Passive RFID Uplink and Downlink Link Budget and Comparison of ASK and BPSK Backscatter Modulations

Abstract

Complete link budget for forward and backwardlink in a RFID system are given with constituent parts. Backward link signallevels with current improvements requires separate TX and RX antenna bistaticconfiguration to overcome reader threshold. To further elaborate on linkbudgets, reflection coefficient and power equations are obtained from a RFIDfront-end model with circuit theory and shown on a passive RFID system. It isdemonstrated that both forward and backward links have limitations on the rangedepending upon tag power dissipation, antennas in use and type of modulation.To make two distances equal, parameters are found from two way link equations.Then, ASK and BPSK modulations are compared on communication distance for givenaverage backscatter difference power, minimum SNR to targeted BER on the readerby the equations obtained on the circuit model and MATLAB simulations.

Keywords

• rfid
• rfid link budget
• reflection coefficient
• transmitted power
• reflected power
• ask and bpsk backscatter modulation
• ber