A design of Balun for UHF mobile RFID system

Mobile RFID system has been obtained much attention since modern trends in wireless communication technologies based on the Ubiquitous Networks. Among many components, Balun act as a converter which convert common mode signal to differential mode signal. There are two type of Balun, active type and passive type. Active Balun act good noise performance in entire communication system, but their linearity is limited by supply voltage. In this paper, we propose passive Balun implemented by IPD technology. Because Large power of TX CW compared to Tag reflecting signal leakages to RX signal path, so their linearity (especially 1 dB-compression point) is very important issue, and read range of Mobile RFID is not exceeding 2 m, so Tag reflected signal power is big compared to input thermal noise power. Besides we implement the Balun using IPD process, we can make entire system including RFID RF front-end chip and Balun into the Single chip. So we finally gained much smaller full-chip package.