1074 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 59, NO. 4, APRIL 2011

UWB Band-Notched Monopole Antenna DesignUsing Electromagnetic-Bandgap Structures

Lin Peng and Cheng-Li Ruan

AbstractA new approach is proposed to reject certain bandswithin the passband of an ultra-wideband planar monopoleantenna. The proposed approach that utilizes a mushroom-typeelectromagnetic-bandgap (EBG) structure is proven to be aneffective way for band-notched designs. The approach has manyadvantages, such as notch-frequency tunability, notch-band widthcontrollable capacity, efficient dual-notch design, and stableradiation patterns. Several design examples using conventionalmushroom-type EBG and edge-located vias mushroom-type EBGare presented. The examples exhibit good bandstop characteristicsto reject the wireless local-area network interference bands (5.2-and 5.8-GHz bands). Besides, the causes that lead to the discrep-ancies between the simulations and measurements are discussed.

Index TermsBand-notched, electromagnetic-bandgap (EBG)structures, notch frequency, ultra-wideband (UWB) antennas.

I. INTRODUCTION

S INCE THE Federal Communications Commission (FCC)released the bandwidth 3.110.6 GHz, ultra-wideband(UWB) technology has become the most promising candidatefor short-range high-speed indoor data communications. Asa key component of UWB communication systems, UWBantenna has received increasing attentions [1][6]. Planarmonopole antennas have been found as good candidates forUWB applications owing to their attractive merits, such aslarge impedance bandwidth, ease of fabrication, and acceptableradiation properties [4][7].

Due to the existence of other wireless narrowband standardsthat already occupy frequencies in the UWB band, such as wire-less local-area network (WLAN) (5.2-GHz (51505350 MHz)and 5.8-GHz (57255825 MHz) bands), an additional require-ment for UWB antennas is to reject certain frequencies withinthe ultra-wide passband [8][22]. Electromagnetic (EM) inter-ferences between the nearby communication systems can thenbe alleviated. Various methods have been proposed for band-notched designs. The conventional methods are cutting slots onthe patch/ground plane [8][12] and putting parasitic elementsclose to the radiator [13][16]. Besides, an embedding resonant

Manuscript received June 09, 2010; revised December 29, 2010; acceptedJanuary 08, 2011. Date of publication March 10, 2011; date of current versionApril 08, 2011. This work was supported by the Fundamental Research Fundsfor the Central Universities under Grant E022050205.

The authors are with the Institute of Applied Physics, University of Elec-tronic Science and Technology of China, Chengdu 610054, China (e-mail:penglin528@hotmail.com).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TMTT.2011.2114090

cell in the microstrip fed line [17], using a fractal tuning stub[18], utilizing a small resonant patch [19], and an embeddingquarter-wavelength tuning stub in a circular ring monopole [20]are also proposed.

Usually, one slot/parasitic element is adequate to generate anotch-band [8], [9], [11], [13], [15]. In some cases, multi-iden-tical elements placed symmetrically are also used for single-notch designs [12], [14]. However, these single-notch antennashave shortcomings. Some designs only reject one WLAN band(such as the 5.8-GHz band) [8], [12]. The others occupy toomuch of a wide notch-band width with notch frequency around5.5 GHz, and then the useful frequencies, especially those be-tween 5.25.8-GHz WLAN bands (5.355.725), are wasted [9],[11], [13][15], [21].

The limitation of single-notch UWB antennas is the mo-tivation to design dual/multinotches UWB antennas. Formultinotches design, multielements are commonly needed.In [10], dual-notch properties are achieved by etching twonested C-shaped slots in the patch. However, strong couplingbetween the two adjacent C-shaped slots makes it difficult totune the two stopbands. In [14] and [22], multielements areused to generate multinotches. However, some rejected bandsof these designs are not desirable notches in UWB operatingband. In [16], the two parasitic strips placed on the fork-shapedmonopole are designed to notch the 5.2- and 5.8-GHz WLANbands, respectively. The lower 5.2-GHz and upper 5.8-GHzbands are then rejected with most of the useful frequenciesbetween them radiated. Although the design in [16] providesus notch-band width controlling (single-notch design), theadjustment of the notch-band width for dual-notch design isnot easy compared with the single-notch design. It is due to thespace restriction and the coupling between the two strips.

Based on the background of the above researches and thegeneralization of [16], the two main problems of frequency-re-jected function design are: 1) the obstacles in achieving efficientdual-notch design (due to strong couplings between notch de-signs) and 2) notch-band width controlling. To overcome theseproblems, the mushroom-type electromagnetic-bandgap (EBG)structures, which have become very popular in the microwaveand antenna community [23][30], are introduced in this paperfor band-notched design.

