15–50 GHz Phased Array Fed Lens for Ultra-Law-Power Receive Pattern Synthesis

This paper presents an extremely wideband 15–50 GHz, ultra-low-power dynamic beamforming receive antenna comprising a phased-array-fed lens (PAFL). Unlike switched-beam lens (SBL) antennas with a single active feed per beam, the PAFL employs a wideband beamformer integrated circuit (BFIC) with multiple complex-weighted feeds to provide dynamic pattern synthesis across a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 52^{\circ}$</tex> field of view (Fo V). And, unlike the phased-array antenna (PAA) which requires all aperture elements to be simultaneously activated, the PAFL uses only a small number (here, four) of active elements to produce high-quality and high-gain beams, representing a dramatic reduction in power consumption relative to a PAA. To the author's knowledge, this work presents the widest bandwidth demonstration of a PAFL system, operating from 15–50 GHz. The wideband PAFL demon-strator employs a four-element, 15–57 GHz PAA receive BFIC and a nine-inch diameter Gradient Refractive INdex (GRIN) lens antenna. Using only four active elements at a time, the PAFL achieves high-gain beamscanning with dynamic beamforming across the band, while consuming less than 800 m W, which is less than 1 % of the power consumption of an equivalent-area (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1140\lambda_{0}^{2}$</tex> at 50 GHz) receive PAA. Beamforming is demonstrated across the 15–50 G Hz band using both analytical expressions and multi-objective optimization pattern synthesis methods to achieve lower sidelobe levels (SLL), and improved beam scan (scan loss exponent reduced from 3.2 to 2.6) out to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 52^{\circ}$</tex>. Unique aspects of wideband PAFL are discussed and design recommendations are provided for improved operation and performance.