scholarly journals Investigating Equations Used to Design a Very Small Normal-Mode Helical Antenna in Free Space

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Dang Tien Dung ◽  
Quoc Dinh Nguyen ◽  
Do Quoc Trinh ◽  
Yoshihide Yamada
Keyword(s):  
Normal Mode ◽  
Radio Frequency Identification ◽  
Electrical Characteristics ◽  
Helical Antenna ◽  
Tire Pressure ◽  
Electromagnetic Simulations ◽  
Short Dipole ◽  
Small Loop ◽  
Frequency Identification ◽  
Helical Antennas

A normal-mode helical antenna (NMHA) has been applied in some small devices such as tire pressure monitoring systems (TPMS) and radio frequency identification (RFID) tags. Previously, electrical characteristics of NMHA were obtained through electromagnetic simulations. In practical design of NMHA, equational expressions for the main electrical characteristics are more convenient. Electrical performances of NMHA can be expressed by a combination of a short dipole and small loops. Applicability of equations for a short dipole and a small loop to very small normal-mode helical antennas such as antennas around 1/100 wavelengths was not clear. In this paper, accuracies of equations for input resistances, antenna efficiency, and axial ratios are verified by comparisons with electromagnetic simulation results by FEKO software at 402 MHz. In addition, the structure of the antenna equal to 0.021 λ is fabricated, and measurements are performed to confirm the design accuracy.

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

2020 ◽  
pp. 004051752094890
Author(s):  
Yong Zhang ◽  
Jiyong Hu ◽  
Xiong Yan ◽  
Xudong Yang
Keyword(s):  
Resonant Frequency ◽  
Normal Mode ◽  
Radio Frequency Identification ◽  
Dipole Antenna ◽  
Uhf Rfid ◽  
Simulation Experiments ◽  
Rfid Tag ◽  
Helical Pitch ◽  
Frequency Identification ◽  
Linear Dipole

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.

Design and Evaluation of Planar Bifilar Helical Antennas for Radio Frequency Identification Tags

2019 ◽  
Vol 18 (12) ◽  
pp. 2642-2646
Author(s):  
Weikang Chen ◽  
Zhenyi Niu ◽  
Mengyuan Li ◽  
Zhuo Li ◽  
Qian Xu ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Radio Frequency Identification ◽  
Frequency Identification ◽  
Identification Tags ◽  
Helical Antennas

scholarly journals Increase of Input Resistance of a Normal-Mode Helical Antenna (NMHA) in Human Body Application

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 958 ◽  
Author(s):  
Norsiha Zainudin ◽  
Tarik Abdul Latef ◽  
Narendra Kumar Aridas ◽  
Yoshihide Yamada ◽  
Kamilia Kamardin ◽  
...  
Keyword(s):  
Normal Mode ◽  
Human Body ◽  
High Performance ◽  
High Efficiency ◽  
Input Resistance ◽  
Resonant Mode ◽  
Helical Antenna ◽  
Antenna Structure ◽  
Electromagnetic Simulations ◽  
Physical Reasons

In recent years, the development of healthcare monitoring devices requires high performance and compact in-body sensor antennas. A normal-mode helical antenna (NMHA) is one of the most suitable candidates that meets the criteria, especially with the ability to achieve high efficiency when the antenna structure is in self-resonant mode. It was reported that when the antenna was placed in a human body, the antenna efficiency was decreased due to the increase of its input resistance (Rin). However, the reason for Rin increase was not clarified. In this paper, the increase of Rin is ensured through experiments and the physical reasons are validated through electromagnetic simulations. In the simulation, the Rin is calculated by placing the NMHA inside a human’s stomach, skin and fat. The dependency of Rin to conductivity (σ) is significant. Through current distribution calculation, it is verified that the reason of the increase in Rin is due to the decrease of antenna current. The effects of Rin to bandwidth (BW) and electrical field are also numerically clarified. Furthermore, by using the fabricated human body phantom, the measured Rin and bandwidth are also obtained. From the good agreement between the measured and simulated results, the condition of Rin increment is clarified.

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