  This paper aims to present a miniaturized novel reconfigurable composite
right/left-handed leaky wave antenna (CRLH LWA) based on metamaterial as well
as slow wave structure. In other words, the effect of interdigital capacitor
(IDC) on LWA with periodic J-shaped metamaterial is investigated. This
microstrip antenna is designed by cascading J-shaped metallic and IDC unit
cells. Then it is simulated by full-wave ADS Momentum software. Advantageously,
the proposed structure has tunable dispersion diagram that can be tuned by the
number of IDC fingers. As will be clarified, altering the number of IDC fingers
is able to adapt the equivalent capacitor of the antenna equivalent circuit.
Thanks to the availability of RF switches technologies, changing the
configuration of the IDCs can be practical. Furthermore, scanning the space
from backward to forward region through broadside is one of the distinguishing
features of the antenna. Indeed, the CRLH LWA continuously scans the space
through broadside from -55 degree to +65 degree in {\phi} = 0 degree plane. The
results of the investigation reveal that the LWA with two fingers, as more
effective configuration, is a circularly polarized CRLH LWA and it is one of
the highly desirable advantages of this structure. The axial ratio in the
direction of the main beam for the backward region is lower than 3dB and it is
improved in comparison to other regions. The deployment of IDC with variable
figures in LWA with J-shaped metamaterial not only brings about the
aforementioned significant features but also plays a pioneering role in this
paper.
