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Performance evaluation of circular microstrip

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  • 1. INTERNATIONAL JOURNAL OF ELECTRONICS AND International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMECOMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)ISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 4, Issue 1, January- February (2013), pp. 236-249 IJECET© IAEME:www.iaeme.com/ijecet.aspJournal Impact Factor (2012): 3.5930 (Calculated by GISI) ©IAEMEwww.jifactor.com PERFORMANCE EVALUATION OF CIRCULAR MICROSTRIP PATCH ANTENNA ARRAY WITH DIFFERENT DIELECTRIC SUBSTRATE MATERIALS K. Karuna Kumari1, Dr.P.V.Sridevi2 1 Department of ECE, GITAM University, Visakhapatnam, A.P., India, 2 Department of ECE, Andhra University, Visakhapatnam, A.P., India, ABSTRACT In high-performance aircraft, spacecraft, satellite, and missile applications, where size, weight, cost, performance, ease of installation, and aerodynamic profile are constraints, and the low-profile antennas may be required. Presently there are many other government and commercial applications, such as mobile radio and wireless communications that have similar specifications. To meet these requirements, micro strip antennas can be used. There are various types of micro strip patch antennas of which circular micro strip patch antenna is considered. This paper involves design, simulation of circular micro strip patch antenna in S-band frequency used for Wi-Fi applications (2.0-2.5GHz) using a conventional coaxial probe feed technique. Using design specifications like frequency range, dielectric permittivity of substrate, substrate height, input impedance the electrical measurements like V.S.W.R, Return Loss, will be carried out in MATLAB software and also observe the Radiation Patterns with the different values of dielectric constants. The array of circular patch antenna is also designed considering the cases of uniform and non-uniform arrays. The uniform array is implemented with a linear array and non-uniform array is designed with Dolph- Tschebycheff array. The radiation patterns of both the arrays are generated. All simulating results are obtained by using MAT Lab soft ware. KEY WORDS:Circular Micro strip Patch Antenna, Antenna Arrays, Dielectric Constant of the Substrate, MATLAB soft ware. 236
  • 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME1. INTRODUCTION 1.1 Theory of Microstrip Antenna: Patch antennas play a very significant role in today’s world of wirelesscommunication systems. A Microstrip patch antenna is very simple in the construction usinga conventional Microstrip fabrication technique. The most commonly used Microstrip patchantennas are rectangular and circular patch antennas. These patch antennas are used as simpleand for the widest and most demanding applications. Dual characteristics, circularpolarizations, dual frequency operation, frequency agility, broad band width, feed lineflexibility, beam scanning can be easily obtained from these patch antennas1.2 Patch Antenna Materials: In the wide range of antenna models there are different structures of Micro stripantennas, but on the whole we have four basic parts. They are:1) The patch 2) Dielectric Substrate 3) Ground Plane 4) Feed Line Fig 1: Micro strip circular Patch AntennaPhysical Radius of the Circular Patch equationgiven by F a = 1/ 2  2h  ∏F   1 +  ln  2 h  + 1 . 7726     ∏εrF     (1) 8 . 791 X 10 9 (2) F = fr ε r The effective radius of the antenna is obtained with equation given by 1/ 2  2h  ∏ a  a e = a 1 +  ln + 1 .7726    ∏ aε r  2 h  (3) 237
