Implementation and extension of a GNU-Radio RFID reader
The development of a flexible software defined RFID is discused. Commercial reader systems only allow a top level view on the communication and restrict the variation for many transmission parameters. Recently a software reader from the CGran project was proposed which uses the GNU Radio environment in combination with an USRP front end. Because most of the signal processing is done on a common host PC, this reader offers high flexibility, but also has several disadvantages. One of the main hardware limitations is the usage of only one separated antenna per transmit and receive path. Commercial readers usually use four antennas which are time multiplexed and can be used as transmitter and receiver. In this work a HF multiplexer for the USRP device is introduced. With this extension up to four transmit and receive antennas can be used in combination with the software reader. It is shown that the multiplexer achieves good read rates for a switching interval of 100 ms. Using this multiplexer the read range of the system decrease compared to the basic software reader, but distances over two meters can still be realized without additional hardware extensions.