IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

International Journal of Research in Information Technology (IJRIT)

www.ijrit.com

ISSN 2001-5569

CPW – FED Microstrip Patch Antenna for Ul Ultra Wideband Applications in S Band, C Band and X Band Arvind Yadav1, Kuldip Pahwa2 1

M.Tech Final Year Student, Department of ECE, M.M.U Mullana Ambala, Haryana, India [email protected] 2

Professor, Department of ECE, M.M.U Mullana Ambala, Haryana, India [email protected]

Abstract This paper presents a coplanar waveguide (CPW) – fed rectangular slot antenna for Ultra Wide Band (UWB) communication, which is printed on a dielectric substrate of FR4 with relative permittivity (εr) of 4.4, thickness of 1.5mm. The results show that the proposed antenna achieves an impedance bandwidth of 6.6GHz (2.4-9 GHz) with VSWR<2. These designed antennas have frequency ranges in Microwave S band, C band and X band. The proposed patch antenna is designed and simulated using Ansoft HFSS 11.0 software. Simulation results are presented in terms of Resonant Frequency, Return Loss, VSWR, Impedance Bandwidth and Antenna Gain.

Keywords: CPW feed line, HFSS, UWB antenna, VSWR, WiMax.

1. Introduction The modern trends in communication system and increasing other wireless applications, wider bandwidth is required, and traditionally each antenna operates at a single frequency band, where a different antenna is needed for different application. This will cause a limited space and place problem. In order to overcome this problem, ultra wideband antenna can be used where a single antenna can operate at wide frequency ranges [1-3]. It is well known fact that microstrip patch antennas offers many advantages such as low profile, light weight, ease of fabrication and compatibility with printed circuits. However, the serious problem of patch antennas is their narrow bandwidth. To overcome their inherent limitations of narrow impedance bandwidth many techniques have been proposed and investigated, for example, slotted patch antennas [4 6], microstrip patch antennas on electrically thick substrate, gap coupled patches, the use of various impedance matching and feeding techniques [7] – [8]. However, simultaneously bandwidth enhancement and size reduction are becoming major design considerations for practical applications of microstrip antennas as improvement of one of the characteristics, normally results in degradation of the other. In recent years, many techniques have been reported to achieve wideband patch antenna for modern wireless communication devices [9]. Our aim is to reduce the size of the antenna as well as increase the operating bandwidth. The proposed antenna (substrate with = εr 4.4) has impedance bandwidth (VSWR < 2) of 88% (2.4 – 9 GHz) centered at

Arvind Yadav,

IJRIT

519

IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

7.5 GHz and presents a size reduction of 37.03% when compared to a conventional microstrip patch (12mm X 9mm). The S, C band and X-Band defined by an IEEE standard for radio waves and radar engineering with frequencies that ranges from 2.0 to 4.0 GHz , 4.0 to 8.0 GHz and 8.0 to 12.0 GHz respectively. Wireless local area network (WLAN) requires three bands of frequencies: 2.4GHz (2400-2484MHz), 5.2GHz (51505350MHz) and 5.8GHz (5725-5825MHz). WiMax (Worldwide Interoperability for Microwave access) has three allocated frequency bands. The low band (2.5-2.8 GHz), the middle band (3.2-3.8 GHz) and the upper band (5.2-5.8 GHz). Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2GHz for their downlinks, and the band of frequencies from 5.925 GHz to 6.425 GHz for their uplinks. For military communications satellites, the International Telecommunications Union (ITU) has assigned the X band uplink frequency band (for sending modulated signals) as from 7.9 to 8.4 GHz. The ITUassigned downlink frequency band (for receiving signals) is from 7.25 to 7.75 GHz. The US military uses all frequencies in this spectrum; however, they use select signals on the frequencies throughout this spectrum. The proposed antenna parameters like return loss ,VSWR, gain, radiation pattern, E & H field distributions, current distributions are simulated using HFSS 11.0 which is a high-performance full-wave electromagnetic(EM) field simulator for arbitrary 3D volumetric passive device modeling that takes advantage of the familiar Microsoft Windows graphical user interface. It integrates simulation, visualization, solid modeling, and automation in an easy-to-learn environment where solutions to your 3D EM problems are quickly and accurately obtained. Ansoft HFSS employs the Finite Element Method (FEM), adaptive meshing, and brilliant graphics to give you unparalleled performance and insight to all of your 3D EM problems. Ansoft HFSS can be used to calculate parameters such as S-Parameters, Resonant Frequency, and Fields.

