Currently, most of TT&C (Telemetry, Tracking and Control) and Earth Observation antenna systems operate in only one or two frequency bands at a time. Most systems provide the operation capability in the main frequency bands (S, X). These systems require one or two feed assemblies, components, and system electronics to operate in the different bands. Moreover the Earth Observation mission services need more data rate due to the new system complexity and more accuracy or better definition of optical payloads. The existing S or X band frequency spectrum allocation could be a handicap to match this increased data rate. For this reason, the World Radio communication Conference recently attributed new additional frequency spectrum allocations in Ka-band range 25.5-27 GHz for Remote sensing application. Our contribution presents our new design of a multi-band S/X/Ka coaxial concentric feed with a monopulse tracking system in each band, designed by the RF & Antenna Laboratory of ZODIAC DATA SYSTEMS company. The present paper describes the concept and the technology achieved. Moreover, this contribution focuses on the electromagnetic simulations of radiating elements, the feed network, the RF tests and RF system integration, as well as the performances measured with the real multi-band feed, allowing us to validate the design.