The approach makes better use of the bandgap property ofEBG by placing the structure close to the microstrip fed lineof an UWB antenna. The EBG structure operates as a band-stop filter. One EBG cell is enough to obtain a notch-band,while two EBG structures (with different size) can generate dualnotch-bands. Furthermore, the mentioned two main problemsof frequency-rejected function design are conquered. The first

0018-9480/$26.00 2011 IEEE

PENG AND RUAN: UWB BAND-NOTCHED MONOPOLE ANTENNA DESIGN 1075

problem is overcame as the two EBG structures that are des-ignated to different notches are placed in different sides of themicrostrip fed line, thereby the coupling between the two EBGstructures is weak. We can then tune one notch frequency withlittle effect on the other. The second problem is solved by ad-justing the coupling gap or the parameter . Moreover, re-search shows that the usages of EBG structures have little ef-fect on the radiation patterns. In this paper, both the conven-tional mushroom-type electromagnetic bandgap (CMT-EBG)and edge-located vias mushroom-type electromagnetic bandgap(ELV-EBG) [30] for band-notched design are studied. The re-search shows that the ELV-EBG has superiority of compact-ness and better frequency-rejected function than the CMT-EBG.Therefore, when further design is desired, the ELV-EBG is pre-ferred. Several design examples with single/dual notch-bandswere investigated, constructed, and measured. The causes thatresult in the discrepancies between simulations and measure-ments are discussed and found to be the error of the substrateparameters.

This paper is organized as follows. In Section II, we givea brief description on the proposed approach based on a mi-crostrip line. Section III presents the single-notch UWB an-tenna design by both CMT-EBG and ELV-EBG. Further in-vestigations of the proposed design approach were presented inSection III-C. Dual-notch UWB antenna design with ELV-EBGis reported in Section IV. The error analysis is presented inSection V.

II. PROPOSED APPROACH

The mushroom-type EBG structure formed by a via-loadedmetal patch can be characterized by an resonator [23] withresonant frequency . When a single cell is uti-lized, a narrow notch at can then be engendered.

A microstrip line based approach [as shown in Fig. 1(a)]is utilized to investigate EBG resonant-frequency character-istics, as this is the very approach applied to design UWBband-notched antennas. Only one cell is adequate for simula-tion. As shown in the figure, the EBG patch is coplanar withthe microstrip line with a gap . A lossless substrate withheight mm and relative permittivity is usedfor simulations. The width of the microstrip line is assumed tobe mm (50 ). The EBG patch width is . Theradius of via is mm. The equivalent-circuit model ofthe structure is derived as shown in Fig. 1(b). The capacitance

denotes the coupling between the EBG and microstrip line.The capacitance is due to the voltage gradients between thepatch and ground plane, while the inductance is generatedby the current flowing through the shorting pin. Therefore, theresonant frequency is and the notchwidth increase with the increasing of .

Now, we can sweep the EBG parameters for further inves-tigation. Note that, when one parameter is changed, the othersare fixed. Fig. 2(a) exhibits the effect of the EBG patch width

on the notch frequency. It is clearly seen from the figure thatthe patch width offers sufficient freedom in selecting notchfrequency. When increase from 4.8 to 8.8 mm, the resonantfrequency decreased from 6.71 to 3.57 GHz. Fig. 2(b) presents

Fig. 1. Microstrip-line-based model. (a) Configuration schematic view.(b) Equivalent-circuit model.

Fig. 2. (a) Bandgap for the mushroom-type EBG in terms of . (b) Effect ofthe coupling gap on the width of the bandgap.

the effect of the coupling gap on the width of the bandgap.It is indicated from the figure that the gap has a great impacton the width of the bandgap. As the gap increase from 0.2 to1.4 mm, dramatic reduction in width of the bandgap is observed.Besides, reflection value at resonant frequency decreased with

increasing.

III. UWB ANTENNA DESIGN WITH SINGLE NOTCH

A. UWB Elliptical Monopole AntennaIn this paper, an elliptical monopole antenna (see Fig. 3(a),

denoted as antenna 1) is used for band-notched antenna design.Note that a lossless substrate with relative permittivity

and thickness mm is utilized for simulations. Asshown in Fig. 3(a), and denote the length and width ofthe substrate, respectively. An elliptical radiator with radius of

and is fed by a 50- microstrip line ( mm). Onthe other side of the substrate, the ground plane with a length of

only covers the section of the microstrip fed line. is thewidth of the gap between the elliptical patch and ground plane.

