Compact Transponder Front-End with Enhanced Gain for Electronic Toll Collection at 5.8GHz

In this paper we present a compact semi-passive front-end designed for Dedicated Short Range Communication (DSRC) at 5.8GHz for vehicular technology applications. The front-end implementation is based on the optimal integration of a low-bias RF diode and a compact circular polarized antenna array. The antenna array natively exhibits the optimum termination to the diode, ensuring the best trade-off between detection and back-scattering on the basis of frequency conversion mechanism. The antenna is characterized by enhanced gain and polarization purity while extremely compact, hence particularly suitable for tag integration. The fabricated prototype is tested in envelope detection, back-scattering and in a functional test conducted according to the ETSI EN300674 communication layer. The best measured Back-Scattering gain exceeds 7.8 dB, with a sensitivity of 54 mVpp with a signal of -45dBm. A range at 9m without communication errors is observed when operating with a EIRP of 33dBm.