ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 IMPACT OF DIEECTRIC CONSTANT ON THE DIMENSION OF SQUARE MICROSTRIP PATCH -BAND ANTENNA Ale Felix 1,, O. A. Agboola 1, Jegede, J. O 3, S. A. Ayegba 1 1 Depatment o Engineeing & Space Systems, National Space Reseach & Development Agency, Abuja, Nigeia Depatment o Electical & Electonic Engineeing, Univesity o Abuja, Nigeia 3 Depatment o Electical & Electonic Engineeing, Fedeal Polytechnic Idah, Nigeia Abstact Micsostip patch antennas ae commonly applied in wieless devices such as in computes, mobile phones, weaable medical devices and the aays ae useul in many othe applications due to thei light weight, ease o abication, lexibility, obustness despite thei low gain, low iciency and low bandwidth. The majo objective o this pape is to assess the impacts o vaiation o di-electic constants on the size and bandwidth o a squae micostip patch antenna. Tansmission line model is used in this design with an RT DUROID 5888 dielectic substate such that its dielectic constant values ae vaied om. to 3. with. step size. All the paametes o the antenna ae obtained manually and though computational simulations. The esults and indings show that the size and bandwidth o a squae o ectangula micostip patch antenna deceases with incease in the values o a dielectic constant o the substate. Keywods: Micostip, dielectic constant, bandwidth, tansmission line, substate 1. Intoduction Antennae ae devices used o eceiving and tansmitting electomagnetic waves signals. Micostip patch antennae consist o conducting patches o plana o non-plana geomety on one side o a dielectic substate with a gound plane on othe side. It is a pinted esonant antenna that is vey populaly equied o wieless links o naow- band micowave because o its semi-hemispheical coveage (Vivek et al. 14). Mico stip patch antennas get moe and moe impotant in these days. This is mostly due to thei vesatility in tems o possible geometies that makes them applicable o many dieent situations (Md. Rabiul et., 13). It is used to send and/o eceive signals in communication devices. Additionally the simplicity o the stuctues makes this type o antennas suitable o low cost manuactuing and this is also one key eatue o mico stip patch antennas ae used in mobile communications applications (Kazi et al, 11). Micostip patch antennas adiate pimaily because o the inging ields between the patch edge and the gound plane. The adiation inceases with equency incease and using thicke substates with lowe pemittivity, and oiginates mostly at discontinuities (Bahl & Bhatia, 198; Rop & Konditi, 1). As a esult o the daily impovement in technology especially in the aea o communication devices used in vaious ields- boadcasting, telecommunication, medical sevices, telemety, etc, thee is need to assess how the change in a dielectic constant o a mictostip patch antenna aects its bandwidth and the oveall size. The thee methods o designing micostip patch antennas ae tansmission line model method, cavity model method and ull wave model method, but tansmission line model method wee used in this pape.. Some undamental paametes o micostip patch antenna design a. Opeating equency: This is the equency at which the antenna eceives and/o tansmits signals. Fequency o opeation o a micostip antenna can be calculated when the height o the patch is known o can be selected beoe the design (Richads, 198). All Rights Reseved 17 IJSETR 3
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 b. Dielectic substate: A dielectic substate is a substate that does not conduct diect cuent and theeoe used as insulato. The dielectic constant is deined as the atio o pemittivity o a substance to the pemittivity o ee space. c. Height o the substate: The height o the substate to be used in the design can be selected beoe calculating the opeating equency o the antenna i thee is a pio knowledge o the size o the equipment in which the antenna will be used it, o the opeating equency can be used to ind the height, o both can be selected beoe the design. Fo any height, the condition in (1) must be met. h.3 1 h = height o the dielectic substate, is the dielectic constant o the substate, and is the wave length. 