Low-profile Circularly Polarized Conformal Antenna Array with Side Lobe Suppression for Vehicular SATCOM Applications

A circularly polarized microstrip antenna array with low side lobe levels is proposed for Vehicular Satellite Communication. The suppression of side lobe levels is accomplished by the non-uniform power distribution utilized to feed the individual patch ele-ments. Impedance matching is ensured by the incorpo-ration of a quarter-wave transformer via a microstrip line fed to the edge of the patch. When the pro-posed amplitude-weighted feed is compared to the conventional corporate feed, simulation results indicate a reduction in side lobe levels of 8.9 dB. The proposed antenna is constructed out of RT/DUROID 5880 mate-rial, which is lighter, more flexible, and less expensive than ceramic materials. The radiation characteristics of the proposed antenna are compared when the antenna is planar versus when it is made to conform to the roof of the vehicle. The measured results indicate a reflec-tion coefficient at the resonant frequency of-31.5 dB and-27.7 dB when conformal, an impedance band-width of 410 MHz and 180 MHz when conformal, an axial ratio bandwidth of 140 MHz and 170 MHz when conformal, and a peak gain of 15.719 dB and 14.335 dB when conformal. The measured results validate the simulation results that this proposed antenna is appropri-ate for a variety of Vehicular Satellite Communication applications.