Microwave Holography Using Infrared Thermograms of Electromagnetic Fields For Testing Phased Array Radar Antennas

The objective of this proposal is to develop a field-deployable infrared (IR) thermal-imaging system capable of determining the operational status (magnitude and phase) of each element in a large phased array radar antenna.A definitive indication of the radiation status of an array element of the antenna can be determined by placing a thin, low-loss, IR detector screen near or on the radiating element. If the element is radiating, the Joule heating of the lossy material in the screen can be detected using an IR scanning camera. The measured temperature of the screen can be correlated to the magnitude of the incident near-field radiation and will give an immediate indication of the radiation condition of the phase shifters. The phase of the incident near-field radiation can be measured using microwave holographic techniques to give an accurate indication of the actual phase of the phase shifter.The near-field magnitude and phase of the radiation can be transformed to the far field using standard Fourier Transformation techniques. In the far field, the gain of the array can be determined . If the far-field radiation pattern is then back-transformed to the aperture plane, the actual phase of each individual array element can also be determined.