GAMMA SHAPED MONOPOLE PATCH ANTENNA FOR TABLET PC

GAMMA SHAPED MONOPOLE PATCH ANTENNA FOR TABLET PC Islam Md. Rafiqul, Mohammad Shawkat Habib and Khaizuan Abdullah Depatment of Electical and Compute Engineeing, Intenational Islamic Univesity Malaysia, Jalan Gombak, Kuala Lumpu, Malaysia E-Mail: afiq@iium.edu.my ABSTRACT With the inceasing demand of using multiple sevices in a single device, instead of using multiple antennas, cuent tend is to use single antenna capable of communicating in multiple fequency bands. Fo the devices like tablet PC, the need of accommodating the physical infastuctue though single multiband antenna is geatly useful. Fo the multiband opeation, a gamma shaped stuctue is poposed fo tablet PC. Gamma shaped monopole stuctue is designed and simulated using the Compute Simulation Technology (CST) Micowave Studio. The Gamma shape monopole is deived by modification fom the oiginal T shaped monopole and the fist thee esonant fequencies ae found to be well impoved than the T shaped one. The typical fequencies at 789.5 MHz, 988.1 MHz,.088 GHz and.376 GHz ae having peak gain of.94 dbi,.11 dbi, 5.81 dbi, 4.84 dbi and adiation efficiencies of 95.57 %, 87.3 %, 96.67 % and 95.36 %, espectively. Compaed to the T shaped monopole antenna, the modified Gamma shaped monopole antenna is pefoming bette fo the fist thee esonant fequencies in tems of etun loss. This wok has achieved to accommodate the multiple fequency bands of GSM750, GSM850, GSM900, LTE800, LTE300, PCS-1900 and UMTS. Poposed antenna size is 40 mm x 15 mm that is suitable to fit inside the commecially available tablet PCs. Keywods: gamma shaped monopole patch, multiband, etun loss, tablet pc. INTRODUCTION The telecommunication industy has expanded a lot ove the past yeas and the ecent maket demands small and multifunctional devices. Days of using extenal antennas fo handheld communication devices ae long ove. Day by day moe and moe new sevices ae being intoduced fo the consumes, intoducing newe bands of fequencies and ceating the need to accommodate geate numbe of sevices within a single device. In ode to meet those needs, instead of using multiple antennas fo connecting to the sevice povides, maket tends to use single antenna capable of communicating in multiple fequency bands. Hence the concept of Multiband antenna comes into existence. Multiband antennas can be defined as the antennas that ae designed to opeate fo a multiple numbe of fequency bands. It is obtained though the modification of conventional antennas. Out of diffeent types of antennas the most convenient type to use in handheld devices is the micostip patch antenna, due to its ease of manufactuing and integability. Fo the handheld communication devices like the tablet PCs, the use fo multiband patch antenna is highly demandable. The intenal GSM/LTE/UMTS antenna occupies a substantial amount of space esulting in less physical distance between the diffeent embedded antennas. It is vey impotant to achieve acceptable isolation between those embedded antennas. Hence, it has become impotant; to develop such antennas that would be able to meet all the equiements fo the tablet computes to get connected using vaious wieless communication technologies at thei defined standad fequencies though maintaining deceased physical stuctue and eplacing multiple antennas with a single one. Since the intoduction of Long Tem Evolution (LTE) on the maket the wieless devices ae equied to be able to cove the existing bands and LTE bands. The opeating bands ae: 700 960 MHz (lowe opeating band) and 1500 500 MHz (uppe opeating band), which also coespond with the LTE bands 1 4 (1710 170 MHz), 8 (880 960 MHz), 1 (699 746 MHz), 17 (704 746 MHz), 0 (791 86 MHz), 4 (155 1660 MHz), and 40 (300 400 MHz) [1-]. The embedded antennas