A frequency-scanned slot-array on a coaxial slow-wave structure

Frequency-scanned antenna arrays usually employ a sinuous feed to obtain a high frequency sensitivity [1], [2]. It has been realized [1] that this effect can alternatively be produced by using a slow-wave feed, such as a helix, in place of the more commonly employed TEM-line or waveguide feed. Such a feed system can be made quite compact and lightweight as compared to the latter types of feed. In this paper, a structure consisting of a coaxial line with a corrugated inner conductor is examined as an array feed. The radiating elements are transversely out half-wavelength slots on the outer conductor and constitute a uniformly spaced linear array. The absorber at the end of the feed ensures that the array is excited in the traveling-wave mode.