Power Measuring Device Internal Calibration Diode Detectors
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Solution Overview
Problem
High-frequency power sensor heads using diode detectors are prone to irreversible damage from power overshooting and electrostatic discharges, and existing calibration methods require external devices, which are not always available or convenient, especially for USB power-sensor heads, leading to inaccurate measurements and unreliable calibration.
Innovation Solution
A power-measuring device with an analog-processing unit and calibration unit that includes two detector diodes in antiparallel configuration, a chopper unit, and a current source to enable internal calibration, allowing for high-precision calibration without external devices by reversing the polarity of the calibration current and eliminating direct-current offsets, and using a control unit to manage the calibration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external calibration sources are used to calibrate HF power sensor heads, then measurement precision is improved, but device complexity and ease of operation deteriorate due to manual connection requirements and unavailability of external devices
Solution Approach 1:
The sensor head performs self-calibration using an internally integrated calibration source and evaluation circuitry. The calibration source generates test signals that are fed through the sensor head's detector to the evaluation circuitry, eliminating the need for external calibration equipment and manual connections.
Solution Approach 2:
The sensor head integrates multiple functions including the calibration source, detector, evaluation circuitry, and measurement functionality into a single device. This multi-functional integration allows the same hardware to perform both calibration and actual power measurements without requiring separate external devices.
2Adaptability or versatility
If detector diodes are operated in the quadratic range for mean power measurement, then measurement capability is improved, but calibration accuracy deteriorates due to inability to accurately judge rectification effect
Solution Approach 1:
The calibration source generates periodic test signals at the detector's operating frequency, allowing the detector to be stimulated in its quadratic range during normal operation. The evaluation circuitry periodically switches between measurement mode and calibration mode, enabling accurate calibration without leaving the detector in the quadratic operating range.
Solution Approach 2:
The evaluation circuitry measures the detector's response to calibration signals and uses this feedback information to accurately determine calibration values. The system continuously monitors the detector's rectification effect and adjusts calibration parameters based on the measured response, ensuring high accuracy even when operating in the quadratic range.
3Measurement precision
If measurement amplifier is configured in non-inverting mode for open-output voltage measurement, then measurement fidelity is improved, but calibration functionality is lost due to inability to measure current
Solution Approach 1:
The evaluation circuitry dynamically switches the measurement amplifier configuration between non-inverting mode for normal measurements and inverted mode for calibration. A switch element controls the connection topology, allowing the same hardware to adapt its configuration based on whether calibration or measurement is currently required, thus maintaining both fidelity and functionality.
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
Enables accurate and precise calibration of high-frequency power measurements, ensuring the detector diodes operate within their quadratic characteristic range, reducing the risk of damage and providing reliable measurements without the need for external calibration sources.
Implementation Method 1
sensor heads for high-frequency (HF) power measurement operate either thermally or use diode detectors, for example, on the basis of Zero-Bias Schottky diodes
Implementation Method 2
the chopper unit may be embodied to reverse the polarity of the flow direction of the calibration current through the detector diodes and to eliminate interfering influences of the amplifier
Data Source
AI summary
A measuring device for measuring a power of a measurement signal comprises an analog-processing unit (1) and a calibration unit (5) for the implementation of a calibration procedure. The analog-processing unit (1) provides two detector diodes (14, 15) connected in an antiparallel manner relative to a signal input (10) and an amplifier (50) for the amplification of signals which are derived from output signals of the detector diodes (14, 15). The analog-processing unit (1) further provides a chopper unit (28) which is connected at two terminals in series between the detector diodes (14, 15) and the amplifier (50). In this context, the calibration unit (5) comprises at least one current source, wherein the current sources (46, 47) is connected to at least one input terminal of the amplifier (50).