show the insertion loss of 2.42 and 1.99 dB at the center fre-

quency of 2.43 and 5.70 GHz, respectively, and the bandwidth

is slightly reduced.

The tapped-line geometry is imported for the second trans-

mission zeros by alternating the coupling section and the

tapped-line structure in the suggested dualband BPF using dual-

mode resonator, as shown in Figure 6. The position of the

tapped-line can be defined by the impedance, zR2, and the value

of the inverter. The electrical lengths of yt and yt0 are calculated

as 7� and 46�, respectively. Figure 6 shows the photograph for

the fabricated dualband BPF using dual-mode resonator with the

coupling and tapped-line geometry for the two transmission ze-

ros and its size is 25.81 � 28.59 mm2. The simulation and mea-

surement results of the dualband BPF using dual-mode resonator

are shown in Figure 7. The dualband BPF is simulated with the

insertion losses of 1.75 and 1.40 dB at 2.43 and 5.68 GHz,

respectively, and measured with the insertion loss of 1.92 and

1.71 dB at the center frequency of 2.42 and 5.65 GHz, respec-

tively. Also, each passband of the suggested dualband BPF has

two transmission zeros.

4. CONCLUSION

In this article, the value of the J-inverter for the dual-mode kg/2BPF is investigated as functions of the impedance and the elec-

trical length of the open-stub for the dual-mode kg/2 microstrip

resonator. As impedance of the open-stub decreases, the dual-

mode kg/2 BPF has a good out-of-band performance and low

value of the inverter. The dualband BPF using dual-mode reso-

nator for 2.45 and 5.8 GHz is suggested by using the second

spurious of the SIR structure that has the ratio of the impedance

of 0.581. To demonstrate the dualband BPF using dual-mode

resonator with two transmission zeros, the coupling structure

and tapped-line geometry are used for the J-inverter. By the

open-stub of the dual-mode kg/2 resonator, the bandwidth and

the frequency of one transmission zero are defined, and the other

transmission zero is defined by the open-stub of the tapped-line

geometry as a function of the J-inverter. The dualband BPF

using dual-mode resonator has been implemented and measured

with good performance. These BPFs can be used in wireless

communication system.

REFERENCES

1. J.R. Lee, J.H. Cho, and S.W. Yun, New compact bandpass filter

using microstrip kg/4 resonators with open stub inverter, IEEE

Microw Guid Wave Lett 10 (2000), 526–527.

2. H. Zhang and K.J. Chen, Bandpass filters with reconfigurable trans-

mission zeros using varactor-tuned tapped stubs, IEEE Microw

Wirel Compon Lett 16 (2006), 249–251.

3. L. Zhu and W. Menzel, Compact microstrip bandpass filter with

two transmission zeros using a stub-tapped half-wavelength line

resonator, IEEE Microw Wirel Compon Lett 13 (2003), 16–18.

4. W.H. Tu, Compact double-mode cross-coupled microstrip bandpass

filter with tunable transmission zeros, IET Microw Antennas

Propag 2 (2008), 373–377.

5. J.S. Hong and M.J. Lancaster, Microwave filters for RF/microwave

applications, Wiley, New York, NY, 2001.

6. T.S. Yun, H.S. Kim, T.S. Hyun, S.S. Kwoun, H.G. Kim, and J.C.

Lee, Tunable stepped impedance resonator bandpass filter using

ferroelectric materials, Asia-Pacific Microwave Conf Dig 3 (2006),

1773–1776.

7. J.R. Crute and L.E. Davis, A compact microstrip interdigital

stepped-impedance band-pass filter with enhanced stop band,

Microwave Opt Technol Lett 34 (2002), 336–340.

8. T.S. Yun, Y.K. Yoon, B. Lee, J.J. Choi, J.Y. Kim, and J.C. Lee,

Analysis and design of stub bandpass filters using tapped-line ge-

ometry, Microwave Opt Technol Lett 51 (2009), 2338–2341.

VC 2010 Wiley Periodicals, Inc.

