Apparatus and method for high resolution complex permittivity sensing using high q microwave sensors for lossy or non-lossy mediums and samples

Abstract

Apparatuses and methods for non-contact sensing of physical or chemical properties of a target sample using a planar microwave resonator are provided. In one aspect, a planar microwave resonator is used in combination with an active feedback loop for increasing the quality factor of the resonator to compensate for an existing signal loss in the sample or environment. In another aspect, an active feedback loop is used in combination with a microwave resonator to compensate for signal loss in a lossy medium. In another aspect, a planar microwave resonator comprising a secondary layer defining a sensing interface may be used to facilitate the sensing by exposing the secondary layer to a substance to be investigated. In another aspect, a planar microwave resonator sensor is provided comprising separate resonator and active feedback loop components that are indirectly connected through an electromagnetically coupling and may be constructed on two separate support structure.

What is claimed: 
     
         1 . A method for microwave sensing of a sample or a physical stimulation, the method comprising:
 positioning a secondary layer proximate to a planar microwave resonator comprising an active regenerative feedback loop;   exposing the secondary layer to the sample or physical stimulation;   applying a signal to the planar microwave resonator to excite the resonator; and   measuring, after the exposing, a value or the variation of at least one of resonance frequency, quality factor, and amplitude of a signal of the planar microwave resonator in response to the excitation of the resonator in proximity to the secondary layer.   
     
     
         2 . The method of  claim 1 , further comprising increasing, before the measuring, the quality factor of the planar microwave resonator with the active regenerative feedback loop. 
     
     
         3 . The method of  claim 1 , wherein the secondary layer is positioned in alignment with a coupling gap of the planar microwave resonator. 
     
     
         4 . The method of  claim 1 , further comprising calculating a complex permittivity of the secondary layer and the sample based on the measured at least one resonance frequency, quality factor (Q), or amplitude. 
     
     
         5 . The method of  claim 1 , wherein the secondary layer comprises a fluidic or microfluidic structure 
     
     
         6 . The method of  claim 1 , wherein the secondary layer comprises an adsorbent material and the sample comprises a gas, wherein the gas interacts with the adsorbent following the exposure to change a permittivity related parameter of the adsorbent.