Far-Field Antenna Performance Investigations Concerning In-Band Effects of Near-Field Structures and Out-of-Band Phased Arrays

Abstract : 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.