Feasibility of backscatter RFID systems on the human body

Abstract

In this contribution, the author examines the feasibility of on-body backscatter radio frequency identification (RFID) systems in the ultra high frequency range. Four different on-body RFID systems are investigated operating monopoles or patch antennas at 900 MHz or 2.45 GHz. The systems' feasibility is analyzed by means of on-body channel measurements in a realistic test environment. The measured channel transfer functions allow to evaluate if enough power is available for a reliable backscatter communication. This evaluation is done with the aid of outage probabilities in the forward link and the backward link of the systems. Using these probabilities, the on-body systems prove feasible when using state-of-the-art reader and transponder chips. In particular, the use of semi-passive RFID transponder chips leads to a reliable performance in the systems' forward links. The robust performance of the systems' backward links is clearly shown for the 900 MHz monopole antenna configuration, while the limitations in the backward links of the other systems have to be overcome by the use of a second reader unit on the person's back. The novel feasibility analysis presented here allows to examine each system parameter individually and thus leads to reliable and robust backscatter RFID systems.

SIMO UHF RFID reader using sensor fusion for tag localization in a selected environment

“…The antenna matching is −13 dB in the tag scenario and −20 dB in the reference scenario. The above mentioned state-of-the-art parameters lead to a forward link threshold F Th and to a backscatter link threshold B Th for both backscatter links of [11]:…”

“…The investigation is based on channel measurements that characterize the communication links within this challenging multipath environment. In particular, the system reliability is investigated with respect to the measured power availability in the communication links at 890 MHz [11,13]. Figure 2 shows the floor plan of the AVL engine test bed (test bed 1) and a neighboring engine test bed (test bed 2).…”

“…P TX,min is determined by the minimum channel gain of the forward link g FL,min at 890 MHz and the tag parameters, i.e., the chip sensitivity and the power transmission coefficient. The minimum transmission power is [11],…”

“…The minimum power of the CW signal received at the tag is limited by the sensitivity of the tag chip (chip sensitivity). The minimum power of the tag signal received at the reader is limited by the sensitivity of the reader receiver (reader sensitivity) [11].…”

“…For the following, only the minimum transmission power of P TX,min = 24.5 dBm is used for the calculations to obtain a lower bound of the reader requirements. With a minimum measured channel gain of g BSL,min = −114 dB and a modulation efficiency of η = −7 dB, the minimum reader sensitivity is calculated as [11],…”