3. Y. Sung, Compact and low insertion loss dual-mode bandpass fil-

ter, Microwave Opt Technol Lett 50 (2008), 3201–3206.

4. Y. Sung, B.Y. Kim, C.S. Ahn, and Y.-S. Kim, Compact and low-

insertion-loss dual-mode patch filter with spur-lines, Microwave

Opt Technol Lett 43 (2004), 33–34.

5. O. Akgun, B.S. Tezekici, and A. Gorur, Reduced-size dual-mode

slotted patch resonator for low-loss and narrowband bandpass filter

applications, Electron Lett 40 (2004), 1275–1277.

6. J.B. Pendry, A.J. Holden, D.J. Robbins, and W.J. Stewart, Magne-

tism from conductors and enhanced nonlinear phenomena, IEEE

Trans Microwave Theory Tech MTT-47 (1999), 2075–2084.

7. D.R. Smith, W.J. Padilla, D.C. Vier, S.C. Nemat-Nasser, and S.

Schultz, Composite medium with simultaneously negative perme-

ability and permittivity, Phys Rev Lett 84 (2000), 4184–4187.

8. J. Martel, J. Bonache, R. Marque’s, et al, Design of wide-band

semi-lumped bandpass filters using open split ring res-onators,

IEEE Microwave Wireless Compon Lett 17 (2007), 28–30.

9. S.H. Fu, C.M. Tong, X.M. Li, et al, Novel dual-mode square patch

bandpass filter using slot-type SRR perturbation for mode splitting,

Microwave Opt Technol Lett 53 (2011), 1703–1706.

10. J.D. Tseng and W.G. Chang, Planar rectangular split ring shape

band-pass structures, Microwave Opt Technol Lett 49 (2007),

2520–2523.

11. G.-L. Wu, W. Mu, X.-W. Dai, and Y.-C. Jiao, Design of novel

dual-band bandpass filter with microstrip meander-loop resonator

and CSRR DGS, Prog Electromagn Res 78 (2008) 17–24.

12. J.S. Hong and M.J. Lancaster, Microstrip filters for RF/microwave

application, Wiley, New York, 2001.

VC 2012 Wiley Periodicals, Inc.

TWO ANTIPODAL VIVALDI ANTENNASAND AN ANTENNA ARRAY FORMICROWAVE EARLY BREAST CANCERDETECTION

Wenyi Shao and Ryan S. AdamsDepartment of Electrical and Computer Engineering, University ofNorth Carolina Charlotte, 9201 University Blvd, Charlotte, NC28262; Corresponding author: wshao1@uncc.edu

Received 29 June 2012

ABSTRACT: Two small antipodal Vivaldi antennas for ultrawide bandearly breast cancer detection are proposed. The antennas are designedto operate in the spectrum from 1 to 10 GHz, according to the

requirements of wave penetration in the breast and imaging resolution.Simulated and measured reflection parameters of the proposed antennas

are evaluated. Numerical results also show the proposed antennas havegood near-field radiation performance. Finally, an antenna arrayconsisting of eight antipodal Vivaldi antennas, appropriate to collect the

tumor scattering signal in the breast is presented. VC 2012 Wiley

Periodicals, Inc. Microwave Opt Technol Lett 55:670–674, 2013; View

this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27384

Key words: breast cancer detection; ultra-wide band (UWB); antipodalVivaldi antenna

1. INTRODUCTION

There has been great demand for a new, nonionizing, reliable,

and inexpensive detection approach for early breast cancer diag-

nosis to complement the current method of X-ray mammog-

raphy. Recent investigations have shown that microwave tomog-

raphy is potentially well suited to this type of application [1].

The image quality provided by microwave imaging techniques

is affected by the number and efficiency of the receivers, the

synthetic aperture of the antenna array, and bandwidth of the

probing signal. It is very important to obtain a high-perform-

ance, broad-band antenna that satisfies these needs.

Antennas that are used in microwave medical imaging, espe-

cially breast cancer imaging, are generally required to be small.

Small antennas reduce the error associated with antenna posi-

tion, and thus, improve the accuracy of the system. To date,

only a few small broad-band antennas for breast cancer detec-

tion have been reported [2–5]. The antipodal Vivaldi antenna

has been recently considered for breast cancer imaging [6] due

to its simple structure, broad-band property, relatively small

size, and ease of fabrication. However, the antenna presented in

Ref. 6 is still quite large, therefore, it can only be reasonably

applied in a monostatic system wherein one antenna serves as a

transmitter as well as a receiver, and is moved across the breast

during the scan. As it has been reported that a multistatic system

is able to provide better imaging results than a monostatic sys-

tem [7] in breast cancer detection, potentially due to more sig-

nals can be obtained for signal processing in imaging, it is nec-

essary to build an even smaller antenna, to allow more antennas

to be positioned around the breast simultaneously.