being used to satisfy the equied opeating bandwidth moe o less incease the antenna complexity and the fabication cost. It has also been found that the adiation pattens ae multilobe. Sometimes undesied highe-ode modes ae also excited to cause some distotions in the esultant adiation pattens. Due to the limited space inside the thin pofile tablet computes, the embedded antennas with the smalle plana stuctue opeational at multiband ae demandable. This equiement fo the long-tem evolution/wieless wide aea netwok (LTE/ WWAN) opeations that equie the antenna to cove a wide lowe band of 704 960 MHz and a wide highe band of 1710 690 MHz is especially challenging [-3]. DESIGN EQUATIONS Using (1)-(6) povided in [3,5-7], the desied Length (L), Width (W), Retun Loss, VSWR of the MPA can be calculated. Hee, the velocity of light (c), the substate dielectic constant (ε ), substate thickness (h), taget fequency (f 0 ), effective dielectic constant (ε e ) and the eflection coefficient (ρ) ae used fo calculation. c W f 0 1 (1) 17433

c L l f 0 1 e l 0.41h 1 1 1 1 VSWR 1 RetunLoss 1 W e 0.3 0.8 h W e h 10h W 0.58 0.8 1 10log Though the usage of these equations the basic patch antenna paametes can be selected. OPERATING FREQUENCIES OF VARIOUS APPLICATIONS The applications of G, 4G/LTE depend on the communicating fequencies of diffeent bands which ae given in Table-1. () (3) (4) (5) (6) that could eveal design guidelines in tems of input match (S11), substate thickness and adiation efficiency. The FR-4 substate having dielectic constant of 4.3 with thickness of 0.8mm was taken as a base on which the coppe pinted design was analyzed. The lengths of the diffeent pats of the uniplana antenna wee vaied and the effects wee analyzed. The complexity of the poposed antenna with diffeent geometic shapes makes the simulation inticate. The changes in the geometic shapes impoved the antenna chaacteistics though sweeping the paametic values one at a time. In such pocedue, the initial stuctue is eplicated multiple times at diffeent scales and with modified stuctues. The analysis of the paametes done in the pevious sections is used to design the poposed Gamma (monopole shaped liked Gamma) shaped monopole impoved antenna and pesented in Figue-1. It displays the schematic of poposed Gamma shaped monopole antenna having intenal pinted matching cicuit fo the UMTS/GSM/LTE opeation in the tablet compute. It is obseved that the left am length of L in [] is esponsible fo impoving the etun loss of the lowe band fequencies and the am L3 has hadly any effect on the pefomance of the antenna. The othe potions of the antenna plays impotant ole on the highe band fequency outputs. Theefoe the am of L is fully emoved fom the stuctue and modifying the L3 along with some othe modifications in length impoves the esults. Table-1. Fequency bands applicable to the epoted antenna in [4][6]. Figue-1. The poposed gamma shaped monopole antenna stuctue. PROPOSED DESIGN In the wok of Lu & Wang [], the T-shaped monopole geomety is poposed to achieve the multiband functionality applicable to tablet pc. Since thee ae no specific fomulas that elates to the complex geomety and antenna behaviou simila to the one being pesented in [], the stuctues that wee elated to the multiband patch antenna wee simulated with a view to identify paametes The antenna is pinted on one side of single side coppe clad FR4 substate consisting dimension of 40 x 15 x 0.8 mm 3, loss tangent 0.05, and elative pemittivity 4.3. The fabicated antenna is mounted along the top-ight.85 mm inside fom the oute edge of the display gound. The selective pope dimensions of the poposed Gamma shaped monopole uniplana pinted antenna ae povided in the Table-. A 0. mm thick coppe plate is used as the display gound and the tablet compute s size is consideed as 10 inch, which is available commecially in the maket fo this wok. The equied paamete values used in the poposed antenna stuctue ae pesented in Table-. 17434