  • 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMEA thin metallic region which has different shapes and sizes of the patch where the groundplane is usually of the same materialthe dielectric material is commonly known as substrate.The dielectric constant for the materials range from 2.1 to ≈ 122.DESIGN OF CIRCULAR MICROSTRIP PATCH ANTENNA2.1Cavity model The circular patch antennas can only be analyzed conveniently using the cavity modeland this can be accomplished using a cylindrical coordinate. The major modes supported by acircular patch antenna are the TMzwhere z is taken perpendicular to the patch and can befound by treating the patch, ground plane and the substrate, whose height is smallas a circularcavity.2.2Equivalent Current Densities and Fields Radiated Applying the Equivalence principle to the circumferential wall of the cavity, theequivalent magnetic current density can be obtained and assuming a TM11z mode the fielddistribution under the patch. The evaluation of equation of the electrical equivalent edge ofthe disk and magnetic current density can be expressed as ) (3) M a = −2nΧ E a ρ = aeSince the thickness of the substrate is very small, the filamentary magnetic current becomes I m = hM = a 0 2 hE 0 J 1 (ka e ) cos φ ˆ a (4) I m = a e 2 V 0 cos φWhereV0 = hE 0 J 1 ( Ka e ) At φ = 0The patch antenna can be treated as a circular loop and using the radiation equations theexpression is given by E r = 0 ; ( ) E ρ = − jk 0 a eV0 e − jk σr / 2 r [cos φJ 02 ] (5) Eφ = ( jk 0 a eV 0 e − jk σ r)[cos θ sin φ J 02 ] (6) 2rThen the field in the principal plane reduced to when E-plane φ = 0 0 ,180 0 , 0 ≤ θ ≤ 180 0 Eρ = ( jk a V e 0 e 0 − jkσr )[ J (7) 02 ] 2r Eφ = 0 238
  • 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME 0 0 0 Also, H-plane ( φ = 90 ,270 ,0 ≤ θ ≤ 90 ) are: Eφ = ( jk a V e )[cosφJ 0 e 0 − jkσr ] 02 2r (8) Where J 02 = J 0 (k0ae sinθ ) − J 2 (k0ae sinθ ) (9) J 02 = J 0 (k0 ae sin θ ) + J 2 (k0 ae sin θ ) (10)3. MICROSTRIP PATCH ANTENNA ARRAYS Microstrip antennas are used not only as single element but are very popular in arrays.Arrays are very versatile and are used to synthesize a required pattern that cannot be achievedwith a single element. Arrays increase the directivity, and perform various other functionswhich would be difficult with any one single element. In this paper presenting the twodifferent arrays3.1. Uniform N-Element Linear Array(Uniform spacing, uniform amplitude, linear phase progression) A uniform arrayis defined as the uniformly-spaced identical elements of equalmagnitude with a linearly progressive phase from element to element. φ1 = 0 φ2 = α φ3 = 2α … φ N = ( N − 1)α Figure: 2Micro strip antenna arrays3.2 Design equations of Uniform Linear Circular Array : In this analysis insertingthe linear phase progression into the formula for the general Nelement of array gives ψ ψ ψ  Nψ  jNψ jN jN − jN ψ sin  e −1 e e − e 2 2 2 j( N−1)  2  AF= jψ = jψ jψ ψ =e 2 Where ψ = α + kd cos θ (11) e −1 −j ψ  e e −e 2 2 2 sin   2 239
  • 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEMEThe function Ψ is defined as the array phase functionand is a function of the element spacing,phase shift, frequency and elevation angle. If the position of the array is shifted so that the center of the array is located at theorigin, this phase term goes away. Then the array factor becomes  N ψ  sin   AF =  2  ψ  (12) sin    2 For the microstrip array antenna, the x-y plane (θ=pi/2, 0 ≤φ≤ pi/2, 3pi/2 ≤φ≤ 2pi) is theprincipal E-plane. For this plane, the expression for the radiated fields is E a (φ ) = E (φ ) × AF k h   Nψ  sin  0 cos φ  sin    2  sin  k 0 L cos φ  ×  2  =   k0h cos φ  2  ψ  sin   2  2  (13)3.3 Non Uniform N (odd)-Element Linear Array(Dolph-Tschebyscheff Array)(Uniform spacing, but non uniform amplitude distribution)Dolph-Tschebyscheff Array is primarily a compromise between uniform and binomial arrays.Its excitation coefficients are related to Tschebyscheff polynomials. A Dolph-Tschebyscheff array with no side lobes (or side lobes of −∞ dB) reduces to the binomialdesign.1.3 Design equations of Non Uniform (Dolph-Tschebyschef) Array: P = 2 M + 1(odd ) (14) (E) = E +.....+ E + E + E + E +....+ E = 2I E {a + a cos( cosθ ) + a cos( kdcosθ) +...a kd 2 cos( cosθ)} Mkd P M +1 2 1 1 2 M +1 0 0 1 2 3 M +1(15) M +1 M +1 ∏ d ( AF ) P = ∑ n =1 a n cos[ 2 ( n − 1 ) λ cos = ∑ n −1 a n cos[ 2 ( n − 1 ) u ] (16) ∏d (17) u= cos θ λ P = 2 M (even ) (18) ( E ) P = E M + ... + E 2 + E1 + E1 + E 2 + ... + E M = 1 3 2M − 1 = 2 I 0 E 0 {a1 cos( kd cos θ ) + a 2 cos( kd cos θ ) + ...a M cos( kd cos θ )} 2 2 2 (19) 240
