ANTENNA ARRAY OF COMPACT VIVALDI RADIATORS WITH ELLIPTICALL SHAPE CUTOUTS ON THEIR OUTER EDGE

Abstract

The influence of elliptical cutouts on the outer edge of a compact Vivaldi radiator, designed as part of an infinite phased array (PA) and a finite antenna array (AA), on its radiation characteristics is investigated. The voltage standing wave ratio (VSWR) and realized gain (RG) of the radiator are estimated. For the radiator as part of the infinite PA, the radiation characteristics were obtained in the sector of angles ±60° in the E– and H–planes. The research determined that the introduction of elliptical cutouts measuring 3 × 2 mm on the outer edges of the Vivaldi radiator as part of the PA makes it possible to expand the operating frequency band in terms of VSWR ≤ 3 in both planes, and improve the average level of matching in wide-angle scanning mode in the E-plane. In the E–plane in scanning mode in the sector of angles ±60°, the overlap ratio at the level of VSWR ≤ 3 increases from 2.86 to 3.41, and in the H–plane in scanning mode in the sector of angles ±45°, the overlap ratio at the level of VSWR ≤ 3 (≤ 3,05 at 45°) increases from 2.74 up to 3.15. A 16-element array from the compact ultra-wideband (UWB) Vivaldi radiators with and without elliptical cutouts is researched. When using elliptical cutouts in the design of finite-size antenna array radiators, the overlap ratio increases from 2.07 to 2.37. It has been determined that the AA, as well as the radiator in the PA, is UWB and can operate in the range from 283.8 to 671.3 MHz at the VSWR level ≤ 3, which corresponds to overlap ratio  2.37. The average VSWR level when all radiators are turned on is located at the VSWR level = 4, and when connecting one row of radiators to matched loads – at the VSWR level = 1.6. Basically, over almost the entire operating frequency band in this case, the VSWR value is below the VSWR level = 2.3. The realized gain in the operating frequency band is in the range from 3.82 to 9.50 dB.