Table-. Designed paametes of the poposed gamma shaped monopole micostip patch antenna. RETURN LOSS The simulated etun loss in db fo the poposed antenna schematic of which is shown Figue-1, is pesented in Figue-. Figue-. Simulated esult of S11 in db fo the poposed Gamma shaped monopole uniplana antenna. The lowe band pesents a measued VSWR of 3:1 (6 db etun loss) bandwidth of 1.83 MHz (754.58 869.3 MHz & 911.91 MHz - 1.01 GHz), on the othe hand the highe band has a bandwidth of 590 MHz (1.85.44 GHz). The desied GSM/UMTS/LTE opeation can be met up with the obtained fequency bands. Consideing upto 3 GHz, thee ae fou esonant fequencies which ae at 788.01 MHz, 988 MHz,.09 GHz and.38 GHz. CURRENT DISTRIBUTION Fo the analysis of the adiation of the antenna and the esonant fequencies, it is impotant to analyze the cuent distibution, which will be discussed in this section. The excitation of the paticula GSM/UMTS/ LTE bands, suface cuent distibutions on the Gamma-shaped diven monopole intenal pinted loop matching cicuit at esonant fequencies ae shown in Figue-3 (a)0.7895 GHz, (b)0.9881 GHz, (c).088 GHz, and (d).376 GHz. Figue-3. Simulated suface cuent distibutions at (a)0.7895 GHz, (b)0.9881 GHz, (c).088 GHz, and (d).376 GHz, on the poposed Gamma shaped monopole uniplana pinted antenna. Fom the suface cuent distibutions in Figue-3 (a), the fundamental mode at 789.5 MHz is found to be excited at point F of the paasitic shoted stip, consisting of a 0. wavelength. the suface cuent is found to be ising in stength at the point F of shoting and the suface cuent gadually decease to null towads the end point of the shoted stip at point E. Similaly fom Figue-3 (b), the matching loop integated with a shoted stip is excited at its fundamental mode at 988.1 MHz with maximum 17435

stength along the shoted stip potion (section KF). Then, at.088 GHz, stong suface cuent on the main diven monopole AC of the Gamma-shaped diven monopole ae obseved in Figue-3(c), which indicate that the fist mode of the uppe band is mainly contibuted by the diven monopole. Finally fom Figue-3(d), at.376 GHz, thee is a suface cuent along the main diven monopole AC and the closed loop esonato, which indicates that those pats ae esponsible fo the second esonant fequency in the highe band. RADIATION PATTERN The simulated adiation pattens at esonant fequencies ae povided in Figue-4. Figue-6. Simulated adiation efficiency of poposed gamma shaped antenna. PEAK GAIN The peak gains of the antenna in the Figue-1 at typical fequencies ae found to be satisfactoy as they ae above the standad.1 dbi isotopic antenna gain limit. The simulated peak gain fo lowe band and the highe band ae povided in Figue-7. Figue-4. Two-dimensional (-D) adiation pattens at (a) 0.7895 GHz and (b) 0.9881 GHz fo the poposed gamma shaped monopole antenna. Figue-5. Two-dimensional (-D) adiation pattens at (a).088 GHz and (b).376 GHz fo the poposed gamma shaped monopole antenna. At fequencies (a) 789.5 MHz and (b) 988.1 MHz in the antenna s lowe band, the adiation pattens ae found to be dissimila to the pattens of dipoles. At highe fequencies (.088 and.376 GHz) in the antenna s uppe band, elatively high vaiations in the adiation pattens (Figue-5) ae obseved. The beam symmety is satisfactoy. ANTENNA EFFICIENY The adiation efficiency of the antenna is also calculated and simulated in the Figue-6. It is seen that the measued antenna efficiency is about 77.48 % ~ 99.43 % ove the lowe bands, while that ove the highe bands is about 93.96 % ~ 97.48 %. The esonant fequencies ae all found to be having efficiency above 87 %. Figue-7. Simulated