<![CDATA[Passive UHF RFID tags communicate by backscatter, so the signal crosses the channel twice, yet most bit error rate analyses still treat the channel as a single path. This study quantifies the cost of that simplification for MLFF toll portals. The BER of amplitude shift keying (ASK) and binary phase shift keying (BPSK) over a dyadic backscatter channel is evaluated by Monte Carlo simulation. Single-path modeling underestimates the required power by 8.2 dB for BPSK and 8.4 dB for ASK without a line-of-sight component, a read-range loss of about 38 percent on the two-way path scale. The fading margin relative to the AWGN channel is independent of the modulation (maximum deviation 0.3 dB), so modulation and channel can be budgeted separately. Margin sensitivity to the Rician K-factor peaks between K = 6 and 8 dB and falls sharply above 12 dB, so a portal should keep K at 12 dB or more for a margin below 3 dB. Full inter-link correlation in a monostatic reader halves the diversity order to 0.5, with a penalty of about 19 dB at a BER of 0.001 that grows as the target BER is tightened, making separate transmit and receive antennas a design requirement.]]>
Copyrights © 2026
