RADC-TR-89-8 (VOL. II OF TWO), FINAL TECHNICAL REPORT: SCANNABLE MILLIMETER WAVE ARRAYS (APR-1989)

RADC-TR-89-8 (VOL. II OF TWO), FINAL TECHNICAL REPORT: SCANNABLE MILLIMETER WAVE ARRAYS (APR-1989)., The complexity usually associated with scanning arrays at millimeter wavelengths produces fabrication difficulties, so that alternative methods are needed that employ simpler structures. This Final Report describes such an alternative scanning approach, and presents a group of new and simpler radiating structures suitable for millimeter-wave applications. The new class of scanning arrays described here achieves scanning in two dimensions by creating a one dimensional array of leaky-wave line-source antennas. The individual line sources are fed from one end and are scanned in elevation by electronic means or by varying the frequency. Scanning in the cross plane, and therefore in azimuth, is produced by phase shifters arranged in the feed structure of the one-dimensional array of line sources. Within the sector of space over which the arrays can be scanned, the radiation has negligible cross polarization, no blind spots and no grating lobes. These are significant, and also unusual advantages. The novel features in the study reported here relate mainly to the new structures employed for the individual leaky-wave line sources and their combination into arrays, but also to analyses of the interactive effects produced when scanning occurs in both planes simultaneously, The analyses of the various antenna structures are believed to be accurate, and for most of the antennas they are notable for resulting in transverse equivalent networks in which all the elements are in closed form, so that the dispersion relations for the propagation properties of the leaky-wave structures are also in closed form. It should be added that for all the array structures the analyses take all mutual coupling effects into account. Although these atudies are predominantly theoretical in nature, sets of careful measurements were made for tvo of the novel leaky-wave line-source antennas: the foreshortened NRD guide structure and the offset-groove-guide antenna. The agreement with the theoretical calculations was excellent in both cases. In the Final Report, seven different novel antennas are described, of which four are leaky-wave line sources that scan in elevation, and three' are arrays that scan in two dimensions. They represent examples of the new class of scannable antennas that are simple in configuration and suitable for millimeter wavelengths. This Final Report is composed of 12 Chapters, of which the first is an introduction and sunary, the secc.id discusses some general features of our approach to the analysis of arrays, and the twelfth contains the list of references. Chapters III through X1 discuss in detail our comprehensive studies on the various specific antennas; the material is presented under three broad categories: ITRD guide antennas, groove guide antennas, and printed-circuit antennas. Becausc of the binding problems created by the size of this report, it is being printed in a two-volume format.