Mechanical scanners for radar antennas

The mechanical scanner is the most versatile and widely used antenna system for airborne radar application. In general, its radiation characteristics are superior to those of electrical scanned systems. There are three basic types of scanners: The wigwag, spiral, and helical. These basic types of scanners, along with various modifications of each, are discussed and compared, insofar as possible, with other than mechanical scanners. Such characteristics as relative size weight, scanning speeds, broadband matching, absolute gain, half-power beamwidth, relative minor lobe intensity, and aperture efficiency are compared and general rules are submitted as to how to choose which type of scanner will best perform in a given type of service.