A High Performance Elevation Phased Array Antenna for the MLS - System

A high performance MLS-phased-array design is presented using high resolution 6-bit phase shifters for the beam steering instead of the commonly used 4 bit phase resolution. Due to the small phase tolerances and the equivalently low amplitude tolerances this design produces not only systematically lower sidelobes but also a very small beam pointing error allowing smaller MLS-antennas having much wider beamwidths without the penalty of a reduced MLS system accuracy. Hence, this design provides a cost effective MLS-phased array having an inherently high MLS accuracy and high multipath immunity and, also, an inherently improved frangibility. All these characteristics are decisively important at least for CAT III operations on high traffic and difficult site airports. Some typical measured antenna pattern results of the realized elevation antenna are presented.