Defected Ground Structure in theperspective of MicrostripAntennas: A Review Ashwini K. Arya, M.V. Kartikeyan , A.Patnaik Abstract – Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. Although the DGS has advantages in the area of the microwave filter design, microwave oscillators, microwave couplers to increase the coupling, microwave amplifiers, etc. , it is also used in the microstrip antenna design for different applications such as antenna size reduction, cross polarization reduction, mutual couplingreduction inantenna arrays, harmonic suppressionetc. , The DGSis motivatedby a study of Photonic/Electromagnetic Band gap structures. The etching of one or more PBGelement creates defect in the ground plane and used for the same purpose. The DGS is easy to be an equivalent L-C resonator circuit. The value of the inductance andcapacitance depends on the areaandsize of the defect. By varying the various dimensions of the defect, the desired resonance frequency can be achieved. In this paper the effect of DGS, to the different antenna parameter enhancement is studied. Index Terms – Defected Ground Structure, Microstrip Antennas. 1 Introduction Microwave components such as filters, couplers, antennas etc. , in the microstrip technology, are used in high perform- ance aircraft, spacecraft, satellite and missiles where size, weight, cost, performance, ease of installation, and aerody- namic profile are constraints. Presently there are many other government and commercial applications, such as mobile radio and wireless communications, microwave communica- tion and millimeter wave communication. In its most basic form, the microstrip technology consists of a microstrip transmission line made of conducting material on one side of a dielectric substrate which has a ground plane on the other side. There are two different type of generic structures used for the design of the compact and high performance microwave components, named as defected ground structure (DGS) and the Elecromagnetic band gap (EBG) structures generally known as the photonic band gap structures (PBG) [1]. These structures have been attractive to obtain the function of unwanted frequency rejection and circuit size reduction. DGS cells have inherently resonant property; many of them have applied to filter circuits. However, it is difficult to use a PBG structure (periodic structure) for the design of the microwave or millimeter wave components due to the difficulties of the modeling. Another difficulty in using the PBG circuit is caused by the radiation from the periodic etched defects. Recently a defected ground structure (DGS) have been introduced, DGS is realized by etching off a simple shape in the ground plane, depending on the shape and dimensions of the defect, the shielded current distribution in the ground plane is disturbed, resulting a controlled excitation and propagation of the electromagnetic waves through the substrate layer. The shape of the defect may be changed from the simple shape to the complicated shape for the better performance. Different shapes of DGS structures, such as rectangular [2, 3], square [4], circular [5, 6], dumbbell [7–12], spiral [13], L- shaped [14], concentric ring [15], U-shaped and V-shaped [16–18], hairpin DGS [19–20], hexagonal DGS [21], cross shaped DGS [22] and combined structures [23–24] have been appeared in the literature. These structures are also used in periodic form [25–26]. DGS have advantages in the area of microwave filter design [2, 3, 6, 7, 9], power amplifiers [27–28], dividers [29, 32], microwave oscillators [8], couplers [30], transmission lines [31], combiners [32] and in microstrip antennas [43–44]. The defect in the ground plane of the planar transmission lines such as microstrip, Coplanar etc. , disturbs the shield current distribution and also changes the characteristics of the transmission line e. g. Capacitance and the Inductance. 