Eliminating Beam-Squinting in Wideband Linear Series-Fed Antenna Arrays Using Feed Networks Constructed by Slow-Wave Transmission Lines

A general configuration of linear series-fed antenna arrays is studied, and three different approaches for eliminating beam-squinting are identified. Two of these approaches result in passive implementations and are based on a degree of freedom provided by the lengths and propagation constants of the branches connecting the feedline to the antenna elements. Specifically, it is proposed that, by either the employment of varying-length branches or low-dispersion slow-wave transmission lines in equal-length branches, the beam-squinting can be eliminated over a very broad frequency range and for any arbitrary angle of beamforming between the backfire and endfire directions. Experimental results are presented for two feed networks, designed using the passive approaches, which can be utilized for a four-element linear series-fed array for beamforming at 30°and 38°with respect to the broadside direction, respectively. The array-factor results show that the beam remains effectively fixed, within ±2°, over more than two-octave bandwidth for these prototypes.