A Bandwidth-Enhanced, Compact, Single-Feed, Low-Profile, Multilayered, Circularly Polarized Patch Antenna

A bandwidth-enhanced, compact, single-feed, low-profile, multilayered, circularly polarized (CP) patch antenna is presented. A corner-truncated patch is introduced as a near-field resonant parasitic element directly beneath a specially engineered radiation patch. Without sacrificing the antenna's low profile and compact size, its presence not only introduces a new pair of orthogonal near-degenerate resonant modes, but also recovers a similar pair from the cross slot of the main patch. With the aid of both circular slots and meander-line slots on these patches, the resulting three pairs of adjacent near-degenerate modes have been successfully combined with the same clockwise polarization to enhance the CP bandwidth by more than a factor of two when compared to the same-height conventional single-layer patch antennas. Measured results are in good agreement with their simulated values and demonstrate that the reported antenna is low-profile: 0.016 λ achieves a -10-dB impedance bandwidth of ∼4.6%, and a 3-dB axial-ratio bandwidth of about 2.33% along with realized gains of 4.5 ± 0.15 dBi, throughout that bandwidth. Analyses of the current distributions are used to explain the contributions of the parasitic patch, and further simulation studies validate our design guidelines and show its advantages.