Linearity Measurement Using Multi-Tone Signal Cancellation
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Solution Overview
Problem
Existing measurement methods for circuit linearity, particularly in power amplifiers for wireless communication systems, require multiple instruments, leading to high costs and complexity, especially when dealing with nonlinear operations that introduce intermodulation distortion.
Innovation Solution
A method and apparatus utilizing a signal generator to output tone test signals and a cancel tone signal, with a signal analyzing device to detect intermodulation power and phase, allowing for the minimization of total power by adjusting the phase of the cancel tone signal, thereby reducing the need for multiple instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple single-tone signal generators are used to output test signals and cancel tone signals separately, then measurement precision can be maintained, but device complexity and cost increase significantly
Solution Approach 1:
The patent combines multiple single-tone signal generators into a single multi-tone signal generator that can output multiple test signals and cancel tone signals simultaneously. This merging reduces the number of instruments from multiple separate generators to one integrated device, thereby reducing system complexity and cost while maintaining the capability to perform precise linearity measurements through multi-tone signal generation.
Solution Approach 2:
The signal generator in this patent is designed with multi-functionality, serving both as a test signal generator and a cancel tone signal generator. This universal device can operate in different modes (single-tone and multi-tone) to perform various measurement functions, eliminating the need for separate specialized instruments and reducing overall system complexity.
2Device complexity
If a multi-tone signal generator is used to output multiple signals, then device complexity is reduced, but measuring both power and phase information becomes more difficult
Solution Approach 1:
The patent introduces a vector signal analyzer as an intermediary device that receives the output from the multi-tone signal generator and performs the complex task of separating and measuring both power and phase information of individual tones. This mediator handles the difficulty of detecting multiple signal parameters simultaneously, allowing the signal generator to focus on multi-tone output while the analyzer manages the measurement complexity.
Solution Approach 2:
The system employs feedback mechanisms where the vector signal analyzer measures the output signals and provides information back to control the signal generator's output. This feedback loop enables precise control and measurement of both power and phase information by iteratively adjusting the multi-tone signal generation based on measured values, thereby simplifying the overall measurement process.
Data Source
AI summary
A method and an apparatus for measuring linearity of a tested circuit are provided. The method includes: utilizing a signal generator to output a first tone signal and a second tone signal, wherein the tested circuit generates an intermodulation signal according to the first tone signal and the second tone signal; utilizing a signal analyzing device to detect an intermodulation power of the intermodulation signal; utilizing the signal generator to further output a cancel tone signal and control a cancel power of the cancel tone signal according to the intermodulation power; and utilizing the signal analyzing device to detect a total power of the intermodulation signal and the cancel tone signal, and controlling a phase of the cancel tone signal according to the total power, in order to minimize the total power in response to the phase of the cancel tone signal being modified to a target phase.