UHF RFID Protocol Interface Testing With Software Deifned Radio

Radio Frequency Identification (RFID) is a widely used technology. HF RFID, the highfrequency type of RFID, nowadays becomes mature one that adapts many actual applications.Corresponding to HF RFID, UHF (Ultra High Frequency) RFID fits more fields because of longerwriting/reading distance and better secrecy. Due to complicatedly and diversified workingenvironment, RFID systems face challenges and higher requirements. Reader of RFID system canbe made up of two parts, radio frequency front-end and digital baseband circuit. Key part of thereader is digital baseband circuit, which processes digital signal and realize communication. As aresult, UHF RFID protocol interface becomes more complex that brings difficult for digitalbaseband testing.A possible solution is soft-defined-radio (SDR). Essentially, the SDR solution builds up ageneral hardware platform, and leaves most functions realized by software or processor. Hardwareplatform finishes general digital functions, such as up-conversion, down-conversion, FFT/IFFT,encode/decode while Graphical-User-Interface (GUI) and man-machine interaction etc. arerealized by software. In this article, hardware platform contains FPGA motherboard and RFdaughterboard. GUI on PC is wired with hardware through UART cable. In that case,transforming and receiving bit-stream can be seen on monitor. That is, making testing intuitivewhile flexible with different application.First of all, hardware platform design in this article includes chipset selecting, schematic design,PCB layout, components welding, overall unit testing and debugging. Final hardware containsFPGA circuit, ADC/DAC, UART, RF circuit, power circuit, oscillation circuit and expansioninterface.After completing hardware platform, QuartusII, Modelsim, MatLab, LabVIEW is used toimplement simulating, test and verify digital signal processing and bring out GUI on PC.According to UHF RFID protocol ISO/IEC 18000-6C, transforming circuit of encoding,modulation, baseband shaping and receiving circuit of decoding and demodulation form thedigital logic circuit in FPGA. Baseband logic circuit has been simulated and verified withModelsim and MatLab.