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Microstrip Antennas for Mobile Wireless Communication Systems

Mobile and wirelessunications: Network layer and circuit level design2 Mobile Antenna Requirements and challengesThe explosive growth in the demand for wireless communication and information transferon(Pcs) dehas created the need foplaced on a small plastime, the system must radiatewer andliable communication of voice and possibly data(d M Pozar d H Schaprofile and easyate with the wireless communication system The antenna designerust also consider the following electrical characteristics of the antenna which include(wtuzman g Theile, 1998; CA Balanis, 1997)antenna tuning (operating frequency)

VSWR and Return loss4-Gain and directivity6-Diversintroduced asThe size of the chassis(exprSAR (Specific absorption rate)of the antennad antenna designentenna structures to meet the often conflicting needs for wireless systems as: operationfrequency, return loss (VSWR), bandwidth, gain and directivity, location and orientation ofthe antenna, radiation pattern and diversitytrip antennas Theseas are widely used on base stations as wehandsetsicrostrip antennas have a variety of configurations and have been the topic of whatthe most active field in antenna research and development The microstrip patPS Hall, 1989) has increasingly wide range of applications interial called the dielectric substrate It is completelyth a metalalled the groundd on the other side where the circuitatterns are printed Components can be included in the circuit either by implantingImped components or by realizing them directly within thet as shown in Figure 1

ems442 Compact PIFA size withUltra compact PIFA with dual band resonant frequencies are investigated(Hala Elsadek,006) The antenna is designed and fabricated on both foam and FR4 cheap substrates withdielectric constants e, 107 and 47, respectively Over 95% reduction in the antennais achieved from conventional 2,/4 rectangular PIFA resonating alThisting two oppositely shorting capacitider the radiarface

Dual band operation is achieved by inserting two parallel slots on the edges of thePIFA radiating surface forming an E-shape In thisfrequency while the two side wingsof 97e, quencies on FR4 substrate are 1 07GHz and 277 GHz with arreductifor the lower and upper resonance frequencies, respectively Thentenna size on FR4 substrate is 13 x 11 x Smm The antenna directivity is 373 withradiation efficiency 97% The radiation pattern has acceptable shaparization in both resonances and at both E-plane and H-plane directions It is worth tod 52GHz with dimensions SmmxSmmx8mm Figure 10 shows the antennachile fisimulated and measured results withtiband comntenna design; however, we concentrated on PlFA with shorting plates and capacitiyloads with different radiator shapes, Since these shapes give excellent results for antennaandidates in mobile communicatisplatFig 10 E-shaped PiFA antenna geometryFR4 substrate and(b) comparisonbetween simulated and measured antenna reflectio

unications: Network layer and circuit level design5 Broad band and UWB Antelillustrate the challenge of small and multiband antenna that can fit inntenna bandwidth was achievedother applicationswirelessmmunicatioBroad band antennas are desired for the increasing demand of communicationbandwidth that accommodates high data rate application like video-on-demand MoreoveUWB technology atattention from the researchers innds instead of modulating sinusoidal signal and, hence broadeningpectrum and tuning its power density beyoel(FCC, 2002) This method inansmission exhibitmultipath effects Also it has penetration capability as its spectrum includeogylications in wireless communications One of the major application is the wirelesork (WSN) which is useful in medical, tracking and localization applicationnsing)(lan Opperman at el, 2004; K P Ray, 2008)As UWB provide security anon that increase the battery life of the portable terminals, On the otheand, broad band communication systems as well as UWB technology faceslenges as the radiation pattern stability and polarization purity along the whole band of52-Different types of broad band antennasMany designs have been investigated in literature for broadening the bandwidth ofantennas This can be achieved by using different probe feeding shapes asarasitic elements to the radiator, folding the ground plane, etc( Fan Yang, 2001; Yassharderation for the stability of the beam patton purity along the bandwidth, the design quality is judged Among the bahe band are inserting slots of differen[U, H, V)on the radipatch antenna to introduce longer current paths and hence add other staggered resonatingmodes