2 Photonic bandgap structures and defected ground structures The photonic bandgap structure is a periodic structure etched in the ground plane. The difference between the PBG and DGS is shown in the table (1). Photonic Band Gap Structure Defected Ground Structure Geometry Periodic Etched Struc- ture One or Few Etched Structure Microwave Circuit Properties Similar Similar Equivalent Circuit Exaction Very Difficult Relatively Simple The PBGmodifies the properties of the microstrip line such as characteristic impedance and propagation constant. De- fected Ground Structure (DGS) is an etched lattice shape (slot), which locates on the ground plane. It is motivated by a study of PBG to change guided wave properties. DGS makes one or a few of PGB etched ground elements in the ground plane .The shape of slot is modified from a simple hole to a more complicated shape. The DGS structure may be found in both one-dimensional [26] and two dimensional forms. [5, 34], as shown in Fig. 1. 3 DGS Unit Cell Aunit DGS (dumbbell) section is created in the ground plane as shown in the Fig. 1. The DGSconsists of the two rectangular areas and one connecting slot in the ground plane [11, 12] as shown in Fig. 2. The DGS with the microstrip line employs an intentional defect on the ground and it provides band rejection character- istic from the resonance property. The cutoff frequency of the DGS is mainly dependent to the etched square area in ground plane. There is an attenuation pole location, which is due to the etched gap distance. Frequenz 64 (2010) 5 – 6 79 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM An attenuation pole can be generated by combination of the inductance and capacitance elements. The capacitance factor is needed to explain the frequency characteristic of the DGS section. The etched gap area, which is placed under a conductor line, provides the parallel capacitance with effec- tive line inductance. Thus, the proposed DGS section is fully described by two parameters: the etchedlattice dimensionandthe gapdistance. The inductance and capacitance are given as [35]: L ¼ 1 4p 2 f 2 o C (1) C ¼ f c 2Z o : 1 2pðf 2 o Àf 2 c Þ (2) 4 DGS Characteristics Defected Ground structures (DGS) have two main character- istics slow wave propagation in Pass band & Band Stop Characteristics in microwave circuits [33]. Slow wave Propagation in Pass Band: The DGS is considered as an equivalent circuit consisting of capacitance and inductance as given in the Fig. 2. The equivalent inductive part increases due to the defect and produces equivalently the high effective dielectric constant, that is, slow wave property due to this fact the DGS line has the longer electrical length than the standard Microstrip line, for the same physical length. By varying the various dimensions of the defect the desired resonance frequency can be achieved. Fig. 1: Defected Ground Structure, (a) 1-D DGS [5] (b) 2-D DGS[34] Fig. 2: DGS (a) Microstrip Line with Dumbbell Shaped DGS [10] (b) DGS unit cell and its L-C equivalent [11–12] . Fig. 3: Microstrip line with DGS (a) Phase characteristics and slow wave factor (b) slow wave factor [35] Frequenz 64 (2010) 5 – 6 80 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM Fig. 3 shows that the microstrip line with DGS unit is a good guiding structure with small distortion due to the linear phase variationof S21 withfrequency. It is tobe notedthat a jumping phenomenon occurs at the resonant frequency. Compared to the microstrip line without DGS unit, the microstrip line with DGS unit exhibits a faster phase variation which exhibits slow- wave behaviors below w 0 and a slower phase variation which exhibits fast-wave behaviors beyond w 0 , where w 0 is angle frequency and equal to 2pf 0 . This phenomenon can be explained as follows: When w < w o (frequencies less than the resonance frequency of defect), w 0 :L < 1=w 0 C, Inductive Microstrip line is obtained, when w > w o ( frequencies greater than the resonance frequency of defect), w 0 :L > 1=w 0 C, Capacitive Microstrip line is obtained and in the case at the resonance frequency (w ¼ w o and w 0 :L ¼ 1=w 0 C) jumping phenomenon occurs [35]. Generally, the slow-wave factor is defined by l 0 /lg, where lg is the guided wavelength and l 0 is the free space wavelength. Band Stop Characteristics: This equivalent circuit of the proposed DGS unit can explain the bandgap effect. The series inductance due to the DGS section increases the reactance of a microstrip with the increasing of the frequency. Thus, the rejection of the certain frequency range can be started. The parallel capacitance with the series inductance provides the attenuation pole location, which is the resonance frequency of the parallel LC resonator. As the operating frequency increases, the reactance of the capacitance de- creases. Thus, the bandgap between the