This paper proposes a dual-band circularly polarized (CP) modified square ring antenna. The resonate structure of this antenna consists of a modified square ring patch and a ground plane, and the antenna is fed by a modified L probe with two unequal branches. A low order CP mode (TM₁₁ Mode) and a high order CP mode (TM₁₂ Mode) are both excited in this simple structure for the dual band operation. The truncated corners of the ring and the embedded corners of the slot are used to obtain the dual band CP operation. The overall size of the antenna is 150 × 150 × 11.7 mm³. The measured 10-dB return loss bandwidths are 13.0% for the lower 2.45 GHz band and 37.4% for the upper 5.8 GHz band. The measured 3-dB axial ratio bandwidths are 2.1% and 5.8% for the lower band and upper band respectively. The measured peak gains of the lower band and upper band are 8.19 dBic and 9.44 dBic respectively.

本文提出了一种双频带圆极化（CP）改进的方形环形天线。该天线的谐振结构由一个经过修改的方形环贴片和一个接地层组成，并且天线由具有两个不相等分支的经过修改的L探头供电。低阶CP模式（TM ₁₁模式）和高阶CP模式（TM ₁₂模式）都以这种简单的结构为双频操作而激发。环的截角和槽的嵌入角用于获得双频段CP操作。天线的总尺寸为150×150×11.7 mm ³。对于较低的2.45 GHz频带，测得的10 dB回波损耗带宽为13.0％，对于较高的5.8 GHz频带为37.4％。测得的低频段和高频段的3-dB轴向比率带宽分别为2.1％和5.8％。测得的较低频段和较高频段的峰值增益分别为8.19 dBic和9.44 dBic。