Structure optimization of an ultrahigh frequency radio frequency identification tag thread based on the normal mode helix dipole antenna

Abstract

This paper describes the design of a novel ultrahigh frequency radio frequency identification (UHF RFID) tag thread that mainly consisted of the common yarn and the normal mode helix dipole antenna. The linear dipole antenna for the UHF RFID tag thread was too long to miniaturize the tag. In order to maximize the read performance and miniaturize the size of the tag, the basic antenna structure parameters, such as the helical pitch and single arm length, were optimized by analyzing the radiation parameter S11 of the normal mode helix dipole antenna based on simulation experiments. The simulation experiments started with optimizing the single arm length to obtain the minimum of the S11 parameter at resonant frequency, then the helical pitch was further optimized to limit the resonant frequency to the UHF range. The simulation results showed the resonant frequency rises with an increase of helical pitch and declines with an increase of single arm length. Furthermore, a series of UHF RFID tag threads with good performance from the simulation cases were prepared, and the performance of the optimized tag was validated. Generally, the UHF RFID tag thread with optimized helix dipole antenna could reduce the axial length of the tag by 57% and improve the reading range by 500%, and its performance was greatly superior to that of the UHF RFID tag thread with the classical linear dipole antenna.

The influence of structure uniformity on resonant frequency of ultra-high frequency radio frequency identification tag thread With normal mode helix dipole antenna

“…For the NMHDA with the helical radius of 0.55 mm and the single arm length of 63.0 mm, when the helical pitch increased from 1.0 mm to 2.0 mm, the resonant frequency increased more than 150 MHz. 10 Obviously, the change of resonant frequency in the above cases were greater than the Chinese UHF RFID band (920–925 MHz). These results demonstrates that the structure uniformity from manufacturing process has a significant impact on the resonant frequency of UHF RFID tag thread with NMHDA.…”

“…Helical pitch. According to the geometric size of the common UHF RFID tag thread with NMHDA, 10,11 the helical radius was set to 0.615 mm. The helical pitches were randomly generated by the normal distribution.…”

Physical relationship between resonant frequency and structure parameters of a normal mode helix dipole antenna for an ultra-high frequency radio frequency identification tag thread

“…Firstly, the helical pitch and single arm length of NMHDAs were set as the extreme values of their respective ranges and are listed in Table 1. In addition, previous work 3 showed that an UHF RFID tag thread with a helical pitch of 1.0 mm, a single arm length of 43.0 mm, and a helical radius of 0.55 mm had good reading performance, and this case was also included in Table 1 to validate Equation (13).…”

“…The geometry structure of the UHF RFID tag thread based on a helical dipole antenna is shown in Figure 1. According to previous work, 2,3 because A ≪ λ , the helix dipole antenna for the UHF RFID tag thread works as a normal mode helix dipole antenna (NMHDA), that is, the radiation pattern of the antenna is maximum in a plane normal to the axis of the helix. The NMHDA mainly works near the resonant frequency for great reading performance.…”