Band Rejection

8/9/2019 Band Rejection

1/13

Published in IET Microwaves, Antennas & Propagation

Received on 24th July 2008

Revised on 10th December 2008

doi: 10.1049/iet-map.2008.0253

ISSN 1751-8725

Miniaturised coplanar waveguide-fed antennaand band-notched design for ultra-widebandapplications

A. Mehdipour1

A. Parsa2

A.-R. Sebak1

C.W. Trueman1

1Department of Electrical and Computer Engineering, Concordia University, Montreal, QC, Canada H3G 2W12

Department of Electrical Engineering, Ecole Polytechnique de Montreal, Montreal, QC, Canada H3T 1J4

E-mail: [email protected]

Abstract: A miniaturised coplanar waveguide-fed ultra-wideband (UWB) antenna is presented here. The

wideband operation is obtained through an optimised curvature of the radiating element. The input

impedance of the antenna is matched using an elliptically tapered coplanar waveguide line. A high-band

rejection characteristic at wireless local area network frequencies is achieved by inserting an v-shaped slot on

the antenna surface. The frequency domain dispersion characteristic is studied by means of the antenna

transfer function both numerically and experimentally. Time domain characteristic of the antenna is

investigated in detail for both UWB single-band and multiband schemes. In order to efficiently characterise

the antenna system for an arbitrary pulse source excitation, the pole/residue model of the antenna systemtransfer function is presented using the matrix-pencil method.

1 Introduction

Since the Federal Communications Commission (FCC)authorised the use of short-range ultra wideband (UWB)signals in the frequency band of 3.1 10.6 GHz for thecommercial applications [1], the demand for design ofhigh-performance UWB antennas has been increased.Planar antennas are one of the most attractive antenna

types considered for the use in UWB radio. This is becauseof their low cost and easy to fabricate characteristics[210]. In addition to high performance, the wirelessindustry always seeks small size antennas for use inhandheld and RF/Microwave devices [510]. However,there is usually a trade-off between the bandwidth and thesize of antenna. As a result, the miniaturisation processrequires compromising between the size and performanceof the antenna [5]. The small size planar antennas such asthe microstrip-fed antennas with ground plane have beenintroduced for UWB applications in [68]. The sizereduction in these antennas usually leads to small ground

plane, which is on the substrate surface, in the oppositeside of the radiation element. The surface current on thesmall ground plane becomes considerable, and it affects the

antenna performance [8, 11]. Owning a balanced structure,the coplanar waveguide (CPW)-fed antennas are very goodcandidates since the feed line and slots are on one side ofthe substrate [9, 10].

In order to judge the performance of an UWB antenna, thedispersive behaviour of the antenna should also be takeninto account. The dispersion behaviour can be analysed in

both frequency and time domain. In time-domaincharacterisation, the antenna can be verified for single-bandand multiband cases [12]. In a single-band scheme that isusually considered in antenna analysis [510], the entirefrequency band is allocated to one pulse. In a multibandapproach, the whole frequency range is covered with severalmodulated pulses in different sub-bands [13, 14]. This isuseful for reducing the interference. The interference can beeasily avoided by stopping the signal transmission in sub-bands, which are used by other systems.

Since UWB antennas are used for radiating different pulse-

sourceexcitations, a parametric model, which characterises theimpulse response of the antenna system can be very useful[1518]. By using a parametric model, the antenna can be

974 IET Microw. Antennas Propag., 2009, Vol. 3, Iss. 6, pp. 974986

& The Institution of Engineering and Technology 2009 doi: 10.1049/iet-map.2008.0253

www.ietdl.org

Authorized licensed use limited to: University Kebangsaan Malaysia. Downloaded on July 19,2010 at 09:58:16 UTC from IEEE Xplore. Restrictions apply.


2/13

characterised by a number of poles and residues for eachorientation. Having the parametric model of an antenna interms of a closed form expression, the antenna response canbe easily obtained for an arbitrary pulse shape excitation. Inother words, the parametric model of the antenna system is

very useful in UWB communication system design.

