This paper describes a modular active antenna forudsatellite communications in the K/Ka band. The application is thought for mobile satellite communications and internet links, mainly for commercial airplanes. The impossibility to build full active antennas, including amplifiers in all the elements, leadsudto a modular semi active antenna. Here the module is a small subarray with complete phase control in the elements. The phase control is made with ad-hoc phase shifters giving the minimum losses. Only two-bit control has been selected to perform phase shifters associated to a circular polarization radiating element. The feeding network has been selected to minimise the losses and the gap waveguide has been designed to perform the network. The radiating element is a circular double patch fed into two points to obtain circular polarization.udThe entire prototype has been designed in LTCC substrate to minimise the losses and stabilise the structure.
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