Multi-Frequency Electro-Thermal Digital Model for Near-Field Electromagnetic Power Dissipation Mapping via Transient IR Thermography

This paper presents a multi-frequency electro-thermal Digital Model framework for accurate mapping and prediction of near-field electromagnetic (EM) power dissipation and localized temperature rise in high-frequency planar microwave structures. The proposed methodology integrates 3D full-wave computational simulations in CST Studio Suite with non-invasive transient infrared (IR) thermography using an Indium Tin Oxide (ITO) coated Polyethylene Terephthalate (PET) thin-film transducer. A high-gain 4 × 4 microstrip patch antenna array operating nominally at 12.00 GHz serves as the experimental benchmark. Numerical and physical evaluations were conducted across five discrete operating frequencies (7.10, 8.05, 9.05, 11.14, and 12.00) GHz at near-field evaluation distances of 1 mm, 16 mm, and 29 mm under a continuous-wave microwave (MW) excitation over a 50 s exposure duration. Transient surface temperature dynamics were recorded using a calibrated Teledyne FLIR A700 LWIR radiometric sensor. Quantitative line profile validation yields an average maximum temperature rise error of 20.75%, an average spatial center shift of 2.70 mm, and an average spatial spread (FWHM) deviation of 21.29%. These moderate discrepancies are physically attributed to evaluating free-space electric field intensity (|E|2) within the numerical domain versus measuring resistive heat generation on the physical ITO film. The developed Digital Model framework provides a robust foundation for real-time thermal monitoring, localized hotspot suppression, and predictive thermal management in advanced phased arrays and high-power MW systems.