Polar Feedback RF Amplifier Linearization Near Saturation
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Solution Overview
Problem
Existing RF signal amplification systems face challenges in achieving linear amplification efficiently, particularly at radio frequencies, due to inefficiencies and complexity in current feedback methods such as direct negative feedback and Cartesian feedback, which are not suitable for all RF applications like two-way radio communication.
Innovation Solution
A system utilizing polar feedback control, including a feedback-controlled modulator, power amplifier, amplitude detector, and polar feedback network to generate and correct amplitude and phase feedback signals, enabling efficient linear amplification of RF signals without the need for complex phase control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct negative feedback is applied to RF amplifiers, then linearization is achieved, but very high system gain is required which is difficult to obtain at radio frequencies
Solution Approach 1:
The patent introduces an intermediary baseband signal as a mediator between the RF output and the feedback control. The RF output is demodulated to baseband, and the feedback is applied in the baseband domain where high gain is easily achievable. This baseband intermediary resolves the contradiction by allowing strong feedback action without requiring high RF gain.
Solution Approach 2:
The patent replaces the direct RF feedback mechanism with a baseband equivalent mechanism. Instead of applying feedback directly at RF frequencies where high gain is difficult, the system substitutes a baseband feedback path that achieves the same linearization effect with much easier gain requirements.
2Manufacturing precision
If Cartesian feedback system is used, then feedback control is implemented, but the system becomes complex and expensive requiring tightly controlled phase characteristics
Solution Approach 1:
The patent extracts only the necessary feedback function from the complex Cartesian feedback system. Instead of implementing full IQ demodulation and modulation with tight phase control, the system takes out the essential feedback action and applies it in a simplified baseband domain, eliminating the need for complex phase control mechanisms.
Solution Approach 2:
The patent replaces expensive, complex Cartesian feedback components with simpler, more economical baseband feedback components. The simplified baseband approach achieves the same linearization effect without requiring costly tightly-controlled phase characteristics and complex auxiliary control systems.
3Loss of energy
If amplifier is operated at maximum power capacity, then efficiency is improved, but distortion increases
Solution Approach 1:
The patent applies feedback control in the baseband domain to correct the nonlinearities that occur when the amplifier operates at maximum power capacity. The feedback mechanism detects distortion and generates correction signals that linearize the amplifier output, allowing efficient operation without sacrificing signal quality.
Solution Approach 2:
The patent applies feedback correction in advance to prevent distortion from affecting the final output. By operating the amplifier at maximum capacity and then applying preliminary feedback correction in the baseband domain, the system achieves both efficiency and linearity.
Data Source
AI summary
A system for power amplification of an RF signal including polar feedback control. The system may include a feedback-controlled modulator configured to modulate an RF signal based on a feedback-corrected control signal. The modulator is further configured to generate a modulated RF signal. The system also may include a phase shifter configured to correct the phase of the modulated RF signal based on a feedback phase control signal. The system further includes a power amplifier in communication with the modulator and/or the phase shifter. The amplifier is configured to amplify the modulated RF signal and to generate an amplified RF output signal. The system also includes a feedback network configured to generate polar feedback signals, including the feedback-corrected control signal and/or the feedback phase control signal.