Parametric RF Electromagnetism Analysis in Ansys Maxwell

Sensimed AG develops integrated microsystems for medical devices. In the development of a new contact lens with strain gauges for the continuous recording of ocular dimensional changes, the efficiency of the wireless coupling between the lens sensor and the antenna (which is placed around the iris) had to be calculated as a function of the eye position. In addition, the influence of the geometric dimensions of the antenna on the equivalent circuit parameters such as resistance, inductance matrix, and parasitic capacitances of each coil had to be accurately determined in order to ensure the proper tuning of the resonant system in the MHz range.

Through the simulation study, Sensimed AG was essentially able to achieve an optimal design for experimental validation and the start of series production without extensive iterative prototyping. In addition, a deeper understanding of the influence of geometric dimensions on resonant circuit tuning was obtained.

Performing parametric studies in Ansys Maxwell using the 3D harmonic eddy current analysis (see figure) and current conduction analysis (including the electric field of the surrounding insulator) enabled the calculation of all required RLC and coupling factors as a function of input parameters such as eye position and antenna dimensions (see diagram). A comparison of calculated and measured inductance values showed an agreement within 0.8%.