Physical Layer Analysis of a Backscatter Transponder Data Link

Sammanfattning

This thesis evaluates the possibility of establishing a bidirectional data link between a radar and a backscatter transponder at the physical layer. The proposed link consists of an uplink, where the transponder communicates by modulating and backscattering incoming radar pulses, and a downlink, where the radar communicates by changing its operational parameters. For the uplink, several modulation schemes are evaluated using analytical bit error rate calculations as well as simulations. The results show that robust low order schemes are most suitable over the intended operating range, while higher order schemes are feasible at shorter ranges or under more favorable channel conditions. More robust schemes are preferable under poor channel conditions, while higher order schemes can be used when the channel conditions are better. The hardware realization of the transponder is also investigated from a circuit perspective, focusing on how practical RF components and transmission line structures can be used to control the reflected signal and generate the required reflection coefficients. These models are constructed and verified using circuit simulators. For the downlink, several radar communication protocols are proposed and evaluated based on data rate, concealment, and their impact on normal radar operations. Finally, the uplink and downlink are combined to form a complete bidirectional data link. The thesis concludes that establishing a data link between a radar and a backscatter transponder is feasible.