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Improved ultra high frequency design of rfid patch antenna.

INTRODUCTION

The RFID based automated and intelligent systems are evolving fast for a very wide range of applications including market, business and health monitoring and controlling. Complex security and safety related solutions are also benefited from RFID technology. The RFID is a tag which is normally attached with object or it is mounted on any surface of the object. It can indicate the location of the object or it holds the product information such as specification and other relevant information. The tag along with object, if moves in the reading range of the reader, is able to communicate with reader device without any physical contact (Tashi et al, 2011). This is possible only because there is complete communication system including antenna for the pair of object and reader system. Only if object is out of the range of transmission, the reader will not be able to communication with the RFID tag. RFID enabled health care systems are automated for fast and accurate exchange of information in big hospitals (Samuel et al, 2012). The automation of healthcare has applications of information and communication technology at much larger scale. The information and communication technology has many advantages and features which are very critical and essential for efficient working of automated healthcare system (Kashwan et al, 2011). The RFID is much more effective automation compared to the bar codes which are normally used in many hospitals (Hsien-Wen et al, 2001). The information transfer can only be faultless and prompt only and only if antenna radiation is robust and fast enough to accomplish the task at hand in time (Ioannides et al, 2005). The tags which are sometimes called as transponders can be used to mark objects and animals. There are quite cheaper and forms low power wireless sensor networks as these communicate automatically for various purposes such as counting, tracking and monitoring.

1. Patch Antenna Design:

The design of the patch is indicated in Figure 1. The design is simulated on ADS software platform for simulation test and verification as physical structure is shown in Figure 1. The RFID tags are designed and operated at ultra high frequency range. At these frequencies, the communication is much adversely affected by material properties over which the tags are mounted or placed. Even metal surfaces are more interfering and act as lossy materials. Not only the parent material affects the radiation but even the surrounding objects cause considerable loss. In these conditions, it becomes more difficult to design an efficient and compact patch antenna. Among many type of possible antenna design, patch antenna design appears to be better choice. The patch antennas are very much suitable for metallic surface mounting (Amsavalli et al, 2014).

In general, if a tag does not have power on board then it is called a passive tag. A reader system transmits the radio signal and activates the tag. Then, the reader reads back as the data are transmitted from the tag mounted on any type of surface (Koo et al, 2007).

In this design, a compact and light weight planar antenna is designed and simulated for the performance test. A very compact patch of size 18 x 14 mm patch is designed on a substrate of thickness 0.4 mm. The substrate of FR4 is chosen with dielectric constant equal to the 4.4 approximately. The feed line width is maintained at 2.98 mm and characteristic impedance is achieved at 50 Q. The dielectric material of FR4 is sandwiched between patch on the top surface and a metallic ground plane. A slotted patch is designed as shown in the figure 1 (b). A slot of width of 1 to 2 mm is chemically etched out on the plated patch. The choice of the substrate is based on the dielectric constant for required frequency range of operations for the tag communications. The feed position is chosen by trivial method to obtain better gain and directivity for the given applications. 2

2. Results and Analysis:

The patch antenna designs, as discussed in the previous section are simulated on ADS software platform for performance evaluation. The gain, directivity and radiation intensity are illustrated in figure 2. The return loss and phase vs. frequency response is illustrated in figure 3, as shown above. As an example simulation for the design, the return loss is achieved at -21.638 dB for a resonance frequency of 2.45 GHz. The results and its analyses are shown in Figure 2 as shown above. The resonance frequency is observed at about 2.4 to 2.5 GHz at which the return loss is minimum most which is desirable for the patch.

The figure 3, also shows phase information at resonance frequency. The figure 4, as shown above illustrates radiation pattern and field distributions in space in all around directions taken into considerations. Table 1 lists important parameters and its values achieved after simulations are carried out. The complex gain and directivity are shown in dBi units in Table 1. The radiation efficiency is achieved at 91.21%. The input power is 0.5145 milli watt and radiated power is measured at 0.4693 milli watt. The patch operates at a very low power as distance range is very small, in the range of few 10s of meters.

