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A new logarithmic method to minimize the size of low-pass filter using multilayer and defected ground structure technique

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ABSTRACT: A novel three-pole low-pass filter is designed employing metal-loaded slots etched in the ground plane, and low impedance microstrip line as microstrip capacitor. An equivalent circuit model of a defected ground structure (DGS) is applied
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  F    o  r    P    e  e  r    R   e  v   i    e  w      A New Logarithmic Method to Minimize the Size of Low-PassFilter Using Multilayer- and Defected Ground Structure-Technique     Journal: Microwave and Optical Technology Letters  Manuscript ID: DraftWiley - Manuscript type: Research ArticleDate Submitted by theAuthor:n/aComplete List of Authors: Boutejdar, Ahmed; University of Magdeburg, Electrical EngineeringIESKOmar, Abbas; University of Magdeburg, Electrical EngineeringBurte, Edmund; University of Magdeburg, SemiconductorTechnologyBatmanov, Anatoliy; University of Magdeburg, SemiconductorTechnologyMikuta, Reinhard; University of Magdeburg, SemiconductorTechnologyKeywords:Low-pass filter, Defected ground structure (DGS), Logarithmicfunction, Multilayer, Compactness John Wiley & SonsMicrowave and Optical Technology Letters  F    o  r    P    e  e  r    R   e  v   i    e  w    A New Logarithmic Method to Minimize theSize of Low-Pass Filter Using Multilayer- andDefected Ground Structure-Technique ABSTRACT :  A novel three-pole low-pass filter isdesigned employing metal-loaded slots etched in theground plane, and low impedance microstrip line asmicrostrip capacitor. An equivalent circuit model of adefected ground structure (DGS) is applied to study thecharacteristics of DGS. Parameters of the model areextracted from the EM simulation results by matching it to a one-pole Butterworth low-pass filter. The theory isvalidated against the commercial Microwave Office. Thenew LPF is very compact, and provides sharp transitionband and a wide stop-band. Additional to the newmathematical method (natural logarithm function), amultilayer technique will be used in order to improve thecompactness of the structure. Finally, the proposed structure is implemented and the measurement results are found to be in good agreement with the simulationresults. Key words: low-pass filter; defected ground structure (DGS);logarithmic function; stop-band; multiplayer; compactness   1. INTRODUCTION R ecently, defected ground structures (DGSs) have beengaining interests for its planar structure and easy fabricationwith photolithographic technique. Period or non-periodicDGSs show property of rejecting microwave in somefrequency, so it has a potentially great applicability torestrain spurious response by rejecting harmonic in themicrowave circuits. Any defect etched in the ground planeof the microstrip line disturbs its current distribution andcan give rise to increasing effective capacitance andinductance . A broader area attached to simple slot headsetched in the ground plane of a microstrip line increasesits effective length [1-3]. In [2-6], it is shown that avariety of attached area shapes such as square, circular,etc. have different effects. The specified structures, showa narrow width stop-band and is not therefore useful forLPF design, harmonics suppressions, or broad out of band rejection. In the first part of this paper, a new procedure fordesigning compact low-pass filters with a wide stop-bandis presented. It uses a DGS cell which is not of theconventional triangular shape, but a π   -arrowhead slot.As has been proved in previous works, the area of thishead has a great influence on the response improvement.In the second part, a filter which is composed of threeDGS slots is presented. Moreover, its equivalent circuitis determined using the extraction method. In the thirdpart, we present a compact low-pass filter with itscorresponding equivalent circuit. In order to verify theimproved performance of the proposed multilayer LPF incomparison with the conventional cascaded low-passfilter, the new low-pass filter has been designed,fabricated and measured. Measurements show that thelatter exhibits better performance by suppressing ripplesand enlarging the stop-band. In the fourth part, we haverealized a new band-pass filter, through a modification inthe geometrical construction of the multilayer Low-passfilter. 2. FREQUENCY CHARACTERISTICS OF DGS The lower part   of Figure 1(a) shows a π   -arrowhead-typeDGS cell with a 50-Ohm microstrip line on top. The DGSis etched in the bottom metallic ground plane [4-11]. Thesimulation is done for a substrate with ε  r  and h = 0.0813cm. The DGS is simulated using AWR MicrowaveOffice. The slot-head area basically controls theinductance, whereas the width g of the connectingrectangular slot controls the capacitance (see Figure1(b)).It has been noticed that the variation of the gap has asmall influence on the performance of the slot. On theother hand, in order to investigate the effect of the headarea, which is connected with the gap capacitance, g waskept constant at 0.6mm and the head area was varied. 