Wideband Phase-Reversal Antenna Using a Novel Bandwidth Enhancement Technique

A novel bandwidth enhancement technique for phase-reversal Franklin-type antennas is proposed. Impedance bandwidth enhancement is achieved by combining several coupled modes of the antenna structure through periodic loading provided by radiating crossover dipoles. This technique is explained by the theory of periodically loaded transmission lines. Radiation pattern bandwidth enhancement is achieved by exciting the antenna in its center so as to suppress beam squinting by superposing the tilted beams of two resulting sub-arrays on either side of the feed. An offset parallel stripline (OPS) phase-reversal antenna using these bandwidth enhancement techniques is demonstrated theoretically and experimentally at 35 GHz. The antenna is printed on a thin substrate suspended over a micro-machined conductor-backed cavity for unidirectional radiation. The overall fractional bandwidth of the antenna is increased from 3% to over 11% compared to the conventional design and the antenna efficiency exceeds 80%.