An On-Body Matched Differentially Fed Magnetoelectric Dipole Antenna for Head Imaging Systems

An on-body matched differentially fed magnetoelectric (ME) dipole antenna is proposed for the head imaging system to detect intracranial hemorrhage (ICH). The ME dipole with its differential feed achieves a wide impedance bandwidth of 137% from 0.45 to 2.4 GHz. The antenna exhibits unidirectional and symmetrical radiation patterns in the near-field region, leading to a stable main beam toward the 2-D imaging domain inside the human head. The high front-to-back ratio (FBR) above 18 dB is realized in the whole frequency band by this antenna. The values of specific absorption rate (SAR) always remain safe level under 0.82 W/kg in the entire band with an input power of 10 dBm. To validate the detection capability of the proposed antenna, a head imaging system composed of eight antenna elements in a co-polarization state is designed and fabricated. The reconstructed 2-D images of the head interior using a confocal imaging algorithm demonstrate the successful detection and localization of the circular bleeding area as small as 3 mm in radius numerically and 5 mm in radius experimentally, and it has the capability to detect multiple bleeding areas of the human brain, which indicates the head imaging system has the potential to be used in clinical trials.