| 摘要 |
PURPOSE: An apparatus is provided to remove the need for the controlling electronics to be mounted near the structure, and to allow the impedance of the structure to be measured with very low signal power. CONSTITUTION: An apparatus for measuring the value of a physical quantity which affects the impedance of an electrically resonant structure, the apparatus comprising an electrically resonant structure, an RF electrical energy source, a bidirectional RF transmission line connecting the source to the resonant structure, a directional coupler associated with the transmission line, the source providing an excitation signal to the structure, the directional coupler detecting the voltage or phase of a reflected signal returned from the resonant structure characterized in that the resonant structure is substantially non energy radiating and, at a given frequency of the source, has an impedance which varies continuously as a function of the value of the physical quantity.
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