In this paper, a miniaturised CPW fed antenna is proposedfor UWB applications. The antenna curvature is composed ofthree elliptical curves. This makes the antenna more flexiblefor optimisation process. In order to have VSWR,2 overthe entire frequency range, the antenna is optimised using

Ansoft HFSS software [19]. The antenna is then fabricatedand successfully tested. To avoid interference with nearby

wireless local area networks (WLANs), a notch isintroduced in the antenna response, covering the WLANbandwidth. This is realised by cutting an v-shape slot onthe surface of the radiation element.

To study the proposed antenna dispersion characteristics,the antenna is analysed in both time and frequencydomain. Using the antenna transfer function, the frequencydomain dispersive behaviour of the antenna is evaluatedboth numerically and experimentally. In time-domaincharacterisation, both single-band and multiband schemesare carefully investigated. Furthermore, a parametric modelof the antenna system (pole/residue model) is obtained byusing the matrix-pencil method [20].

The organisation of this paper is as follows. The antennastructure and parametric studies are demonstrated inSection 2. The radiation pattern and time/frequencydomain dispersion characteristics of the proposed antennaare discussed in Section 3. Using the directional transferfunction of Tx/Rx setups, the pole/residue model of theantenna system is presented for different orientations inSection 4. Section 5 contains the conclusion.

2 Antenna design

2.1 Antenna geometry

The proposed antenna structure is shown in Fig. 1a. The

antenna is printed on the top of a light-weight 0.508 mmthick Rogers RT Duroid 3003 (1r 3, tan d 0.0013)substrate. The feed line is a 50-ohm CPW line, which isconnected to the radiating element through a widebandtapered structure formed by two ellipses. These ellipses aredefined by L1, L2, L3 and g2 parameters. This taperedtransition matches the antenna input impedance to a 50-ohmSMA connector. The radiating element curvature iscomposed of three quarter-ellipses defined byR1, R2, R3, R4,R5 and R6 parameters. By using these ellipses in shaping theradiating element, it is possible to form a smooth curvedstructure. Furthermore, this curvature shape provides more

flexibility for a further antenna optimisation. Theseparameters control both the bandwidth and its lowerfrequency limit. Making the antenna size as small as possible,

we optimise the antenna geometrical parameters forVSWR, 2 (S11,29.5 dB) over the entire frequency range(3.1 10.6 GHz). The optimisation procedure is done byusing Ansoft HFSS software optimisation tool. Thegeometrical parameters are obtained as: R1 R2 4,R3 8.8, R4 5.5, R5 0.5, R6 1.8, L1 6.6, L2 9,

L3 7.1, g1 18, g2 1, s1 2 and s2 1.4 where the unit is millimetre. The substrate size isD1 D2 35 35 mm2. Referring to Fig. 1b, the 50-ohmCPW line dimensions are w 3 mm and g 0.2 mm.Using these parameters, the antenna is fabricated as shown inFig. 1d. Fig. 2ashows the simulated and measured VSWR ofthe proposed antenna. A good agreement is observed.

In order to have the notch-band characteristics at WLANfrequencies (5.155.825 GHz), a kind of slot known as half-

wave resonant structure has been introduced in [2123] so

Figure 1 Geometry of the proposed antenna

a Top-viewb Cross-section viewc Band-Notched designd Photograph of the fabricated antennas

Figure 2 VSWR of the proposed antenna

IET Microw. Antennas Propag., 2009, Vol. 3, Iss. 6, pp. 974 986 975

doi: 10.1049/iet-map.2008.0253 & The Institution of Engineering and Technology 2009

www.ietdl.org



3/13

far so that it resonates at the frequencyf0when thelength of slotis l0/2 where l0 is the wavelength at the central notchfrequency ( f0). In fact, the slot behaves like a quarter-

wavelength short-circuit stub in a series configuration withthe equivalent input impedance circuit of the antenna or likea half-wavelength short circuit stub parallel with the input

impedance of the antenna [24]. The simplest half-waveresonant structures are slits or triangular slots on the radiationelement as introduced in [2123]. The slits can be used inboth vertical and horizontal forms on the radiation elementsurface where sometimes they would be large in size.However, one of the disadvantages of the physically large slitsis that they affect the radiation pattern of the antenna at outof notch-band frequencies, which is not desirable [25].Moreover, for small antennas with compact size, the length ofslot resonators is limited by the size of antenna, which limitsus in adjusting the centre notch frequency to the lowerfrequencies of interest. To compact the slot size, curved-shape

resonators (such as U or t shapes) are commonly used toachieve the band-rejected characteristics [7]. The fractal shaperesonators were introduced to improve the notch behaviour ofthe antenna response at the desired centre frequency[25, 26].

