Design and analyses of a dipole patch tag antenna on the novel henna-based biocomposite substrate for UHF-RFID application

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Nadzeefah Bt Zamil, Ms.
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Radio-frequency identification (RFID) technology is widely employed for tracking, detection and identification of an object automatically such as animal tracking and warehouse. The performance of the RFID system is highly-dependent on the performance of the tag. Passive ultra-high frequency (UHF) RFID tag which consists of an integrated circuit (IC) chip and antenna is very popular as it can offer far read range with the smaller antenna size. Normally, the tag antenna is designed on the existing substrate material in the market such as flame retardant 4 (FR-4), Rogers and polyethylene terephthalate (PET). However, the aforementioned substrates are difficult to decompose due to the usage of polymer which can harm the environment in the long run. On the other hand, these commercial substrates have fixed dielectric constant properties. The dielectric constant values are inversely proportional with the resonant frequency, but each country has its own standard frequency RFID band. Hence, the optimization on antenna design is required in order to achieve various resonant frequencies which is time consuming especially during mass production. In order to overcome the problem of substrate decomposition, this study proposed to develop a new substrate material made of henna leaves. The proposed biocomposite was not only beneficial for the green environment, but it also offered multiple values of the dielectric constant by adjusting the proportion of henna loading and treatment process. In this study, the thermal and morphological properties of the henna leaves were characterized. This research also investigated the effect of henna loading on mechanical, electrical and morphological properties of the henna-based biocomposites. Based on the thermal analysis, it can be highlighted that the henna leaves had good thermal properties while the proposed substrates had acceptable mechanical and electrical properties. The treated henna loading showed better mechanical result compared to the untreated one and the best mechanical properties are attributed by 20 vol% of henna loading. However, the untreated henna loading experienced better electrical characteristics and 40 vol% of henna loading has the highest dielectric constant value. Then, it was used for designing a novel UHF RFID tag antenna using graphene sheet operating at 915 MHz through the Finite Element Method (FEM) in Computer Simulation Technology Microwave Studio (CST MWS). The development of antenna design was started with basic dipole antenna and followed by implementing few miniaturization structures such as meander-line, matching stub and capacitive loading based on resonant frequency, reflection coefficient, surface current distribution, antenna impedance and power transmission coefficient. The dimension of tag antenna design was finalized to a compact size of 70 mm × 40 mm (0.214λ × 0.122λ). The effect of the dielectric constant of the substrates on RFID tag performance was experimentally investigated. Based on the simulation results, the dipole patch tag antenna provided a far theoretical read range of 7.91 - 8.57 m with a good power transmission coefficient up to 98.8% and conjugate match impedance which has reduced the length by 57.55% compared to a basic dipole antenna. It can be concluded that variation on dielectric constant values offers to tune the resonant frequency within UHF band.
UHF-RFID Application