2. Proposed Antenna The three essential parameters for the design of a rectangular microstrip patch antenna are; a) Frequency of operation ( f 0 ): The resonant frequency of the antenna must be selected appropriately. The resonant frequency selected for design is 7.5 GHz. b) Dielectric constant of the substrate ( ε r ): The dielectric material selected for the design is FR4-epoxy which has a dielectric constant of 4.4. A substrate with a high dielectric constant reduces the dimensions of the antenna. c) Height of dielectric substrate (h): For the microstrip patch antenna it is essential that the antenna is not bulky. Hence, the height of the dielectric substrate is selected as 1.5mm. The design parameters that are assumed and evaluated are shown in Fig. 1(a) and Fig. 1(b) as below:

Fig. 1(a) Side View of Antenna

Arvind Yadav,

IJRIT

520

IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

Fig. 1(b) Top View of Antenna Step 1: Calculation of the Width (W): The width of the Microstrip patch antenna is given by [10] following equation:

Substituting εr=4.4, c=3x108m/sec, fo= 7.5GHz gives: W=12mm Step 2: Calculation of Effective Dielectric Constant (εreff): The following equation gives the effective dielectric constant as[10]:

Substituting εr=4.4, W=12mm, h=1.5mm gives: εreff =3.7 Step 3: Calculation of Effective Length ( Leff ): The effective length is given [10]as:

Substituting: fo=7.5GHz, c=3x108m/sec, εreff =3.7 gives: Leff =10.2mm Step 4: Calculation of the Length Extension (∆L): Equation below gives the length extension [10] as: ) Substituting the values, the length extension (∆L) is obtained as: ∆L=.6mm Step 5: Calculation of Actual Length of Patch (L): The actual length of the antenna can be calculated [10] as: Substituting Leff =10.2mm and ∆L=0.6mm the actual length come out to be: L=9mm Table 1 PARAMETERS

DIMENSIONS

Substrate Length

21mm

Substrate breadth

18mm

Substrate thickness

1.5mm

Arvind Yadav,

IJRIT

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IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

Dielectric constant of substrate

4.4

Tangent loss

0.02

Patch length

9mm

Patch breadth

12mm

Input resistance of the Patch (Rin)

50 Ω

Length of slot (L1)

5mm

Width of slot (w1)

8mm

3. Simulated Results 3.1 Return Loss It can be said that when the load is mismatched the whole power is not delivered to the load, there is a return of power to the source which is considered as loss and is termed as Return Loss”. The Return Loss is determined in dB as follows:

Where, Γ define the reflection coefficient. During the process of the design of the rectangular microstrip patch antenna there is a response taken from the magnitude of S11 Vs the frequency (this is known as return loss) as shown in Fig. 2.

Fig. 2 Return Loss A return loss of -25.610 is obtained at 7.59GHz. 3.2VSWR Voltage Standing Wave Ratio (VSWR) is the ratio between the maximum voltage and the minimum voltage along the transmission line. The VSWR, which can be derived from the level of reflected and incident waves, is also an indication of how closely or efficiently antenna terminal input impedance is matched to the characteristic impedance of the transmission line.

For an antenna, if VSWR≤2 and RL≤-9.5dB, it is said to have performed well.

Arvind Yadav,

IJRIT

522

IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

Fig. 3 VSWR VSWR at resonant frequency 7.5GHz is 1.11 3.3 Bandwidth The bandwidth of an antenna is defined as “the range of usable frequencies within which the performance of the antenna, with respect to some characteristic, conforms to a specified standard.” The bandwidth can be the range of frequencies on either side of the center frequency where the antenna characteristics like input impedance, radiation pattern, beam width, polarization, side lobe level or gain, are close to those values which have been obtained at the center frequency.

Fig. 4 Bandwidth 3.4 Gain Antenna gain is usually defined as the ratio of the power produced by the antenna from a far-field source on the antenna's beam axis to the power produced by a hypothetical lossless isotropic antenna, which is equally sensitive to signals from all directions. As a transmitting antenna, the figure describes how well the antenna converts input power into radio waves headed in a specified direction. As a receiving antenna, the figure describes how well the antenna converts radio waves arriving from a specified direction into electrical power.

Arvind Yadav,

IJRIT

523

IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 519- 524

Fig. 5 3D Gain Plot

4. Conclusion A CPW-FED rectangular slot patch antenna is designed and simulated through HFSS 11.0. The designed antenna is very simple in look and small in size .This antenna may be used for UWB applications in S band, C band and X band. Simulation results show that the antenna has VSWR < 2 from 2.4- 9 GHz and bandwidth of antenna is 6.6GHz (88%).The antenna parameters such as return loss, VSWR, impedance bandwidth, gain have been studied. Simulated results show that the proposed antenna could be a good candidate for UWB application.

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