3. Methodology and Design pocedues Fig. 1: Schematic diagam o a squae micostip patch antenna The opeating equency o the antenna can be selected beoe calculating the height o the substate o the height beoe the equency. When the equency is ist selected beoe the height, the ollowing steps ae ollowed. Calculation o the height (h): This is the height o the dielectic substate upon which the metallic patch is mounted o placed. The height o the dielectic substate o a micostip antenna in calculated using the omula given as;.3c h Whee C = speed o light, given as 3. x 1 8 m/s, = the dielectic substate b. Calculation o the width (W) o the patch: The width o the patch is calculated using the omula give as; w F o C ( 1) 3 c. Calculation o the ective dielectic constant ( ): The ective dielectic constant is calculated using the omula given as; All Rights Reseved 17 IJSETR 31
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 ( 1) ( 1) 1 1 4 h 11 w Whee h and w ae the height and the width o the patch in that ode. The ective dielectic constant is always less than the dielectic constant itsel because o inge ect. d. Calculation o the ective length o the patch ( ): The ective length o the patch antenna is the sum o the actual length o the antenna and its extension o the inge ects. C 5 e. Calculation o the length extension ( ): ength extension is the additional length at the end o the patch as a esult o the inging ield along its width. It is calculated using the omula given as;.41h w.3.64 h w.58.8 h 6 Whee is the patch length extension, h and w ae the height and width o the patch espectively, and is the ective dielectic constant o the substate.. Calculation o the actual length () o the patch: The actual length o the patch, is the dieence between the ective length and twice o the length extension o the patch. It is epesented mathematically as; 7 g. Calculation o the gound plane dimensions: The gound plane dimensions ae calculated o the length and the width. The gound plane length and width dimensions ae moe than the length and width in that ode by six times thickness o height o the patch. They ae calculated using the omula given as; g 6h 8 W g w 6h 9 Whee and w, ae the length and the width o the patch antenna h. Calculation o eed point: The point o location o eed to the patch antenna can be located in x-y coodinates as X,Y. Coaxial-pobe eeding technique is used o this pape. This eeding scheme is advantageous in tems o ee and desied placement location in ode to match with the input impedance (Sahaya & Anselin, 13). The omulas o calculating the eed point locations ae given as; X 1 w y 11 All Rights Reseved 17 IJSETR 3
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 Whee X F and Y ae the eed point location along X-Y coodinates. i. Calculation o bandwidth: The bandwidth o an antenna is deined as the ange o equencies within which the peomance o the antenna, with espect to some chaacteistic, conoms to a speciied standad (Milligan, 1985; Mohammed & Sabidha, 15). In pecentage, bandwidth o a squae o ectangula micostip patch antenna is calculated by the omula given as: 1 w h BW 3.77 x 1 1 3.1 Methodology An -band equency spectum has the band width o 1-GHz. In this design, a equency o 1Ghz will be used. The design will employ tansmission line method o micostip antenna design, using mathematical computations. The computation pocesses involve manual and sotwae (ms excel) computations. In the pocess o the design, same dielectic substates with dieent values o dielectic constant will be used. These values ae.,.,.4,.6,.8, and 3.. Fo simplicity, manual computation will be used to detemine the paametes o the antenna when the dielectic constant, is.. Although, the dielectic constant will be vaied duing the pocess, all othe paametes such as the equency, wave length, and the speed o the wave will be the same. The othe computations using =.,.4,.6,.8, and 3., will be caied out using Micosot excel sotwae package. 3. Manual Computation Analysis a. Calculation o the height (h): This is the height o the dielectic substate upon which the metallic patch is mounted o placed. Using the equation: h.3c Whee =., = 1GHz, C = 3 x 1 8 m/s, = 3.14. The substitution o these values will yield; h.3 x 3 x 1 x 3.14x 41x 1 8 9. =.113m = 1.1mm b. Calculation o the width: The width o the metallic is calculated using the equation given as: W C ( 1), Thus, substitution gives; W x 1x 1 3 x 1 9 8. 1 All Rights Reseved 17 IJSETR 33