The rule of thumb in adding another resoesonating modes are far from each other, the structure willnna But ifne design is changedhesenear from each other, they will complementch other forming staggnating behavior and broad band antenna structure Alsadding parasitic or stacked patch has been proposed in(Mohamed A Alsharkawy at el2004) Another types as aperture stacked and multi resonator stacked patches in(Ki-Hakkimrer forming multi resonators and hence broaden thebulky and not adequatespite there are successful attempts for this In addition they don't exhibit enough bandwidthmunication bowadays(3 1-106GHz) Recently UWB slotantenna in(Girish kumar, 2003; Yashar Zehforoosh at el, 2006)and printed monopoleDek H Choi at el, 2004)are proposed They attract a lot of interests due to their

Microstrip Antennas for Mobile Wireless Communication Systemsde bandwidth Next section will fUwB printed monopole antennaiderations should be taken for UWB antenna design such(Hung- Jui Lam, 2005)l-It should have bandwidth ranging from 3 1GHz to10 6GHz in which reasonable effie2-In this ultra-wide bandwidth, an extremely low emission power level shouldIn 2002, the Federal Communication Commission(FCC) has specified the-413 d Bm/MHz)The antenna propagates short-pulse signal with midistortionthe frequrangerinted monopole antenna structure is shown in Figure 12 and it could be explained as anf the microstrip antenna1982:Calanis, 1997) it is known that the substrate thickness(h) is directly proportional to the Bwd as(h)is extended to infinity by eliminating the ground plan the bw become very wide

Also, the resonant frequency is functionpatch printed on very thick substrate it excites higher order modes each enables broadeeding pointopole antennaIf these higher order modes are close to each other the overall bandwidth isnventional monopole but with the cylindrical metallic rod flatted to be plane of anyifferent shapes(KP Ray, 2008)(rectangular, circular, elliptic)as itt impedancbandwidththe diameof the metallic rod, Thternate the metallic rod is considered of diameter extended to infinity exciting higherof large bandwidth Upon optimizing the dimensions of the arse to each others to yield very broad bandwidth as will

Mobile and wireless Communications: Network layer and circuit level design541Aprevious section, printed monopole anteanalog to thequarterve monopole antenna Thisedge frequency by equating its area (in this case rectangular monopole) to an equivalenteight L and equivalent radius2TTrL= WLis half the input impedance of thin A/2 dipoleand equal is slightly less than quarter wavelength and given by (15, 38KK=(L/y)/(1+L/r)=L/(L024Previous equation doesn't account for the distance between the radiator and thedplane(h)illimeters, This analysis is valid for free space but in our casewhere antenna is printed on a dielectric substrate which decrease the effectiof thelength (g) ModificatiIt is worthwhile toalthough previous analysis was on rectangular sharintedhapes of radiators butAfter inspecting the lower edge frequency we need to control the bandwidth of the antennaptimization is needed to give the required bandwidthell as theAnother important thing that affects severely the bandwidth is the bottom shape of theradiator in contact with the 50Q2 feeder As long as we avoid abrupt change in themensions of the transition from the feeder to the radiatorng as we obtain broaderandwidth

That's why circular radiator inherent wider band than rectangne by using stepped or tapered feeders( I Latif005: AP Zhao and J Rahola, 2005) Finally using CPW(tvguide feednstead of microstrip feed enhances the bandwidth As printedesonating around quarter wave length so they have similar radiation pattern as normal

emsthe H-plane and eight shaped in the E-plane Follemples about broad band and UwA antenna designsrostrip antenna designs551 Broad band antenThe geometry of the proposed antennas is as shown in figure 13 The antenna consists of Vtch with v- unequal arms with dimensions(Ll, Wi)and(L, W2) Theelngular antenna is with dimensions (LT, WT) The shorting wall width is equal to Wr foze reductionrectangular shape of dimensions Lg Wo) The tof the structure, V-shaped patchand triangular PIFAth unequalthgths and widths are (Lsl, Wsi) and(L2, Ws2) The two arms of the v-shaped patchMon mode The length of the two arms of the v-shaped patch is different in order to excitet staggered resonant modes The unequal spacing/widths between the coaxiallyfed triangular shorted patch and the V-shaped patch are for different values of couplingt modes, To add two more resonating modes, equalshaped slot can be loaded on the triangular patch radiation surface The substrate is fth dielectrictantE,-107 and substrate height h 6mm The arntenna behavior changes to be wide bandwidth antenna rather than multiband antennanating freqbe approximately determined from following equationWhere: t, ist band i

