Inset Fed Rectangular Microstrip Patch Antenna for UHF Radio Frequency Identification

DOI : 10.17577/IJERTV4IS080501

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Inset Fed Rectangular Microstrip Patch Antenna for UHF Radio Frequency Identification

Pawan Kumar Punia

M. Tech Student Dept. of EEE

JCD College of Engineering Sirsa, India

Ria Kalra Assistant Professor Dept. of EEE

JCD College of Engineering

Sirsa, India

B. Mohapatra

Professor, Dept. of ECE

Noida Institute of Engg & Technology Greater Noida, India

Abstract In this paper a 0.92 GHz inset line fed rectangular microstrip patch antenna has been designed for UHF RFID application with return loss more than -32db, bandwidth 2.71 %

The width is given by W = 2

2 +1


and VSWR 1.0473. Design and simulation of this antenna has been done on HFSS software.

Keywords UHF RFID, Inset-Feed Line, Rectangular Microstrip Antenna, VSWR, Return loss, HFSS.

Where, is the resonant frequency of the patch antenna, is the free space velocity of light. The effective dielectric constant for the space of ()> 1) [12] is given by

= +1 + 1 [1 + 12/]1/2 (3)


Microstrp patch antenna is a type of antenna that offers a low profile, i.e. thin and easy manufacturing ability, which provides great advantages over traditional antennas [1]. Some of the disadvantages of microstrip antenna configurations

The extension of patch length due to fringing effect can be determined by

includes narrow bandwidth, however this disadvantage turn

= 0.412 (+ 0.3) ( + 0.26)


out to be advantage for UHF RFID reader as RFID

application do not need much bandwidth because antenna

( 0.258) (+ 0.8)

rejects the signals that are out of the band and accordingly increases the quality factor. [2] These antennas can be placed on land or space vehicles, easy to networks for tens or

The effective length of patch after taking into fringing effect can be calculated by

hundreds element, connected directly to the power supply device that goes in the direction of integrating the antenna and power supply. [3] [4]

Radio Frequency Identification (RFID) is a technology

L =


– 2 (5)


    to transmit the identity of an object or person at a distance without a direct line of sight using radio waves. Now days RFID is widely used in logistics management, inventory control, service industries, and goods flow systems etc. Recently there have been many studies on RFID antenna mostly on Ultra High Frequency, UHF band [8] and even on dual band antenna. [6] [7] RFID system demands low profile, low cost and easily fabricated antenna. So microstrip patch antenna offers a potential solution and therefore it is a popular printed resonant narrow band antenna for this application. [5] [10]


      In the most basic form, patch antenna consist of radiating element and a ground plane separated by a dielectric substrate. In this work we have used transmission line modal. All the dimensions of the antenna are calculated based on equations (1)-(5) [9] [11]. The length is given by

      Fig. 1 shows the proposed inset fed line rectangular microstrip patch antenna constructed on substrate layer of material Rogger TMM4 ™ having relative permittivity () = 4.5 and thickness (h) = 1.5mm with Tangent (tan)

      = 0.002.

      L = 0.49


      Fig.1. Geometry of the proposed antenna


        Antenna resonant frequency () is 0.92GHz which was intended for UHF RFID applications. As shown in Fig. 2, the length (L) of patch antenna is 77 mm and its width (W) is 98 mm. The inset feed line () is 7 mm, with feed line width () of 1 mm and inset gap (1) is 3 mm. The patch antenna and the power line are engraved on the same substrate.

        Fig. 2. HFSS design model of proposed antenna

        After the laborious iteration work of antenna dimensions, such as length (L), width (W) and inset feed line () -26 dB return loss is achieved as shown in table 1 and Fig. 3.


        Inset Gap (1)

        Return loss


        -11.9264 db


        -7.9610 db


        -25.8950 db


        -14.2506 db


        -3.0481 db

        Fig. 3. Inset gap plot against return loss

        As by changing the dimensions of proposed patch antenna, resonant frequency can be controlled. The Fig. 4 shows return loss as the function of frequency. Here we see that reflection coefficient (11) is more than -32db. Which implies that antenna is well suitable with bandwidth of 2.71%.

        Fig. 4. Return loss in db

        The standing wave ratio (VSWR) is shown in Fig. 5 depending on the frequency. The result and order of VSWR 1.0473 is shows high suitability.

        Fig. 5. Standing Wave Ratio

        Table II summaries the result obtained in our work. Fig. 6 and Fig. 7 shows radiation pattern and 3D polar plot of antenna proposed.




        11 (db)






        Bandwidth (%)


        Fig. 6. Radiation pattern of proposed antenna

        Fig. 7. 3D Polar plot of designed antenna


From the simulation analysis of proposed antenna it can be easily observed that the designed inset fed rectangular microstrip patch antenna is a suitable option for UHF RFID application with its numerous advantages over the other antenna, it is light weight, inexpensive and easy to integrate with accompanying electronics. Detail knowledge of antenna parameters and HFSS software is required to design and simulate desired results. Here return loss of -32.73 db and VSWR 1.0473 with 2.71% bandwidth is achieved by estimated variation of antenna dimensions.


  1. Constantine A. Balanis, Antenna Theory: Analysis and Design. New York: John Wiley& Sons Inc., 1997.

  2. L. I. Basilio, M.A. Khayat, J.T. Williams and S.A. Long, "The Dependence of the Input Impedance on Feed Position of Probe and Microstrip Line-fed Patch Antennas," IEEE Trans. Antennas and Propagation, Vol. AP-49, pp. 45-47, Jan. 2001

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