RF Amplifier Gate Bias Modulation Using Shaped Envelope Signals
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Solution Overview
Problem
Existing RF power amplifiers face challenges in achieving high efficiency, high fractional bandwidth, and high linearity simultaneously, as many designs with high theoretical power efficiencies often have lower fractional bandwidths and reduced linearity.
Innovation Solution
The use of gate bias modulation with a shaped envelope signal, applied to the transistors of RF amplifiers, facilitated by attenuators and phase shifters that can be digitally controlled, to enhance amplifier performance by optimizing transistor operation for both efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high theoretical power efficiency amplifier designs are used, then power efficiency is improved, but fractional bandwidth and linearity deteriorate
Solution Approach 1:
The patent applies dynamics by making the amplifier's operating class可调 (adjustable) through envelope signal shaping. The amplifier can dynamically transition between different operating classes (e.g., Class C to Class A) based on the instantaneous envelope signal characteristics, enabling high efficiency during peak power operation while maintaining linearity during low power operation, thus resolving the bandwidth-efficiency tradeoff
Solution Approach 2:
The patent changes the bias parameter dynamically through envelope signal shaping. By shaping the envelope signal to provide appropriate gate bias modulation, the amplifier's operating point is continuously adjusted to optimize both efficiency and linearity across different signal conditions and frequency ranges, thereby improving fractional bandwidth without sacrificing efficiency
2Loss of energy
If high theoretical power efficiency amplifier designs are used, then power efficiency is improved, but linearity deteriorates
Solution Approach 1:
The amplifier dynamically adjusts its operating class based on the envelope signal amplitude. During low power operation, it operates in a more linear mode (Class A/AB), while during peak power operation, it transitions to a more efficient but less linear mode (Class C), with the envelope shaping compensating for the non-linearity, thus achieving both high efficiency and high linearity simultaneously
Solution Approach 2:
The envelope signal shaping mechanism provides a form of feedback control where the instantaneous envelope of the input signal is detected and used to modulate the gate bias. This feedback loop continuously optimizes the amplifier's operating point to maintain linearity while maximizing efficiency, resolving the contradiction between these two parameters
3Loss of energy
If gate bias modulation with shaped envelope signal is applied, then power efficiency and linearity are improved, but device complexity increases
Solution Approach 1:
The envelope signal generator and shaping circuitry serves multiple functions: it generates the envelope signal, shapes it to provide gate bias modulation, and simultaneously controls the amplifier's operating class. This multi-functionality reduces the need for separate control circuits, thereby minimizing the increase in device complexity while achieving improved efficiency and linearity
Data Source
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AI summary
The embodiments described herein include amplifiers configured for use in radio frequency (RF) applications. In accordance with these embodiments, the amplifiers are implemented to generate a shaped envelope signal, and to apply the shaped envelope signal to transistor gate(s) of the amplifier to provide gate bias modulation. So configured, the shaped envelope signal may facilitate high linearity in the amplifier.