Contents I. Introduction
A Ka-band mobile satellite communication system uses a circularly polarized (CP) beam towards the satellite (uplink) over the frequency bandwidth (29.5–30 GHz), and a CP beam from satellite to ground station (downlink) over the frequency bandwidth (19.7–20.2 GHz) for wideband on-move commercial applications. Such systems must be designed to meet very stringent radiation requirements such as very low side lobe levels. A high effective isotropic radiated power (EIRP) of the order of 48.4 dB/W is required to provide the users a reliable high data rate connectivity. A wide steering range (±70°) in elevation over the entire azimuth range to afford a continuous connectivity over the globe. A high pointing accuracy (> 0.2°) to avoid adjacent satellite interference is also needed. The antenna should have a circularly polarized pattern over the same angular range with high cross-polarization discrimination (low axial ratio (AR) level) [1], [2]. Moreover, since it will be used for thin structures for on-the-move-terminals (e.g., cars, ships, trains, airplanes), a low-profile (conformal) and fast beam steering capability are among other essential characteristics of such systems to mitigate any mechanical drawback and ensure continuous connectivity while the ground terminal moves and maneuvers. Active phased-array antenna is viewed as an ultimate solution that can meet all the aforementioned requirements [2].
