No abstract

A novel backfire‐to‐endfire leaky‐wave antenna is presented with ability to scan from −25° to +45°. 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 0.0302λ0 × 0.0357λ0 × 0.0008λ0, where λ0 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° to +45° 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.

This paper presents a simple technique to extend the aperture of planar composite right/left‐handed (CRLH) metamaterial antennas with minimal impact on the antenna's dimensions. Unlike most CRLH antenna structures the proposed antenna is via‐free. The proposed antenna is shown to operate over a wideband from UHF to C‐band with good radiation characteristics. The antenna configuration consists of a vertically stacked CRLH unit cells comprising a patch and meandered lines, where the patch is engraved with an S‐shaped slot. The design uses minimal ground plane area. The meander line inductance is grounded using coplanar waveguide (CPW) ground which eliminates conventional CRLH transmission line metallic via into ground plane. The antenna is feed through a coplanar waveguide (CPW) match stub that is electromagnetically coupled to the unit cells. Antenna dimensions are 17.5 × 32.15 × 1.6 mm3, which corresponds to 0.204 λ0 × 0.375 λ0 × 0.018 λ0 where free‐space wavelength (λ0) is 3.5 GHz. Parametric study enabled the optimization of the antenna performance in terms of impedance bandwidth, radiation gain, and radiation efficiency. Measured results confirm that the antenna can operate from 850 MHz to 7.90 GHz, which is equivalent to a fractional bandwidth of 161.14%. The antenna has a maximum gain and radiation efficiency of 5.12 dBi and ~80%, respectively, at 3.5 GHz.