UHF RFID reader constructed by discrete components has achieved major market in many applications such as logistic, traffic distribution, asset management and industrial flow line controlling using non-battery-powered system. With the rapid growth of mobile internet service, the authors hope UHF RFID readers can be integrated into portable devices such as Smartphone, PDA and tablet PC. UHF RFID systems use low data rate less than 640 kbps and simple coding schemes like FM0 and miller, the digital baseband signal processing can easily be realized using popular ARM-based processor.