On Channel Gain Performance of Car Roof-Glass Embedded 5G Antenna

5G antennas for vehicular connectivity are often mounted on the car roof to optimize signal reception. The trend of replacing metal roof with glass in modern cars opens an opportunity for embedding the 5G antennas inside the glass roof. In this work, we compare the channel gains of reference dipole, and loop antennas positioned at the roof center. Then, by considering the requirements of glass integration and the channel gain performance, a nontransparent wideband monopole antenna with an extended feedline is designed to be embedded inside a real glass roof. To recover the optical transparency of the roof glass while retaining the wideband performance, the metal conductor is replaced with non-uniform metal mesh structure. The proposed semi-transparent wideband monopole antenna covers both 5G and legacy bands. Within the operating frequency range from 617 MHz to 5 GHz, the channel gain and radiation efficiency are above -4.5 dB and 37%, respectively.