Aperture-Shared CP High Gain Antennas for Mobile Communication: Challenges and Recent Advancements

In the field of mobile communication, the use of circularly polarized (CP) antennas has become increasingly important in order to counteract multipath reflections. This creates a need for CP antennas. However, there are limited studies available 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 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 often have narrow bandwidth or low gain, making them impractical for practical applications. To address these challenges and improve gain and bandwidth, reflective/transmit arrays (RAs) have been developed with satisfactory performance [18]-[21]. Additionally, there has been a growing interest in Fabry-Pérot cavity (FPC) antennas due to their simple structure, low profile, and high gain compared to bulky horns and complicated arrays. Recent advancements in extending the bandwidth of FPC antennas [22] have further increased attention for their use in high gain and high frequency applications [23] [24], leading to an increase in co-design examples of FPC antennas being investigated [25] [26].