In this paper we propose a broadband equivalent circuit model of coupled integrated antennas using a generalized Foster approach. A largesignal multi-harmonic X-parameter model representation of On-Chip Schottky Diodes is derived for effective Antenna-Detector Co-Simulation, Co-Design and Co-Verification. Concurrent optimization of the Schottky Diode arrays geometry and large-signal electrical performances (such as with respect to cutoff frequency, parasitics, quality-factor, sensitivity, responsiveness, etc.) is carried out based on careful experimental characterizations.