Low-cost intelligent antenna with low profile and broad bandwidth

In this paper, a low-cost intelligent antenna, which has a low profile, high gain and broad bandwidth, is presented. The proposed antenna is an extension of the conventional Electronically Steerable Parasitic Array Radiator (ESPAR) antenna. It consists of one short monopole and twelve folded monopoles. The short monopole is placed in the centre and serves as the driven element, and the twelve folded monopoles serve as parasitic elements. The coupling between the driven and parasitic elements provides capacitive loading to the driven element, leading to a low profile antenna. The use of twelve PIN diodes enables the beamforming being performed by using Transistor-transistor logic (TTL) supply. When interference signals exist, an adaptive beamforming algorithm is employed to choose a radiation pattern with the best signal-to-noise ratio (SNR). The front-to-back ratio (FBR) and SNR is improved by introducing a reconfigurable chock ring (RCR) surrounding the antenna. To validate the concept, a prototype at S band is developed. Both measured and simulated results are presented. The antenna has a height of 24 mm only (0.16 at 2.0 GHz). The measurement results confirm that the antenna is capable of beamforming and beam scanning over 360°range in horizontal plane. The antenna has a broadband bandwidth from 2.0 to 2.5 GHz. Finally, the antenna is employed in a wireless communication system in an office environment and the system link quality is tested. It is shown that the antenna can boost the throughput of wireless system significantly.