Far field antenna performance investigations concerning in band effects of near field structures and out of band phased arrays

The report presents the results of studies involving (1) the effects on far-field antenna performance of obstacles located in the near-field of an antenna, and (2) derivation of statistical models for predicting the out-of-band performance of waveguide phased-array antennas. In the first area, empirical data were recorded to determine the degrading effects of near-field blocking obstacles and reflecting objects on gain loss (decoupling), beamshift, beamwidth, and sidelobe levels of microwave radar antennas. The data were recorded for two parallel-polarization senses. In the second area, a previously-derived basic theoretical statistical model for predicting out-of-band phased-array characteristics was expanded to include arrays of waveguide elements which randomly propagate higher-order modes. Statistical equations were derived to predict and describe the out-of-band radiation pattern characteristics and median gain as a function of the in-band scan angle of the array.