  • 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME M M ∏d ( AF ) P = ∑a n cos[ 2 n − 1) λ cos θ ] = ∑a n cos[( 2 n − 1) u ] n =1 n −1 (20)4.SIMULATED RESULTS&DISCUSIONS All simulated results are possible with the help of MAT Lab software. Outputparameters of physical radius &Effective radius of the circular patch and Directivity of microstrip antennas with different values of dielectric constants are tabulated in table 1. From theoutput parameters, observed that with the high value of dielectric constant 9.8(Alumina),Theantenna physical parameters like Physical Radius(a), Effective Radius(ae) of the antenna1.1236cm, 1.1022cm. As well as The Directivity of the antenna is 5.33dB also reducedButwith the low value of dielectric constant 2.23 (Duriod), the size of the antenna, a= 2.3585cm,ae=2.25cm and Directivity of the antenna 7.3496dB are also increased. Dielectric Dielectric Dielectric Constant of Dielectric Dielectric Dielectric Constant Constant of the Constant Constant Constant of of the the substrate of the of the the substrate Parameters substrate substrate 4.7 substrate substrate 2.1 9.8 2.55 (FR4 ) 2.6 2.23 (Teflon) ( Alumina) (Rexolite14 (Noryl) (Duroid) (PTFE) 22) PhysicalRadius of the 1.1236 2.4307 1.6231 2.1837 2.2051 2.3585 patch ( cm) Effectiveradius of the 1.1022 1.5749 2.0918 2.1112 2.2500 2.3149 patch ( cm) Directivity 7.3496 (dB) 5.3306 5.9865 6.9879 7.0310 7.5044 E-PLANE HPBW 180.0000 180.0000 104.0000 102.0000 90.0000 94.0000(in degrees) H-PLANE HPBW 86.0000 80.0000 84.0000 80.0000 78.0000 78.0000(in degrees) Table: 1 Physical Parameters Circular Microstrip Patch AntennaThe design of this circular micro strip patch antenna exhibits different values of VSWR andReturn Losses with different values of dielectric constants at the operating frequency of2.5GHz. Shown inFig.3&Fig.4 241
  • 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Frequency Verses Return Losses for different values of Dielectric constant of 0 -2 -4 -6 Return Loss(dB) -8 -10 -12 Er=9.8, Return Loss=-11dB Er=4.7, Return Loss=-13dB -14 Er=2.55, Return Loss=-14dB Er=2.23, Return Loss=-16dB -16 Er=2.1, Return Loss=-17dB -18 1 1.5 2 2.5 3 3.5 4 4.5 5 Frequency (Hz) 9 x 10 Fig: 3 Return losses of circularmicrostrip with differentvalues of dielectric Constants At the operating frequency of 2.5 GHz Frequency Verse VSWR for Different Values of Dielectric Constant of 5.5 Er=2.1 5 Er=2.23 Er=2.55 4.5 Er=4.7 Er=9.8 4 VSWR 3.5 3 2.5 2 1.5 1 1 1.5 2 2.5 3 3.5 4 4.5 5 Frequency (Hz) 9 x 10 Fig: 4 VSWR at the different Values of dielectric Constants at center frequency of 2.5 GHz 242
  • 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME S-Band Frequency Verses Return Loss 0 -2 -4 -6 F6=2GHz ReturnLoss(dB) -8 F5=2.1GHz -10 F4=2.2GHz -12 F3=2.3GHz -14 -16 F2=2.4GHz -18 F1=2.5GHz -20 1 1.5 2 2.5 3 3.5 4 4.5 5 Frequency (GHz) 9 x 10Fig: 5 Return losses of Circular Microstripantenna at the different frequencies (2- 2.5GHz) with low value of dielectric constant 2 S-Band Frequency verses VSWR(dB)&Return Loss(dB) 5 0 VSWR (dB)&Return Loss(dB) VSWR(dB) -5 Return Loss(dB) -10 -15 -20 2 2.05 2.1 2.15 2.2 2.25 2.3 2.35 2.4 2.45 2.5 S-Band Frequency (GHz)Fig: 6Return losses of Circular Microstrip antenna at the different frequencies (2- 2.5GHz) with low value of dielectric constant 2The design of the antenna exhibits good VSWR (2-1.1dB), Return Loss equal to -19dB to -8dB) at2- 2.5 GHz(S-Band) frequency shown in Fig.5& Fig.6 243
