Designs of compact microstrip antennas with a slotted ground plane

It has been demonstrated that by embedding suitable slots in an antenna´s radiating patch, compact microstrip antennas can be obtained. However, for such designs, the antenna gain and impedance bandwidth are also decreased, causing severe limitations for practical applications. We propose a new design of compact microstrip antennas with a slotted ground plane. It is found that by properly embedding a pair of narrow slots in the ground plane of a microstrip antenna, the antenna´s fundamental resonant frequency can be lowered. Reduced antenna size at a fixed frequency can thus be achieved. Moreover, enhanced bandwidth and gain for the proposed design are also observed, which is different from that observed for compact designs with a slotted radiating patch (see Wong, K.L. and Yang, K.P., Electron. Lett., vol.33, p.1916-17, 1997; Lu, J.H. et al., IEEE Trans. Antennas Propagat., vol.47, p.1174-8, 1999). The proposed design with two pairs of narrow slots in the ground plane for achieving dual polarized or circularly polarized radiation has also been successfully implemented. Details of the experimental results are presented.