PROBE-FED STRIP-ELEMENT MICROSTRIP PHASED-ARRAYS - E-PLANE AND H-PLANE SCAN RESONANCES AND BROADBANDING GUIDELINES

A comprehensive investigation is presented of E- and H-plane scan-freq uency characteristics of probe-fed microstrip strip-element phased arr ays with a single probe per unit cell, A parametric study of the princ ipal, large mismatch producing scan resonances is carried out utilizin g Galerkin-type analysis and an associated computer code, While the E- plane scan characteristics confirm earlier findings, those of the H-pl ane exhibit a heretofore not reported array blindness condition which is traced to excitation of a strip-line mode of the periodic array str ucture, The largest element spacing is identified which, independently of substrate thickness, excludes the principal E- and H-plane scan re sonances, Element broadbanding is then achieved via interplay between substrate thickness and strip width. For a fixed scan angle with an ap propriately configured element geometry, the unmatched active impedanc e exhibits a double-tuned behavior, The form of the equivalent network in the neighborhood of the double-tuned resonance is established via computer-aided approach, Finally, an example of scan-frequency array p erformance (without using suppressor pins) for a +/-15% frequency rang e and a 40-degree E- and H-pIane scan coverage with voltage standing w ave ratio (VSWR) less than or equal to 2 is presented.