Construction of MIMO Testbed for RFID and Its Application to FM0 Tag Signal Detection

Abstract

RFID (Radio frequency identification) is an automatic wireless data collection technology with long history. RFID consists of chip, tag, reader, middleware, and application service platform and is used in conjunction with wired or wireless communication network. This technology is replacing traditional barcodes and can manage product conveniently. It can be also used for security, safety and environmental management. Nowadays, various detection techniques for RFID system have been studied.In a passive RFID system, the reader transmits a tone signal to the tag, and the tag that is powered only by tone signal and then transmits the FM0 encoded signal, i.e., the tag backscatters the tone signal, back to the reader. FM0 is one of the two encoding schemes used in Gen2 tags and is broadly utilized in commercial tags (the other scheme is Miller or biphase-mark encoding).Passive UHF RFID system has a self-interference problem because UHF RFID readers are transceivers which transmit and receive at the same time at the same frequency. Such a strong self-interference may saturate the low noise amplifier in radio frequency (RF) chain and it requires a high resolution bits from analog-to-digital converter (ADC). Therefore, it makes difficult to detect the correct signal from the received signal. For this reason, in this thesis, we propose self-interference cancellation methods and choose one that is suitable for the RFID system. A detector structure is also proposed. To resolve the timing offset problem that is caused by the mismatch because of mismatching between local oscillators and tag clock, a timing offset compensation method is also proposed.The UHF RFID multi-input multi-output (MIMO) testbed is established to verify the proposed methods. Using the testbed, measurement campaigns are also conducted in LG Research Building and two RFID tag detection structures are compared.