Circularly Polarized Patch-Helix Hybrid Antenna With Small Ground

A new design of circularly polarized (CP) patch-helix hybrid antenna with small ground is presented. The proposed antenna consists of a driven patch, a parasitic patch, and a helix connected with the parasitic patch. The hybrid antenna has a relatively small ground, making the overall antenna compact. The proposed antenna can be packaged in a thin cylinder and can be easily mounted in the space-limited systems. Good impedance matching was achieved by capacitive coupling between the driven patch and the parasitic patch, while high gain was obtained with a small ground due to relatively uniform current along the helix. A prototype antenna for 5.8-GHz Wireless Local Area Network (WLAN) was fabricated and tested to verify the design idea. The measured impedance bandwidth (S₁₁ ≤ -10 dB) was 19% (5.22-6.30 GHz), and the corresponding peak gain was 10.85-13.35 dBic. Excellent CP performance (axial ratio AR ≤ 3 dB) was achieved over the whole impedance bandwidth.