Dsign and simulation of th microstrip antnna for 2.4 GHz HM rmot control systm Dng Qun 1,a,Zhang Wiqiang 2,b,Jiang Jintao 3,c 1,2,3 Institut of Information Enginring &Tchnical, Ningbo Univrsity,Ningbo, China a qunqun_dng@163.com, b zhangwiqiang@nbu.du.cn, c Jiangjintao@nbu.du.cn Kyworlds: HM rmot control systm; microstrip antnna; ADS Abstract. Along with th dvlopmnt of th aviation industry, HM sports gt mor and mor attntion, it was a vry hot sport at hom and abroad, th rmot control tchnology of modl aircraft is also hav bn dvlopd. In th prsnt modl aircraft rmot control systms, th antnna is usually dipol antnna, dipol antnna is largr, highr powr consumption. In viw of th abov shortcomings, this papr proposs a way that using micro-strip antnna instad of th traditional antnna. Through th discussion of th microstrip antnna's working principl, this papr dsignd a microstrip antnna works in 2.4 GHz modl aircraft rmot control systm. According to its actual application, th matrial, shap, and th typ of th microstrip antnna ar dtrmind, and th siz of th antnna is calculatd by th quation and th softwar, thn th modl of th antnna is built and simulatd in ADS, finally th bst paramtrs ar obtaind through optimizing and matching to mts th rquirmnts. Introduction For a wirlss modl aircraft rmot control communication systm, it is a basic rquirmnt to corrctly snd and rciv data. Thrfor, th antnna is an indispnsabl part of HM communication. But th usd antnna now is too bulky for th HM rmot controlr. To solv this problm, th papr choos to us a microstrip antnna to instad th triditional antnna,it can not only rduc th volum of th wirlss transmission quipmnt, but also rduc powr consumption and costs [1]. Th HM rmot control systm using CYWM6936 RF chip to build th wirlss transmission modul,and using sprad spctrum communication tchniqus for transmitting data, so this articl compltd th microstrip antnna dsign of 2. 4 GHz sprad spctrum communication systm basd on CY6936 chip,laid th foundation so as to constitut a small volum, low-powr modl aircraft rmot control systm hardwar [2].Th following dtaild discuss th microstrip antnna dsign principls, th dsign procss as wll as impdanc matching program. Principls of microstrip antnna dsign Radiation principl of microstrip antnna. Microstrip antnna is a microwav antnna which consisting of dsird shap mtal ground conductor patchs or attachd to th floor of th dilctric substrat, typically by a microstrip transmission lin or a coaxial prob fd, so that btwn th conductor patchs and th ground plat xcit high-frquncy lctromagntic filds, and lctromagntic wavs radiat outward through th gap btwn th patch around th ground plat [2,3]. 0225
Fig. 1 Rctangular microstrip patch antnna structur Choic of th antnna shap. SMD has varity of shaps, circular microstrip antnna's bamwidth is narrowr than rctangular microstrip antnna,but thir dirctional cofficint almost idntical,and th rctangular microstrip antnna rquird a mor big ara for radiating than circular microstrip antnna.at th sam tim,w can caculat that th dsird siz of rctangular patch in th rang can mt th rquirmnts, and also th fficincy and th width of rctangular microstrip antnna ar suprior to th circular microstrip antnna [4]. Th rctangular microstrip antnna structur diagram is shown on Fig.1. Antnna fding lctric mod slction. Th microstrip antnna has many kinds of fd ways, but mainly dividd into microstrip transmission lin fd and coaxial prob fd [5]. Whr in th microstrip transmission lin fd is a conductor strip, typically having a narrowr width. Microstrip transmission lin fd is simpl to manufactur, asy to match, and also asy modling. Coaxial prob fd by conncting coaxial innr conductor to th radiating patch, and th outr conductor rcivd a ground plan. Th coaxial fdr also has th advantag of manufacturing simpl, asy to match, whil a rlativly narrow bandwidth, but th modling is rlativly difficult [6]. Dsign procss Antnna siz calculation.to dtrmin th siz of th rctangular patch, i.. th lngth and th width[7]. Width calculation. Width affcts th dirctivity function of th microstrip antnna, th radiation rsistanc, and th input impdanc, which also affcts th bandwidth and th radiation fficincy.in addition, it controls th total siz of th microstrip antnna.tak an appropriat considration of th installation conditions, a largr W is bnficial to th band,fficincy, and th