scope:

This specification establishes the performance, design, test, manufacture, and acceptance requirements for the Mode S Antenna Group, En Route Array.

This specification describes the services, material, equipment, and performance required to provide an en route array antenna group which is to be colocated with long range radar antennas at en route Mode S sites. The antenna group is intended for mounting on a variety of en route radar antennas protected by a radome. The antenna group provides a conventional directional pattern, sidelobe suppression (SLS) pattern, and a monopulse difference pattern. The patterns have sharp underside cutoffs to control ground lobing. The purpose of the monopulse pattern is to support single reply estimates of the azimuthal positions of transponders within the main lobe of the sum pattern. This specification also includes a multi-channel rotary joint and an azimuth encoder.