propagating frequency bands can be occurred as shown in Fig. 4. In order to explain the cutoff and attenuation pole characteristic of the proposed DGS section simultaneously, the equivalent circuit should exhibit performances of low-pass and bandstop filter at the same time [37]. Generally it is accepted that the microstrip line should have the impedance around 100–130 ohms. By using the defected ground structure in the ground plane the effective inductance will increase and at the same time the capacitance will be decrease and finally the impedance of the transmission line increases and becomes more than 200 ohms. This high impedance of the DGS is used in the interconnects used in the digital systems [38]. 5 Classification of Defected Ground Structures: The shape of the slot affects the response of the DGS unit section. For this it is divided into the two categories. Rectangular slot without head and with different heads (like circular, square, arrow). Different slot configurations (rectangular slot, with circular head, square head, arrow head respectively) for the DGS are shown in Fig. 5 [36]. The dumbbell shaped DGS gives the slow wave effect in the pass band and band gap both at the same time that is very useful for the microstrip antennas [11]. Quasistatic theory and neural network model has been used for the explanation and analysis of the unit DGS cell. A brief discussion is given here. 5.1 Quasistatic Theory of DGS: In many of the microwave circuits, the dumb-bell shaped DGS pattern is commonly adopted because of its ease in design and simplicity [40]. The quasi-transverse electromagnetic (TEM) mode propagates under the microstrip filament and the infinite ground plane in the conventional microstrip trans- mission line. The field (electric and magnetic) is mostly confined under the microstrip line. The return current on the ground plane is the negative image of the current distribution on the microstrip line. The return path of the current is fully disturbed using the DGS and this current is confined to the periphery of the perturbation and returns to the underneath of the microstrip line once the perturbation is over as shown in Fig. 6. On the basis of the observation of the maximum concentration of the return surface current on the ground plane, the width of the side filament arms, which contribute to the inductance of the Fig. 4: Band stop characteristics of DGS (S21 Parameter) [11] Fig. 5: Different Slots for DGS (a). Rectangular slot without head and with circular head (b) with rectangular slot and triangular slot [36] Fig. 6: Current distribution in the Ground Plane of DGS Microstrip line [39] Frequenz 64 (2010) 5 – 6 81 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM DGS, is determined. The gap is represented by the equivalent capacitances, The inductances and capacitances are derived from the physical dimensions using quasi-static expressions for microstrip crosses, lines and gaps available in the open literatures [39]. On the basis of this observation, an equivalent circuit model is developed. It is to be noting down that the line and ground plane does not affect the behavior of this circuit in terms of location of the attenuation pole. Only the bandwidth of the stop band decreases. In this approach, the mode of propagation of wave is considered to be purely TEM. In the high frequency region, small changes in inductance, character- istic impedance and effective dielectric constant (hence to capacitance) take place. The small corrections are incorpo- rated by curve fitting, as well as with interpolation. 5.2 Neural network model for analysis of DGS Artificial Neural Network has been implemented to address the problem of accurate determination of frequency of dumbbell shaped DGS for a desired dimension of the dumbbell shaped DGS. The feed forward back propagation algorithm [42] is used for training of the network. The ANN black box is shown in Fig. 7. in which various input variable to ANN are the dimensions a, b and g and the resonant frequency of the antenna obtained from the output of ANN for a chosen dielectric substrate and microstrip line. . Out of 37 data generated from the CAD software, 28 were used for training and the rest used for testing of the trained neural network. The optimized value of the different param- eters for the DGS structure, which are obtained by the trial and error for the training of the network, are, 1) the no. of inputs=3; 2) the no. of neurons in the hidden layer=50;3) the no. of outputs = 1;4) no. of epochs are 5000 during training [12]. 