The parameters of antenna 1 are mm, mm,mm, mm, mm, mm,

mm, and mm. The simulated voltage standing-waveratio (VSWR) of the antenna is shown in Fig. 3(b). It is foundthat good impedance matching of the antenna is obtained as thebandwidth covers the entire UWB band (3.110.6 GHz) andgoes beyond the required 10.6 GHz with VSWR .

1076 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 59, NO. 4, APRIL 2011

Fig. 3. UWB elliptical monopole antenna (antenna 1). (a) Configuration and(b) simulated VSWR.

Fig. 4. Single-notch UWB antennas. (a) Utilizing CMT-EBG (antenna 2).(b) Utilizing ELV-EBG (antenna 3).

B. Single-Notch UWB Antenna Design

When there exists only one interference band in the UWBoperating band, UWB antennas with a single notch are desired.Single-notch UWB antennas design utilizing CMT-EBG andELV-EBG are demonstrated in Fig. 4. The antennas are denotedas antenna 2 and antenna 3, respectively. Note that, when theEBG structure was applied to the antennas, there is no returningwork required for the previously determined dimensions. Asshown in the figure, the EBG cell is placed close to the mi-crostrip fed line with a gap . The patch width of the EBG is

. The distance between the upper edge of the ground planeand the EBG is . The radii of the via is . The parameters forantenna 2 and antenna 3 are as follows.

Antenna 2: mm, mm, mm, andmm.

Antenna 3: mm, mm, mm, andmm.

Fig. 5 presents the simulated VSWRs of antenna 2 and an-tenna 3. As shown in the figure, the notch frequencies of antenna2 and antenna 3 happen at 5.80 GHz (5.155.96 GHz, VSWR

) and 5.78 GHz (5.275.94 GHz, VSWR ), respectively.Compared to antenna 2, antenna 3 has a higher VSWR value atthe notch frequency and exhibits a better sharp skirt. Thus, ingeneral, the ELV-EBG has priority over the CMT-EBG when itis applied to the design of a UWB band-notched antenna. Be-sides, the additional EBG structure has little effect on the pass-band. The proposed approach then presents good reason to rejectcertain frequencies.

Fig. 5. Comparison of the VSWRs (simulated) between antenna 2 andantenna 3.

C. Investigation and DiscussionThe operational mechanisms of antenna 2 and antenna 3 are

identical. Therefore, one antenna has similar performances asthe other. The design approach was studied in this section byinvestigating the antennas.

The simulated current distributions of antenna 2 are shownin Fig. 6 for further investigation. It is seen from the figure thatthe EBG current distributions are weak at the frequencies of 3.5,7.5, and 10 GHz. However, the current distributions are approx-imately symmetrical distributed on the ground plane and the ra-diator at these frequencies. These phenomenon mean the exis-tence of the EBG have little effect on the UWB antenna at thesefrequencies. However, as shown in Fig. 6(b), the current distri-bution of 5.8 GHz is concentrated on the EBG. In this case, theinput impedance is singular, making large reflection at the de-sired notch frequency.

Fig. 7 presents the comparison of the radiation patterns be-tween antenna 1 and 2 at 3.5, 7.5, and 10 GHz. The antennasare printed in the -plane, and they are -polarized becausethe monopoles are in the -direction. Therefore, the -plane forthese antennas is the -plane and the -plane is the -plane.The radiation patterns of antenna 2 are identical with their coun-terparts of antenna 1. Thus, the introduction of EBG has littleeffect on the radiation patterns. It is shown in Fig. 7 that the an-tennas have good omnidirectional radiation patterns at 3.5 GHz.The radiation patterns at 7.5 and 10 GHz present some distor-tions. However, generally speaking, the radiation patterns in the

-plane are roughly a dumbbell shape, and the patterns in the-plane are quite omnidirectional, as expected. In keeping with

the main focus of band-notched design, the radiation patternsfor subsequent antennas are not depicted in this paper for sim-plicity.

