are applied, then non-linear operation is corrected, but system complexity and cost increase
Solution Approach 1:
The peak amplifier is designed to self-regulate its output impedance through bias current control based on its operating state. This self-service mechanism inherently linearizes the amplifier operation without requiring external digital pre-distortion circuits, thereby maintaining linearity while reducing system complexity.
3Loss of energy
If peak amplifier output impedance is fixed, then circuit simplicity is maintained, but efficiency and linearity performance degrade at millimeter wave frequencies
Solution Approach 1:
The patent implements dynamic output impedance control in the peak amplifier by adjusting bias current. The output impedance monotonically increases as output power increases, which is a dynamic adaptation to operating conditions. This dynamic impedance control improves power added efficiency and linearity without requiring complex external impedance matching networks.
Data Source
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AI summary
A load modulation amplifier is disclosed. The load modulation amplifier includes a carrier amplifier for amplifying a radio frequency signal when input power of the radio frequency signal is below a predetermined power threshold value and a peak amplifier coupled in parallel with the carrier amplifier for amplifying the radio frequency signal when input power of the radio signal is above the predetermined power threshold value. The load modulation amplifier further includes an output quadrature coupler configured to combine power from both the carrier amplifier and the peak amplifier for output through an output load terminal. Output impedance of the peak amplifier monotonically increases with increasing output power at the output load terminal.