Implementation and Testing of a Wearable Microwave Antenna System for Brain Imaging

This thesis presents the implementation, validation, and extensive experimental testing of a custom-dielectric monopole printed antenna system for microwave brain stroke imaging applications. The antenna consists of two stacked flexible thin bricks, one acting as a matching medium with the head and the other as the substrate layer between the antenna itself and a ground plane. The antennas are designed as wideband antennas, with a 400 MHz bandwidth at -10 dB and a central frequency of 1 GHz. They are tested by performing a singular antenna check to validate their reflection coefficients and a two antenna check to validate their TX and RX coefficients. Both tests are done with a jar containing a liquid mimicking the brain tissues, as to test the antennas in realistic conditions. These tests yielded favorable results in terms of S-parameters and antenna characteristics repeatability, validating the custom-dielectric flexible design. To test the 24 antennas needed for the complete system, a 3D Head phantom with the desired antenna positions is designed. Finally, the experimental setup of the system is a realistic human head phantom, filled with a liquid mimicking the brain tissues, and equipped with the 24 antennas. Its measurement process consisted of acquiring the phantom's scattering matrix before and after introducing a target that assimilates a stroke in different positions of the head and observing if variations of the S-parameters are noticeable. Preliminary tests revealed that the differential scattering matrices between cases allow detecting a target, and are in range for imaging algorithms, as well as probable employment in other brain-related applications.