A NOVEL WIDEBAND ANTENNA ARRAY WITH TIGHTLY COUPLED OCTAGONAL RING ELEMENTS

A novel phased array antenna with wide bandwidth and wide scan angle is presented. The radiating aperture of the phased array consists of periodically and closely spaced octagonal ring elements. Tight capacitive coupling between adjacent elements is realized by interdigitating the end portions of the ring elements. To improve the impedance matching of the individual antenna elements over wide frequency band, a novel impedance matching layer consists of periodic octagonal ring element is subtly designed and placed over the radiating aperture. Both of the radiating elements and impedance matching layer are printed on a flexible membrane substrate with a thickness of 0.04 mm. Measured results of a 16-element linear array demonstrate that good impedance matching over a 4.4: 1 bandwidth can be obtained for beam scan angles within +/- 45 degrees from broadside. As compared to conventional wideband phased array such as tapered slot antenna array, the proposed phased array has the features such as low cost, low profile, light weight, and ease of fabrication.