This letter reports two small antipodal Vivaldi antennas oper-

ating in the 1–10 GHz spectrum that meet the breast-cancer-

microwave-imaging-bandwidth requirement [1]. The simulated

and measured results show that the proposed antenna may be

used as an element of a synthetic aperture array for breast sur-

vey. Finally, eight antennas with the same structure are placed

on the same substrate, to compose an antenna array which is

expected to form the core of a multistatic imaging system.

2. THE GEOMETRY OF THE ANTENNA

The proposed antipodal Vivaldi antennas both have exponential

structures. Figure 1 presents the geometry and parameter values

of the antennas. The inner and outer curvatures of this antenna

(inner curves form the gap) are defined by

xin ¼ c1½ec2ðy�L�CÞ � 1� �W (1)

xout ¼ W 2ey� L� C

6� 1

� �(2)

where W, L, and C are shown in Figures 1(a) and 1(c). The coef-

ficients c1 and c2 for the proposed antennas are listed in Table 1.

In both designs, the radiating elements are terminated with a

tilted half disc, to reduce the reflection from the end. The

antenna is assumed to be fed through an SMA connector fol-

lowed by a gradual transition from microstrip to parallel strips

transmission line. Along the transition, the conductor width

increases linearly while the ground width decreases exponen-

tially to retain constant impedance. The parallel strips transmis-

sion line extends for a short distance before the bottom and top

conductors start to flare in opposite directions with the exponen-

tial curves of Eqs. (1) and (2) to create the antenna aperture.

The substrate is constructed using TMM 10 (Rogers Corpora-

tion) that has thickness 1.27 mm, and a relative permittivity of

9.2, which is close to the typical relative permittivity of healthy

breast tissue (9.0) [1]. Antenna #2 [in Figs. 1(c) and 1(d)] has a

longer feeding leg and a reduced gap width, compared to

Antenna #1 [in Figs. 1(a) and 1(b)). The overall sizes of

Antenna #1 and Antenna #2 are 29 � 32 � 1.27 mm and 33 �32 � 1.27 mm, respectively. Note that the wavelength at 1 and

10 GHz in the coupling liquid with relative permittivity of 9.2 is

98.9 and 9.89 mm, respectively. Thus, the length and width of

the presented antennas are approximately 13k1GHz or 10

3k10GHz.

The constructed antennas are shown in Figure 2.

670 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 3, March 2013 DOI 10.1002/mop

The antennas are assumed to be immersed in a coupling me-

dium when operating in either transmit or receive mode during

the breast scan. Figure 3 shows the HFSS-simulated electric

field on the x–y plane generated by the proposed antennas when

fed from the origin and immersed in an ideal coupling liquid

with relative permittivity of 9.2. As breast cancer detection is a

type of near-field imaging, the desired detection area is approxi-

mately several wavelengths (at the center frequency) away from

the antenna (typically several centimeters deep into the skin).

The images in Figure 3 indicate a better radiation at the center

(designed) frequency than at the edge frequency (10 GHz) for

both designs.

It has been reported that ethanol is a useful coupling medium

in microwave breast cancer detection [4], with relative permit-

tivity �24.3–5.5 and conductivity �0.7–2.7 S/m during 1–9

GHz spectrum [4]. In our measurement, we used a commercial

fuel (E85) as the coupling liquid, which contains 85% ethanol,

plus gasoline. We selected this composition because gasoline

has even lower conductivity than ethanol, such that the liquid

can have less dissipation but does not change the effective per-

mittivity much. Figure 4 shows the HFSS-simulated and meas-

ured reflection coefficient S11 of Antenna #1 over the frequency

span 1–10 GHz. The measurement matches the main features of

the simulation, especially in the low frequency range. The main

source of error may come from the actual dielectric properties

of the coupling liquid which may not match the parameters used

in our simulation.

From Figure 3, one can find that the field generated by

Antenna #2 does not present significant differences from that

generated by Antenna #1. The measured and simulated S11 pa-

rameter for Antenna #2 is illustrated in Figure 5.

