Calibrated RF Voltage Measurement Using Directional Coupler Error Matrix
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Solution Overview
Problem
Current methods for measuring high-frequency currents and voltages or absolute wave quantities in the time domain are limited, as they only permit the determination of relative values and cannot be used without modification for non-linear devices under test.
Innovation Solution
A method involving a directional coupler with an error matrix E=(e00e01e10e11) is used to determine error terms, transforming time-variable signal values into the frequency domain and then back into the time domain to calculate absolute wave quantities, allowing for the measurement of electric voltage u(t) and/or electric current i(t) in the calibration plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration methods are used to determine scattering parameters, then measurement precision is improved, but the method is limited to linear devices and only provides relative values
Solution Approach 1:
The patent transforms the measurement domain from frequency domain to time domain by applying inverse Fourier transform to the calibrated scattering parameters. This parameter transformation enables the measurement method to capture transient behaviors and non-linear effects that are invisible in frequency domain measurements, thereby extending applicability to non-linear devices while maintaining calibration-based precision
Solution Approach 2:
The patent performs calibration measurements first to determine error terms and systematic errors, then applies these calibration data to correct subsequent time domain measurements. This preliminary calibration action establishes a reference framework that enables both linear and non-linear device measurements with high precision, resolving the contradiction between measurement accuracy and device type adaptability
2Adaptability or versatility
If time domain measurement is used to capture transient signals, then adaptability to non-linear devices is improved, but measurement precision deteriorates due to lack of calibration
Solution Approach 1:
The patent introduces frequency domain scattering parameters as an intermediary medium. Time domain signals are transformed to frequency domain for calibrated measurement, then transformed back to time domain with calibration corrections applied. This intermediary approach allows precise calibration-based measurements while maintaining time domain capability for non-linear device characterization
Solution Approach 2:
The patent replaces direct time domain measurement with a transformed measurement approach using Fourier transform. Instead of measuring time domain signals directly without calibration, the system transforms to frequency domain where calibration is applied, then transforms back, substituting the direct measurement mechanism with a transformed measurement process that achieves both precision and adaptability
Data Source
AI summary
A method for determining electric voltage u(t) and/or electric current i(t) of an RF signal in the time domain in a calibration plane, wherein by at least one directional coupler having two outputs and one signal input a first component of a first RF signal that runs from the signal input in the direction of the calibration plane, and a second component of a second RF signal that runs from the calibration plane in the direction of the signal input is decoupled. For a two-port error of the directional coupler, the error terms e00, e01, e10 and e11, are determined as a function of a frequency f and the signal values v1(t) and v2(t) are transformed into the frequency domain as wave quantities V1(f) and V2(f), and absolute wave quantities a1 and b1 in the frequency domain in the calibration plane are calculated from the wave quantities V1(f) and V2(f) by the error terms e00, e01, e10 and e11.