Notice that the rejection band of the UWB antenna may causewaveform distortion for signal transmission and reception. Inthis regard, radiation patterns of rejected frequency are helpfulfor waveform correction through sophisticated approach (e.g.,waveform equalizer). Fig. 8 shows the 3-D radiation patterns ofantenna 1, antenna 2, and antenna 3 at corresponding notch fre-quencies. The used coordinate is indicated in Fig. 3. It is shownin the figure that the pattern of antenna 1 is omnidirectionalwhile some distortion has happened to antenna 2. The pattern of

PENG AND RUAN: UWB BAND-NOTCHED MONOPOLE ANTENNA DESIGN 1077

Fig. 6. Current distributions of antenna 2 at different frequencies. (a) 3.5 GHz.(b) 5.8 GHz. (c) 7.5 GHz. (d) 10 GHz.

antenna 3 presents some kind of directional. This is because ra-diation of antenna 3 at notch frequency is mainly from the EBGstructure, while some radiation from the elliptical patch happensto antenna 2 due to its smaller VSWR value at notch frequency.We must point out that our design approach has the advantage ofadjusting notch-band width, and then minimal waveform distor-tion can be acquired by carefully tuning the notch-band width.The transfer coefficient of antenna 3 and antenna gains ofantenna 1, antenna 2, and antenna 3 are exhibited in Fig. 9,which present a sharp decrease in the notch-band and good per-formances at the other frequencies, as expected. Note that thetransfer coefficient of antenna 3 is acquired by orientating twoidentical antennas face-to-face with a distance of 120 mm.

Fig. 7. Comparison of the radiation patterns (simulated) between antenna 1 andantenna 2. (a) 3.5 GHz. (b) 7.5 GHz. (c) 10 GHz.

Fig. 8. 3-D patterns. (a) Antenna 1 at 5.79 GHz. (b) Antenna 2 at 5.80-GHznotch frequency. (c) Antenna 3 at 5.78-GHz notch frequency.

Fig. 9. Antenna gains and transfer coefficient .

As indicated in Fig. 2(a), the EBG patch width is di-rectly relate to the notch frequency, therefore, only the param-eters and that are used to adjust the width of the notch-band are discussed for simplicity. Fig. 10(a) demonstrates the

1078 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 59, NO. 4, APRIL 2011

Fig. 10. Effect of the parameters of antenna 2 on the width of the notch-band.(a) and (b) .

Fig. 11. Photographs. (a) Antenna 2. (b) Antenna 3.

effect of the coupling gap on the width of the notch-band.The results shown in Fig. 10(a) agree well with the predic-tion of Fig. 2(b). The width of the notch-band reduced with

increasing. Meanwhile, the increasing of also results in asmaller VSWR value. The gap is then a valuable parameterfor notch-band width tuning. The effect of the parameteron the width of the notch-band is exhibited in Fig. 10(b). It isseen from the figure that has a significant impact on width ofthe notch-band. The notch-bands VSWR are 5.155.96,5.275.85, and 5.355.83 GHz for mm, mm, and

mm, respectively. A frequency shift of 70 MHz is observedwith changing from 0 to 2 mm.

D. Fabrication and MeasurementAntenna 2 and antenna 3 were fabricated as shown in Fig. 11.

The antennas were fabricated on an mm height FR4substrate with believed relative permittivity . Unfor-tunately, as revealed in Section V, the FR4 substrate parametersare unstable. A SMA connector is soldered at the end of themicrostrip fed line. The measurements were conducted with anAgilent E5071C ENA series network analyzer with the highestmeasurable frequency at 8.5 GHz. Though it does not cover thewhole UWB band (3.110.6 GHz), it reaches our requirementsas concerns our notch-bands located in the measurable band.

The measured and simulated results of the antennas are ex-hibited in Fig. 12. As shown in the figure, the notch-band isobtained for all the antennas by both simulation and measure-ment. The simulated stopband of antenna 2 ranges from 5.15 to5.96 GHz VSWR with notch frequency at 5.80 GHz, asexhibited in Fig. 12(a). The measured stopband range is from5.36 to 6.38 GHz VSWR with a notch frequency at6.17 GHz. A deviation of 370 MHz (6.4% at 5.8 GHz) betweenthe simulated and measured notch frequencies is observed. Asshown in Fig. 12(b), the simulated and measured notch frequen-cies of antenna 3 are 5.78 GHz (5.275.94 GHz, VSWR )

Fig. 12. Simulated and measured results. (a) Antenna 2. (b) Antenna 3.

and 6.13 GHz (5.62 to 6.31 GHz, VSWR ), respectively. De-viation of the notch frequencies is 350 MHz (6% at 5.8 GHz).

As shown in Fig. 12, discrepancies between the simulationsand measurements occur. However, the measured results stillconfirm our design approach with certain frequency rejection.The causes that lead to these discrepancies were discussed inSection V.