3. Conclusion:

In this paper the author have designed and implemented a microstrip antenna for the RFID tags mounted on the surface of the antenna. The frequency range is chosen between 2.4 GHz and 2.5 GHz range. A microstrip antenna is further tested by simulating the design on ADS software platform. The performance analysis for return loss and phase vs. frequency indicates a return loss of -21.638 dB. The directivity and radiation patterns are analysed. The range of antenna is about 20 to 40 meters depending upon actual frequency and radiated power. The radiation efficiency is estimated as 91.21%. The patch antenna has applications in RFID tags for various purposes.

ARTICLE INFO

Article history:

Received 12 October 2014

Received in revised form 26 December 2014

Accepted 1 January 2015

Available online 25 February 2015

REFERENCES

Amsavalli, A. and K.R. Kashwan, 2014. "Smart Patch Antenna Array for Uplink in 4G Mobile Communication Based LMS Algorithm for DS-CDMA Technique", Journal of Convergence Information Technology, 9(1): 16-24.

Hsien-Wen Liu, Chung-Hsun Weng and Chang-Fa Yang, 2011. "Design of Near-Field Edge-Shorted Slot Microstrip Antenna for RFID Handheld Reader Applications", IEEE Antenna and Wireless Propagation Letters, 10: 1135-1139.

Ioannides, P. and C.A. Balanis, 2005. "Uniform Circular Array for Smart Antennas", IEEE Antennas and Wireless Propagation Magazines, 47(4): 192-206.

Kashwan, K.R., V. Rajesh Kumar, T. Gunasekaran and K.R. Shankar Kumar, 2011. "Design and Characterization of Pin Fed Microstrip Patch Antenna" In the Proceedings of Eighth IEEE Fuzzy Systems and Knowledge Discovery, 4: 2258-2262.

Koo, B.W., M.S. Baek and H.K. Song, 2007. "Multiple Antenna Transmission Techniques for UWB System", Progress in Electromagnetic Research Letters, 2: 177-185.

Samuel Fosso Wamba, 2012. RFID-Enabled Healthcare Applications, Issues and Benefits: An Archival Analysis (1997-2011), Journal of Medical Systems, Springer, 36: 3393-3398.

Tashi, Mohammad S. Hasan and Hongnain Yu, 2011. "A Complete Design of Microstrip Patch Antenna for a Passive UHF RFID Tag, Proceedings of the 17th International Conference on Automation and Computing", University of Huddersfield, Huddersfield, UK, pp: 12-17.

(1) Thirumalai, T. and (2) Kashwan, K.R.

(1) Electronics Corporation of India (Government of India Enterprize), IGCAR, Kalpakkam, Chennai--603102, Tamil Nadu, India.

(2) Department of Electronics and Communication Engineering, Sona College of Technology (Autonomous Institution), Salem --636005, India.

Corresponding Author: Thirumalai T., Electronics Corporation of India Limited (Government of India Enterprise), IGCAR, Chennai--603102, Tamil Nadu, India.

Ph: +91 9442213923, E-mail: ttm_jayala@yahoo.com

Table 1: Antenna Parameters.

Sl. No.       Antenna Parameters      Performance Metrics

1                 Frequency                 2.4 GHz
2                Input Power               0.5145 mW
3               Radiated Power             0.4693 mW
4                Directivity               5.76 dBi
5                    Gain                  5.36 dBi
6            Radiation Efficiency           91.21 %
7               Max. Intensity         0.14 W/Steradian
8              Effective Angle          3.33 Steradian
9          E(theta), Mag. and Phase    0.316 and 109.36
10          E(Phi), Mag. and Phase      0.77 d -31.122
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Article Details
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Title Annotation:radiofrequency identification
Author:Thirumalai, T.; Kashwan, K.R.
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Date:Jun 1, 2015
Words:1361
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