Fresnel region boresight methods

The task of "boresighting" a monopulse antenna in the fresnel region of propagation is described with two approaches to the problem. In the first case a tower method is described with its limitations. Included is a discussion of a fresnel region equation with a theoretical null position variation with range shown along with measured results. The aperture distribution considered is the sum of a uniform and sinusoidal function. A second method entitled "Auto Collimation" boresighting is described which employs a boresighting screen positioned at ranges in the order of a reflector diameter. For the problem of field distribution behavior, a different employment of the same basic equation is discussed. This method reduces the limitations of the fresnel region equation at points close to the aperture. Computed and measured results of the Auto Collimation method are presented. The results including advantages and disadvantages of this technique are compared to the tower method.