Monitoring techniques for phased-array antennas

The problem of monitoring phased-array antennas in general and microwave landing system (MLS) in particular is considered. Various methods of monitoring phased-array antennas are suggested. One is based on changes in the far-field radiation pattern arising from defects in the array. Another method uses the near-field to far-field transformation, based on the concept of the plane-wave spectrum, for the detection of defects in the antenna. A third method is based on near-field measurements and uses the properties of the Fresnel integral. The methods were simulated on the computer and, where possible, were tested by experiment. A comparative assessment of the methods is given, and an operational monitoring system is suggested for the MLS phased army.