A PLL-based retro-directive antenna system for communications with arbitrary frequency gaps

Retro-directive antenna systems are of special interest in satellite communications due to their self-tracking capabilities. Since frequency bands are regulated, a key issue is the realization of a large frequency gap between transmitted and received signal. In this paper, we present simulations of a novel retro-directive antenna system for C-band based on phase-locked loops (PLLs). It can realize arbitrary frequency translation between received and transmitted signal. It is also able to work with different array element spacings and can correct beam pointing errors. We show bistatic radiation patterns which are the response to plane waves impinging from different directions on a system with a four-element array. A frequency translation from 5.8 to 7.0 GHz is shown for different array element spacing. We demonstrate the suitability of the proposed system architecture for retro-directive applications. It can realize large frequency gaps while keeping system complexity on a reasonable level.