MINIATURIZATION OF RECTANGULARMICROSTRIP PATCH ANTENNA USINGOPTIMIZED SINGLE-SLOTTED GROUNDPLANE

S. Sarkar,1 A. Das Majumdar,1 S. Mondal,1 S. Biswas,2

D. Sarkar,2 and P. P. Sarkar21 Kalyani Government Engineering College, Kalyani, Nadia, WestBengal, India2 USIC, University of Kalyani, Kalyani, Nadia, West Bengal, India;Corresponding author: parthabe91@yahoo.co.in

Received 20 April 2010

ABSTRACT: In this article, a new design for single-layer rectangularmicrostrip patch antenna has been proposed. This design uses a groundplane with a single slot. It has been shown that by using this slotted

ground plane, the resonant frequency has been lowered considerably,

Figure 6 Fabricated dualband BPF using dual-mode microstrip resona-

tor with tapped-line geometry for two transmission zeros. [Color figure

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

wileyonlinelibrary.com]

Figure 7 Simulation and measurement results of dualband BPF using

dual-mode microstrip resonator with tapped-line geometry for two trans-

mission zeros. [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. 53, No. 1 January 2011 111

thus, reducing the size of the antenna. Using this design, the size of theantenna is reduced by about 90%. It has been also shown that theresonant frequency can be reduced further by increasing the length of

the slot. VC 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett

53:111–115, 2011; View this article online at wileyonlinelibrary.com.

DOI 10.1002/mop.25661

Key words: microstrip antenna; patch antenna; compact antenna

1. INTRODUCTION

Microstrip antenna, due to its inherent advantages of being low

cost, lightweight, and low profile structure, is being extensively

used in handheld communication devices such as mobile phones,

GPS, etc. One of the physical characteristics of these handheld

devices is small size. To reduce the size of these devices, the size

of the components used inside these devices has to be reduced. As

microstrip antenna is one of the components being used, the size of

these devices depends on this antenna to a large extent. Therefore,

one of the techniques of reducing the size of the handheld commu-

nication device is to reduce the size of the microstrip antenna.

A number of techniques have been reported to reduce the

size of a Microstrip antenna. The simplest of them is by modify-

ing the radiating patch or by modifying the ground plane. A

large number of compact antenna design has been reported

based on the radiating patch modification and ground plane

modification technique [1–14]. It was reported by Kuo and

Wong [1] that by embedding three meandering slots in the

ground plane of the rectangular microstrip patch antenna, the

size of the antenna can be reduced by 56%.

In this article, we are proposing a novel design for compact

microstrip antenna in which only one slot is used in the ground

plane and the feeding point is positioned to get the optimum

result. It was also found that the proposed antenna has higher

impedance bandwidth compared with the reference antenna.

2. ANTENNA DESIGN

Figure 1 shows the geometry of the proposed antenna. The fig-

ure has been drawn in third-angle projection. The design of the

antenna is asymmetrical in nature. The slot of width 1 mm and

length S is embedded in the ground plane parallel to the edge

A. It is embedded at a distance R from the edge A and at a dis-

tance P from edge B. The radiating patch is coaxially probe fed

through a via hole in the ground plane at 1.5 mm from the

edge B and 20.5 mm from edge C. The probe is fed at this

position to obtain optimum impedance matching. The size of

the radiating patch is chosen 20 � 30 mm2. The antennas

(antennas 1–6) with mentioned geometry has been constructed

using PTFE substrate (er¼ 2.4) with thickness of 1.5875 mm (1/

16 inch).

