AS AN ALTERNATIVE to monopole-type antennas, many commercial vehicles now provide frequencymodulation (FM) reception via antennas that are printed directly on the rear or quarter glasses of a vehicle. Unfortunately, these on-glass antennas tend to possess a low vertical gain and narrow bandwidth. They also exhibit nulls in their radiation patterns, as they are placed in close proximity to the conducting frame of the vehicle and are printed on glass with high dielectric losses. To serve the unique needs of a recreational vehicle (RV), an on-glass antenna with a multiloop structure for FM radio reception has been developed by Seungbeom Ahn, Dongwook Park, and Hosung Choo from Seoul's Hongik University together with Seulgi Park from LIG Nex1 Co. Ltd. and Yongho Noh from Hyundai-Kia Motors.
The antenna consists of conducting stripline that is printed on glass and fed by a coaxial cable from the upper left corner of the quarter glass. It uses a multiloop structure with three differently sized loops and a common feed line. This structure broadens the operating band by efficiently using the available glass area while raising the vertical gain by maximizing the z-directed currents.
After the antenna was installed in a commercial RV, its performance was measured. On average, the antenna exhibits gain of roughly −9.5 dBi with deviation of less than 4 dB compared to the gain of a conventional quarter-wavelength roof-mounted monopole. To examine the omnidirectional property, the azimuth radiation pattern also was measured. The result was a gain deviation below 20 dB. The transparency of the antenna body was improved by adjusting the stripline widths based on the induced current distribution. See "Design of an On-Glass Vehicle Antenna Using a Multiloop Structure," Microwave And Optical Technology Letters, January 2010, p. 107.