Intenational Confeence on Compute Netwoks and Communication Technology (CNCT2016) Ti-fequency Micocosmic Factal Dipole Antenna with PBG Stuctue Used fo 2G, 3G and 4G Systems Bin LIN 1,* 1 Xiamen Univesity Tan Kah Kee College, Fujian Zhangzhou 363105, China * Email: linbin@xujc.com Keywods: Hilbet factal stuctue, Micocosmic factal stuctue, Dipole antenna, Mioing compensation stuctue, PBG stuctue, Canto factal stuctue. Abstact. Basing on the equiement of the second geneation, the thid geneation and the fouth geneation mobile communication systems, a ti-fequency micocosmic factal dipole antenna is designed with a novel PBG stuctue. A sample of this antenna has been tested afte simulation analysis and discussed the influence of the pefomance of this antenna by changing the PBG paamete in detail. The simulated and tested esults show that this antenna has low etun loss, wide woking bandwidth and hemisphee diection adiation chaacteistic, at thee woking cente fequencies of 0.92 GHz, 1.80 GHz and 2.58 GHz. Utilizing factal stuctue in PBG, the antenna pefomance can be impoved and the woking bandwidth can be boadened effectively. This antenna can completely coveed the GSM, TD-SCDMA, WCDMA and TD-LTE communication fequency band; it successfully achieved the compatibility of the second geneation, the thid geneation and the fouth geneation mobile communication systems. Intoduction With the development of mobile communication technology, the second geneation (2G), the thid geneation (3G) and the fouth geneation (4G) mobile communication systems will coexist fo a long time [1-2]. This equies that the mobile communications antenna should have the multi-band compatibility function, cove the woking bands of GSM, TD-SCDMA, WCDMA, TD-LTE and othe mobile communications standad. At pesent, the GSM standad communication bands ae 0.905-0.915 GHz, 0.950-0.960 GHz, 1.710-1.785 GHz and 1.805-1.880 GHz [3], the TD-SCDMA standad communication bands ae 1.880-1.920 GHz and 2.010-2.025 GHz, the WCDMA standad communication bands ae 1.920-1.980 GHz and 2.110-2.170 GHz [4], the TD-LTE standad communication bands ae 2.300-2.390 GHz and 2.555-2.655 GHz [5]. Dipole antenna has been applied widely in mobile communication systems, due to wide woking band, low cost and whole diection adiation chaacteistic [6-8]. Howeve, thee ae still some deficiencies to be ovecome such as weak adiation ability and woking only in single-fequency band [9-11]. Fo the dipole antenna, micocosmic factal stuctue is an effective impoved stuctue. The dipole antenna am has a cetain width, the small factal stuctue is used in each small squae aea of the antenna am, and this micocosmic factal stuctue can impove the bandwidth pefomance of the antenna. Mio compensation stuctue has the same stuctue and size as metal dipole antenna adiation patch, and it is installed symmetically to metal dipole antenna. By easonably adjusting the spacing, can make the adiation signal of metal dipole antenna and mio compensation stuctue in-phase Copyight 2017, the Authos. Published by Atlantis Pess. This is an open access aticle unde the CC BY-NC license (http://ceativecommons.og/licenses/by-nc/4.0/). 347
stacking, it can geatly impove the antenna's etun loss pefomance and adiation pefomance, extend the antenna's woking bandwidth. Exploiting some photonic band gap (PBG) stuctues on the gounded plane of antenna, the adiation signal geneated by the antenna ams can let metal PBG stuctues poduce induction adiation. The adiation chaacteistics of antenna could be stengthened by the induction adiation of PBG [12-13]. Combining micocosmic factal stuctue, mio compensation stuctue, PBG stuctue with dipole antenna, we designed a ti-fequency micocosmic factal dipole antenna with minimized size and bette popeties fo 2G, 3G and 4G systems, taking ceamic mateial with high dielectic constant as the substate. Bief Intoduction of Hilbet Factal Stuctue The iteation pocess of Hilbet factal stuctue is shown as Figue 1. The initial unit is a vetical thee-segment line which composed with thee segments with equal length. To get fist-ode Hilbet Factal stuctue, divide each segment into thee pats with equal length and constuct a small thee-segment line which has 1/3 length of initial unit. Clockwise substitute the small thee-segment line with the fome pat of the fist segment, the middle pat of the second segment and the ea pat of the thid segment. To get second-ode Hilbet Factal Stuctue, similaly iteate each thee-segment aea of the fist-ode Hilbet Factal Stuctue. Iteating as this way, we