Figure 1 Structure of the proposed antenna

TABLE 1 Simulated Results

Antenna

R(mm)

P(mm)

S(mm)

Resonant Frequency,

Return Loss

(GHz, dB)

10-dB

Bandwidth

(MHz, %)

Antenna 1 18.5 3 46 1.6055, �12.3 42, 2.61

Antenna 2 18.5 2 47 1.5365, �19.1 54, 3.51

Antenna 3 18.5 1 48 1.5235, �25.5 55, 3.64

Antenna 4 19.5 3 46 1.5875, �16.6 57, 3.59

Antenna 5 19.5 2 47 1.5085, �44.8 58, 3.87

Antenna 6 19.5 1 48 1.4456, �16.1 46, 3.23

Reference 0 0 0 3.0800, �8.08 –

TABLE 2 Measured Results

Antenna

R(mm)

P(mm)

S(mm)

Resonant Frequency,

Return Loss

(GHz, dB)

10-dB

Bandwidth

(MHz, %)

Antenna 1 18.5 3 46 1.5920, �14.0 117.8, 7.4

Antenna 2 18.5 2 47 1.4810, �26.2 189.8, 12.8

Antenna 3 18.5 1 48 1.4700, �22.4 108.8, 7.4

Antenna 4 19.5 3 46 1.4800, �19.0 140.0, 9.5

Antenna 5 19.5 2 47 1.3800, �38.6 168.4, 12.2

Antenna 6 19.5 1 48 1.3660, �17.2 100.0, 7.3

Reference 0 0 0 2.8700, �6.8 –

112 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 1 January 2011 DOI 10.1002/mop

3. RESULTS AND DISCUSSION

The return losses of the proposed antennas were studied using

IE3DTM (based on Method of Moment (MoM)) and the results

are shown in Table 1. The return losses of the fabricated anten-

nas were studied using network analyzer and the results are

shown in Table 2.

During simulation, it was observed that largest reduction in

resonant frequency is obtained if the slot is placed at position

with R ¼ 19.5 mm. It was also observed that if the slot is posi-

tioned in any other position, then the resonant frequency

increases for a given slot size. This can be verified from the

measured return loss of antenna 1, antenna 2, and antenna 3

(each of whose return loss plot is shown in Figures 2–4, respec-

tively) by comparing with that of antenna 4, antenna 5 and

antenna 6 (each of whose return loss plot is shown in Figures

5–8, respectively). From the result, it is also observed that if the

length of the slot is increased toward edge B, then the resonant

frequency is decreased. Using the proposed design, we have

achieved size reduction of 88% (simulated result) and 90%

Figure 3 Measured and simulated return loss of antenna 2 having R ¼18.5 mm, P ¼ 2 mm, and S ¼ 47 mm

Figure 4 Measured and simulated return loss of antenna 3 having R ¼18.5 mm, P ¼ 1 mm, and S ¼ 48 mm

Figure 2 Measured and simulated return loss of antenna 1 having R ¼18.5 mm, P ¼ 3 mm, and S ¼ 46 mm

Figure 5 Measured and simulated return loss of antenna 4 having R ¼19.5 mm, P ¼ 3 mm, and S ¼ 46 mm

Figure 6 Measured and simulated return loss of antenna 5 having R ¼19.5 mm, P ¼ 2 mm, and S ¼ 47 mm

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 1 January 2011 113

Figure 10 Radiation pattern of antenna 2 having R ¼ 18.5 mm, P ¼2 mm, and S ¼ 47 mm at 1.481 GHz

Figure 11 Radiation pattern of antenna 3 having R ¼ 18.5 mm, P ¼1 mm, and S ¼ 48 mm at 1.47 GHz

Figure 12 Radiation pattern of antenna 4 having R ¼ 19.5 mm, P ¼3 mm, and S ¼ 46 mm at 1.48 GHz

Figure 8 Measured and simulated return loss of reference antenna

Figure 7 Measured and simulated return loss of antenna 6 having R ¼19.5 mm, P ¼ 1 mm, and S ¼ 48 mm

Figure 9 Radiation pattern of antenna 1 having R ¼ 18.5 mm, P ¼ 3

mm, and S ¼ 46 mm at 1.5920 GHz

114 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 1 January 2011 DOI 10.1002/mop

(measured results). We also achieved bandwidth of more then

12 and 7% (for most compact fabricated antenna) which indi-

cates tremendous improvement of bandwidth over traditional

antennas (which normally has bandwidth of about 2–4%). The

radiation pattern of the designed antennas (Figs. 9–14) shows

that the antennas have very broad beamwidth which matches

with the original patch antenna (Fig. 15).

