Aperture-Shared CP High Gain Antennas for Mobile Communications: A Review

In the field of mobile communications, the use of circularly polarized (CP) antennas has become increasingly important due to their ability to counteract multipath reflections. As a result, there is a growing need for CP antennas. However, there is a lack of available literature on aperture-shared CP high gain antennas with a large frequency ratio. Some examples can be found in the microwave band [14]-[17].

In the mm-wave band, it is particularly challenging to simultaneously control the phase difference for lower and higher bands in order to achieve CP wave realization, while also maintaining high directivity and a wide operating bandwidth. Furthermore, existing CP antennas either have narrow bandwidth or low gain, making them impractical for mobile communications. In order to enhance gain and achieve a wide bandwidth, reflective/transmit arrays (RAs) with satisfactory performance have been developed [18]-[21].

Additionally, there has been a surge of interest in FPC (Fabry–Pérot cavity) antennas due to their simple structure, low profile, and high gain compared to bulky horns and complicated arrays. With recent advancements in extending the bandwidth of FPC antennas [22], this type of antenna has attracted increasing attention for high gain and high frequency applications [23] [24]. As a result, more and more co-design examples of FPC antennas have been investigated [25] [26].