IV. UWB DUAL-NOTCH ANTENNA DESIGN BY ELV-EBGWe have learnt from Section III that, though CMT-EBG is

an outstanding candidate for band-notched design, ELV-EBGis preferable in terms of better frequency-rejected function andcompactness. In this section, ELV-EBG for dual-notch designis investigated.

A. ELV-EBG for Dual-Notch UWB Antenna DesignAs mentioned in Section I, most of the single-notch antenna

has a wide notch-band width that covers the whole 56-GHzband with notch frequency around 5.5 GHz. The useful fre-quencies between the 5.2- and 5.8-GHz WLAN bands are thenwasted. This provides motivation to design a dual-notch antennato reject the 5.2- and 5.8-GHz interference bands.

The design methodology is simple by utilizing two ELV-EBGstructures at different sides of the microstrip line with differentsize to reject the 5.2- and 5.8-GHz interference bands, respec-tively. The configuration of the antenna is demonstrated inFig. 13(a) (denoted as antenna 4). The antenna parameters areas follows.

Antenna 4: mm, mm, mm,mm, and mm.

Three parameters ( and ) of antenna 4 were studiedas shown in Fig. 13(b)(d). The researches show that the twomain problems for frequency-rejected function design, whichare are: 1) the obstacles in achieving efficient dual-notch designand 2) notch-band width controlling, are solved.

Simulated VSWR curves of antenna 4 for different valuesof are illustrated in Fig. 13(b). It is seen from the figurethat the changing of the patch width has a great impacton the lower notch frequency with little effect on the upperone. The lower notch frequency for mm, mm,

mm, and mm are 5.55, 5.31, 5.02, and 4.77 GHz, re-spectively, while the upper notch frequencies for variousvalues are approximately maintained at 5.78 GHz. In Fig. 13(c),VSWR curves of antenna 4 for different values of are demon-strated. As shown in the figure, the upper notch frequency can

PENG AND RUAN: UWB BAND-NOTCHED MONOPOLE ANTENNA DESIGN 1079

Fig. 13. Dual-notch UWB antenna with ELV-EBG (antenna 4). (a) Configura-tion. (b) Lower notch frequency in terms of . (c) Higher notch frequency interms of . (d) Notch-band width in terms of .

be tuned by adjusting the patch width , while the lower onestands at 5.31 GHz. The upper notch frequencies for

mm, mm, mm, and mm are 6.32, 6.04, 5.78,and 5.55 GHz, respectively. The high-efficiency tuning of thetwo notches are due to the weak coupling between the two EBGstructures. Thus, the aforementioned first main problem is con-quered.

The second main problem for band-notched design canbe overcome by adjusting the coupling gap . As shown inFig. 13(d), the increasing of gap results in smaller notch-bandwidth, as expected. Note that the coupling gap is identical forthe two EBG structures in this case. Moreover, the width of thenotch-bands can also be tuned by adjusting the parameter .For simplicity, these results are not presented in this paper.

B. Fabrication and Measurement

Antenna 4 was constructed as shown in Fig. 14(a) withmm FR4 substrate. Fig. 14(b) demonstrates the

measured and simulated results of antenna 4. Two adjacentmeasured notch-bands are observed. The measured notchfrequencies are 5.59 GHz (5.205.72 GHz, VSWR )and 6.11 GHz (5.996.23 GHz, VSWR ). The simulatedresonant frequencies are 5.31 (4.985.43 GHz, VSWR )and 5.80 GHz (5.645.93 GHz, VSWR ). Deviations ofthe lower and upper notch frequencies between simulationand measurement are then 280 MHz (5.3% at 5.3 GHz) and310 MHz (5.3% at 5.8 GHz), respectively.

V. ERROR ANALYSIS

As illustrated in Figs. 12 and 14, discrepancies between sim-ulations and measurements were observed. The deviations aregeneralized in Table I. As demonstrated in the table, notch-fre-quency deviations for 5.2- and 5.8-GHz WLAN bands range

Fig. 14. Antenna 4. (a) Photograph. (b) Results.

TABLE IDEVIATIONS BETWEEN THE SIMULATED AND MEASURED NOTCH FREQUENCIES

from 280 to 370 MHz with deviation percentage from 5.3% to6.4%. Notice that the discrepancies between the simulated andmeasured notch frequencies have common points: all the mea-sured notch frequencies are higher than the corresponding sim-ulated ones with similar deviations, and the measured VSWRvalues at the notch-bands are smaller than that from simulations.The causes that lead to these discrepancies are probably due to:1) the joining of the SMA connector (solder roughness); 2) theindoor measurement environment; 3) the error of fabrication;4) the error of simulation; and 5) the error of substrate parame-ters.

