Transparent Antennas for Indoor Communications

The explosive growth of indoor traffic requires evolved wireless equipment. Smart cities and homes led by the 5G and beyond urgently need densely distributed indoor base stations (BSs). However, the current antennas for indoor deployment rarely consider integration with the environment. To integrate multi-function for various applications, indoor BSs will inevitably increase in size. To avoid the inconvenience caused by the indoor BSs in a limited space, using transparent antennas (TAs) suitable for indoor communication to improve space utilisation and reduce visual crowding is optimal. In the thesis, six TAs using different materials or mechanisms are designed and verified. Firstly, the glass-integrated antenna sandwiched by double-layer glass achieves triple band resonances for GSM, WLAN and 5G low-frequency band. Secondly, the 4-element MM TA array achieves high gain and high efficiency at 2.4 GHz. Thirdly, a 4-element wired MM TA firstly achieves ultra-wideband (UWB) and multiple-input multiple-output (MIMO). A parasitic decoupling structure for the MM antenna is proposed. The antenna achieves high isolation and comparable gain and efficiency to the conventional metal antenna while achieving high transparency. Fourthly, a UWB MIMO TA using transparent conductive film (TCF) is designed with low coupling. Fifthly, a double-layer Fabry-Perot cavity (FPC) TA achieves breakthrough high gain and efficiency of TCF antennas. Finally, the first all-dielectric transparent lens (ADTL) antenna is proposed. The lens uses the mechanism of the optic that can provide adjustable beamforming according to indoor environment needs, including gain enhancement, flat-top beam and dual beam. This thesis comprehensively demonstrates the research methods of various TAs, verifies the feasibility and provides strong guidance for the application of commercial TAs in the future.