This paper addresses the problem of radio interface in Wireless Sensor Network (WSN). We study the specific constraints of WSN and we expose how, by using a reconfigurable mostly digital IR-UWB radio, we can solve this problem. WSN context implies constraints such as low power, low cost, small size and simplicity on the radio layer. We present the reconfigurability as a solution to the large diversity of WSN applications. Dynamic reconfigurability is implemented over an IR-UWB radio interface. A two level development is exposed, based on system architecture modelling and hardware implementation. This design flow permits to obtain a reconfigurable IR-UWB transceiver on an ASIC/FPGA implementation. The proposed solution allows data rate, spectrum, and radio range reconfigurability.