  • 9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME S-Band Frequency S.No VSWR(dB) Return Loss(dB) (GHz) -8 1 2 2 -9 2 2.1 1.8 -11 3 2.2 1.6 -13 4 2.3 1.5 -16.5 5 2.4 1.1 -19 6 2.5 1.05 Table: 2 return loss & VSWR of S-Band (2GHz- 2.5GHz) frequency.The design of Circular Microstrip patch antenna is extended to implement with the antennaarrays and their performance is evaluated for both Uniform and Non-Uniform circular arrays.The Uniform Array is implemented with Linear Array and Non-uniform arrays isimplemented using Dolph-Tschebyscheff Arrays ,The radiation pattern of the array circulararray are plotted with different values of dielectric constants εr =2.23&9.8. Non Uniform Linear Array with er=2.23) Uniform Linear Array with 0 0 -5 -5 -10 -10 Relative Amplitude in -15 Relative Amplitude in -15 -20 -20 -25 -25 -30 -30 -35 -35 -40 -40 -45 -45 -50 -50 -50 0 50 -50 0 50 θ In Degrees θ In DegreesFig: 7 Radiation patterns for non uniform and uniform linear array with εr =2.32&10 Element circular array 244
  • 10. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Non uniform Linear Array with er=9.8 Uniform Linear Array with 0 0 -5 -5 -10 -10 Relative Amplitude (dB) Relative Amplitude (dB) -15 -15 -20 -20 -25 -25 -30 -30 -35 -35 -40 -40 -45 -45 -50 -50 -50 0 50 -50 0 50 θ (Degrees) θ(Degrees)Fig: 8 Radiation pattern for non uniform and uniform linear array with εr =9.8 &10 Element circular array Uniform Linear array with er=2.23 vs er=9.8 0 er=2.23 -5 er=9.8 -10 -15 Relative Amplitude(dB) -20 -25 -30 -35 -40 -45 -50 -80 -60 -40 -20 0 20 40 60 80 θ (Degrees) Fig.9 Radiation pattern for uniform linear array with εr = (2.23&9.8) &10 Element circular array 245
  • 11. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Non-Uniform array with er=2.23 vser=9.8 0 er=2.23 -5 er=9.8 -10 Relative -15 -20 -25 -30 -35 -40 -45 -50 -80 -60 -40 -20 0 20 40 60 80 θ (Degrees) Fig: 10 Radiation pattern for Non uniform (Dolph-Tschebyscheff) linear array with εr = (2.23&9.8) &10 Element circular array Rectagular Plot of Non-Uniform vs Uniform array with er=2.23 0 Non Uniform array -5 Uniform array -10 -15 Relative Amplitude in dB -20 -25 -30 -35 -40 -45 -50 -80 -60 -40 -20 0 20 40 60 80 θ in Degrees Fig: 11 Comparison Radiation patterns of Uniform& Non uniform (Dolph-Tschebyscheff) linear array with εr = 2.23&10 Element circular array 246
  • 12. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME Rectagular Plot of Non-Uniform vs Uniform array with er=9.8 0 Non Uniform Array -5 Uniform -10 Relative Amplitude (dB) -15 -20 -25 -30 -35 -40 -45 -50 -80 -60 -40 -20 0 20 40 60 80 θ (Degrees) Fig: 12 Comparison Radiation patterns of Uniform& Non uniform (Dolph-Tschebyscheff) linear array with εr = 2.23&10 Element circular array Relative Non Uniform array with er=2.23 vs 9.8 0 er=2.23 -10 er=9.8 -20 -30 -40 -50 -80 -60 -40 -20 0 20 40 60 80 θ (Degrees) Relative Uniform array with er=2.23 vs 9.8 0 er=2.23 -10 er=9.8 -20 -30 -40 -50 -80 -60 -40 -20 0 20 40 60 80 θ (Degrees) Fig.13Comparison Radiation patterns of Uniform&Non uniform (Dolph-Tschebyscheff) linear array with different εr = 2.23&9.8,10 Element circular array 247
  • 13. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME er=2.23 0 Relative Amplitude(dB) Non Uniform array -10 Uniform array -20 -30 -40 -50 -80 -60 -40 -20 0 20 40 60 80 θ(Degrees) er=9.8 0 Relative Amplitude(dB) Non Uniform array -10 Uniform array -20 -30 -40 -50 -80 -60 -40 -20 0 20 40 60 80 θ(Degrees) Fig: 14 Comparison Radiation patterns of Uniform& Non uniform (Dolph-Tschebyscheff) linear array with different εr =2.23&9.8, 10 Element circulararray Dielectric SLL of Non SLL of Uniform linear S.No constant of Uniform linear circular array Substrate (εr) circular array 1 1 -30 -13.5 2 2.23 -29 -13.5 3 4.4 -28 -13.5 4 9.8 -27 -13.5 Table: 3comparisons between uniform &non uniform circular array SLL with different εr values Dielectric constant of substrate verses Side Lobe Level(dB) -12 -14 -16 Uniform array -18 Non Uniform array id o e e l(d ) S e L b L ve B -20 -22 -24 -26 -28 -30 1 2 3 4 5 6 7 8 9 10 Dielectric constant of substrate(er) Fig: 15 Plot between dielectric constant of substrate verses Side Lobe Level (SLL) of for uniform & Non uniform 248