peak gain fo the poposed gamma shaped antenna at (a) Lowe bands, (b) Highe bands. Fom the Figue-7 it can be obseved that the peak gain at 789.5 MHz, 988.1 MHz,.088 GHz and.376 GHz ae.94 dbi,.11 dbi, 5.81 dbi and 4.84 dbi espectively INPUT IMPEDANCE The poposed antenna s input impedance is pesented in Figue-8. It can be obseved that the fist peak of the eal pat of the input impedance is 7.39 ohms and the second peak at 09.46 ohms, wheeas the thid, fouth and fifth peak at 54.64 ohms, 75.3 ohms and 157.6 ohms espectively. It can be efeed that the thid peak at 54.64 ohms is closest to the 50 ohms impedance matching connecto feed and theefoe it can be seen fom Figue- that the esonant fequency at.088 GHz is having the best adiation as the etun loss is aound -55 db. The oveall input impedance diagam is well epesented simila to the monopole antenna input impedance diagams. 17436

REFERENCES [1] Shen S., Chen I., Peng C. and Lin D. 013. Pinted Asymmetic Dual-Dipole Antenna fo Tablet PC Applications. IEEE Antennas and Wieless Popagation Lettes, 1, 1003-1005. doi:10.1109/lawp.013.77877 Figue-8. Input impedance (simulated eal and imaginay pat) of the poposed Gamma monopole antenna. The detailed chaacteistic infomation of the Gamma shaped monopole antenna is povided in Table-3: Table-3. Gamma shaped monopole antenna popeties. [] Lu J. and Wang Y. 013. Intenal Uniplana Antenna fo LTE/GSM/UMTS Opeation in a Tablet Compute. IEEE Tansactions on Antennas and Popagation, Vol. 61, No. 5, pp. 841-846. doi:10.1109/tap.013.43693. [3] Habib M.S., Rafiqul I., Abdullah K. and Jakpa M. 014. U-Slot Rectangula Patch Antenna fo Dual Band Application. Spinge Intenational Publishing Advanced Compute and Communication Engineeing Technology, Vol. 315, pp. 111-10. doi:10.1007/978-3-319-07674-4_1. [4] Chang S. and Liao W. 01. A Boadband LTE/WWAN Antenna Design fo Tablet PC. IEEE Tansactions on Antennas and Popagation, Vol. 60, No. 9, pp. 4354-4359. doi: 10.1109/TAP.01.07075. CONCLUSIONS The Gamma shape monopole is deived fom the oiginal T shaped monopole and the fist thee esonant fequencies ae found to be well impoved than the oiginal T shaped one. The typical fequencies at 789.5 MHz, 988.1 MHz,.088 GHz and.376 GHz ae having peak gain of.94 dbi,.11 dbi, 5.81 dbi, 4.84 dbi and adiation efficiency of 95.57 %, 87.3 %, 96.67 % and 95.36 % espectively. The input impedances ae also found to be ageeable with the adiation efficiency and peak gain as the fist, second, thid and fouth peaks ae found at 7.39-j19.35 ohms, 09.46-j67.03 ohms, 54.64+j1.9 ohms and 75.3-j4.5 ohms espectively. Compaed to the T shaped antenna, the Gamma shaped monopole antenna is pefoming bette fo the fist thee esonant fequencies in tems of etun loss and is found to be stengthened by 107 %, 48.8 % and 0.17 % espectively. Finally the simulated esult has achieved to accommodate the fequency bands of GSM750, GSM850, GSM900, LTE800, LTE300, PCS-1900 and UMTS. [5] Mohd. Moniuzzaman, Md. Rafiqul Islam, Kamauzzaman Sopian and Saleem H. Zaidi. 011. Clusteed Paticle Swam Optimization fo Plana Antenna Design, Jounal of Science, Technology and Envionment, ISSN: 34-1857, Vol., No. 1, pp. 46-48. [6] Abutaboush H., Nasif H., Nilavalan R. and Cheung, S. 01. Multiband and Wideband Monopole Antenna fo GSM900 and Othe Wieless Applications. IEEE Antennas and Wieless Popagation Lettes, Vol. 11, pp. 539-54. doi:10.1109/lawp.01.19849. [7] A.H.M. Zahiul Alam, Md. Rafiqul Islam, Sheoz Khan, Nik Noo Atikah Nik Mohd. Salleh and Noaini Aziz. 009. Tunable Bandpass Filte Using RF MEMS Switches, IIUM Engineeing Jounal (ISSN: 1511-788X), Vol. 10, No., 009, pp. 69-79. ACKNOWLEDGEMENT Authos ae gateful to Kulliyyah of Engineeing and Reseach Management Cente, Intenational Islamic Univesity Malaysia to suppot this eseach. 17437