can get high-ode Hilbet factal stuctue. Hilbet factal stuctue with cetain line width has stong space filling ability, and it suitable fo the factal tansfomation of the small squae metal egion on the antenna [14-16]. (a) 0-ode (b) 1st-ode (c) 2nd-ode (d) 3d-ode Figue 1. The iteation pocess of Hilbet factal stuctue The Stuctual Design of the Ti-fequency Micocosmic Factal Dipole Antenna with PBG Stuctue Setting the elative dielectic constant and thickness of ceamic substate as = 20 and h = 4 mm espectively, we have designed a ti-fequency micocosmic factal dipole antenna with PBG stuctue, the size of antenna is 30 mm 30 mm. The schematic diagam of the antenna stuctue is shown in Figue 2. We use the adiation of dipole antenna stuctue to cove the 0.905-0.915 GHz and 0.950-0.960 GHz fequency bands. The length of dipole antenna am meets the fomula (1). l 0 c (1) f 4 0 In these fomula, light velocity c = 3.0 10 8 m/s, ceamic substate elative dielectic constant = 20. Afte calculating, when f 0 = 0.90 GHz, the l 0 = 18 mm. In ode to educe the antenna's size, the antenna am has been folded, the hoizontal am's length is 9 mm, and the longitudinal am's length is 9 mm. We use the mio compensation stuctue to impove the antenna's adiation pefomance. 348
(a) micocosmic factal dipole antenna stuctue (b) 3d-ode Hilbet factal stuctue (c) PBG stuctue Figue 2. The schematic diagam of the antenna stuctue In ode to impove the antenna's woking bandwidth, we use the micocosmic factal stuctue in the dipole antenna am; eplace dipole antenna am's small squaes aea which the size is 1.5 mm 1.5 mm with 3d-ode Hilbet factal stuctue which line width is 0.1 mm. In the macoscopic view, the antenna's adiation patch emained the shape of folded dipole antenna; in the micoscopic view, each 1.5 mm 1.5 mm small squaes metal aea is a mico 3d-ode Hilbet factal stuctue. The metal adiation aea inside have self-simila stuctue, the antenna's woking bandwidth will extend geatly. A novel PBG stuctue is intoduced on the gounded plane to impove the pefomance of antenna. This PBG stuctue can be egaded as metal squae slices peiodic distibution in ceamic substate. The PBG stuctue is constituted by fou big metal squae slices and five small metal squae slices, these metal squae slices will 349
absob the adiation enegy geneated by the dipole antenna ams, and poduce new adiation signals by induction adiation. We use the adiation of the PBG stuctue to cove the 1.710-1.785 GHz, 1.805-1.880 GHz, 1.880-1.920 GHz, 1.920-1.980 GHz, 2.010-2.025 GHz, 2.110-2.170 GHz, 2.300-2.390 GHz and 2.555-2.655 GHz fequency bands. The fequency of induction adiation signals f and the edge length of metal squae slice L should satisfy the fomula (2). L 1 12 ( 0.3)[ ( ) 0.264] c 2fh 2 0.412h 4 f 1 12 c ( 0.258)[ ( ) 0.8] 2fh 2 c Assigning the light velocity c = 3.0 10 8 m/s, the = 20 and h = 4 mm, when f = 1.80 GHz, the L = 7.75 mm; when f = 2.60 GHz, the L = 4.72 mm. So we use big and small metal squae slices which sizes ae 8 mm 8 mm and 4 mm 4 mm espectively. The Simulation Analysis of the Pefomance of Antenna By finite-diffeence time-domain method (FDTDM), the simulated etun loss and adiation patten of designed antenna, with = 20 and h = 4 mm, ae given in Figue 3 and Figue 4 espectively. (2) Figue 3. The simulated etun loss value of antenna 350
(a) Lowe fequency band (0.90 GHz) (b) Middle fequency band (1.75 GHz) (c) Highe fequency band (2.60 GHz) Figue 4. The simulated adiation patten of antenna Figue 3 shows that thee ae thee woking cente fequency, 0.90 GHz, 1.75 GHz and 2.60 GHz espectively, at which the etun loss values S 11 ae 27.22 db, 22.31 db and 22.36 db espectively. Fo VSWR less than 2, the absolute woking bandwidths ae up to 0.667 GHz (0.584 ~ 1.251 GHz), 0.688 GHz (1.398 ~ 2.086 GHz) and 1.112 GHz (2.086 ~ 3.198 GHz), also the elatively woking bandwidth up to 72.69%, 39.49% and 42.09% espectively. All the esults show that the etun loss chaacteistic and the woking bandwidth can satisfy the equest of 2G, 3G and 4G systems. Accoding to E-plane adiation patten and H-plane adiation patten at 0.90 GHz, 1.75 GHz and 2.60 GHz, it is obvious that this antenna has hemisphee diectional adiation chaacteistic. The adiation patten at diffeent fequency have diffeent otation angle, it is due to the adiation signal in lowe fequency band is geneated by the dipole antenna ams, but the adiation signal in middle and highe fequency bands ae geneated by the big and small metal squae slices of PBG stuctue. In ode to make bette use of this antenna in eal pocess, the influences of the squae PBG slice size on the pefomance of antenna have been discussed in detail. While changing the squae PBG slice size, we keep h = 4 mm and = 20, made a seies of simulation calculating, and the esult is listed in Table 1. The simulated esults show that appopiate squae PBG slice size would be benefit fo the woking bandwidth and adiation chaacteistic of antenna. When the size of small squae slice close to the dipole antenna am's width, like 3 mm 3 mm, the gain of antenna is to be enhanced, it especially fo lowe fequency band. 351
