Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Patent
1992-09-14
1994-08-02
Wieder, Kenneth A.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
324638, 324642, 333230, H01P 308
Patent
active
053349415
ABSTRACT:
A highly sensitive, direct-contact, in situ sensor for nondestructively measuring or monitoring the complex dielectric and conductive properties of solids, liquids, or gasses at microwave frequencies. A metal microstrip dipole resonator (11) is etched on the surface of a dielectric substrate (12) which is bonded to a copper ground plane (14). The dipole resonator is electromagnetically driven by mutual inductive coupling to a short nonresonant feed slot (13) formed in the ground plane (14). The slot (13) is driven by a coaxial feed line (7) or a microstrip feed line (16) extending from a swept microwave frequency source (2) which excites the incident wave (17). Alternatively, the metal resonator is omitted and the length of the slot (15) is increased so that it becomes the resonator. In use, the sensor is placed in close physical contact with the test material (9) having complex dielectric constant .epsilon.* (=.epsilon.'-j.epsilon.") or conductivity .sigma.. As the frequency of the microwave source (2) is swept, a sharp dip in the reflected wave (18) occurs at the resonant frequency, provided that the coaxial feed line (7) or microstrip feed line (16) is nearly critically coupled to the sensor input. Measurement of the resonant frequency and input coupling factor determines small changes in .epsilon.', .epsilon." and .sigma. with great resolution. To diminish the electromagnetic coupling between the resonator (11) and the test material (9), and to protect the resonator (11) from damage and wear, a superstrate (26) may be added.
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KDC Technology Corp.
Sartorio Henry P.
Tobin Christopher
Wieder Kenneth A.
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