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 =.15m =1.5mm c. Calculation o the ective dielectic constant: The ective dielectic constant is calculated using the equation given as: ( 1) ( 1) 1, H 11 W Thus, a caeul substitution gives;. 1 (. 1) 1 1.113 11.15 1.85 d. Calculation o the ective patch length: The ective length o the patch antenna is the sum o the actual length o the antenna and its extension o the inging ects. It is given as: C, Then, caeul substitution will poduce; 3 x 1 x 1x 1 9 8 1.85.113m = 11.3mm e. Calculation o the length extension: This is additional length at both ends o the metallic patch it is calculated using:.41h w.3.64 h, w.58.8 Thus, substitution gives; h.15 1.85.3.64.113.41 x.113.15 1.85.58.8.113 =.53m = 5.3mm All Rights Reseved 17 IJSETR 34
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17. Calculation o the actual length o the patch: This is the dieence between the ective length and twice the length extension o the length extension at both ends. It is calculated using:, Whee =.113m and =.53m. :..113 ( x.53) =.99m = 99mm g. Calculation o the gound dimensions: The gound length, g and the gound width w g ae calculated using g 6h and w g w 6h Thus, g =.99 + (6 x.113) =.15978m = 159.78mm And, W g =.15 + (6 x.113) =.1838m = 183.8mm h. Calculation o eed point location: This is the coodinate point o the eed along x-y axes. The eed point is calculated using: X and w Y Whee and w ae.99m and.15m espectively while = 1.85 Theeoe, X.99 1.85 X =.3639m = 36.39mm, and, w Y Y.15 Y =.615m = 61.5mm i. Calculation o bandwidth: The bandwidth o an antenna is deined as the ange o equencies within which the peomance o the antenna, with espect to some chaacteistic, conoms to a speciied standad (Balanis, 1997). In pecentage, bandwidth o a squae o ectangula miccostip patch antenna is calculated by the omula given as: All Rights Reseved 17 IJSETR 35
1 w h BW 3.77 x 1 ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 Whee =., w =.15m, h =.113m, =.99m and =.3m. Thus, when substituted, 1.15.113 BW 3.77 x 1.99,.3 BW = 3.938% The above pocesses wee caied out o the value o dielectic constant o the substate,, equals. The computations o =.,.4,.6,.8, and 3., will be peomed in excel woksheet, and the answes will be povided as ollows. When; i. =., h =.966m, w =.1186m, =.6713, =.15365m, =.519m, =.9537m, g =.15387m, W g =.17656m, BW = 3.744%, X =.3348m and Y =.593m. ii. =.4, h =.945m, w =.11545m,.9173m, g =.147m, W g =.17515m, BW = 3.543%, iii. =.6, h =.888m, w =.111183m, =.1995, =.11143m, =.475m, = X =.396m and Y =.575m. =.3743, =.97386m, =.444m, =.8856m, g =.141798m, W g =.16595m, BW = 3.336%, X =.87385m and.55915m. iv. =.8, h =.8559m, w =.1881m,.85591m, g =.136945m, W g =.16175m, BW = 3.1397%, v. = 3., h =.869m, w =.1666m, Y = =.54555, =.9416m, =.413m, = X =.68m and Y =.5441m. =.71879, =.9971m, =.415m, =.894m, g =.13555m, W g =.155568m, BW =.9531%, X =.5158m and Y =.5333m. 4. Results and Discussions Table 1 shows the summay o the esults with opeating equency, RT DUROID 5888. 1GHz and Dielectic substate: s / n Table 1: Paametes o the designed antenna h w (mm ) g W g BW X Y 1. 1.1 1.5 1.855 11.3 5.3 99.4 159.78 183.8 3.938 36.39 61.5. 9.66 118.6.67 15.37 5. 95.33 153.9 176.56 3.744 33.48 59.3 3.4 9.4 115.5.1995 11.14 4.71 91.73 147. 17.5 3.543 3.93 57.3 4.6 8.88 111.8.374 97.39 4.44 88.51 141.8 165.1 3.336 8.73 55.9 5.8 8.56 18.8.555 94. 4.1 85.59 136.95 16.175 3.14 6.8 54.41 6 3. 8.7 16.7.7188 9.97 4.15 8.94 13.56 155.57.953 5.15 53.3 All Rights Reseved 17 IJSETR 36
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 Fig. : Gaph o dielectic constant ( ) against the width (w) Fig. 3: Gaph o dielectic constant ( ) against the length () Fig. 4: Gaph o h, w, and All Rights Reseved 17 IJSETR 37