Table 1. Influence of the PBG slice size on antenna pefomance The Fabication and Test of Antenna Sample Accoding to the design mentioned above, we fabicate the ti-fequency micocosmic factal dipole antenna sample, which is shown in Figue 5. (a) Micocosmic factal dipole antenna stuctue (b) PBG stuctue Figue 5. The photo of antenna sample We use RF integated vecto netwok analyze to test the etun loss of the antenna, with the esult is shown in Figue 6; we set up an open aea test site (OATS) to test antenna's adiation patten chaacteistics, with the esult is shown in Figue 7. Figue 6. The tested etun loss value of antenna 352
(a) Lowe fequency band (0.92 GHz) (b) Middle fequency band (1.80 GHz) (c) Highe fequency band (2.58 GHz) Figue 7. The tested adiation patten of antenna The tested esults show that thee ae thee woking cente fequency, 0.92 GHz, 1.80 GHz and 2.58 GHz espectively, at which the etun loss values S 11 ae 25.85 db, 22.66 db and 21.32 db espectively. Fo VSWR less than 2, the absolute woking bandwidths ae up to 0.567 GHz (0.586 ~ 1.153 GHz), 0.544 GHz (1.648 ~ 2.192 GHz) and 0.592 GHz (2.192 ~ 2.784 GHz), also the elatively woking bandwidth up to 65.21%, 28.33% and 23.79% espectively. Accoding to E-plane adiation patten and H-plane adiation patten at 0.92 GHz, 1.80 GHz and 2.58 GHz, this antenna has hemisphee diectional adiation chaacteistic. In a whole, the tested and simulated esults ae simila, but the tested adiation chaacteistic, bandwidth pefomance and adiation pattens with a little wose. It is due to that the manufactuing eo and welding in engineeing pocesses cause the antenna to have lost matching a little. The Design of Impoved Antenna Stuctue To impove the antenna pefomance in futhe, we tied an effective ways and did some compaative analysis. This way is to apply factal stuctue in the designed antenna's PBG stuctue. Hee, each squae slice of PBG stuctue is eplaced by a 2nd-ode Canto factal stuctue, the scheme of which is shown in Figue 8. 353
(a) 1st-ode (b) 2nd-ode Figue 8. The iteation pocess of Canto factal stuctue By simulation, two cuves in Figue 9 pesent the etun loss of antenna with 2nd-ode Canto factal stuctue and without factal stuctue in squae PBG slices espectively. It can be seen that the application of factal stuctue can impove the adiation chaacteistics of antenna and boaden the woking bandwidth obviously. Applying this impoved stuctue, the antenna have thee woking cente fequency, 0.90 GHz, 1.75 GHz and 2.64 GHz espectively, at which the etun loss values S11 ae 25.04 db, 20.83 db and 24.84 db espectively. Fo VSWR less than 2, the absolute woking bandwidths ae up to 0.946 GHz (0.506 ~ 1.452 GHz), 0.722 GHz (1.452 ~ 2.174 GHz) and 1.164 GHz (2.174 ~ 3.338 GHz), also the elatively woking bandwidth up to 96.63%, 39.82% and 42.24% espectively. Figue 9. The etun loss values of designed antenna with 2nd-ode Canto factal stuctue and without factal stuctue Conclusions Fist of all, the stuctue design of a ti-fequency micocosmic factal dipole antenna with PBG stuctue is intoduced in this pape. Simulated and tested esults show that this antenna has a small size, lage bandwidth, good etun loss chaacteistic and hemisphee diection adiation chaacteistic. This antenna can completely coveed the 0.905-0.915 GHz, 0.950-0.960 GHz, 1.710-1.785 GHz, 1.805-1.880 GHz, 1.880-1.920 GHz, 1.920-1.980 GHz, 2.010-2.025 GHz, 2.110-2.170 GHz, 2.300-2.390 GHz and 2.555-2.655 GHz communication fequency bands, it successfully achieved the compatibility of the GSM, TD-SCDMA, WCDMA, TD-LTE mobile communications standad. Moe discussion suggests that appopiate squae PBG slice size would be benefit fo the bandwidth and adiation chaacteistic of antenna. At last, the application of Canto factal stuctue in PBG stuctue has been tied fo the designed antenna successfully. This antenna can be applied in the 2G/3G/4G mobile communication systems, and thus has boad application pospects. 354
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