3. THE ANTENNA ARRAY

In the multistatic mode, the transmitter and the receiver are

located at different points. The antenna elements proposed in

the previous section are both able to be employed as a transmit-

ter in a multi-static imaging system. Considering Antenna #1 is

smaller, we selected Antenna #1 as the element used in the

antenna array to receive signals. As shown in Figure 6, eight

antennas were built on one substrate and have the same polar-

ization. This arrangement makes the antennas easy to feed. The

patient is assumed to be prone such that the breast turns out to

be in a drop shape. The hole in the middle allowing for mea-

surement of a breast is 100 mm in diameter, which is enough to

accommodate a drop-shaped breast. By moving the array up and

down in the z-direction, the array can collect the signal from the

breast at different heights, shown in Figure 8, to conform to syn-

thetic aperture imaging. As the signal-collection step measures

the backscattered signal from the breast at tens of locations,

with this receiving array, the signal collection step can be con-

ducted more efficiently.

The constructed antenna array with SMA connectors is

shown in Figure 9. The overall size of the array is 152.4 �152.4 � 1.27 mm3. The substrate material is Rogers TMM 10

(relative permittivity 9.2). Our measurements show that very

weak coupling is observed between each pair of elements in the

TABLE 1 The Coefficients Used in Eq. (1)

Coefficients Antenna #1 Antenna #2

c1 0.25 0.06

c2 0.15 0.2

Figure 1 Geometry and parameters of two Vivaldi antennas: (a) top view and (b) 3D view are for Antenna #1; (c) top view and (d) 3D view are for

Antenna #2. Unit in all subfigure is mm. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 3, March 2013 671

Figure 2 Two constructed antipodal Vivaldi antennas: (a) top view and (b) bottom view for Antenna #1; (c) top view and (d) bottom view for

Antenna #2. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

Figure 3 The 2D electric field of the antennas in the x–y plane when the frequency is 6 or 10 GHz. Antennas are assumed to be immersed in a cou-

pling liquid with dielectric constant ¼9.2. (a) 6 GHz and (b) 10 GHz for Antenna #1; (c) 6 GHz and (d) 10 GHz for Antenna #2. [Color figure can be

viewed in the online issue, which is available at wileyonlinelibrary.com]

672 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 3, March 2013 DOI 10.1002/mop

array. Because of the symmetry of the array, only S37 and S57

are illustrated in Figure 7, as the highest correlation can only

exist in these two pairs. Note that ethanol is a lossy medium in

the microwave range, as well as the healthy breast tissue (r �0.4 S/m), so it is reasonable that the value of S57 turns out to be

very low. All elements are polarized in the same direction; a

rotation of 90�creates an array with vertical polarization. Hence,

a multi-polarization detection method [8, 9] is likely to be per-

formed by this antenna array.

4. CONCLUSION AND OUTLOOK

Two small antipodal Vivaldi antennas are designed for micro-

wave early breast cancer detection. Both antennas are fabricated

on a substrate with relative permittivity of 9.2, and intended to

operate in a coupling liquid across the UWB spectrum. The

receiving array consists of eight antipodal Vivaldi antennas

polarized in the same direction. Although its synthetic aperture

is fixed in the horizontal plane, it may be easily moved verti-

cally to form a three-dimensional (3D) synthetic aperture.

Finally, due to the symmetry of the array, it can be rotated

about its center to produce multipolarized-signal detection. In

out next step, we will use this antenna (array) to detect targets

buried in some kind of tissue-mimic material. We look forward

the proposed antenna (array) being applied in our real breast-

cancer-detecting system.

Figure 4 The measured (solid line) and HFSS-simulated (dashed line)

S11 for Antenna #1. [Color figure can be viewed in the online issue,

which is available at wileyonlinelibrary.com]

Figure 5 The measured (solid line) and HFSS-simulated (dashed line)

S11 for Antenna #2. [Color figure can be viewed in the online issue,

which is available at wileyonlinelibrary.com]

Figure 6 The designed antenna array in HFSS. All the elements have

been numbered. Unit: mm. [Color figure can be viewed in the online

issue, which is available at wileyonlinelibrary.com]

Figure 7 Measured S57 (thin solid line) and S37 (thick dashed line)

for the elements in the array. [Color figure can be viewed in the online

issue, which is available at wileyonlinelibrary.com]

Figure 8 The designed antenna array for breast cancer imaging.

[Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com]

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 3, March 2013 673

REFERENCES

1. E.C. Fear, S.C. Hagness, P.M. Meaney, M. Okoniewski, and M.A.

Stuchly, Enhancing breast tumor detection with near-field imaging,

IEEE Microwave Mag 3 (2002), 48–56.

2. X. Li, S.C. Hagness, M.K. Choi, and D.W. van der Weide, Numer-

ical and experimental investigation of an ultrawideband ridged py-

ramidal horn antenna with curved launching plane for pulse

radiation, IEEE Antenna Wireless Propag Lett 2 (2003), 259–262.