4. CONCLUSIONS

A novel design for miniaturization of antenna by cutting a single

slot in the ground plane of the coaxially feed microstrip patch

antenna has been proposed and fabricated. The fabricated

antenna has been experimentally studied which showed that the

proposed antenna design not only reduces the size of the

antenna but also increases the impedance bandwidth of

the antenna. Further, it has been shown that miniaturization

of the antenna for the proposed design depends on the length of

the slot.

REFERENCES

1. J.S. Kuo and K.L. Wong, A compact microstrip antenna with

meandering slots in the ground plane, Microwave Opt Technol Lett

29 (2001), 95–97.

2. K.L. Wong and W.S. Chen, Compact microstrip antenna with dual-

frequency operation, Electron Lett 33 (1997), 646–647.

3. S.Y. Lin and K.L. Wong, Enhanced performances of a compact

conical-pattern annular-ring patch antenna using a slotted ground

plane, In: Proceedings of the IEEE Asia Pacific Microwave Con-

ference, Vol. 3, Taipei, 2001, pp. 1036–1039.[zaq no¼aq4]

4. T.W. Chiou and K.L. Wong, Designs of compact microstrip anten-

nas with a slotted ground plane, In: Proceedings of the IEEE

Antenna and Propagation Society International Symposium, Vol. 2,

Boston, MA, 2001, pp. 732–735.

5. H.D. Chen, Compact circularly polarized microstrip antenna with

slotted ground plane, Electron Lett 34 (2002), 616–617.

6. N. Herscovici, M.F. Osorio, and C. Peixeiro, Miniaturization of

rectangular microstrip patches using genetic algorithms, IEEE

Antenna Wireless Propag Lett 1 (2002), 94–97.

7. W.K. Kim and J.M. Woo, Miniaturization of 3-D microstrip

antenna using fylfot-shaped structure, In: Proceedings of the IEEE

ICECom, Dubrovnik, 2005, pp. 1–4.

8. G.A. Mavridis, C.G. Christodoulou, and M.T. Chryssomallis, Area

miniaturization of a microstrip patch antenna, In: Proceedings of

the IEEE Antenna and Propagation Society International Sympo-

sium, Honolulu, HI, 2007, pp. 5435–5438.

9. S. Bhunia, D. Sarkar, S. Biswas, P.P. Sarkar, B. Gupta, and K.

Yasumoto, Reduced size small dual and multi-frequency microstrip

antennas, Microwave Opt Technol Lett 50 (2008), 961–965.

10. S. Bhunia, M.K. Pain, S. Biswas, D. Sarkar, P.P. Sarkar, and B.

Gupta Investigations on microstrip patch antennas with different

slots and feeding points, Microwave Opt Technol Lett 50 (2008),

2754–2758.

11. J.Z. Huang, P.H. Yang, W.C. Chew, and T.T. Ye, A compact

broadband patch antenna for UHF RFID tags, In: Proceedings of

the IEEE Asia Pacific Microwave Conference, Singapore, 2009,

pp. 1044–1047.

12. L. Guo, S. Wang, X. Chen, and C.G. Parini, Study of compact

antenna for UWB applications, Electron Lett 46 (2010), 115–116.

13. K.G. Thomas and M. Sreenivasan, Compact CPW-fed dual-band

antenna, Electron Lett 46 (2010), 13–14.

14. C.Y.D. Sim, W.T. Chung, and C.H. Lee, Compact slot antenna for

UWB applications, IEEE Antenna Wireless Propag Lett 9 (2010),

63–66.

VC 2010 Wiley Periodicals, Inc.Figure 15 Radiation pattern of reference antenna at 2.87 GHz

Figure 14 Radiation pattern of antenna 6 with R ¼ 19.5 mm, P ¼ 1

mm, and S ¼ 48 mm at 1.366 GHz

Figure 13 Radiation pattern of antenna 5 having R ¼ 19.5 mm, P ¼2 mm, and S ¼ 47 mm at 1.38 GHz

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 1 January 2011 115