Microwave antenna module for use in an antenna system installed on board a space platform, including a transmit/receive module, which comprises: • a first package and a second package, that are hermetically sealed to one another and that are multilayer ceramic substrate packages; and • an interposer connector, that is interposed between said first and second packages (7,8) and comprises a body and connection means provided in said body; wherein first electronic circuitry is arranged within a first hermetic internal cavity of the first package, and second electronic circuitry is arranged within a second hermetic internal cavity of the second package; wherein the first and second electronic circuitries are connected to the connection means of the interposer connector for routing microwave, control and power signals through said connection means; wherein the connection means of the interposer connector include one or more microwave connection assemblies connected to the first and second electronic circuitries for microwave signals routing between said first and second electronic circuitries; characterized in that the first electronic circuitry includes a directional coupler in stripline-coplanar configuration; wherein each microwave connection assembly includes: • a respective first metal element, that extends through the body perpendicularly to a top surface and a bottom surface of said body, protruding from said top and bottom surfaces; • a respective first dielectric element, that - is coaxial with, and extends around, the respective first metal element surrounding completely said respective first metal element, and - extends through the body between the top surface and the bottom surface thereof; and • respective second metal elements, that - are spaced apart from, and surround at least partially, the respective first dielectric element, - extend through the body perpendicularly to the top and bottom surfaces thereof, protruding from said top and bottom surfaces, and - are in electrical contact with the body, thereby being at the same electrical potential as said body. • a first package and a second package, that are hermetically sealed to one another and that are multilayer ceramic substrate packages; and • an interposer connector, that is interposed between said first and second packages (7,8) and comprises a body and connection means provided in said body; • a respective first metal element, that extends through the body perpendicularly to a top surface and a bottom surface of said body, protruding from said top and bottom surfaces; • a respective first dielectric element, that - is coaxial with, and extends around, the respective first metal element surrounding completely said respective first metal element, and - extends through the body between the top surface and the bottom surface thereof; and - is coaxial with, and extends around, the respective first metal element surrounding completely said respective first metal element, and - extends through the body between the top surface and the bottom surface thereof; and • respective second metal elements, that - are spaced apart from, and surround at least partially, the respective first dielectric element, - extend through the body perpendicularly to the top and bottom surfaces thereof, protruding from said top and bottom surfaces, and - are in electrical contact with the body, thereby being at the same electrical potential as said body. - are spaced apart from, and surround at least partially, the respective first dielectric element, - extend through the body perpendicularly to the top and bottom surfaces thereof, protruding from said top and bottom surfaces, and - are in electrical contact with the body, thereby being at the same electrical potential as said body.