Comparison of three UWB microwave antennas intended for brain stroke detection system

Introduction: Brain stroke is after heart attack the second main reason for sudden death in the Czech Republic. Early start of appropriate treatment is crucial for patient's perspectives. The brain stroke detection system is offering a relatively cheap diagnostic tool which could be able to distinguish two types of brain strokes: ischemic stroke and hemorrhagic one (detection of changes in permittivity and conductivity). Both of these strokes need different type of treatment. In this paper a comparison study of three types of UWB antennas through numerical simulation is performed. All three antennas are working in the frequency bandwidth 1.5-3 GHz. Methods: Antenna is very important part of brain stroke detection systems. Currently, we are using simple UWB bowtie antennas of relatively low sensitivity to detection of hemorrhagic strokes. The main task was to choose the best antenna through the sensitivity of detection. We choose three different type of antennas 1) bowtie antenna, 2) double ridge horn antenna (adopted from [2]) and 3) microstrip antenna. For numerical simulation the numerical simulator SIM4LIFE 2.0 was used. Antennas were facing to the numerical homogenous model of human brain with dielectric parameters ε
_r
= 48.9 and σ = 1.31[S/m] (at 1 GHz). At the distance 40 mm from antenna the hemorrhage represented by blood of cylindrical shape of ε
_r
= 61.1 and σ = 1.54 [S/m] (at 1 GHz) was placed. The basic configuration can be seen in Fig. 1. We observed S
₁₁
parameter differences at certain frequencies between two cases 1) without hemorrhagic stroke and 2) with hemorrhagic one. Results: The simulations show that the best antenna for stroke detection is the microstrip antenna. The sensitivity was higher by 11% (24%) against horn antenna (bowtie antenna)