6 Development of the defected ground structure in Microstrip antennas In this part a discussion is given in more detail about some significant developments in the field of microstrip antenna with defected ground structure, along with the references. 6.1 Micrstrip Patch Antenna Size Reductions The designed antenna, with the transmission line model for a particular frequency is larger and is not compatible for many applications. So antenna size reduction becomes necessary. Different techniques have already been used for the antenna size reduction such as using the substrate with high dielectric constant, edge shorted patched with shorting plates or short- ing walls, use of the shorting pin at the suitable position etc. The etching of a defect in the ground plane is also a unique technique for the antenna size reduction [11, 43]. The Transmission Line model is used to design the main patch for resonant frequency 6.2 GHz. The antenna size 12 mmÂ15 mmÂ1.524 mm is better compatible for the differ- ent applications. The creation of a Dumbbell shaped DGS in the ground plane of the antenna is used for the size reduction of the antenna for working at the frequency of 5.2 GHz. From the analysis methods the antenna size 14.5 mmÂ18.0 mmÂ1.524 mm is calculated for the frequency 5.2 GHz and is optimized with the IE3D simulator, with the dumbbell defect in the ground plane the antenna size reduced to 12 mmÂ15 mm 1.524 mm for the same resonance. 6.2 Harmonics reduction One of the useful phenomenons in the active antennas is to reduce the harmonics. For active antennas, the radiation level of the both active and passive devices is wanted for being very low at the harmonic frequencies. By integrating the active device very close to the radiating patch along with the feed line, the feedline losses are reduced. But these antennas suffer from the harmonic radiation and resulting a non linear process. Thus harmonic radiation is a drawback of active integrated microstrip antennas, and PBG/DGS structures are suggested to reduce higher-order harmonics in microstrip antennas. The DGS antenna strongly eliminates the harmonic resonance [44–48]. Different DGS units has been used in the harmonic reduction in antennas such as H-shaped DGS, spiral shaped, dumbbell shaped, and tapered DGS. 6.3 Cross polarization reduction A defected ground structure (DGS) in microstrip antennas is used to reduce the cross-polarized (XP) radiation. The DGS pattern is simple and easy to etch on a commercial microstrip substrate. This defect reduces only the XP radiation field without affecting the dominant mode input impedance and co-polarized radiation patterns of a conventional antenna. This new concept is examined and verified experimentally for a particular DGS pattern employing a circular patch as the radiator [48]. 6.4 Mutual coupling reduction In an array, the field radiated by one element induces voltages across the terminals of other elements and scatters from the other elements into the far field. Mutual coupling affects input impedances, radiation patterns, gain, effective receiving area, and other parameters of the array. It is very important to reduce the mutual coupling between the elements of the antenna array. The defected ground structure (dumbbell shaped) is successfully used to mutual coupling reduction of a two-element microstrip antenna array. Using the DGS is a unique technique in comparison of the DGS antenna with other techniques to reduce the mutual coupling. [49]. 6.5 Design approach for circular polarization The DGS is used under the feed lines including feed line structures which are edge coupled to the microstrip patch antennas in a single layer substrate for the circular polar- ization of the patch antennas. The presented designs can easily be extended to other bands satellite and terrestrial systems that require circularly polarized antennas [50]. This type of antenna can be easily integrated with the RFIDreader system and also useful for other wireless communication systems, which involve circular polarization. Fig. 7: ANN Model [12] Frequenz 64 (2010) 5 – 6 82 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM 6.6 Broadband RCS reduction It is an important parameter to decide the stealth ability in the stealth technology. The surface of an aircraft can have low radar cross section by using some radar- observing materials or other shaping methods. Thus the antenna becomes more important contributor to the overall RCS signature of the same object. An antenna with two circular apertures and a shorting pin is used for the RCS reduction. The shorting pin is used for the RCS reduction at the frequencies outside the desired band. [51]. 