This paper presents a method for system architecture modeling of an IR-UWB (Impulse Radio Ultra WideBand) receiver for sensors networks applications. We expose the way for designing an FPGA (Field Programmable Gate Array) receiver starting from a previous study based on system modeling on Matlab. The proposed receiver architecture is first designed and validated on Matlab, before being implemented, thanks to VHDL language, on a FPGA. Our study shows the interest and the advantages of co-design Matlab-VHDL. We will propose here different IR-UWB receiver architecture depending on the modulation used. We will also introduce in this paper a data-rate and TH-code reconfigurable receiver. Using co-simulation Matlab-VHDL, we have compared three kind of IR-UWB receiver: TH-PPM, TH-OOK, TH-BPAM, with respect to BER/SNR criteria and in the specific context of wireless sensors networks, at high level (Matlab) and hardware level (FPGA-Xilinx).