CRLH structure-based high-impedance surface for performance enhancement of planar antennas

摘要

A composite right/left-handed (CRLH) structure-based high-impedance surface (HIS) is investigated to improve gain and front-to-back ratio of planar microstrip antennas. An unbalanced CRLH unit cell with a wide band-stop region from 2.0 to 6.44 GHz is modelled and designed for HIS to enhance the antenna performance. A novel via-less structure composed of an interdigital capacitor and four spiral arms is used for the microstrip implementation of the CRLH unit cell. The HIS is formed by the repetition of the unbalanced CRLH unit cells in two-dimensional form. The microstrip patch antennas operating at three different frequencies: 2.34, 3.77 and 5.64 GHz in the band-stop region of the HIS are designed with and without HIS to compare the antenna performances. An increase in gain of 1.91, 2.03 and 0.7 dB and an improvement in the front-to-back ratio of 4.9, 6.0 and 4.2 dB are achieved for the patch antennas operating at 2.34, 3.77 and 5.64 GHz, respectively. To demonstrate the effectiveness of HIS, a patch antenna over HIS is fabricated and measured results show good correlation with the simulated results. An overall antenna size at 2.26 GHz is 0.378λo × 0.303λo × 0.012λo.