The first two reasons may have some impact on the measuredresults. However, they cannot remove the notch frequencies. De-pending on the printed circuit board (PCB) technique, fabrica-tion error can also be neglected.

A possible cause is the errors of simulations. However, ap-propriate simulation setup produces accurate results. The sim-ulated results of antenna 3 by HFSS [31] and CST MWS [32]are illustrated in Fig. 15. As shown in the figure, the simulatedresults agree well with each other. The simulated notch frequen-cies with HFSS and CST MWS are 5.78 GHz (5.275.94 GHz,VSWR ) and 5.79 GHz (5.205.98 GHz, VSWR ), re-spectively. Deviation is then just 10 MHz (0.17% at 5.8 GHz).Thus, we can conclude that the simulation setups are proper topredict the performances of the antennas.

Thus, the most probable cause that leads to the discrepanciesis the error of substrate parameters. To validate this conclusion,we discussed the effects of substrate parameters on the antennaperformances.

In the previous simulations, we have assumed the used sub-strate is lossless for simplicity. Now we will first investigatethe effects of the loss tangent on antenna performances to

1080 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 59, NO. 4, APRIL 2011

Fig. 15. Comparison of the simulated results (antenna 3) utilized HFSS andCST MWS.

Fig. 16. (a) Simulated results with and without loss. (b) Results: without loss, and , and measurement (FR4 substrate).

evaluate its impact on the discrepancies. The simulated resultswith and without loss are presented in Fig. 16(a). As shown inthe figure, the notch frequency of the antenna without loss is5.78 GHz (5.275.94 GHz, VSWR ), while the one with

is 5.75 GHz (5.355.90 GHz, VSWR ).The notch-frequency deviation (30 MHz, 0.52% at 5.8 GHz)was then ignorable. Moreover, the VSWR value at notch fre-quency is greatly reduced while loss was imported. This is dueto strong resonance of the EBG structure that happened at thenotch frequency [as indicated in Fig. 6(b)]. These may do a favorto a UWB system by transforming the unwanted frequenciesinto a quantity of heat (loss) without reflecting them back to thesystem. In the passband, VSWR values have little effect thanksto the UWB antenna not being a strong resonant structure.

We have learned from Fig. 16(a) that the loss tangentis not responsible for notch-frequency deviations, while it re-sults in smaller VSWR values at notch frequency. It is thenmost probable that the error of and of the substrate to-gether make for the discrepancies. Fig. 16(b) exhibits the an-tenna results: without loss, with

, and measurement (FR4 substrate). We generalize the re-sults in Table II. The notch frequencies for the caseswithout loss, with ), and measure-ment are 5.78 GHz (5.275.94 GHz, VSWR ), 6.15 GHz(5.696.33 GHz, VSWR ) and 6.13 GHz (5.626.31 GHz,VSWR ), respectively. Besides, the VSWR values at notchfrequencies for the three cases are 26, 4.16, and 4.32, respec-tively. Thus, the results of the case with and

is coincide with the measurement.Thus, we can conclude from the above discussion that the

cause of the discrepancies is apparently the error of the unstableFR4 parameters. The parameters of the used FR4 substrate is

TABLE IICOMPARISON OF THE RESULTS SHOWN IN FIG. 16(b)

(or approximately) and . Therefore, thediscussions in this section verify the validity and effectivenessof the proposed approach for band-notched design.

VI. CONCLUSIONA new approach for UWB band-notched antennas design has

been proposed. The design methodology is simple by placingan EBG structure couple to the microstrip line. It is convenientfor single/dual-notch design. Furthermore, the two main prob-lems that are indicated in [16] for frequency-rejected functiondesigning were overcame. Notch frequencies can be tuned byadjusting the corresponding patch width with little effect on theother in a dual-notch case, even though the notch frequenciesare close to each other. The width of the notch-bands can becontrolled by adjusting the coupling gap or the parameter .Moreover, the in existence of the EBG has little effect on theradiation patterns. Thus, the design approach is very efficient.

ACKNOWLEDGMENTThe authors would like to thank the reviewers for their com-

ments and suggestions, which greatly help increase the qualityand applicability of this paper.

REFERENCES[1] Y. J. Ren and K. Chang, Ultra-wideband planar elliptical ring an-

tenna, Electron. Lett., vol. 42, no. 8, pp. 447449, Apr. 2006.[2] Z. N. Chen, T. S. P. See, and X. M. Qing, Small printed ultrawide-

band antenna with reduced ground plane effect, IEEE Trans. AntennasPropag., vol. 55, no. 2, pp. 383388, Feb. 2007.