The fractal shapes are efficient resonators due to the smalldimension and high-Qoperation where Qis the quality factordefined as f0/Df. Because of the high-Q operation, theantenna performance deterioration occurs only at the desirednotch-band frequencies, not out of this band. However,because of the complicated structure of fractal shapes, thenumber of design parameters would be large. Thereforeintroducing a much simpler structure with high band-rejection performance and good Q-characteristic is desirable.

As shown in Fig. 1c, we propose a semi-fractal v-shapeslot (called Slot-A) on the radiating element surface, whichshows a high-band rejection characteristic with appropriateQ characteristic. The length of Slot-A can be obtainedapproximately from [24]

Lstub c2f0ffiffiffiffiffiffiffiffi1reff

p (1)

where Lstub 3pr0. Slot-A is composed of two 3p/2 arcswith radius r0. In order to compare the performance of theproposed notch-band slot with other techniques, we haveinserted different types of slots on the antenna surface asshown in Fig. 3a. In Fig. 3b, the performances of differentnotch-band techniques are compared with the performanceof the v-shape slot. The centre notch frequency ( f0) isadjusted to be around 5.7 GHz. The dimensions of v-slotare obtained as r0 2.5 mm and s0 22 mm. The width

of slot is 0.5 mm. The dimensions of other slots are shownin Fig. 3a. It can be seen that for slit type resonator(Config. I), although the band rejection is high at thecentre notch frequency, the resonator shows a poor Qfactor, which deteriorates the antenna VSWR for a widerange of frequencies around the centre notch frequency. Forcurved U and t shape slots, the resonator shows areasonable Q-characteristic, but the band rejectionmagnitude (VSWR, 10) is not high at the centre notchfrequency. It is observed that by using the v-shape slot, a

very high notch-band rejection (VSWR 22.5) is achievedat the centre notch frequency with acceptable Q-characteristic (VSWR. 3 for 5.4 GHz,f, 5.95 GHz).

Figure 3 Different types of slots

a Different notch-band techniquesb VSWR of the proposed antenna using different notch-band techniquesc Simulated and measured VSWR of the proposed notch-band technique



www.ietdl.org



4/13

For notch-band design, we determine the best location ofslot (s0) through a parametric study to obtain the highestVSWR at the centre frequency of notch. The simulated

and measured VSWR of the band-notched design withr0 2.5 mm and s0 22 mm are displayed in Fig. 3c. Themeasured central notch frequency is 5.81 GHz, which is insatisfactory agreement with the simulation result.

Because of compact size, considerable band rejection, andhigh Q-characteristic, the proposed v-shape slot is a verygood candidate for use in this notch-band UWB antenna.Furthermore, as will be shown in the next section, thedesired centre notch frequency ( f0) can be easily adjustedby sweeping one parameter, the radius r0.

2.2 Parametric study

A numerical parametric study is carried out to evaluate theperformance sensitivity to the design parameters and toobtain the optimum values. For brevity, we only evaluatethe effects of two important geometrical parameters, g2 andR1 on the return loss of the proposed antenna as shown inFigs. 4a and 4b, respectively.

The distance gap (g2) adjusts the capacitance couplingbetween the radiation element and ground plane, which playsan important role on the antenna impedance matching

behaviour. As shown in Fig. 4c, the current distribution onRegion-A where the feed line is connected to the radiationelement is high compared to other parts of radiating element

Figure 4 VSWR of the proposed antenna against

a g2b R1 parametersc Surface current distribution at 3.5, 6.5 and 9.5 GHz frequencies, when g2 1 mm and R1 4 mm

Figure 5 Band-notched design

a Normalised surface current distribution on the band-notchedantenna with r0 2.5 mmb Centre frequency of notch versus r0 parameter



www.ietdl.org



5/13

over the frequency range of interest. As a result, the geometricalparameters of this region (such as g2) play an important role onmatching performance. Fig. 4a indicates that the lower andupper frequencies of the bandwidth depend highly on theparameterg2. It is seen from Fig. 4b that the low edge of theVSWR ,2 bandwidth does not change considerably with

respect to R1, whereas the high-frequency performance issensitive to the variation of this parameter with an optimumvalue of 4 mm. As shown in Fig. 4c, it is observed that the

ground plane, Region-B, is close to the region of radiatingelement characterised by parameterR1 and has a large currentdistribution at high frequencies compared to the currentdistribution at lower frequencies. Therefore the couplingbetween Region-B and radiation element is significantlyaffected at high frequencies by changing the R1 parameter.

