The study of the MLS angle deviation due to the phase shifter failure

Abstract

A linear phased array antenna of MLS (Microwave Landing System) contains a large number of digital phase shifters. The failure of phase shifters affects the beam direction which is defined as beam center in ICAO SARPs.

It needs a large amount of calculation to estimate the guidance error due to the phase shifters failure. The authors noticed that the deviation of the beam peak direction approximates the deviation of the beam center direction.

The authors propose simple equations to obtain the deviation of the beam peak direction. The results of the calculation show that the difference of the beam peak and beam center is less then one fifth of the maximum beem center deviation. The result of the ground experiment of MLS azimuth antenna failure with a phase cycling technique shows that the equations are available to estimate the deviation of the beam direction.