Tunable Dual-Band Loop Antennas with Simple Parametric Control for Brain Implant Applications

This paper presents a scalable antenna design with only five geometric parameters, optimized for dual-mode operation at 402 & 2450 MHz and 915 & 2450 MHz. The antenna structure simplifies the parametric study by utilizing a limited set of design variables, making it more cost- and time-effective. The antenna length (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l_{1}$</tex>) shows an inverse relationship with resonance, while the thickness of the top dielectric layer (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$h_{1}$</tex>) directly influences the lower frequency bands (402 and 915 MHz) and inversely affects the 2450 MHz band. The slot length (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$l_{s}$</tex>) exclusively controls the 2450 MHz band, while the feed position and antenna width independently adjust the impedance for the lower and higher bands, respectively. The proposed antennas achieve impedance bandwidths of 2.5%, 2.2%, and 4%, with peak gains of −33.2, −24.4, and −24.9 dBi at 402, 915, and 2450 MHz, respectively. These characteristics, combined with the antenna's straightforward design, make it an ideal candidate for efficient fabrication with minimal measurement errors.