CORNER TRUNCATED MICROSTRIP PATCH ANTENNA Nazia Hasan 1, D.S.C.Gupta 2 1 Student ECE Deptt. UTU Dehadun,Uttaakhand Technical Univesity, Dehadun(India) 2 ECE Deptt. DIT Dehadun,Dehadun Institute of Technology Dehadun(India) ABSTRACT A squae Micostip patch antenna at fequency of 3.4 GHz is designed in this pape. This stuctue will give linea polaization. We have tuncated the opposite cones fom squae patch antenna to achieve cicula polaization. Micostip feed line is used in this design. Ansoft HFSS is used to design this stuctue. Keywods: Micostip Patch Antenna, Micostip Feed Line, Ansoft HFSS I.INTRODUCTION Mico-stip patch antennas have always been an attactive choice fo the eseaches, especially in the field whee cheap, low pofile, light weighted and easy to fabicate stuctues ae desied such as in Wieless o Mobile communication. Micostip patch antennas used because of its vaious advantages like compatibility with integated cicuits, confomal configuation, light weight, easy to fabicate and so on. Micostip patch antennas usually designed with linea polaization but in some applications such as satellite communication cicula polaization is desied because ciculaly polaized antennas ae vey insensitive to tansmitte and eceive oientation. A mico-stip patch is one of the most widely used adiatos fo cicula polaization geneation. A micostip patch antenna which is linealy polaized may be easily conveted in to ciculaly polaized patch antenna afte some modifications in the shape of stuctue and afte cutting slots in the stuctue. In the wok pesented in this pape a micostip patch antenna is designed at the fequency of 3.4 GHz and this stuctue will poduce linea polaization. The opposite cones of the stuctue ae tuncated as a esult of which the linea polaization of the antenna is conveted in to cicula polaization. In this way cicula polaization is achieved. Polaization divesity of eception is also vey impotant to counte the ects of fading in communication, especially in mobile communication. Table 1 shows the design paametes of simple mico-stip patch antenna without tuncated opposite cones. II.THE ANTENNA STRUCTURE The stuctue of the antenna is shown in figue.1 and vaious dimensions of the patch antenna ae given in Table 352 P a g e
S.no. Paamete Value 1. Fequency 3.4 GHz 2. Dielectic constant of substate Duoid (tm) 2.2 2. Width of patch 23.82 mm 3. Length of patch 23.82 mm 4. Width of quate wave tansfome 1.144 mm 5. Length of QWT 20.8325 mm 6. Width of 50 ohm tansmission line 4.84 mm 7. Length of 50 Ω TL 20 mm 8. Polaization Linea Table 1 vaious dimensions of Patch antenna Fig.1. Mico-stip Patch Antenna at 3.4 GHz The patch antenna was designed on the basis of tansmission line model (TLM). The width of the patch is calculated fist, given by the fomula, W c 2 2 f 1 (1) whee ε the dielectic constant of substate, W is is the width of the patch and H is the height of the substate. The patch we have used in this model is squae patch, so the length and the width both ae the same. The dimensions of the patch ae extended to account the finging ect; the extension is given by, L ( 0.412 h ( 0.3).( W 0.258 ).( W / h 0.264 ) / h 0.8 ) (2) Since the length of patch has been extended by Δ on each side of the patch, the ective length is given by, 353 P a g e
L c (3) 2 f Patch esonant length L is given by, L = L 2Δ (4) Using the values given by TLM appoximation, paametes fo the antenna wee calculated fo 3.4 GHz. The dielectic substate Duoid (ε = 2.2) with height h = 1.57 mm is used. Quate wave tansfome is a vey useful and pactical cicuit fo impedance matching and it also povides a simple tansmission line cicuit that futhe illustates the popeties of standing waves on a mismatched line. When it is desied to match a load esistance R L with a feed line of chaacteistic impedance Z 0, a piece of lossless tansmission line of chaacteistic impedance Z 1 and λ/4 length is used to connect them, so to make the eflection coicient Γ=0 looking into the λ/4 matching section. The matching impedance Z 1 is given by the expession. Z Z R 1 0 L (5) Quate wave tansfome The length of the tansfome is λ/4, which gives length 20.8325. The width of the conducto is given by the fomula w h 8 exp( A ) exp( 2 A ) 2 (6) fo Z 0 (ε ) 1/2 >89.91, that is A > 1.52 and fo Z 0 (ε ) 1/2 <= 89.91, that is A <= 1.52 Whee, w 2 1 0.61 B 1 ln( 2 B 1) ln( B 1) 0.39 h 2 (7) A Z 0 60 1 / 2 1 1 0. 11 0.23 2 1 (8) The width of 50-ohm tansmission line is calculated by eq. ( 7) and we get 4.84mm. 354 P a g e
