双频圆极化天线
这是一篇关于双频圆极化天线的文章，文中提出了一个新的概念，在此笔记下来加以分析。
文章2011年发表在IEEE AWPL上，二作里Atef教授和清华的杨帆教授都是领域中知名科学家。今年与Atef教授有过短暂的接触，其严谨的作风和积极的态度非常让人敬佩，从北京到成都一路上随时都能看到在工作，一点都不像是60多岁的老年人。
这篇文章中提出的新概念（本人第一次获知，没有深究前人是否已经提出）
双频带宽之比
目前有研究过多频辐射的天线，对于每个工作频段之间的关系从来没有考虑并分析过。
以此为参考，之后将观察实物和仿真中多个频带之间的关系。
A new design for a single-feed dual-band circularly polarized
microstrip antenna has been presented. This is achieved by designing
two patches with asymmetrical U-slots that are stacked
together. The dimensions of the U-slot are optimized to provide
different current paths for the two orthogonal modes required for
circular polarization. In addition, this antenna can be designed
to have similar or opposite polarizations in the two bands. In
comparison to the available designs for dual-band CP microstrip
antennas, the advantages of this new design are the simplicity of
fabrication, wide CP bandwidth in the upper band, mono- and
dual- sense CP capability, and a similar gain level at both bands.
A prototype has been fabricated and measured. A dual-band circularly
polarized antenna with a bandwidth of 1.0% at 3.5 GHz
and 3.1% at 5.8 GHz has been demonstrated.
