Common-Mode Harmonic Feedback Circuit for RF Amplifier Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power amplifiers generate undesirable harmonics in output RF signals, which violate spectrum mask regulations and cause error vector magnitude issues, impacting operational reliability.
Innovation Solution
Implementing a harmonic cancellation feedback circuit that uses a common mode sense circuit to generate a phase-shifted feedback signal, which is injected into the amplifier to cancel out harmonics in the output RF signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier amplifies an input RF signal, then the output signal power is increased, but harmonics are generated that violate spectrum mask regulations and cause EVM issues
Solution Approach 1:
The patent implements a feedback circuit that samples the output RF signal, extracts harmonic components, and feeds them back to the amplifier input with appropriate phase shifting and filtering. This feedback mechanism continuously monitors and corrects harmonic distortion, allowing the amplifier to maintain high output power while suppressing harmful harmonics through closed-loop control
Solution Approach 2:
The patent introduces an intermediary feedback network consisting of phase shifters, filters, and combiners that mediates between the amplifier output and input. This intermediary circuitry processes the output signal to extract harmonic components, applies necessary phase and amplitude transformations, and injects the processed signal back to cancel harmonics without directly affecting the main amplification path
2Object-generated harmful factors
If traditional feedback circuits are used to reduce harmonics, then harmonic suppression is achieved, but the circuit complexity increases significantly
Solution Approach 1:
The patent designs a feedback circuit where common mode components perform multiple functions: they sense output signal levels, extract harmonic information, provide phase shifting, and enable feedback injection. By making the common mode sense circuit and injection circuit multi-functional, the patent reduces the need for separate dedicated components for each function, thereby simplifying the overall circuit architecture while maintaining effective harmonic suppression
Solution Approach 2:
The patent merges the common mode sense circuit, phase shifting functionality, filtering, and feedback injection into an integrated feedback network. Rather than using separate independent circuits for each function, the patent combines these elements into a unified structure where the common mode injection circuit receives input from the common mode sense circuit and performs multiple operations in sequence, reducing component count and circuit complexity
Data Source
AI summary
An apparatus including: an amplifier configured to amplify an input radio frequency (RF) signal having a fundamental frequency to generate an output RF signal including the fundamental frequency and a harmonic of the fundamental frequency; a common mode sense circuit configured to generate an output common mode signal related to the output RF signal; a harmonic cancellation feedback circuit configured to generate a common mode feedback signal based on the output common mode signal; and a common mode injection circuit configured to inject the common mode feedback signal into the amplifier, wherein the common mode feedback signal reduces the harmonic in the output RF signal.