Numerical Analysis of Antenna Parameter Influence on Brightness Temperature in Medical Microwave Radiometers

The article presents a comprehensive study of the influence of key parameters of antenna systems of medical microwave radiometers on the accuracy of brightness temperature measurements of biological tissues. By methods of numerical modelling, it is established that changing the antenna diameter in the range of 5-50 mm significantly affects the depth of tissue probing, while reducing the diameter below 10 mm increases the sensitivity to deep layers by 20-35 percent. The factor of mismatch S 11 is shown to reduce the systematic error of the measurements by 0.7 °C, which is critical for diagnostics taking into account the basic error of modern radiometers (±0.2 °C). The optimal frequency range of 2.5-3.5 GHz provides a balance between penetration depth up to 3.5 cm and spatial resolution of 5-7 mm. The results are confirmed by experimental data on tissue phantoms, which shows good agreement with an error of less than 0.5 °C. The dependencies obtained allow us to purposefully optimise the antenna design for specific medical tasks, including early diagnosis of tumour processes and monitoring of therapy efficacy.