Correlation-Based Noise Figure Measurement Without Pre-Amplifier
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Solution Overview
Problem
Existing measuring systems for determining the noise figure and amplification of devices under test are limited by the noise figure of the measuring device, leading to reduced accuracy, especially in broadband applications where the power of the measuring signal can overpower the first stage of the analyzer.
Innovation Solution
A measuring system that includes a noise source, a signal splitter, a correlator, and a processor to split and correlate measuring signals, reducing noise generation and allowing for accurate measurement of amplification and noise figure independent of the signal power, without the need for a pre-amplifier, thereby maintaining dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low noise pre-amplifier (LNA) is used to reduce the noise figure of the measuring device, then the noise figure of the measuring system is significantly reduced, but the available dynamic range is reduced and the first stage of the analyzer can be overpowered by the power of the pre-amplified measuring signal
Solution Approach 1:
The patent extracts and removes the pre-amplifier from the measuring system. Instead of using an LNA to amplify the signal before analysis, the system directly feeds the signal from the DUT to the spectrum analyzer, thereby eliminating the dynamic range limitation while maintaining measurement accuracy through the Y-method correlation technique
Solution Approach 2:
The patent uses a signal splitter to create two copies of the measuring signal from the DUT. One copy is used for the measurement path and the other for the reference path in the Y-method, allowing correlation-based noise figure measurement without requiring signal amplification that would limit dynamic range
2Measurement precision
If the power of the measuring signal is increased to improve the signal-to-noise ratio, then the measurement accuracy improves, but the first stage of the analyzer becomes overpowered and the dynamic range is reduced
Solution Approach 1:
The patent implements a feedback mechanism through the Y-method where the spectrum analyzer measures noise power in both the signal path and reference path, and the controller uses this feedback information to calculate the noise figure through correlation, allowing accurate measurement without increasing signal power that would overload the analyzer
Solution Approach 2:
The patent introduces a signal splitter as an intermediary device that divides the measuring signal into multiple paths before analysis. This allows the system to work with lower signal power levels while still achieving accurate measurements through the correlation of split signals, preventing analyzer overload
Data Source
AI summary
A measuring system comprises a noise source adapted to provide a noise signal to a device under test. Moreover, it comprises a measuring device adapt to measure a measuring signal generated by the device under test in reaction to the noise signal. The measuring device further comprises a signal splitter adapted to split the measuring signal into at least a first split measuring signal and a second split measuring signal. Moreover it comprises a correlator adapted to correlate a signal derived from the first split measuring signal and a signal derived from the second split measuring signal. Also the measuring device comprises a processor adapted to determine an amplification factor and/or a noise figure of the device under test based upon the correlated signal derived from the first split measuring signal and signal derived from the second split measuring signal.