For the band-notched design, the normalised surface currentdistributions at three frequencies, 3.5, 5.7 and 8.5 GHz are

Figure 6 Normalised radiation pattern of the proposed antenna at three frequencies

a E-plane at 3.5 GHzb H-plane at 3.5 GHzc E-plane at 6.5 GHzd H-plane at 6.5 GHze E-plane at 9.5 GHzf H-plane at 9.5 GHz



www.ietdl.org



6/13

depicted in Fig. 5a. It can be seen that Slot-A resonates at thecentre frequency of the notch. The effect ofr0 variation on thecentre notch frequency is also shown in Fig. 5b.

3 Radiation pattern and

dispersion analysis3.1 Radiation pattern

The radiation patterns of the proposed antenna and band-notched design were measured in an anechoic chamberusing a standard double Ridge Horn. The normalisedradiation patterns in the E-plane (yz-) and H-plane (xz-)at three different frequencies are shown in Fig. 6. There isgood agreement between the simulation and measurementresults. The antenna shows nearly donut shape radiationpattern in the E-plane and almost omnidirectionalradiation pattern in the H-plane over the entire frequency

range of interest. It is also observed that the cross-polarisation is more than 10 dB lower than the co-polarisation in both E- and H-planes at most frequencies.

The relatively high cross-polarisation at a few cases can beexplained by observing the surface current distribution onthe radiation element (Fig. 4c). The cross-polarisation isproduced by the x-directed surface current. It is observedthat at frequencies where cross-polarisation exists, thecurrent distribution is large along the parts of the radiatingelement, which contain the x-directed current. Forexample, it is seen that the x-directed current distributionat 9.5 GHz is strong at the corners of radiating element,

which leads to a high cross-polarisation. The cross-polarisation can also be explained in terms of an array oftwo out of phase x-directed current dipoles at the topcorners of the radiating element. The notches at 08 and1808 in the cross-polarisation pattern shown in Fig. 6fcorrespond to the notches of the array factor, while thenotches at 908 and 2708 are due to the dipole element factor.

Fig. 7 shows the measured radiation pattern of the band-notched design, which is normalised with respect to the

reference antenna (antenna without Slot-A) for thefrequencies 3.5, 5.7, 6.5 and 8.5 GHz. For simplicity, onlythe co-polarisation patterns are reported. It can be seen

Figure 7 Measured normalised radiation pattern of the

band-notched design with respect to the reference antennaH-plane (2) and E-plane (O) of Ref. antenna, H-plane () andE-plane (o) of band-notched design

Figure 8 Transfer function measurement

a Tx/Rx setupb The transfer function of the proposed antennac The transfer function of the band-notched design



www.ietdl.org



7/13

that at the central notch frequency ( f0 5.7 GHz), theradiation pattern in both E- and H-planes deteriorates anddrops more than 10 dB lower than the radiation pattern ofthe reference antenna. The presence of the slot does not

change the radiation pattern significantly at the frequenciesout of the notched bandwidth.

3.2 Antenna transfer function

The dispersion characteristics of the antenna can be definedby the magnitude of the transfer function (jS21j) and groupdelay of the antenna Tx/Rx setup. Fig. 8a shows theconfiguration used for the transfer function measurement.