c is the veof light a=3×10°m/ s andLisoperating band i ThePIFA Part is excited by coaxial probe feed The probe ispositioned in the centerline of the shorted patch at distance d from shorting wall The dalue controls the antenna characteristics For multibannatingfrequencies are at 288GHz, 364GHz, 395GHz, 438GHz, 481GHz and 56GHz, the distanced is 1675mm while for broadband operation, the distance d increased to be 1851illustrates comparison between the simulated and measured results for thethe antenna istely omni directionalin both E-plane and H-plane with back to front ratio of less than 5dB and 3dB beoout 60Moving coaxial feeding towards open end of triangular PIFA antenna at d-185mm,thewideband operation The bandwidth is 3% at the fundamental mode 295 GHz, hence thefundamental resonating frequencyproximately not affected by changing the feed

Mobile and wirelessunications: Network layer and circuit level designandwidth is 27% at 4721GHz Figure 15ts themparison between the simulated and measured results of the wideband antenolding the shorting wall of the triangular PIFA as in figure 13, converts the antenna toUwB with bandwidth of 53% atting frequency 465GHz The antenna gain is105 dBi↓ V-shaped patch公W2 wFig, 13

Configuration of the proposedComeasured results of the multi-band antennaand measured rest552 UwB aConsider we have substrate material of 8=338 and h=0813mm and we need to designining lower edgefrequency at 5Ghz and obtain BW as widerom above equations in subsection 5 4 1, to satisfy 5GHz a lot of solutions could bebtained for L, w, h but not all of them will give the maximum Bw, so optimization is

Microstrip Antennas for Mobile Wireless Communication Systemsneeded for obtaining the optidimensions parametric anaor the effects of thesearee dimensions on bandwidth is shown in figures 16-18(Hakim Aissat at el, 2006; MinHau Ho at el, 2005 ) Starting with L-W=0 25M0/V8 8mm and h 2mm From the th

reefigures below, the optimum dimensions are W=12, L=115 and H=oFig 16 The effect ofFig 17

The effect ofFig 18 The effect ofchanging Won the returnthe returnn the return lossand h-2and L- 11561 Introduction to recorable aasing demandwirelessmmunication dand radar systems, reconfigurable antennasesearcher's attention One type of these antennas capable for operation atcommunication systems(KPCS/ WiMAX/GSM/WCDMA)with lower co-site interference Other types exhibit diversity in transmission or recepof its specification or characteristics could bees/MEMsour types: 1-Frequency reconfigurable, 2-poalrization diversity, 3-radiation patterneering, 4-combination of the three previous types Advantages of reconfigurable antennasre integration with wireless and radar devices instead of multiple antenna systemsterference and make efficient use of the electromagnetic spectrum Polarization diversityand radiation pattern steering antennas could leadpacity and fading immunity Moreover they open thegingunication systems like MIMO and cognitive radio Also from future potential for thentroduction of smartness and intelligence to the handheld terminals Switching andning takes place with the aid of pin diodes or MEMs switches oradopted withOn the other hand mems have lower insertion loss, easibut it needs highgcurrentlmany modern wirelessunication systems(DCS/GSM/WCDMA/Bluetooth/WLAN), hand held GPS and other navigation systen

Microstrip Antennas for Mobile Wireless Communication SystemsMicrostrip antenna offers certain advantag2 Low power-handling capability of printed circuitsgical Considerafions: integral with other circuit dhenceduction in Size: printed circuitshin and thus requthan theirde or coaxial linerealized a circuit, and tested it successfully, additional copies can be producedidly and consistently in largeOn the other hand it suffers from somedvantageNarrow bandwidtLow gainfeed networkExcitation of surface wavesFirstly, thesend space applications

Then this technology isial sector Specifications for defense and space applicationntennas typically emphasize maximum performance with little constraint on cost On thether hand, commercial applications demand low cost components, often at the expense ofw-cost materialsle and inexpensive fabrication techniSome of the commercialsystems that presently use microstrip antennas are listed in the Table 1

