Design of a Dual-Band Bow-Tie Slot Antenna with Two Feeds for Radiometric Medical Applications

Design of a dual-band, body-contact, bow-tie slot antenna with two feeds to function at frequency bands L and S, respectively, for radiometric medical application, is described in this paper. A multilayer substrate structure has been introduced in the design and the effective permittivity of the structure is estimated using the variational method and used to calculate the dimensions of the slot antenna. The simulation model has the reflection coefficient S-11 less than -10 dB in the frequency range of 1-2 GHz and S-22 less than -10 dB in the frequency range of 1-5 GHz. Flower foam soaked in saline water solution (6g/l NaCl) is used as human tissues phantom to measure the reflection coefficients and SAR distribution of the fabricated antenna. The radiometric efficiency is estimated from the simulations and verified by the approximations from the SAR measurements obtained from thermal distributions in the phantom close to the antenna taken through thermal camera. The radiometric temperature sensitivities are calculated for the target diameters of 20mm and 10mm being 30mm and 7mm away from the center of the antenna for 1.3 GHz and 3.5 GHz frequency bands respectively. A good agreement is achieved in comparison between the simulated results and the measured values of reflection coefficients and radiometric efficiencies.