The transfer function S21 can be written as

S21 f HTx f HCH f HRX f (2)

where HTX ( f) and HRX ( f) are the Tx and Rx antennatransfer functions, respectively. Furthermore, HCH ( f) isthe channel transfer function in free space. As a result,ideally, when the antenna transfer function possesses almosta flat magnitude and linear phase (constant group delay)over the desired frequency range, the received pulse is notnoticeably distorted. In measurement setups, the antennasare located d 20 cm away in front of each other in ananechoic chamber. Using HP 8720 network analyser, the

Figure 9 Simulated and measured boresight gain of the

antenna

Figure 10 The single-band scheme

a Pulse signalb Normalised spectrum

Figure 11 The multiband schemea Normalised pulse signalb Normalised spectrum of each subband pulse () and total spectrum of the signal (o)



www.ietdl.org



8/13

transfer function of the antenna is measured as shown inFig. 8b. It is observed that the magnitude of the transferfunction has low ripples and almost constant group delayover the entire frequency range. As illustrated in Fig. 8c,the transfer function of the band-notched design showsthat the antenna is non-responsive at notch band

frequencies. About 40 dB reduction of S21 ( f) magnitudeand more than 5 ns variation of group delay is observed atthe centre frequency of the notch. Here, we only analysethe boresight transfer function of the antennas. Thedirectional transfer function study will be discussed in thenext section in more detail.

The IEEE standard antenna gain can be obtained bymeans of the antenna transfer function [17]

G f HTX f HRX f = 1 jS11 f j2 (3)

where S11 ( f) is the input reflection coefficient of theantenna. Using (2), (3) can be written as

G f S21 f HCH f 1 1 jS11 f j2 1 (4)

which gives the measured boresight gain of the proposedantenna as shown in Fig. 9. The measured results are alsocompared with the simulated gain obtained by AnsoftHFSS software. Good agreement is observed between thesimulated and measured results. It should be also notedthat compared to results reported in [3, 6, 7], the

boresight gain of the proposed antenna is positive in the4 9.5 GHz frequency range where the UWB pulsespectrum contains the main energy of signal. The peak

gain of the proposed antenna varies between 2.15 and4.25 dB.

3.3 Time-domain characteristics

Since the pulse source consideration and optimisation are very important for UWB systems [27], the time-domainperformance of the proposed antenna is carefullyinvestigated in this section. For wireless systems usingUWB antennas, it is critical to evaluate the dispersivebehaviour for different angles between Tx and Rx antennas.

This is due to the fact that the antenna couldbe low-dispersive at some limited angles, but high-dispersive at other angles. We consider two schemes knownas single-band and multiband schemes for numericalstudies [12].

In the single-band scheme, we assume the fourth derivative

of the Gaussian function as a pulse source with the followingexpression

st(t) Amax 3 6t

s

2 t

s

4 !e t=s

ffiffi2

p 2 (5)

whereAmax is the peak power spectral density that FCC allows. The parameters can be opted in order to satisfy the FCCspectral mask. With Amax 1.27 V/m and s 50 ps, thepulse signal and its normalised Fourier transform are shownin Fig. 10.

In order to investigate the multiband scheme, we choose apulse source, which is the sum of the modulated Gaussian

Figure 12 Virtual probes signals for single-band schemea xz-Planeb yz-Plane



www.ietdl.org



9/13

Figure 13 Virtual probes signals for multiband scheme

a xz-Planeb yz-Plane

Table 1 Fidelity factor for single-band and multiband schemes

Probe position (u) 08 308 458 608 908

single-band H-plane 0.97 0.962 0.92 0.855 0.812

E-plane 0.97 0.927 0.9 0.877 0.821

multiband H-plane 0.94 0.873 0.794 0.734 0.71E-plane 0.94 0.863 0.838 0.828 0.82



www.ietdl.org



10/13

pulses with different carriers [13] expressed as

st(t) XNn0

sin 2p fc nDfm

t nT0

e tnT0=s 2

(6)

By choosings 558 ps, we have T0 2.7 ns (%5s). Thisgenerates six modulated pulses with Dfm 1.25 GHz 10-dBbandwidth to cover the whole frequency range of interest(3.1 10.6 GHz). The carrier frequencies are opted to be( fc 3.5 1.25n) GHz where n 0, . . . , 5. Fig. 11 showsthe modulated pulse in multiband scheme and its relatednormalised spectrum. Using CST Microwave Studio software[28], we performed the transceiver setup, which consists of anantenna as transmitter and nine virtual probes (co-pol) asreceivers. The virtual probes are located in both xz- (H-) and

yz- (E-) planes atu 08, 308, 458, 608 and 908. Note thatthe probe located at u 08 is identical for the H- and

