RF Calorimeter Self-Calibration with Integrated Reference Source
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Solution Overview
Problem
Existing RF calorimeters face challenges in achieving high accuracy due to various error sources, resulting in a measurement uncertainty of around ±0.4%, which is not sufficient for precise RF power measurement.
Innovation Solution
The RF calorimeter design includes a load electrically coupled to a single-pole, double-throw RF switch, allowing connection to either an unknown RF power source or a known low-frequency reference power source. This design utilizes coolant temperature measurements to calculate RF power, with an integrated reference source for real-time calibration and a high thermal efficiency load to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RF calorimeter methods are used, then RF power measurement is performed, but measurement uncertainty remains around ±0.4% due to various error sources
Solution Approach 1:
The patent changes the frequency parameter of the reference source from low-frequency (traditional method) to RF frequency (same as measured signal). This parameter change allows the reference source to operate at the same frequency as the unknown RF power being measured, eliminating frequency-dependent errors and achieving measurement uncertainty better than ±0.25%
Solution Approach 2:
The patent creates a reference RF power source that copies the characteristics of the unknown RF power being measured. By generating a reference signal at the same frequency and using it for comparison, the system eliminates the need for separate calibration procedures and reduces measurement uncertainty without requiring complex external calibration equipment
2Measurement precision
If substitutionary approach with low-frequency reference sources is used, then some error sources are reduced, but measurement uncertainty only improves to around ±0.4% due to vast number of remaining error sources
Solution Approach 1:
The patent makes the RF reference source multi-functional by using it both as a calibration reference and as a direct comparison standard for RF power measurement. This universal reference source eliminates the need for separate calibration equipment and procedures, reducing the number of error sources while maintaining measurement precision better than ±0.25%
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves a total uncertainty of less than ±0.25%, significantly improving the accuracy of RF power measurement compared to traditional methods.
Implementation Method 1
a coolant thermally coupled to the load
Implementation Method 2
an inlet temperature sensor thermally coupled to the coolant, the inlet temperature sensor being positioned to measure the temperature of the coolant without any heating by the load; an outlet temperature sensor thermally coupled to the coolant, the outlet temperature sensor being positioned to measure the temperature of the coolant due to heating by the load
Data Source
AI summary
Disclosed is a radio frequency (RF) calorimeter having National Metrology Institute (NMI) traceable measurement accuracy with uncertainty of less than about +0.25%, including the incorporation of a low-frequency reference source integral to the calorimeter for the purpose of self-calibration, a load with very high thermal efficiency, a temperature-controlled load enclosure, a vacuum relay high-power RF switch, an integrated low-frequency reference source, a non-reactive coolant liquid, a liquid-to-liquid heat exchanger, a self-calibration routine that can be performed on demand, and machine learning algorithms to create more accurate data models.