[3] C. Y. D. Sim, W. T. Chung, and C. H. Lee, Compact slot antenna forUWB applications, IEEE Antennas Wireless Propag. Lett., vol. 9, pp.6366, 2010.

[4] A. M. Abbosh and M. E. Bialkowski, Design of ultrawideband planarmonopole antennas of circular and elliptical shape, IEEE Trans. An-tennas Propag., vol. 56, no. 1, pp. 1723, Jan. 2008.

[5] J. X. Liang, C. C. Chiau, X. D. Chen, and C. G. Parini, Study ofa printed circular disc monopole antenna for UWB systems, IEEETrans. Antennas Propag., vol. 53, no. 11, pp. 35003504, Nov. 2005.

[6] C. Y. Huang and W. C. Hsia, Planar elliptical antenna for ultra-wide-band communications, Electron. Lett., vol. 41, no. 6, pp. 296297,Mar. 2005.

[7] N. P. Agrawall, G. Kumar, and K. P. Ray, Wide-band planar monopoleantennas, IEEE Trans. Antennas Propag., vol. 46, no. 2, pp. 294295,Feb. 1998.

[8] K. L. Wong, Y. W. Chi, C. M. Su, and F. S. Chang, Band-notchedultra-wideband circular-disk monopole antenna with an arc-shapedslot, Microw. Opt. Technol. Lett., vol. 45, no. 3, pp. 188191, May2005.

[9] Y. J. Cho, K. H. Kim, D. H. Choi, S. S. Lee, and S. O. Park, A minia-ture UWB planar monopole antenna with 5-GHz band-rejection filterand the time-domain characteristics, IEEE Trans. Antennas Propag.,vol. 54, no. 5, pp. 14531460, May 2006.

[10] Q. X. Chu and Y. Y. Yang, A compact ultrawideband antenna with3.4/5.5 GHz dual band-notched characteristics, IEEE Trans. AntennasPropag., vol. 56, no. 12, pp. 36373644, Dec. 2008.

PENG AND RUAN: UWB BAND-NOTCHED MONOPOLE ANTENNA DESIGN 1081

[11] L. Peng, C. L. Ruan, and X. C. Yin, Analysis of the small slot-loadedelliptical patch antenna with a band-notched for UWB applications,Microw. Opt. Technol. Lett., vol. 51, no. 4, pp. 973976, Apr. 2009.

[12] Y. D. Dong, W. Hong, Z. Q. Kuai, and J. X. Chen, Analysis of planarultrawideband antennas with on-ground slot band-notched structures,IEEE Trans. Antennas Propag., vol. 57, no. 7, pp. 18861893, Jul.2009.

[13] K. H. Kim and S. O. Park, Analysis of the small band-rejected antennawith the parasitic strip for UWB, IEEE Trans. Antennas Propag., vol.54, no. 6, pp. 16881692, Jun. 2006.

[14] A. M. Abbosh and M. E. Bialkowski, Design of UWB planarband-notched antenna using parasitic elements, IEEE Trans. An-tennas Propag., vol. 57, no. 3, pp. 796799, Mar. 2009.

[15] L. Peng, C. L. Ruan, Y. L. Chen, and G. M. Zhang, A novel band-notched elliptical ring monopole antenna with a coplanar parasitic el-liptical patch for UWB applications, J. Electromagn. Waves Appl., vol.22, no. 4, pp. 517528, Apr. 2008.

[16] K. S. Ryu and A. A. Kishk, UWB antenna with single or dual band-notches for lower WLAN band and upper WLAN band, IEEE Trans.Antennas Propag., vol. 57, no. 12, pp. 39423950, Dec. 2009.

[17] S. W. Qu, J. L. Li, and Q. Xue, A band-notched ultrawideband printedmonopole antenna, IEEE Antennas Wireless Propag. Lett., vol. 5, pp.495498, 2006.

[18] W. J. Lui, C. H. Cheng, Y. Cheng, and H. Zhu, Frequency notchedultra-wideband microstrip slot antenna with fractal tuning stub, Elec-tron. Lett., vol. 41, no. 6, pp. 294296, Mar. 2005.

[19] K. G. Thomas and M. A. Sreenivasan, A simple ultrawideband planarrectangular printed antenna with band dispensation, IEEE Trans. An-tennas Propag., vol. 58, no. 1, pp. 2734, Jan. 2010.

