Radio-frequency identification (RFID) is a wireless technology for identification of objects based on attached tags. RFID readers used for identification of tags are already commercially available. A recent research field is the localization of passive RFID tags. During the course of this thesis an electronic product code ultra high frequency RFID reader based on a National Instruments USRP software defined radio (SDR) platform was designed and evaluated. This work provides a versatile platform for developing real time localization systems in upcoming research projects. Therefore, special requirements for a localization algorithm based on a superimposed Direct Sequence-Spread Spectrum signal were considered. Since some of the requirements couldn't be fulfilled with the driver framework provided by the manufacturer of the SDR platform a custom field-programmable gate array implementation was necessary. The implementation is based on a soft core processor system with attached user generated custom logic peripherals. An important element of the design is the decoder, which not only decodes the backscattered data, but also provides real time sub-symbol synchronization for the planned localization algorithm. Different decoder strategies have been analyzed and compared within the thesis. Considerable attention was drawn on a hardware efficient design, such that future developments are possible and have enough free FPGA resources left. Finally, tests with commercially available tags were made to verify the overall reader design.