Extending the Functionality of Resonator Aperture Sensors for Microwave Diagnostics of Small-sized Objects

The paper discusses the basic principles of functioning of resonator sensors with a movable probe-forming central conductor and approaches aimed at optimizing their measuring characteristics. The effectiveness of changing the coefficient of inclusion of an object in the electromagnetic field of the resonator is shown by introducing a mechanism into the sensor design that provides axial movement of the central conductor of the coaxial. This design allows the probing tip to be positioned both coplanar with the end aperture and displaced inside or outside the coaxial. It is shown that in order to diagnose objects with low dielectric losses, the probing tip must be pulled out of the coaxial, thereby transferring the probe to the mode of a monopole antenna. When the object has high dielectric losses, the required sensitivity of the sensor is achieved by shifting the probing tip into the inside of the coaxial, and the shortened capacitance mode is implemented. Quantitative data are presented that characterize the operation of the tunable sensor within each of the two modes of operation considered, as well as convincing of the need to optimize the geometry of the resonator probe (RP) construct. The contribution of losses associated with the appearance of a wave field, the mismatch of propagation conditions in the volume of a resonant measuring transducer (RMT), as well as techniques aimed at eliminating their influence is shown. A comparative analysis of the use of conical and cylindrical probes as RMT is presented. It is shown that the shielding of samples makes much more sense for the use of a cylindrical construct in the diagnostics of objects with a low loss tangent. It is shown that it is possible to significantly reduce the influence of interfering factors caused by a change in the geometry of the sensor aperture assembly when the probe tip is moved, by using a hybrid signal (δQ/Q)/(δf/f).