Rectangular Waveguide-Based CRLH Frequency Scanning Array Antenna Operating at W-Band

We present the design, modeling, and characterization of a prototype metallic waveguide-based composite right/left-handed (CRLH) frequency scanning array (FSA) operating in the frequency range of 77.8 GHz to 110 GHz. The FSA, comprising 101 cascaded CRLH unit cells, radiates through a continuous slot cut into the top wall of the unit cells. An empirical equation was used for the initial antenna design, which was further optimized using full-wave numerical simulations. The FSA was fabricated from brass using a highprecision CNC tool, achieving a surface roughness of less than 3 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex>. Its performance was characterized in a fully anechoic chamber, focusing on both port matching, directivity, and radiation patterns. The measurements showed a frequency scanning range of 62.1°, spanning from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-44.7^{\circ}$</tex> to 17.4° over the operating frequency range.