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Range maximization of passive RFID tags is a challenging problem and one that has been consistently overlooked in the literature on RFID system deployment. Our research intends to maximize range for a single passive RFID tag as a function of key system parameters, namely tag sensitivity and bit error rate at the reader. Also, the inclusion of multiple RFID tags on the same object introduces unwanted crosstalk that must be minimized to maximize uplink range.
RFID tags consist of antennas that necessitate EM simulation for accurate characterization. The multiple tag scenario makes EM simulation absolutely essential since accurate derivation of mutual impedance between tag antennas becomes intractable for three or more tags.
Range Maximization: Uplink versus Downlink Range Trade-Offs
Range maximization primarily arises due to uplink versus downlink range trade-offs brought about by technology scaling. This is a constrained optimization problem that involves maximization of read/write range while equating read and write range. Our research proposes optimal impedance modulation indices for ASK/PSK backscatter modulation scheme in order to maximize range for a single passive RFID tag. This is depicted in the figure below that shows one optimal ASK modulation index and the maximum achievable range. The other optimal state for the tag is a conjugate match with the antenna impedance.
Improved Uplink Range for Multiple RFID Tags
We investigate crosstalk effects among multiple RFID tags embedded on a single object in order to maximize uplink range. The goal of this research is to propose optimal ASK/PSK impedance modulation indices for each tag to maximize uplink range.