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 Fig. 5: Gaph o dielectic constant ( ) against bandwidth (BW) 4.1 Discussion Tansmission line model method o antenna design which is one o the methods o micostip patch antenna design was used o this design. The equency at which the squae micostip antenna will opeate is 1GHz, an -band equency. This design made use o an RT-DUROID 588 dielectic substate, and its dielectic constant values wee vaied om. to 3.units with an incement o. unit. The paametes o the designed antenna(s) ae shown in table 1. The esult indicates that the height, length and the width o the antenna deceases as the dielectic constant. This means that, in ode to have a educed size o micsotip patch antenna, highe value o the dielectic substate should be used. Figues, 3, and 4 show the gaphical compaisons between the dielectic constant and height, dielectic constant and length as well as dielectic constant and width o the patch. Figue shows the sloping downwad om let to ight o the gaph which indicates that the width o the antenna inceases with decease in dielectic constant. Also, igue 3 shows the same tend in tems o length, while igue 4 shows the combination o the ou paametes in which it was seen that the length, height and width deceased as the dielectic constant values wee inceasing. Thus, the size o a squae o ectangula micostip antenna is invesely popotional to a dielectic constant. Futhemoe, om igue 5, it was obseved that the elationship between the dielectic constant and the bandwidth o the antenna is invesely popotional. Thus, the bandwidths at lowe values o the dielectic constant ae lage than the bandwidths at the highe values o the dielectic constant. 4. Conclusion The design o a squae micostip antenna that will opeate at a equency o 1GHz has been done using tansmission line method. The vaious paametes o the antenna have been gotten while vaying the dielectic constant and keeping the equency o opeation constant. One o the common dielectic substate o micsotip patch antenna design-rt DUROID 5888 dielectic substate was used in this pape. The esults show that the size o a squae o ectangula micostip antenna will educe when the value o dielectic constant is lage and vice vesa. In an antenna design o equipment in which space is a poblem, highe values o dielectic constant is to be used. Howeve, the highe the value o a dielectic constant, the lesse the bandwidth as in ig. 6, thus, in a design o an equipment whee space is a poblem and highe bandwidth is needed, aay o it will be used. Finally, it can be concluded that incease in dielectic constant causes decease in micostip patch antenna size as well as its bandwidth, and vice vesa. All Rights Reseved 17 IJSETR 38
ISSN: 78 7798 Intenational Jounal o Science, Engineeing and Technology Reseach (IJSETR) Volume 6, Issue 1, Januay 17 4.3 Recommendation The design o this antenna was done using tansmission line model and RT DUROID 5888 dielectic substate. Futue wok in this aea can caied out using iceint antenna design methods with dieent but bette dielectic substate athe than RT DUROID. Reeence Balanis C.A (1997). Antenna Theoy, Analysis and Design John Wile and Sons New Yok. Bahl I. J and P. Bhatia, (198) Micostip Antennas Dedham, M. A: Actech House. Kazi Toayel Ahmed, Md. Bellal Hossain, Md. Javed Hossain (11). Designing a high bandwidth Patch Antenna and compaison with the ome Patch Canadian Jounal on Multimedia and Wieless Netwoks. Md. Rabiul Hasan, Abdulla Al Suman, and Md. Suaibu Rahman (13). Design and Simulation o 4 1 Copoate Feed Cicula Micostip Patch Aay Antennas o Wieless Communication. Ameican Academic & Scholaly Reseach Jounal. Milligan T. A. (1985), Moden Antenna Design, nd ed., John Wiley and sons, New Yok Mohammed N. and Sabidha B., (15). Design A Squae Micostip Patch Antenna o S-Band application, Intenational Jounal o Electonics and Communication Engineeing. Richads, W. F. (198), Micostip Antennas,. Theoy, Application and Design. Van Reinhold Co. New Yok Rop K.V. and Konditi D.B.O. (1). Peomance analysis o a ectangula micostip patch antenna on dieent dielectic substates. Innovative Systems Design and Engineeing. Sahaya A. and Anselin N., (13) Design and Analysis o Multiband Hybid Coupled Octagonal Micostip Antenna o Wieless Applications Reseach Jounal o Applied Sciences, Engineeing and Technology. Vivek Hanumante, Panchatapa Bhattachajee, Sahadev Roy, Pinaki Chakaboty, Santanu Maity (14). Peomance Analysis o Rectangula Patch Antenna o Dieent Substate Heights. Intenational jounal o innovative eseach in electical, electonics, instumentation and contol engineeing. All Rights Reseved 17 IJSETR 39