6.7 Elemination of scan blindness in antenna arrays A dumb-bell shaped DGS is used to remove the blindness angle of a linear array microstrip antenna. The frequency band gap of the DGS forbids the propagation of surface waves at the antenna design frequency and hence eliminates the scan blindness. This approach is much easier to implement than other methods such as EBG and PBG [52]. 6.8 Radiation properties enhancement Surface waves are undesired because when a patch antenna radiates, a portion of total available radiated power becomes trapped along the surface of the substrate. It can extract total available power for radiation to space wave. Therefore, surface wave can reduce the antenna efficiency, gain and bandwidth. For arrays, surface waves have a significant impact on the mutual coupling between array elements. One solution to reduce surface waves is using electromagnetic band gap (EBG) or photonic band gap structure (PBG) or DGS [21]. 7 Conclusion In this paper the Defected ground structure in the microstrip technology is discussed. The etched lattice (DGS) in the ground plane plays an important role in the design of compact and high performance microwave circuits. It consists of L-C parallel circuit having a resonant frequency characteristic. It is having band gap property, which is used in the many micro- wave applications. The given applications in the microstrip antennas with the DGS are in a good performance in the microwave circuits. Further we can use the DGS for other parameters improvement in the antennas also. References [1] Yang, F. , and Rahmat Samii, Y. , “Electromagnetic band gap struc tures in antenna engineering”, Cambridge University press, USA, 2009 [2] Qiang, R. , Wang, Y. , and Chen, D. , “A novel microstrip bandpass filter with two cascaded PBG structures,” IEEE AP-S Digest, 510– 513, 2001. [3] Kim, J. P. and Park, W.S. , “Microstrip lowpass filter with multislots on ground plane,” Electronics Letters, Vol. 37, No. 25, pp. 1525–1526, Dec. 2001. [4] Sharma, R. , Chakravarty, T. , and Bhooshan, S. , “Design of a novel 3 db microstrip backward wave coupler using defected ground structure,” Progress In Electromagnetics Research, PIER 65, 261– 273, 2006. [5] Radisic, V. , Qian, Y. , Coccioli, R. , and Itoh, T. , “Novel 2-D photonic bandgap structure for microstrip lines,” IEEE Microwave and Guided Wave Letters, Vol. 8, No. 2, 69–71, Feb. 1998. [6] Oskouei, D. , H. R. and Z. Atlasbaf, Z. , “Amodified dual-mode band pass filter with DGS structures,” 13th Conference on Microwave Techniques, Prague, 2005. [7] Ahn, D. , Park, J.S. , Kim, C.S. , Kim, J. , Qian, Y. , Itoh, T. , “Adesign of the low-pass filter using the novel microstrip defected ground structure,” IEEE Trans. Microwave Theory and Techniques. , Vol. 49, No. 1, 86–91, Jan. 2001. [8] Joung,M.S. , Park,J.S. , and Kim, H.S. , “A novel modeling method for defected ground structure using adaptive frequency sampling and its application to microwave oscillator design,” IEEE Transaction on Microwave Theory and Techniques, Vol. 41, No. 5, 1656–1659, May 2005. [9] Cho, Y. B. , Jun, K. S. , and Kim, I. S. , “Small-size quasi-elliptic function microstrip low pass filter based on defected ground structures and open stubs,” Microwave Journal, February 2004. [10] Li, G.H. , Jiang, X.H. and Zhong, X.M. , “A novel defected ground structure and its application to a low pass filter,” Microwave and Optical Technology Letters, Vol. 48, No. 9, 453–456, Sep. 2006. [11] Arya, A. K. Kartikeyan, M.V. , Patnaik, A. , “Efficiency enhancement of microstrip patch antennas with Defected Ground Structure,” IEEE proc. Recent Advanced in Microwave theory and applications (MICROWAVE-08), pp.729–731 November 2008. [12] Arya, A. K. , Kartikeyan, M.V. , Patnaik, A. , “Neural Network Model for analysis of DGS structure,” National Symposium on Vacuum Elect. Devices & Applications, (VEDA-2009), pp.EMS1.1-EMS1.2, Jan 