E-planes. The received probe signals for the single-band andmultiband schemes are shown in Figs. 12 and 13,respectively. In the single-band scheme, the received pulses inH- and E-planes show that the antenna does not imposesignificant distortion on the transmitted pulse. As shown inFigs. 13a and 13b, the received signals envelope complies

with the magnitude of the transfer functions between theantenna and each of the probes in the multiband scheme. Toevaluate the similarity between the transmitted and receivedsignals more precisely, we use the fidelity factor (F) which isdefined as [29]

F maxt

11 st(t) sr(t t)dtffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi11 st(t)

2dt 11 sr(t) 2dtq (7)

where st(t) and sr(t) are the transmitted and received pulses,respectively. The fidelity factor between virtual probe signalsand the transmitted pulse for both single-band and multibandschemes are reported in Table 1. A fairly satisfactory fidelityfactor is observed for both schemes. In the single-bandscheme, the antenna shows a fidelity factor greater than 0.8 inboth E- and H-planes. In the multiband scheme, the fidelityfactor is greater than 0.7 and 0.8 in H- and E-planes,

respectively. It should be noted that a pulse in the multibandscheme is more distorted compared to a pulse in the single-band scheme. Since the transfer function between the

antenna probes is directional, the received pulse shapedepends on the location of the probes (u).

4 Parametric model of theproposed antenna

In this section, the matrix-pencil method [20] is used tocalculate the pole/residue model of the Tx/Rx system usingthe proposed antenna. The parametric model of the antennasystem transfer function is expressed as

HSYS f S21 f

HCH f

(8)

It is noted that the transfer function of the antenna ( S21)depends on the signal propagation direction and thedistance between the transmitter and receiver. As a result,

the antenna system transfer function (HSYS) should bedetermined for several Tx/Rx setups with differentorientations. Different Rx orientations are displayed inFig. 14. By measuring the S21( f) parameter for differentdirections, the directional HSYS( f) can be achieved from(8). The impulse response of the antenna system transferfunction can then be calculated as

hsys t =1 HSYS f XN

n1Rn e

snt (9)

Figure 14 Tx/Rx system for different orientations

Figure 15 Impulse response of the proposed antenna

systema At u 08b Pole/Residue schematic



www.ietdl.org



11/13

where =1 is the inverse Fourier transform,sn (a

nj2pf

n) are the poles, R

nare residues, which are

obtained by using matrix-pencil method. N is the order ofthe model. Here a

nand f

nare damping coefficients and

frequencies, respectively. The frequency domain model canthen be obtained as

HSYS v XNn1

Rnjv sn

(10)

By performing the Tx/Rx system (Fig. 14) at threeorientations (u 08, 458, 908), the directional S21( f) ofthe proposed antenna is measured. The distance between

Tx and Rx is d 20 cm for each u. Using (8), HSYS( f)of the proposed antenna is then obtained at differentorientations. Consequently, the impulse response ofsystem transfer function is achieved by taking the inverse

Fourier transform. The pole/residue model of theantenna system is then calculated using the matrix-pencilmethod.

Fig. 15ashows the impulse response of the antenna systemwhen u 08. The measured result is obtained from themeasured S21( f) shown in Fig. 8b. It is found thatN 22provides an accurate pole/residue model. The poles andresidues are reported in Table 2 and are shownschematically in Fig. 15b. The number of samples used inthe matrix-pencil method is K 100. Following [30], thepencil parameter L K/2 is chosen so that K/

3,

L,

2K/3. More details on the matrix-pencil methodare given in [20, 30, 31].

The measured transfer function of Tx/Rx system for twoother orientations (u 458, 908) is shown in Fig. 16a. Sincethe poles obtained for one optional orientation (here u 08)can be used in model calculation for other orientations with a little accuracy degradation, the antenna system model for

458 and 908 orientations is calculated using the poles ofthe model for u 08 as demonstrated in Fig. 16b. Theresidues for these orientations are obtained from themeasured S21. For brevity, the related residues foru 458and 908 are not reported. It can be seen that the measuredresult is in very good agreement with the obtained model.

As a result, the antenna system can be efficientlycharacterised for other orientations using the directionalpole/residue model.

