A five elements reconfigurable beam-steering parasitic patch array antenna is proposed in this letter. For patch-type antenna with parasitic array technique, the achievable beam scanning range is very limited in the range of -30° to +30° from the broadside. Increasing the number of parasitic elements does not provide significant beam scanning improvement where only additional 3° to 5° is achieved. Therefore, this research proposed an intergration of an additional parasitic elements with a novel approach of ground plane reduction that eventually improved approximately 43% steering angle. Five measured directive beam patterns of -50°, -30°, 0°, +30°, +50° are succesfully obtained with the respective switching conditions.
Introduction: Reconfigurable beam steering with patch antenna has gained significant interest due to its compact, simple and low cost design [1,2]. Various techniques has been developed to perform beam-steering with patch antennas [2-4]. In this work, further investigation is carried out in designing a broadly beam-steerable antenna with linear switched parasitic array. Enhanced beam tilt angle is achieved with the novel introduction of ground plane reduction technique at the parasitic patch array antenna. The fabricated antenna is capable to reconfigure the radiation pattern into five different directions with the optimized switching location at the parasitic elements. The beam steering is achieved at 5.8 GHz operating frequency with a little influence on the other antenna characteristics such as gain and S11. For the sake of simplicity and proof of concept, the representation of a shorting pin is considered as the artificial switch at the specified switching locations. The presence and absense of the shorting pin is considered as ON and OFF state respectively.
Antenna design: Fig.1 illustrates the physical structure of the beam-steering parasitic patch array antenna. The antenna consists of five parallel patches on a partially grounded Taconic dielectric substrate with a thickness of 1.6 mm and a dielectric constant (εr) of 2.2. The center rectangular patch has a width of W = 19 mm and length of L = 16.1 mm. This is the driven element of microstrip array where it is fed through a subminiature (SMA) probe from the back of the antenna.
Fig. 1 Geometry of the antenna.(a) Front (b) Back
The feed location a is optimized to achieve a desired input impedance of 50Ω. The size of the antenna is given by substrate width, Ws = 36 mm and substrate length, Ls = 108 mm. The parasitic elements are smaller than the driven element where the width and length are denoted as W' and L' (for the first order parasitic elements) and W" and L" (for the second order parasitic elements) respectively. The optimized parasitic elements’ physical dimension is as follows: W' = 0.9 x W mm, L' = 0.98 x L mm, W" = 0.88 x W mm and L" = 0.96 x L mm. The gaps between all elements are kept to 2 mm. In Fig. 2(b), the Wr denotes the ground...