impdanc matching,but whn th siz gratr than th valu that formula (1) givs, it will b gnrat a high-ordr mod, causing th distortion of th fild. W C r 2f 2 r -1 2 (1) C is th spd of light;r is th dilctric constant ;f r is th rsonanc frquncy. lngth calculationth lngth of a rctangular microstrip antnna is th half of th valu of its wavlngth in thory, but taking th influnc of th fring fild into account, it should b subtractd 2 L, L can b calculatd by formula (2). g L = λ -2ΔL 2 (2) In th formula (2),λ g is th corrsponding wavlngth of f r ; L is actually a corrction valu influncd by th fring fild, rspctivly, calculatd by th formula (3) to (5). is th corrction 0226
constants. λ = g f r C r+1 r-1 h = + 1+12 2 2 W (3) (4) ( +0.3)( W h+0.264) Δ = (5) L 0.412 h ( -0.258)( W h +0.8) In this dsign, with th FR4 dilctric substrat (Er = 4.4, tan δ = 0.02 and h = 1.6mm), f = 2.4GHz, th rlativ bandwidth gratr than 1%. According to th abov formulas,th lngth and width( L = 3cm. W=2.5mm) can b obtaind.th way of fd is microstrip fd. Simulation Build th modl and simulat in ADS [8]. Th rsults ar shown blow: Fig. 2 S-paramtr simulation rsults of th first antnna As can b sn from th figur.2, thortical calculation rsult is consistnt with th actual cntr frquncy of approximatly 2.4 GHz. Optimization In ordr to furthr rducd th rflction cofficint, and to achiv th dsird match, vn to mak th cntr frquncy mor accuratly, nd impdanc matching of th antnna. Th impdanc matching is a vry important aspct of RF circuit dsign, w can s from th imag abov, th input impdanc is 259.369-j * 38.576, not qual with 50 ohm (th transmission lin impdanc ),so it is ncssary to add a matching circuit to incras th charactristic impdanc of th antnna patch, in ordr to achiv th maximum powr transmission [9,10].Th mthods of impdanc matching including capacitanc inductanc mthod and microstrip lin mthod, bcaus of th highr frquncy,so w slct microstrip lin matching mthod in this dsign. Using ADS tool-- smith chart,matching can b obtaind asily,it nd to add a charactristic impdanc of 116 0227
ohm microstrip lin to achiv th antnna input impdanc to a 50-ohm matching; whil using ADS LinCalc tool can calculat th width and lngth of th microstrip lin, th calculation procss and th final rsults ar that th match lin of lngth is 17.1mm, th width is 0.45mm, th 50 ohm microstrip fd linr can b st arbitrary lngth, th final matching schmatic as follows. Fig. 3 Optimizd circuit schmatics Fig. 4 Th simulation rsults aftr optimization Th simulation aftr optimization is shown on fig.4, it can b sn that th antnna oprats in th frquncy 2.44GHz, th radiation charactristics, th main radiation dirction prpndicular to th antnna surfac,can wll mt th practical application of th HM control systm. Summary This papr dscribls th dsign principls and procsss of microstrip antnna, calculats th siz according to th classic formula of rctangular microstrip antnna, Modling and simulating by th ADS simulation softwar, through continuous adjustmnt of th antnna's prformanc, so as to achiv th most optimizd and dsignd prformanc that can wll mt th rquirmnts of th practical application. Rfrncs [1] Yin Jiji.Microwav antnna. Bijing: Elctronic Industry Prss, 2004. [2] Song Zhng, Zhang Jianhua, Huang Zhi.Antnna and Propagation. Xi'an: Xi'an Elctronic Scinc and Tchnology Univrsity Prss, 2002. 0228
[3] Huang Qiuyuan, Dong Shibo, RF circuit matching ntwork dsign and analysis. Wuhan Univrsity of Tchnology: Transportation Scinc and Enginring, 2007,31 (6): 1061-1063. [4] Yang Yongxia, Yang Lin. 2.4GHZ microstrip antnna dsign Basd on CC2430. Th Elctronic Tchnology.2011.24 (9): 34-41. [5] Jia Png, Huang Xiping, Gao Hongming. Dsign and Implmntation of 2.4GHZ microstrip antnna for RFID applications. Elctronic products world.2010. [6] Li Yan. Rctangular microstrip patch antnna simulation study and dsign. Wuhan: Wuhan Univrsity of Tchnology, 2011. [7] Zhang Jian. Rctangular microstrip patch antnna (MPA) principls and EDA dsign. Intgratd circuit communication, 2008, 26 (3) 31-37. [8] Xu Xingfu.Th RF circuit dsign and simulation by ADS2008.Bijing: Elctronic Industry Prss, 2009. [9] Yang Hanhua. RFID fractal antnna dsign and rsarch in Min fild.zhnjiang: Jiangsu Univrsity, 2008. [10] Chn Yongliang.Prliminary dsign and optimization of th linar array of rctangular microstrip patch antnna.chngdu: Southwst Jiaotong Univrsity, 2005. 0229