2009. [13] Kim, C. S. , Lim, J. S. , Nam, S. , Kang, K. Y. and Ahn, D. , “Equivalent circuit modeling of spiral defected ground structure for microstrip line,” Electron. Lett. , Vol. 38, No. 19, 1109–1120, 2002. [14] Hamad, E. K. I. , Safwat, A. M. E. and Omar, A. S. , “Controlled capacitance and inductance behaviour of L-shaped defected ground structure for coplanar waveguide,” IEE Proc. Microwave Antennas Propag. , Vol. 152, No. 5, 299–304, October 2005. [15] Guha, D. , Biswas, S. , Biswas, M. , Siddiqui, J.Y. and Antar, Y.M. M. , “Concentric Ring-Shaped Defected Ground Structures for Micro- strip Applications”, IEEE Antennas and Wireless Propagation Letters, vol. 5, 2006 [16] Woo, U. , Lee, T.K. , Pyo, C.S. and Choi, W.K. , “high-q band rejection filter by using u-slot DGS”, Microwave Conference, 2005 Europian , Vol.2, oct 2005. [17] Ting, U.S.W. , Tam, K.W. and Martins, R. P. , “Miniaturized Micro- strip Lowpass Filter With Wide Stopband Using Double Equilateral U-Shaped Defected Ground Structure”, IEEE Microwave and Wireless Components Letters, vol. 16, no. 5, may 2006 [18] Woo, D.J. , Lee,T.K. , Lee,J.W. , Pyo, C.S. and Choi, W.Q. , “Novel U- Slot and V-Slot DGSs for Bandstop Filter With Improved Q Factor”, IEEE Transactions on Microwave Theory and Techniques, vol. 54, no. 6, june 2006 [19] Dahlan, S.H. , Aizam, S. , Shipun, E.A.H. , “Stepped hairpin shape defected ground structure (SH-DGS) study”, Asia-Pacific Confer- ence on Applied Electromagnetics, 2007. APACE 2007. , pp 1–5, December 2007. [20] Boutejdar, A. Batmanov, A. Elsherbini, A. Burte, E.P. Omar, A.S. , “Anew compact tunable bandpass filter using defected ground structure with active devices”, Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE, pp.1–4, July 2008. [21] Zulkifli, F.Y. , Rahardjo, E. T. and Hartanto, D. , “Radiation proper- ties enhancement of triangular patch microstrip antenna array using hexagonal defected ground structure”, Progress in Electromagnetics Research, vol. 5, 101–109, 2008 [22] Chen,H.J. , Tsung H. , Chang, C. S. , Chen, L. S. , Wang, N.F. , Wang, Y.H. and Houng, M.P. , “a novel cross-shape DGS applied to design ultra-wide stopband low-pass filters “IEEE Microwave and Wireless Components Letters, vol. 16, no. 5, may 2006 [23] Xue, Q. , Shum, K. M. and Chan, C. H. , “Novel 1-D microstrip PBG cells,” IEEE Microwave and Guided Wave Letters, Vol. 10, No. 10, 403–406, Oct. 2000. [24] Chen, J. , Weng, Z. B. , Jion, Y. C. and Zhang, F. S. , “Lowpass filter design of hilbert curve ring defected ground structure,” Progress In Electromagnetics Research, PIER 70, 269–280, 2007. [25] Lim, I.-S. , Kim, C.S. , Lee, Y.T. , Ahn, D. and Nam, S. , “Vertically periodic defected ground structure for planar transmission lines”, Electronics Letters, Vol. 38, No. 75, 803–804, July 2002. [26] Kim, C.S. , Park, J.S. , Ahn, D. , and Lim, J. B. , “A novel 1- D periodic defected ground structure for planar circuits,” IEEE Microwave and Guided Wave Letters, Vol. 10, No. 4, 131–133, April 2000. [27] Radisic, V. , Qian, Y. and Itoh, T. , “Broadband power amplifier using dielectric photonic bandgap structure,” IEEE Microwave Guide Wave Letters. , Vol. 8, 13–14, Jan. 1998. [28] Lim, J.S. , Lee, Y.T. , Han, J.H. , Park, J.S. , Ahn, D. , Nam, S. , “Application of defected ground structure in reducing the size of amplifiers”, IEEE Microwave and Wireless Component lett. , Vol.12, No.7, July 2002. [29] Lim, J. S. , Lee, S. W. , Kim, C. S. , Park, J. S. , Ahn, D. , and Nam, S. W. , “A 4:1 unequal Wilkinson power divider,” IEEE Mcrowave and Wireless Components Lett. , Vol. 11, No. 3, 124–126, March 2001. [30] Kim, D.J. , Jeong,Y. , Kang,J.H. , Kim,J.H. , Kim,C.S. , Lim, J.S.and Ahn, D. , “ A Novel Design of High Directivity CPW Directional Coupler Design by Using DGS”, IEEE Conference, pp-1239-1242, 2005 Frequenz 64 (2010) 5 – 6 83 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM [31] Jemg,S. , Hwang,D. , Jeong, Y.C. , Kim, C.D. , “Amplifier Design using h/4 High Impedance Bias Line with Defect Ground Structure (DGS)”, IEEE SlTT-S , pp-1161-1164, 2002 [32] Tokomitsu, T. , Hara, S. , Tekenaka, T. , Aikawa, M. , “Divider and combiner line-unified fets as basic circuit function modules-part -I,” IEEE Transactions on Microwave Theory and Techniques, vol. 38, no. 9, september 1990 [33] Oskouei, H.D. , Forooraghi, K. and Hakkak, M. , “Guided and leaky