In this paper we present a novel digital baseband processor designed for UWB transceiver on RFID tag. It is a low power and low voltage (1.8V) full digital ASIC which is implemented in 0.18 ? m CMOS technology. The processor receives serial signals (consist of data and commands) from the RF Receiver, and based on received command carries out various functions such as receive data and write to the memory, compare data, send data, set/reset tag, kill tag and etc. The processor mainly consists of eight sub modules: Receive Buffer, Transmit Buffer, Random Number Generator (RNG), Slot Counter, Memory Controller, Reset Counter, Comparator, Controller.