Differential RCS of Multi-Port Tag Antenna With Synchronous Modulated Backscatter

This paper introduces a new method, called multi-port load modulation, allowing one to improve the delta RCS of any passive transponder. By switching simultaneously the loads connected to a multi-port antenna, we show that the associated delta RCS can be higher than the one predicted by the equations of R. Green in 1963. We demonstrate analytically that the delta RCS of the multi-port tag can be improved by 6 dB compared to a single port antenna. This improvement corresponds to an increase of the round-trip read range of 41%. This result can still be improved if the modulation of the structural mode adds constructively with the modulation of the antenna mode. Simulation and measurement of a fully compliant dual-port tag validate the model and achieve a large part of the predicted improvement.