[20] Y. Gao, B. L. Ooi, and A. P. Popov, Band-notched ultra-widebandring-monopole antenna, Microw. Opt. Technol. Lett., vol. 48, no. 1,pp. 125126, Jan. 2006.

[21] J. W. Jang and H. Y. Hwang, An improved band-rejection UWBantenna with resonant patches and a slot, IEEE Antennas WirelessPropag. Lett., vol. 8, pp. 299302, 2009.

[22] Y. Zhang, W. Hong, C. Yu, Z. Q. Kuai, Y. D. Dong, and J. Y. Zhou,Planar ultrawideband antennas with multiple notched bands based onetched slots on the patch and/or split ring resonators on the feed line,IEEE Trans. Antennas Propag., vol. 56, no. 9, pp. 30633068, Sep.2008.

[23] D. Sievenpiper, L. J. Zhang, R. F. J. Broas, N. G. Alexopolous, and E.Yablonovitch, High-impedance electromagnetic surfaces with a for-bidden frequency band, IEEE Trans. Microw. Theory Tech., vol. 47,no. 11, pp. 20592074, Nov. 1999.

[24] F. Yang and Y. Rahmat-Samii, Microstrip antennas integrated withelectromagnetic bandgap (EBG) structures: A low mutual coupling de-sign for array applications, IEEE Trans. Antennas Propag., vol. 51, no.10, pp. 29362946, Oct. 2003.

[25] R. Mkinen, V. Pynttri, J. Heikkinen, and M. Kivikoski, Improve-ment of antenna isolation in hand-held devices using miniaturized elec-tromagnetic bandgap structures, Microw. Opt. Technol. Lett., vol. 49,no. 10, pp. 25082513, Oct. 2007.

[26] C. L. Wang, G. H. Shiue, W. D. Guo, and R. B. Wu, A systematic de-sign to suppress wideband ground bounce noise in high-speed circuitsby electromagnetic-bandgap-enhanced split powers, IEEE Trans. Mi-crow. Theory Tech., vol. 54, no. 12, pp. 42094217, Dec. 2006.

[27] R. Baggen, M. Martinez-Vazquez, J. Leiss, S. Holzwarth, L. S. Drioli,and P. de Maagt, Low profile galileo antenna using EBG technology,IEEE Trans. Antennas Propag., vol. 56, no. 3, pp. 667674, Mar. 2008.

[28] J. M. Bell, M. F. Iskander, and J. J. Lee, Ultrawideband hybrid EBG/ferrite ground plane for low-profile array antennas, IEEE Trans. An-tennas Propag., vol. 55, no. 1, pp. 412, Jan. 2007.

[29] H. Nakano, K. Kikkawa, N. Kondo, Y. Iitsuka, and J. Yamauchi, Low-profile equiangular spiral antenna backed by an EBG reflector, IEEETrans. Antennas Propag., vol. 57, no. 5, pp. 13091318, May 2009.

[30] E. Rajo-Iglesias, L. Inclan-Sanchez, J. L. Vazquez-Roy, and E. Garcia-Muoz, Size reduction of mushroom-type EBG surfaces by using edge-located vias, IEEE Microw. Wireless Compon. Lett., vol. 17, no. 9, pp.670672, Sep. 2007.

[31] Ansoft HFSS. Ansys Corporation, Pittsburgh, PA, 2010. [Online].Available: www.ansoft.com

[32] CST MWS. Comput. Simulation Technol., Darmstadt, Germany, 2010.[Online]. Available: www.cst.com

Lin Peng was born in Guangxi Province, China,in 1981. He received the B.E. degree in scienceand technology of electronic information and M.S.degree in radio physics from the University of Elec-tronic Science and Technology of China (UESTC),Chengdu, China, in 2005 and 2008, respectively, andis currently working toward the Ph.D. degree in radiophysics at the Institute of Applied Physics, UESTC.

His research interests include antenna theory anddesign, microwave filter design, EBG structures, andcomposite right/left-handed (CRLH) transmission

lines.

Cheng-Li Ruan received the Ph.D. degree in EMfield and microwave technology from the Universityof Electronic Science and Technology of China(UESTC), Chengdu, China, in 1983.

From 1985 to 1988, he was an Associate Professorwith UESTC. Since 1988, he has been a Professorwith the Institute of Applied Physics, UESTC. Hehas authored or coauthored over 90 papers. His cur-rent research interests include millimeter-wave tech-niques, EM scattering, antenna theory, EM missiles,and UWB electromagnetics.

Prof. Ruan is a member of the Chinese Institute of Electronics and the ChineseElectricity Society.