5 Conclusion

In this paper, a miniaturised CPW-fed antenna is presented forUWB applications. Besides the acceptable impedancebandwidth, the antenna shows a stable radiation pattern overthe entire frequency range of interest. Extended from theproposed antenna, a band-notched design is introduced toreject the WLAN frequency band (5.155.825 GHz). It is

shown that by cutting av-shape slot on the antenna surface,more than 10 dB gain reduction can be achieved in both E-and H-planes at the notch-band frequencies. The sensitivity

Table 2 Poles and residues (N 22)

Pole (109) Residue (109)20.617+ 16.969j 0.0372+ 0.0709j

21.563+ 21.331j 0.5076+ 0.0753j

22.166+ 25.881j 0.1878+ 1.2849j

22.849+ 31.184j 21.8813+ 0.3344j

24.202+ 38.260j 22.4963+ 1.7690j

23.831+ 42.207j 3.4848+ 2.4418j

21.071+ 70.605j 0.2373+ 0.0673j

22.047+ 67.308j 20.1366+ 0.5522j

22.628+ 60.943j 21.1025+ 0.0575j

24.201+ 49.485j 3.7285+ 0.8484j

23.488+ 52.941j 22.1644+ 2.8005j

Figure 16 Directional impulse response of the proposed

antenna system

a Transfer function of Tx/Rx setup (S21( f)) for u 458 and 908casesb hsys(t) for u 458 and 908 cases



www.ietdl.org



12/13

analysis is performed to evaluate the effect of some designparameters variations on the antenna performance. Theproposed antenna and band-notched design performance isalso investigated experimentally. A good agreement isobserved between the simulation and the measurementresults. The frequency domain dispersion analysis is studied

by means of the antenna transfer function. The antennashows a low-dispersive behaviour with almost constant groupdelay over the desired frequency range. In order to evaluatethe time-domain performance of the antenna, both thesingle-band and multiband schemes are considered. Theresults show that the transmitted pulse distortion is notsignificant for both schemes. Considering that the proposedantenna shows an acceptable performance over the UWBfrequency band, the Tx/Rx antenna system is characterised byan efficient parametric model. The parametric model isprovided by a number of poles and residues after applying thematrix-pencil method. It is shown that the antenna system

can be modelled by a set of 22 poles in all directions.

The proposed antenna characteristics such as small size,light weight, low-manufacturing cost, sufficient bandwidth,stable radiation pattern, and low-dispersive behaviour showsthat the proposed antenna is a very good candidate forUWB applications.

6 References

[1] FCC: FCC first report and order on ultra-wideband

technology, 2002

[2] CHAIR R., KISHK A.A., LEE K.F.: Ultrawide-band coplanar

waveguide-fed rectangular slot antenna, IEEE Antennas

Wirel. Propag. Lett., 2004, 3, pp. 227229

[3] MA T.-G., TSENG C.-H.: An ultrawideband coplanar

waveguide-fed tapered ring slot antenna, IEEE Trans.

Antennas Propag., 2006, 45, pp. 11051110

[4] LI P., LIANG J., CHEN X.: Study of printed elliptical/circularslot antennas for ultrawideband applications, IEEE Trans.


[5] MA T.-G., JENG S.K.: Planar miniature tapered-slot-fed

annular slot antennas for ultra-wideband radios, IEEE

Trans. Antennas Propag., 2005, 53, pp. 11941202

[6] BAHADORI K., RAHMAT-SAMII Y.: A miniaturized elliptic-card

UWB antenna with WLAN band rejection for wireless

communications, IEEE Trans. Antennas Propag., 2007, 55,

pp. 33263332

[7] CHO Y.J., KIM K.H., CHOI D.H., LEE S.S., PARK S.-O.: A miniature

UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics, IEEE

Trans. Antennas Propag., 2006, 54, pp. 14531460

[8] CHEN Z.N., SEE T.S.P., QING X.: Small printed ultrawideband

antenna with reduced ground plane effect, IEEE Trans.


[9] LIN Y.-C., HUNG K.-J.: Compact ultrawideband rectangular

aperture antenna and band-notched designs, IEEE Trans.


[10] CHEN S.-Y., WANG P.-H., HSU P.: Uniplanar log-periodic slot

antenna fed by a CPW for UWB applications, IEEE Trans.


