A novel monofilar-Archimedean metamaterial inspired leaky-wave antenna for scanning application for passive radar systems

A novel backfire-to-endfire leaky-wave antenna is presented with ability to scan from -25 degrees to +45 degrees. The antenna is based on metamaterial transmission-lines and is implemented using monofilar Archimedean spiral and rectangular slots, spiral inductors, and metallic via-holes. The slots act as series left-handed capacitances, and the spirals with via-holes provide the shunt left-handed inductances to realize the metamaterial antenna. A prototype antenna was fabricated prototype on FR4 dielectric substrate, which has an electrical size of 0.0302(0)x0.0357(0)x0.0008(0), where (0) is free space wavelength at 165 MHz. Measured bandwidth of the antenna is 710 MHz (165-875 MHz) corresponding to a fractional bandwidth of 136.5%. The main advantage of the antenna is its ability to scan over a wide angle from -25 degrees to +45 degrees with acceptable gain and radiation efficiency of 1.2 dBi and 50.1%, respectively, measured at 400 MHz. The wide scanning attributes of the antenna make it suitable for passive radar applications to scan across the VHF-UHF bands for FM-Radio, television, mobile phones, and GPS applications.