wave characteristics of periodic defected ground structures”, Prog- ress in Electromagnetics Research, PIER 73, 15–27, 2007 [34] Liu,H. , Li, Z. and Sun, X. , “ Compact defected ground structure in microstrip technology”, IEEE, Electronics Letters vol. 41 no. 3, february 2005 [35] Liu, H. , Li, Z. , Sun, X.W. , Kurachi, S. , Chen,J. ,and Yoshimasu, T. ,“theoretical analysis of dispersion characteristics of microstrip lines with defected ground structure”, Journal. of Active and Passive Electronic Devices, vol. 2, pp. 315–322,2007 [36] Rahman, A. , “Design and Development of High Gain Wideband Microstrip Antenna and DGS Filters Using Numerical Experimen- tation Approach”, Dissertation, Magdeburg, 2005 [37] Yun, J. and Shin, P. , “Design Applications of Defected Ground Structures”, Ansoft Corporation. [38] Weng, L.H. , Guo, Y.C. , Shi, X.W. and Chen, X. Q. , “An Overview of Defected Ground Structure”, Progress in Electromagnetics Research B, Vol. 7, 2008. [39] Roy, S.M. , Karmakar, N.C. , Balbin, I. , “Quasi-Static Modeling of Defected Ground Structure”, IEEE Transaction on Microwave Theory and Technique, vol.54, no.5, pp.2160–2168, may 2006. [40] Roy, S.M. , Karmakar, N.C. , Balbin, I. , “Dumbbell-shaped defected ground structure,” International Journal of RF and Microwave Computer-Aided Engineering, Volume 17 Issue 2, Pages 210 – 224, 2007. [41] Wong, C.C. and Free, C.E. , “DGS pattern with enhanced effective Capacitance”, Electronics Lett. 13th Vol. 42 No. 8, pp. April 2006. [42] Patnaik, A. , Mishra, R.K. , Patra, G.K. , Dash, S.K. , “An artificial neural network model for effective dielectric constant of microstrip line,” IEEE Trans. on Antennas Propagation, Vol. 45, no. 11, p. 1697, November 1997. [43] Lim,J.S. , Lee,Y.T. , Han, J.H. , Park,J.S. , Ahn, D. and Nam, S. , “A Technique for Reducing the Size of Amplifiers Using Defected Ground Structure”, IEEE MTT-S, pp1153–1156, 2002. [44] Chang, I and Lee, B. , “Design of Defected Ground Structures for Harmonic Control of Active Microstrip Antenna”, IEEEConference 2002, pp 852–855. [45] Liu, H. , Sun, X. and Mao, J. , “harmonic suppression with photonic bandgapanddefected groundstructure for a microstrip patch,” IEEE Microwave and Wireless Component Letters, pp.1–2, 2005. [46] Sung, Y. J. , Kim, M. and Kim, Y.S. , “Harmonics Reduction With Defected Ground Structure for a Microstrip Patch Antenna”, IEEE Antennas and Wireless Propagation Letters, vol. 2, 2003 [47] Isik,O. , Esselle, K.P. , and Ge,Y. , “Harmonic control of active microstrip antennas using spiral defected ground structures” , 10th Australian Symposium on Antennas, Sydney, Australia, 14–15 Feb. 2007 [48] Sun, J. , Yang, X. and Sheng, J. , “Circularly polarized microstrip antenna with harmonics suppression”, Microwave and Optical Technology Letters, Vol. 49, No. 11, November 2007 [49] Guha,D. , Biswas, M. and Antar, Y.M.M, “Microstrip patch antenna with defected ground structure for cross polarization suppression”, IEEE Antenna and Wireless Propagation Lett, Vol.4, pp.455–458, 2005. [50] Salehi,M. , Motevasselian, A. , Tavakoli,A. , Heidari, T. , “Mutual coupling reduction of microstrip antenna using defected ground structure”, IEEE Singapore International Conference on Communi- cation System, pp. 1–5, 2006. [51] Thakur, J.P. and Park, J.S. , “An Advance Design Approach for Circular Polarization of the Microstrip Antenna With Unbalance DGS Feedlines”, IEEE Antennas and Wireless Propagation Lett. vol. 5, 2006 [52] Moghadas,H. , Tavakoli, A and Salehi, M. , “Elimination of scan blindness in microstrip scanning array antennas using defected ground structure” Int. J. Electron. Communication. (AEÜ) 62 pp.155–158, 2008 [53] Zhao, S.C. , Wang, B.Z. and He, Q.Q. , “broadband radar cross section reduction of a rectangular patch antenna” Progress In Electro- magnetics Research, PIER 79, 263–275, 2008 First Author Ashwini K. Arya, Dept. of Electronics and Computer Engineering Indian Institute of Technology Roorkee Roorkee-247667. Uttarakhand, India. E-mail :
[email protected] Other authors Prof. Dr. M.V. Kartikeyan, Asst. Prof. Dr. A. Patnaik Dept. of Electronics and Computer Engineering Indian Institute of Technology Roorkee Roorkee-247667. Uttarakhand, India. E-mail :
[email protected] Frequenz 64 (2010) 5 – 6 84 Brought to you by | provisional account Unauthenticated | 99.28.36.139 Download Date | 7/5/14 7:45 AM