Mobile and wirelessunications: Network layer and circuit level designApplicationGlobal Positi6 MHz and 935-960 MHzWireless Local Area Networks48GHz 54GHzCellular VideoDirect BroAutomatic Toll collecti905 MHz and 5-6 GHz60GHZ,77GHz,and94GHzArea60 GHZTable 1 Microstrip Antenna Applications2nlafnother area of research which is closely linked to adnna dnt is thenalytical modeling techniques(such as Transmission line model and cavity model)is notent anymore The use of full-wave modeling techniques, has thtable The most commonly used full-wave modeling techniques are the Method(MoM), the Finite Element method (FEM) and the Finife Difference Time Domain(FDTDA microstrip structure is illustrated in Figure 2

Fig 2 Microstrip construction31 Wavesvithin four distinct categories(W Stuzman G Theile, 1998)e toward free opendistance from antenna In transmission lines and circuits, they are undesirable as theyproduce spurious leakage, however they contribute directly to antenna radiationefficiency as in figure 3(a)

2)Guidedthey are trapped between the uphe normal operation for transmission lines and circuits but it is not favorable for patchtenna as in figure 3 (b)(3)Leaky waves: they are directed more sharply downward, with e lying betweand丌/2

Thesentribute to radiation thus they areseful for antennas as in figure 3(c)ving elevation anglesbetween T/2and丌Va,), experience total reflection between the trexponentially above thece as shd) Surface waves take uppart of the signal's energyhe antenna efficienc(a)strip patch antenna is important as single radiating element, butOIcations that require moderate sizediscrete radiators are combined toan array, some characteristics can be achieved orenhanced; such as high gain and beam scanning

Mobile and wirelessunications: Network layer and circuit level designtrip antennabe classified with different criteria The elements of thearray can be distributed to formd to obtain certain characteristics The feed network of phased arrorporate)feed has single input port and multiple feed lines If thehas multiplts and multiple output ports so it is called Multi-element-array(MEA)or MIMO arraysD M Pozar D H Schaubert, 1995)Array (MEAy p antenna array (a)phased array,(b)series-fed array,(e)Multi-Eleme4 Compact and Multiband Microstrip Antennas41 Introduction to compact and multi band antennason applications, the demand for low profilpact size planantenna is increasing day by day

The light weight, smalldeveloped and they are fairly efficient radiators that can be easily manufactured at low coonal microstrip patch is not a good candidate for the mobile wirelessapproaches are investigated for multiband antenna with reduced size operation Differplications, due to certain disadvantages asbandwidth therefore more unusuther microstrip structures are successful candidates as microstrip Planar Inverted Fntenna(PIFA) with different geometrical radiator shapes Thegoal is to designantennas for wirelommunicationcations where thef theuite limited while it reserves the characteristics of multiband, light weight, low cost,bustness, diversity, packaging capabilities and ability for mEMs integration for smartntenna systems Several researches in literature concentrate on these antenna types andtheir developments In this part the author will try to highlight the important results anderal corresponding shapesenna size reduction include dielectric loading to reduce thengins or plates(Dalia Nashaat et al, 2003) Dielectric loading usually is accompanied by bandwidthso it is not a likely approach Thus, we will investigate antennastop hat loading and shorting pins or plates, either separately or in combination

Microstrip Antennas for Mobile Wireless Communication SystemsCircuitalRadiation patternown sizin!F區ymmetry vs loss polarization)enhancement ratioMaterial: highdielectric slow wayack, etcTable 2

Downsizing techniques and performance affecting on antennasws of nature(BW), gain (g), etc For small size antennas, therea tradeoff amongadiation quality factor(Q), Bw and efficiency (n)c P Huang, 1999; Dalia Nashaat et al,2003)The rule of thumb isBWn- Constanthe antenna bandwidth, n is the antenna efficiencindicates that the smaller the antenna, the higher the Qthe microstrip antennaonsidered small if its largest dimensionthanequal to(a) whereWhere a is the wavelength of the electromagnetic fields radiated by the antennaple, for antenna operates at 5GHz, A-60mm so a 10mm,that theantenna can be considered small if its dimensions are less than 1omm