  • 14. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 1, January- February (2013), © IAEME5. CONCLUSIONS In this paper, we presented the design of a circular patch antenna with operating frequency of2.5 GHz. The design of antenna with lower value of substrate dielectric constant of exhibits goodVSWR approx.1.1dB, Return Loss approx equal to -17dB, Directivity equal to 7.5 dB The design isextended to microstrip antenna array and the performance is evaluated for both Uniform and Non-Uniform arrays. The Uniform Array is implemented with Linear Array and the Non-Uniform array isimplemented using Dolph-Tschebyscheff Array .The radiation pattern is plotted with different valuesof dielectric constant εr =2.23 (RT Duroid 5880) &9.8(Alumina) From the simulated results observedthat in the case of uniform linear arrays, as array size is increased to increase the directivity but theSide Lobe Levels are at -13.5dB, with εr=2.23&9.8. But in case of Non Uniform Linear Array (Dolph-TschebyscheffArray) with εr=2.23&9.8, provides optimum beam width and Side Lobe Levels arereduced to -30dB&-28 dB. From the simulated results we concluded that for the Design of CircularMicro strip Antenna with Non Uniform Distribution of(Dolph-Tschebyscheff) Array with lowervalues of dielectric constant, εris preferred to get the optimum Directivity, Reduced Side Lobe Level,Good VSWR, Good Return Losses . Circular microstrip antenna array is good choice to usein Wi-FiModems, Wi-Max applications.6. REFERENCES[1] Balanis C.A. (2005) Antenna Theory: Analysis and Design, John Wiley & Sons[2] Ramesh G, Prakash B, Inder B, and Ittipiboon A. (2001) Microstrip antenna design handbook, Artech House.[3] G. Breed, “The fundamentals of patch antenna design and performance,” From Highfrequency electronics Summit technical media, LLC, March 2009.[4] J. R James and P. S Hall, Handbook of microstrip antennas, Stevenage, UK: Peregrines, 1989.[5] K. A Michalski and D. Zheng, “Analysis of microstrip resonators of arbitrary shape,” IEEE Trans. Microwave Theory Tech, vol. 40 pp. 112-199, Jan. 1992[6] K. R. Carver and J. W. Mink, “Microstrip Antenna Technology,” IEEE Transactions on Antennas and Propagation, vol. AP-29, pp. 2- 24, January 1981.[7] Gonca, C. (2005) Design, Simulation and Tests of Low-cost Microstrip Patch Antenna Arrays for the Wireless Communication Turk J Elect Engin, 13 (1)[8] Burkholder, R and Lundin, T. (2006). Antenna and Radiation Pattern.IEEE Transactions on Antennas and Propagation, 53(2)[9] Richards, W.F. (1988) Microstrip Antennas. Theory, Application and Design Van Reinhold Co., New York[10] Kin-Lu Wong, Compact and Broadband Microstrip Antennas, Jon Wiley & Sons, Inc., 2002[11] J. R. James and P. S. Hall, Handbook of Microstrip Antennas, Peter Perigrinus Ltd.,London, 1989[12] K. O. Odeyemi, D. O. Akande, E. O. Ogunti, “Design of an S-Band Rectangular Microstrip Patch Antenna” European Journal of Scientific Research Vol.55 No.1 (2011), pp.72-79[13] B.Ramarao, M.Aswini, D.Yugandhar andDr.P.V.Sridevi, “Dominant Mode Resonant Frequency Of Circular Microstrip Antennas With And Without Air Gap” International journal of Electronics and Communication Engineering &Technology (IJECET), Volume 3, Issue1, 2012, pp. 111 - 122, Published by IAEME.[14] Mahmoud Abdipour, GholamrezaMoradi and Reza SarrafShirazi, “A Design Procedure For Active Rectangular Microstrip Patch Antenna” International journal of Electronics and Communication Engineering &Technology (IJECET), Volume 3, Issue 1, 2012, pp. 123 - 129, Published by IAEME. 249