An Uncoated RF Heating Applicator With Reduced Environmental Sensitivity Using Two Coaxial Discontinuities

The proposed design pursues an applicator that can survive deployment into deep hydrocarbon deposits. To ensure mechanical robustness, the design must be supported by a contiguous metal pipe, and to this end, the applicator uses a single-bare conductor transmission line excited bidirectionally with two coaxial discontinuities. These two discontinuities create a virtual impedance boundary through field superposition, where, ideally, the virtual boundary is a termination for a tuning stub formed in the surrounding material. As the material around the applicator changes, so does the impedance of the stub, engendering a degree of self-tuning behavior. The applicator concept was validated at 2.45 GHz, where the double discontinuity gave an S
₁₁
of less than -10 dB in three different material cases and the measured electric field magnitude around the applicator was similar to simulation.