RF Power Sensor Thermal Isolation and Self-Calibration
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Solution Overview
Problem
Existing RF and microwave power meters require calibration and zeroing, which is inconvenient, error-prone, and increases complexity and cost, especially in large systems, and introduces uncertainty and discontinuities in signal paths.
Innovation Solution
A method that eliminates the need for calibration and zeroing by using thermal isolation, direct temperature measurement, and a log detector with amplifiers and filters to ensure accurate power measurement for both CW and complex signals, while managing thermal effects and signal bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration and zeroing procedures are implemented, then measurement accuracy is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The power sensor performs self-calibration by using its own internal reference source to automatically establish measurement accuracy without requiring external calibration equipment or user intervention. The sensor autonomously compares its measurements against the internal reference and adjusts accordingly, eliminating the need for manual calibration procedures while maintaining measurement precision.
Solution Approach 2:
The power sensor integrates multiple functions including measurement, calibration, and reference provision within a single device. The internal reference source serves dual purposes as both a calibration standard and a measurement reference, reducing the need for separate calibration equipment and simplifying the overall system architecture.
2Measurement precision
If calibration and zeroing procedures are implemented, then measurement accuracy is improved, but ease of operation worsens
Solution Approach 1:
The automatic self-calibration eliminates the need for users to perform manual zeroing and calibration steps. The sensor autonomously executes the calibration process using its internal reference, transforming a complex multi-step user operation into a transparent automated function that requires no user intervention while maintaining measurement accuracy.
Solution Approach 2:
The power sensor performs calibration automatically upon initialization or when triggered, preparing the measurement system in advance before actual measurements are taken. This preliminary automatic calibration ensures the sensor is ready for immediate use without requiring users to perform preparatory calibration steps.
3Ease of operation
If internal switches are added for zeroing and calibration, then ease of operation is improved, but reliability and measurement precision worsen
Solution Approach 1:
The invention extracts the switching function entirely from the system by using a solid-state power sensor that electronically adjusts its state without mechanical or electronic switches. This removal of switching components eliminates the reliability issues associated with switch contacts and discontinuities while maintaining automated calibration capability through software-controlled sensor adjustment.
Solution Approach 2:
The patent replaces mechanical switching mechanisms with solid-state electronic control within the power sensor. The sensor uses electronic adjustment of its detection circuitry rather than physical switching, eliminating contact resistance, wear, and signal discontinuities while achieving the same functional outcome of enabling automated calibration and measurement.
4Measurement precision
If multiple measurement points are added for path loss compensation, then measurement precision is improved, but device complexity worsens
Solution Approach 1:
The power sensor is designed to perform multiple measurement functions including direct power measurement and path loss compensation using the same single measurement point. The sensor's software and processing capabilities enable it to calculate path loss by comparing transmitted and received signals without requiring additional physical measurement points or hardware components.
Solution Approach 2:
The invention uses software and signal processing as an intermediary to achieve path loss compensation without physical measurement points. The system processes the signal data mathematically to determine path loss characteristics, replacing the need for additional hardware measurement points with computational methods that achieve the same measurement precision.
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 provides accurate and automated power measurements, reducing user intervention, hardware complexity, and cost, while minimizing the impact of thermal changes and signal disruptions, leading to improved measurement accuracy and reliability.
Implementation Method 1
isolating the incoming signal detector from the measurement port to ensure that any thermal transient appearing on the center conductor of the input port is not allowed to propagate to the detector
Implementation Method 2
The present invention combines techniques that were present on the first power meters (in the 1950s) but adds novel elements and method steps. The inventive elements include: (1) adding thermal isolation between the detector at the measurement port; (2) measuring detector temperature directly or as directly as possible (some designs measure the temperature of the 'sensor'); (3) adding gain in low signal level paths, using (a) linear amplifier, and (b) a log detector.
Data Source
AI summary
An improved power sensor having an input connector connected to an input port having a center pin and a ground side; an amplifier; first and second detectors; and a thermal stabilization system, including a thermal mass disposed between the ground side of the input connection and the detectors, a ground plane for holding the temperature of thermally sensitive components constant to within 2 degrees C., and a thermal impedance disposed between the center pin of the input port, preferably including a splitter and at least one DC capacitor, and a temperature sensor disposed on the ground plane.