Design and development of a low-cost high-performance vehicle mounted UHF RFID system for tracking goods and inventory.

Abstract

This research work investigates how to design and implement a low-cost high-performance vehicle mounted ultra-high frequency (UHF) radio frequency identification (RFID) system to keep track of cargo whilst in transit. The vehicle mounting include – inside or on cargo vehicle enclosures, the shipping containers, and so forth. In order to achieve a low-cost system, a low cost circularly polarized microstrip patch antenna, which also had a low axial ratio (AR) was designed. Since multiple antennas will be used, the cost factor will be reduced substantially if the cost of each antenna was reduced as compared to reducing the cost of a single RFID reader. The proposed antenna design, measuring 200mm x 200mm x 6.4mm, utilized the corner truncated technology with a thicker substrate and larger ground plane. Two independent simulations were done as well as empirical work. One of the simulations used Computer Simulation Technology (CST) studio suite software and the other used gpr Max simulation software. The investigations aimed at determining how different materials (steel, plastic, and wood) worsen the performance of the UHF RFID system inside a steel container as well as in free space. The investigation involved placing these materials onto the RFID tag and then varying the thickness of the material. The simulation results showed that the proposed antenna has a reflection coefficient of less than -10dB from 886.23 MHz to 924.96 MHz with a bandwidth of 38.73 MHz. The antenna provides the AR less than 3 dB for the frequency range from 915 MHz to 919 MHz. The designed and fabricated antenna has a bandwidth of 57.527 MHz and achieves a minimum reflection coefficient of -27.97 dB at 914.045 MHz. These results were then compared to other similar antenna designs. The antenna designed in this research achieved a lower axial ratio while still offering a respectable amount of gain, directivity and bandwidth. Previous papers showed that there was always a notably trade-off between having a low axial ratio and a high gain, directivity or bandwidth. The results for the simulation tests indicated that wood performs the best, followed by plastic and then steel. Wood and plastic were still detected by the RFID reader’s antenna at their maximum thickness of 20cm and 5cm respectively. It was further found out that the RFID system performs better inside a steel container than in free space. In conclusion the design of a low-cost high-performance circularly polarized microstrip patch antenna allows the cost of the overall UHF RFID system to be reduced, making it a more cost-effective solution for tracking containerized cargo. The antenna also achieved circular polarization which is beneficial to the performance of the UHF RFID system. A circularly polarized antenna allows the UHF RFID reader to detect RFID tags in almost any orientation. The simulation results emulate the data obtained when a horizontally orientated paper RFID tag was used. The results obtained showed the use of steel performed optimally when it is placed directly in line with the receiver. When using plastics, placing them directly in line with the receiver at a distance of 2.36 m, does not offer the best performance. If the plastic material is placed 3 m to the side of the receiver, it is best to use thicker material. The power increased by 3.73 dBm when the thickness of the plastic, increased from 5 mm to 50mm. The system’s performance increased with wood when the RFID tag is in line with the receiver at a distance of 2.36 m, and as the thickness was increased from 20 mm to 200 mm. When the RFID tag was placed 3 m to the side of the receiver, the system’s performance decreased as the thickness was increased from 20 mm to 200 mm.