Microwave front-end subsystems design for ITS/GPS applications

This paper reports the design, simulation and characterization of adaptable band pass filter, planar microstrip antenna and filtenna for GPS and ITS (intelligent transportation systems) applications. The designed microstrip slotted antenna has a 300 MHz of measured bandwidth and 5.7 dBi of measured gain, which is sufficient to cover the ITS band (5.85-5.925 GHz). On the other hand, the developed filtenna operates in dedicated ITS band at 5.9 GHz and have 1.5 dBi of measured antenna gain. The reduction in filtenna gain is due to the additional insertion loss introduced by the hairpin bandpass filter incorporated in the feed of the proposed filtenna. Two adaptable bandpass filters have also been designed for GPS applications. First tunable filter operates at 1575 MHz (GPS L1 frequency) while rejects 1227 MHz frequency (GPS L2 frequency band). The (measured) return loss of the filter is better than 20 dB from 1.5 GHz to 1.6 GHz; while insertion loss at 1575 MHz is ∼5.5 dB. Second tunable filter has been designed to cover both 1575 MHz (L1 frequency band) as well as 1227 MHz frequency ranges (L2 frequency band). The return loss (measured) of this filter is better than 10 dB from 1.15 GHz to 2.15 GHz, and insertion loss is ∼5.5 dB. The developed sub-systems can be used to build a low cost RF transceiver system for GPS and ITS applications.