The dimensions of the gound plane wee taken accoding to the lengths of the patch, the quate wave tansfome and the 50-Ohm tansmission line. So the length of the gound plane, we calculated is given by; L g = L + L QWT + L TL (9) Whee L is the length of the patch, L QWT is the length of the quate wave tansfome; L TL is the length of the 50-Ohm tansmission line. The Patch antenna and the gound plane ae made of coppe sheet; the thickness of coppe sheet is taken to be 0.1 mm. The antenna is fed RF signals anging fom 2 to 5 GHz, at the pot with the help of a wavepot as shown in fig.1.the antenna without tuncated opposite cones has linea polaization. S-paamete plot of without tuncated cones patch antenna is shown in figue given below Fig.2 S-paamete plot of simple patch antenna Next step is to change the polaization of this antenna fom linea to cicula. Fo this pupose, opposite cones of the patch ae tuncated. The dimensions of the tuncated cones being calculated accoding to the following equation Length a = length of patch / 5 (10) The design of opposite cone tuncated mico-stip patch antenna is shown in figue 3. Fig.3. Opposite cones tuncated patch antenna 355 P a g e
Fig.4 Axial atio plot of opposite cones tuncated This tuncated opposite cones changes the polaization of the antenna fom linea to cicula this cicula polaization can be veified by plotting the axial atio as shown in figue3. Fo cicula polaization the axial atio should be 1. The axial atio of cone tuncated patch antenna is 1.01. The axial atio plot of opposite cone tuncated antenna is shown in figue 4. Fig 5. S11 plot of opposite cones tuncated antenna As desied the polaization of this antenna has now changed to cicula because of the tuncated cones but the esonant fequency is changed because of tuncating the cones of the patch, s-paamete plot showing the esonant fequency of cone tuncated micostip patch antenna. III. RESULTS & ANALYSIS Softwae and settings This ciculaly polaized antenna was simulated on EM solve Ansoft HFSS (High Fequency Stuctue Simulato), the adiations wee measued with the help of an infinite sphee setup in fa field. The RF signals wee setup fom 3 GHz to 5 GHz, simulated adaptively. 356 P a g e
Analysis of esults The simulation esults ae shown in figues below; fom figue 2. it can be obseved that the eflection coicient S11 fo linealy polaized antenna without any tuncation showing esonance at fequency 3.3 GHz. Figue 4 shows the axial atio fo opposite cones tuncated antenna, as desied its magnitude is 1.01, which shows that this antenna posses cicula polaization. Figue 5 shows s-paamete plot of cone tuncated patch antenna its esonant fequency has changed afte tuncating the cones that is 3.15 GHz. The 3D Gain pola plot fo linealy polaized patch was shown in figue 6, fo cicula polaization and polaization tunable patch antenna, the 3D Gain pola plot is shown below in figue 7. Fig.6 Gain of simple micostip patch antenna Fig.7 Gain of cone tuncated patch antenna These esults wee compaed with theoetical ones, fo the stuctue good ageement between simulated and expeimental esults wee achieved. 357 P a g e
IV. CONCLUSION AND FUTURESCOPE The poposed antenna is suitable fo use in communication, defense applications, suveillance and countemeasues. ACKNOWLEDGEMENT The authos ae thankful to DEAL (Defense Electonics Applications Laboatoy), Dehadun fo extending thei laboatoy to use Ansoft HFSS. REFERENCES [1] Symeon Nikolaou, Ramanan Baiavasubamanian, Cesa Lugo, Ileana aasquillo, Dane C. Thompson, Geoge E. Ponchak, Manos M. Tentzeis, Patten and Fequency econfiguable Annula Slot Antenna Using PIN Diodes IEEE tansactions on antennas and popagation, vol. 54, No.2, Febuay 2006. [2] S. Silve, Micowave Antenna Theoy and Design. New Yok: McGaw-Hill, 1949. [3] Y. J. Sung Reconfiguable Patch Antenna fo Polaization Divesity IEEE Tansactions On Antennas And Popagation, vol. 56, NO. 9, Septembe 2008. [4] Boyon Kim, Student Membe, IEEE, Bo Pan Student Membe, IEEE, Symeon Nikolaou,Young-Sik Kim, Membe, IEEE, John Papapolymeou, Senio Membe, IEEE, and Manos M. Tentzeis, Senio Membe, IEEE A Novel Single-Feed Cicula Micostip Antenna With Reconfiguable Polaization Capability IEEE tansactions on antennas and popagation, vol. 56, No. 3, Mach 2008. [5] Y. J. Sung, T. U. Jang, and Y.-S. Kim A Reconfiguable Micostip Antenna fo Switchable Polaization IEEE micowave and wieless components lettes, vol. 14, No. 11, Novembe 2004. [6] Hall P.S., Micostip linea aay with polaization contol, IEEE Poc.,Vol. 130, Pt.H, pp.215-224. [7] P.-S. Kildal, S. A. Skyttemy, and A. A. Kishk, G/T maximization of a paaboidal eflecto fed by a dipole-disk antenna with ing by using the multple-eflection appoach and the moment method, IEEE Tans. Antennas Popag., vol. 45, no. 7, pp. 1130 1139, Jul. 1997. [8] A. Clavin, A new antenna feed having equal E -and H-plane pattens, Tans. IRE Pofessional Goup on Antennas Popag., vol. 2, no. 3, pp. 113 119, Jul. 1954. 358 P a g e