Abstract
In the context of the UHF (Ultra High Frequency) passive RFID (Radio Frequency Identification) technology, recent works have proposed a new paradigm demonstrating the possibility to perform short distance tag to tag (T2T) communications. This paper presents a study that focuses on the performance evaluation of T2T systems. Without loss of generality as to the methodology followed, dipole antennas are considered here (assumed ideal in the theoretical part, then printed for the rest of the study). The results obtained show that the modulation depth, which can be considered as an evaluation metric for the T2T systems, is strongly impacted by three main parameters: the switching impedances (here chosen as short-circuit and open-circuit); the geometrical configuration constituted by the two tag antennas forming the T2T system; and also, the position of the external source on which the backscatter communication relies. As the modulation depth is very sensitive to these three parameters, which are more or less directly related, it is very difficult to predict the communication quality for a given configuration. For example, when the two tags are in parallel and the source is symmetrically positioned, the modulation depth shows a decreasing trend by oscillating when the distance between the tags increases from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.1~\lambda $ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\lambda $ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> being the wavelength): with values going from 70% to less than 5%. As a consequence, from a very complete set of scenarios considered, the presented study helps to illustrate and explain the interactions of these parameters and their impact on the modulation depth. And at the same time, the paper provides guidelines for defining the specifications of such a system based on quantified results. The set is completed by introducing the BER (Bit Error Rate) as an evaluation metric by considering then a more complete T2T system (for instance listener tag including a non-coherent envelope detector).
Highlights
T HE backscatter technique was first introduced by Stockman in 1948 [1] and quickly became the key technology for low-power wireless communication systems with a broad range of scenarios such as tracking devices, remote switches, low cost wireless sensor networks and, more generally, the Internet of Things (IoT) [2]–[4]
PERFORMANCE EVALUATION OF THE T2T COMMUNICATION SYSTEM Based on the previous study, this section aims at evaluating the performance of T2T communication by considering a given scenario, i.e. the geometrical configuration constituted by the two tag antennas forming the T2T system, and the position of the external source on which the backscatter communication relies
In the context of the new passive RFID T2T systems, this paper investigated the impact of the relative position between the tags, and the orientation
Summary
T HE backscatter technique was first introduced by Stockman in 1948 [1] and quickly became the key technology for low-power wireless communication systems with a broad range of scenarios such as tracking devices, remote switches, low cost wireless sensor networks and, more generally, the Internet of Things (IoT) [2]–[4]. Multi-antenna backscatter transmitter able to improve the communication performance and the transmission range by using multiple antennas Their system is able to eliminate interference from the ambient RF signals thereby increasing the communication range of about 75%. The antenna’s characteristics such as the radiation pattern or the input impedance are modified These modifications have an impact on the T2T’s communication performance since the difference between the modulation states and implicitly the modulation depth is impacted [13]. In [14], a novel multi-phase backscattering technique is proposed to suppress phase cancellation and demonstrated the capability of T2T link to operate at longer distances (above three meters) in presence of an excitation signal strength of only −20 dBm. In [15], the design of a power efficient demodulator is investigated to increase the T2T communication range with a modulation depth higher than 75%.
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