A fully integrated 900-MHz direct-conversion transceiver for mobile RFID system is presented. The transceiver consists of a low noise amplifier, a down-conversion mixer, a band pass filter, and programmable gain amplifier (PGA) for RX path; and a power amplifier, an up-conversion mixer, a low-pass filter, and a PGA for TX path. In addition, the fractional N PLL is integrated to cover different frequency standards for different nations. The transceiver meets the dense reader environment specifications.