A Fern Antipodal Vivaldi Antenna for Near-Field Microwave Imaging Medical Applications
Alexandre M. de Oliveira, Antonio M. de Oliveira Neto, Marcelo Bender Perotoni, Nurhayati Nurhayati, H. Baudrand, A. de Carvalho, João F. Justo
Abstract
This investigation presents an oval slot edge (OSE) antipodal Vivaldi antenna (AVA), hereinafter referred to as Fern AVA (FAVA), with an optimized radiation pattern. The use of OSE provided improvements in the antenna characteristics, especially regarding a lower frequency limit reduction, an increase in the main lobe (ML) gain, and the sidelobe level (SLL) reduction. Those contrasting characteristics are simultaneously obtained through the class of the Palm Tree antennas. The proposed FAVA at 1.5 GHz shows an improved gain of 6.66 dB, −12.9 dB of SLL, and 0° of ML squint (MLS), in contrast with 4.41 dB of gain, −4.5 dB of SLL, and 4° of MLS in the conventional AVA. For the FAVA, the notches in an elliptical shape, in addition to mitigating the SLL, direct the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -fields distributions toward the ML, which categorizes it into the same class as the Palm Tree Vivaldi Antenna. To study the performance of the proposed antenna for medical applications of near-field microwave imaging, a conceptual proof was performed, thus obtaining the microwave image of a Child Head Phantom, homogeneous, and semirealistic, being possible to detect a brain tumor.