[11] ZHANG Y., CHEN Z.N., CHIA M.Y.W.: Effects of finite ground

plane and dielectric substrate on planar dipoles for UWB

applications. Proc. IEEE Int. Symp. Antennas Propagation,

June 2004, pp. 25122515

[12] AIELLO G.R., ROGERSON G.D.: Ultra-wideband wireless

systems, IEEE Microw., 2003, 4, pp. 3647

[13] CHEN Z.N.: Novel bi-arm rolled monopole for UWB

applications, IEEE Trans. Antennas Propag., 2005, 53,

pp. 672677

[14] WU X.H., CHEN Z.N.: Comparison of planar dipoles in UWB

applications, IEEE Trans. Antennas Propag., 2005, 53,

pp. 19731983

[15] LICUL S., DAVIS W.A.: Unified frequency and time-domain

antenna modeling and characterization, IEEE Trans.


[16] DUROC Y., VUONG T.-P., TEDJINI S.: A time/frequency modelof ultrawideband antennas, IEEE Trans. Antennas Propag.,

2007, 55, pp. 23422350

[17] DUROC Y., GHIOTTO A., VUONG T.P., TEDJINI S.: UWB antennas:

systems with transfer function and impulse response,

IEEE Trans. Antennas Propag., 2007, 55, pp. 14491451

[18] DUROC Y., GHIOTTO A., VUONG T.P., TEDJINI S.: Parametric

modeling of ultrawideband antennas, IEEE Trans.


[19] HFSS, High Frequency Structure Simulator, Ansoft

Corp., Pittsburgh, PA, 2008

[20] SARKAR T.K., PEREIRA O.: Using the Matrix Pencil method

to estimate the parameters of a sum of complex

exponentials, IEEE Antennas Propag. Mag., 1995, 37,

pp. 4855

[21] SCHANTZ H.G., WOLENEC G., MYSZKA E.M.: Frequency notched

UWB antennas. Proc. IEEE Ultra Wideband Systems and

Technologies, 2003, pp. 214218

[22] SUH S.-Y., STUTZMAN W.L., DAVIS W.A., WALTHO A.E., SKEBA K.W.,

SCHIFFER J.L.: A UWB antenna with a stop-band notch in the



www.ietdl.org



13/13

5-GHz WLAN band. Proc. IEEE/ACES WirelessComm unications and Applied Computational

Electromagnetics, 2005, pp. 203207

[23] YUAN T., QIU C.-W., LI L.-W., LEONG M.S., ZHANG Q.: Elliptically

shaped ultrawideband patch antenna with band-notch

features, Microw. Opt. Technol. Lett., 2 00 8, 50,pp. 736738

[24] LEE W.-S., KIM D.-Z., KIM K.-J., YU J.-W.: Wideband planar

monopole antennas with dual band-notched characteristics,

IEEE Trans. Microw. Theory Tech., 2006, 54, pp. 28002806

[25] KIM J., CHO C.S., LEE J.W.: 5.2 GHz notched ultra-wideband

antenna using slot-type SRR, Electron. Lett., 2006, 42,

pp. 315316

[26] LUI W.-J., CHENG C.-H., ZHU H.-B.: Improved frequency

notched ultrawideband slot antenna using square ringresonator, IEEE Trans. Antennas Propag., 2007, 55,

pp. 24452450

[27] CHEN Z.N., W U X .H., L I H.F., YA NG N ., CHIA M.Y.W.:

Considerations for source pulses and antennas in UWB

radio systems, IEEE Trans. Antennas Propag., 2004, 52,

pp. 17391748

[28] CST Microwave Studio. Computer Simulation

Technology, Framingham, MA, 2008

[29] MONTOYA T.P., SMITH G.S.: A study of pulse radiation from

several broad-band loaded monopole, IEEE Trans.


[30] HUA Y., SARKAR T.K.: Matrix pencil method for estimating

parameters of exponentially damped/undamped sinusoidsin noise, IEEE Trans. Acoust. Speech Signal Process., 1990,

38, pp. 814824

[31] HUA Y., SARKAR T.K.: Generalized pencil-of-function

method for extracting poles of an EM system from itstransient response, IEEE Trans. Antennas Propag., 1989,

37, pp. 229234



www.ietdl.org

Band Rejection

Documents

Transcript of Band Rejection