Optimized design of beam-tilted linearly-polarized radial-line slot-array antennas

High-gain low-profile antennas for microwave and millimeter-wave applications have been a topic of exhaustive research during last decades. More specifically, radial-line slot array-antennas (RLSAs) demonstrated their suitability for massive production in low-cost applications, e.g. TV-DBS. In this context, RLSAs became very attractive due to their simplicity, low profile, low fabrication cost and high efficiency. In a standard RLSA design, slots are arrayed on the upper plate of a radial line, i.e. parallel plate waveguide, which is fed at its center, typically by a coaxial probe. Overall, any polarization and radiation pattern can be synthesized by a proper arrangement of slots. Unfortunately, while the circularly-polarized RLSA (CP-RLSA) demonstrates an excellent performance, its counterpart with linear polarization (LP-RLSA) [1] presents an annoying drawback. Standard arrangement distributes slots in concentric rings spaced half wavelength so as to produce a directive beam pointing to broadside direction with linear polarization. Such disposition exhibits rather poor matching performance, which is inherent in traveling-wave series-fed broadside arrays because of coherent reflections.