Parasitic-Based Electrically Small CLL Antenna

Based on near-field coupling design strategy, an electrically small antenna is presented. The antenna is composed of a driven element fed differentially, and a parasitic capacitive loaded loop. The parasitic based antenna is printed on an RF substrate and has a maximum dimension of 28.80 mm, electrical size ka=0.261, designed to resonate at 868 MHz. The antenna is optimized with CST-MWS to realize maximum possible radiation efficiency where predictions shows nearly 76% for lossless loading capacitor and 69% for a lossy capacitor. A complete impedance matching is directly obtained by acting on the antenna geometry resulting in a proper near field coupling between driven element and parasitic element.