3. P.J. Gibson, The Vivaldi aerial, In: Proc. 9th Europe microwave

conference, 1979, pp. 101–105.

4. S.M. Salvador and G. Vecchi, Experimental tests of microwave

breast cancer detection on phantoms, IEEE Trans Antenna Propag

57 (2009), 1705–1712.

5. Y. Wang and M.R. Mahfouz, Novel compact tapered microstrip

slot antenna for microwave breast imaging, In: Proc IEEE AP-S

international symposium, Spokane, WA, 2011, 2119–2122.

6. J. Bourqui, M. Okoniewski, and E.C. Fear, Balanced antipodal

Vivaldi antenna with dielectric director for near-field microwave

imaging, IEEE Trans Antenna Propag 58 (2010).

7. Y. Xie, B. Guo, J. Li, and P. Stoica, Novel multi-static Adaptive

microwave imaging methods for early breast cancer detection,

EURASIP J Appl Signal Process 91961 (2006), 1–13.

8. W. Shao and R.S. Adams. UWB imaging with multi -polarized sig-

nals for early breast, In: Proc IEEE AP-S international symposium,

Toronto, Canada, 2010, pp. 1–4.

9. W. Shao and R.S. Adams, Multi-polarized microwave power imag-

ing algorithm for early breast cancer detection, Pier M, 23 (2012),

93–107.

VC 2012 Wiley Periodicals, Inc.

UWB PRINTED PLAQUE MONOPOLEANTENNAS FOR TRI-BAND REJECTION

Tapan Mandal1 and Santanu Das21 Department of Information Technology, Government College ofEngineering and Textile Technology, Serampore, Hooghly 712201,India; Corresponding author: tapanmandal20@rediffmail.com2Department of Electronics & Tele-Communication Engineering,Bengal Engineering and Science University, Shibpur, Howrah711103, India

Received 30 June 2012

ABSTRACT: In this article, a printed plaque monopole antenna fed bya microstrip line for ultrawideband (UWB) width with triple notch band

has been presented. The antenna is then modified to possess bandrejection at the wireless local area network (5.1–5.8 GHz) by aninverted U-shape slot or P-shape slot, or K–shape slot within the

radiating patch. In addition, two half wavelength slots (U-slot) are cutin the radiating patch to generate the first and third notch band in

3.25–3.75 GHz for WiMAX and 7.25–7.75 GHz for down link of X-bandsatellite communication system. Surface current distributions andtransmission line model are used to analyze the effect of these slots. The

proposed antennas are simulated and fabricated. Radiation patternshows good omnidirectional radiation patterns in the H-plane and

monopole like patterns in the E-plane. The proposed antenna gainvaries from 1.63 to 5.05 dB over the whole UWB region excluding atnotch band. The design antenna has a compact size of 30 � 30 mm2.VC 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:674–

680, 2013; View this article online at wileyonlinelibrary.com. DOI

10.1002/mop.27359

Key words: ultralwide band; plaque monopole; microstrip antenna;wireless local area network band; U-slot

1. INTRODUCTION

As the approval of ultrawideband (UWB) system by the US-

Federal Communication Commission [1], researchers pay much

attention on the modern Personal Area Network wireless com-

munication applications with high data transmission rate, high

security, simple configuration, low profile, compactness, and

low fabrication cost. Some of the numerous attractive features

of monopole antenna are relatively wide bandwidth (BW) with

near omnidirectional characteristic, high radiation efficiency,

and low power operation. The release of 10-dB impedance BW

of an extremely wide spectrum of 3.1–10.6 GHz (7.5 GHz) for

commercial numerous applications has generated lots of interest

in the research and development for UWB such as remote sens-

ing, radar, imaging, localization, and medical applications. The

planar monopole antenna, for example, rectangular, square, cir-

cular, elliptical, annular, and hexagonal, in shape are mainly

used to cover the entire UWB BW [1–4]. However, the existing

worldwide interoperability for microwave access (WiMAX/

IEEES02.16: 3.25–3.75 GHz), wireless LAN band wireless local

area network (WLAN/IEEES02.11a: 5.15–5.825 GHz) and

downlink of X-band satellite communication (7.25–7.75 GHz)

system can cause the performance degradation of UWB system

Figure 9 The constructed antenna array: (a) top view and (b) bottom

view. [Color figure can be viewed in the online issue, which is available

at wileyonlinelibrary.com]

674 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 3, March 2013 DOI 10.1002/mop