Mobile and wireless Communications: Network layer and circuit level design3-PIFA as compactas shown in figure 5(T Taga, 1992 6 design These antennas offer reduced size ovresonance frequency is at about quarter wavrather than at half wave in conventiothe shorting pins/ walls in its strucating slot(a) Conventional Microstrip patch antg 5 Comparison between conventional microstrip patch antenna and conventional PIFAantennaThe selection of PiFa is due to certain advantages asPIFA impedance matching can be obtained by the correct positioning of feeding andounding pins

Thickness of the antenna and permittivity of the substrate material usedso affect the impedance of the feeding point To shrink the size of the PIfA, high constantelectric substrate materials can be used This weakens the performance of the antennabecause dmaterial gathersletic fields and therefore it dediatealated PIFA Also part of the feedbes into the dielectric losses ofthe substrate material The height of the PlFA is a very critical dimensionit has a greatradiator and ground plane is, the better the gain and thethe impedance bandwidththe effect of different piearameters,(height, widthlength, location of feed and shorting pin/wall andhe ground planecharacteristicsParametersEffectControl bandwidthWidthIncrease inductance of the antenna and determinequencyresonance and increase bandwicFeed position from Affefrequency and bandwidth

Microstrip Antennas for Mobile Wireless Communication Systems44 PIFA structures for multiband and compact size applications441 Rectangular PIFA shape with U-shaped slotson cellular bands is developed (Dalia Nashaat et al, 2005; Hala Elsadek, 2005; R Chair et al,99) From the commercialportable cellular/non cellular devices as the conventional 0 9GHz GSM band for mobilephones and 1 8GHz DCs band for wireless cellular applications Furthermore the Bluetoothwireless technology at 24 GHz is already applied in many portable devices and in mostakerstc(Bluetooth information web site)

Moreover the band of Wlan at 5 2GHzed in some applications The compact and multiband functionalitynly required demand in such antenna systems for wireless communication applicationsut, also other characteshould be satisfied as small size light weight, omni directionalQuad band PiFA with single coaxial probe feeding is investigated Foam substrate is usedasy shielding purposes Three U-shaped slotsded with certain dimensions and at appropriate positions for operation at theforementioned four frequency bands Thereduction is 30% from conventional quarterwavelength PIFA Additional reduction by 15% is achieved by adding a capacitance load inatisfactory and the radiation pattern is quasi isotropic at the respective four bandsterest The proposed concept of adding U-shaped slots is a distinct advantage of thethe bands of operation are independent on each other except the smallntrollable mutupling between the slots Figure 6 illustrates the suggestS ots widthFig 6 Geometrical dimensions of the fabricated quad band antennaThe rule of thumb in antenna design isd W1=61mm, 40mm) of the PIFA(Li, Wi)are replaced by the dimensions of the largest U-slot (Le, W2)=(23mm, 30mm

Mobile and wirelessunications: Network layer and circuit level designnerate the secondfref2(1 8GHz) They are also replaced by the length(La, W3 )=(18mm, 20mm)of the middle U-slot to get the third5GHz) Finally, (L, Wi)are replaced by(L4, Wa)=(9 5mm, 8mm) of the smallest U-slot tohave the fourth reproximately thea single-band PIFA oat the lowest frequency bandrounded with a shorting wall It is found that theandwidth is achieved when the width of this wall is equal to the width of the PlFaradiating plate

Thetble at the appropriate matching pointthe four bands of operation The antmpedance can be matched to 5032 bhe distance between the feeda foam substrate with diele07 in order to have rigid structure thatasily shielded Adding U-slots on the PIFA radiating surface, reduces its size by about 30om the conventional PIFA shape For further reduction in size, a capacitor plate load isdded between the radiating surface and the ground plane Thisthe reduction inze to be about 45%, The results of the structure simulations as well as experimentmeasurements are illustrated in following three figuresipacitancecmeasuredmulated reflection coefficients of quad bandantennaPIFA with three U-shaped slots at operating095,18,245and52GHz,-band PIFa with 10PF shortinglate at four ddonating frequencies, a) at parallel E-plane at phi 0 and b)atrpendicular H