A new type of printed periodic leaky-wave antenna is proposed, which is able to continuously scan a beam from backward to forward endfire. The unit cell consists of a microstrip line loaded with long lengths of transmission line folded as a U-stub and an interdigital capacitor. This U-stub geometry, which is characterized by a compact longitudinal size, permits operation at frequencies lower than other conventional periodic leaky-wave antennas. At the same time, the presence of the interdigital capacitor makes the radiating U-stub discontinuity self-matching, thus allowing for an elimination of open-stopband effects and for an achievement of an almost constant gain while the beam is scanned through broadside. A noteworthy aspect of the present design is that it represents the first periodic leaky-wave antenna that scans through broadside by radiating from the fundamental n = 0 harmonic, without being a quasi-homogeneous metamaterial structure.
Baccarelli, P. (2014). A self-matched wide scanning U-stub microstrip periodic leaky-wave antenna. JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS, 28(2), 151-164 [10.1080/09205071.2013.858609].