3. EQUIVALENT CIRCUIT MODEL ANDPARAMETER EXTRACTION In order to calculate the equivalent circuit parameters,the resonance and the cutoff frequencies will be obtainedfrom the S -parameters simulation results. Then, equatingthe cutoff and resonance frequencies of the simulation tothose of the equivalent circuit, two linear equations in twounknowns (the equivalent circuit parameters  L , C  ) will beobtained. By solving the two equations simultaneously, 1 Ahmed Boutejdar, 1 Abbas Omar, 2 Edmund Burte, 2 Anatoliy Batmanov, and 2 Reinhard Mikuta 1 Chair of Microwave and Communication Engineering 2 Chair of Semiconductor Technology   Otto von Guericke University Magdeburg, GermanyAhmed.Boutejdar@ovgu.de   Page 1 of 9John Wiley & SonsMicrowave and Optical Technology Letters 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960  F    o  r    P    e  e  r    R   e  v   i    e  w    we will obtain the equivalent circuit parameters  L and C   [12-14]. g 1   = 2 one-pole Butterworth prototype LPF. As thetriangle dimension a is increased, keeping the value of  g  constant, the equivalent inductance increases, so the polefrequency moves to a lower frequency, as illustrated inFigure 2. Also, because of the cascading, a large stop-band can be realized. The simulated results show that thechange of the DGS-dimensions allows the control of theresonance frequency of the structure. This characteristicswill be used in order to choose easy the work area of theproposed filter. 4. CONVENTIONAL CASCADED LOW-PASSFILTER STRUCTURE A schematic diagram of the periodic DGS with thesame arrowhead slot for planar circuit is shown Figure 3.The DGS-filter has a 50-Ohm microstrip line and threecascaded identical arrowhead-slot elements separated bythe same distance p = 5.2 mm. Figure 4 shows thesimulations results of this cascaded low-pass filter 3.order. 5. DESIGN OF THE LOGARITHMIC CASCADEDLPF Based on the first structure, the uniform distribution of three arrowheads is replaced by a non-uniformdistribution as shows Figure 5. The area of the π   -arrowheads is varied proportionally to the relativeamplitudes distribution of the logarithmic function[ln(10)] 1/n .In the method of distribution the areas is defined asfollows:In this work, we have a Low-pass filter with three DGS,then n (the number of resonators minus one). In our casethe n is equal 2 and the relative amplitudes are calculatedas follows:by comparing the corresponding ratios, the optimum headareas have been calculated as follows: F  1   = 9mm 2 F  0   =   6mm 2   F  1   = 9mm 2  Based on this logarithmic structure (structure 2), wecould better improve S 11 in the lower frequency domainas compared with the conventional LPF structure asshown in Figure 6.In Figures 7(a) and 7(b) are depicted the current densitydistributions at transmission zero or attenuation pole andat pass-band. Figure 7(a) shows the filter response at  f  =1.5 GHz (pass-band). The power is transmitted betweenthe input and output, thus the filter loss is zero. On theother hand, as the Figure 7(b) shows, the power is fullreflected at  f  = 8 GHz (reject-band), which means, thatthe filter has infinite loss (or attenuation) in the stop-band. Based on structure 2, we have designed anotherimproved cascaded open-stubs filter with the sameperiodic DGS as structure 3. The bottom of the metallicground plane includes three non-uniform arrowheadelements separated by a distance  p = 5.2 mm and the gapdistance g is kept constant. On the top, the compensatedmicrostrip line was replaced by open-circuited stubs,which are represented by two capacitances C  1 = C  2 asshown in Figure 8, [5]. The design of this filter has beendone using Microwave Office, and TX-Line. 6. DESIGN OF THE IMPROVED MULTILAYERLPF We’ll presented here a design similar to structure 3, asshown in Figure 9. This new structure (structure 4) hasthe same dimensions as the preceding structure (structure3), except that the central DGS is shifted towards the toplayer as Figure 9(a) shows. This new modification of theequivalent circuit does not have a significant influence onthe performance of the filter as compared to the previousones. We can therefore use the top layer without having agreat modification on the response of the filter. Figure 10shows the corresponding results.In order to further improve the compactness of the laststructure (structure 4), without having a greatmodification on its geometry or performance, thecapacitors C  1 and C  2 , which are dominated by the topresonator and play a negligible role, will be eliminated asshown in Figure 9(b). A simple and more compactstructure (structure 5) (as compared with the preceding )(11112 000 ω ω ω ω ω ω ω π  ω  −=⇒+=≈+== =  →   ∞ C  X  L jC  j jB R jB X Y  f   LC  LC  LC  ( ) ( )  )(1 220100001001 cccc L LC cc g Z C C  X  X g Z  L  Z  Lg eqc ω ω ω ω ω ω ω ω ω ω  ω ω  −=⇒−====⇒= = (2)(3)(1) ( ) [ ] ( ) [ ] ( ) [ ] ( ) [ ] ( ) [ ] 1111111 10ln...10ln10ln10ln...10ln −− nnn ( ) [ ] ( ) [ ] ( ) [ ] .302.210ln ,517.110ln ,302.210ln 1211 === (7)(8)(9) 2020200 1known thenis C  11 1 ω ω ω ω  C  L LC C  LC  L =⇒=⇒=⇒= (4)(5)(6) Page 2 of 9John Wiley & SonsMicrowave and Optical Technology Letters 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960  F    o  r    P    e  e  r    R   e  v   i    e  w    one (structure 4)) is obtained. The same field simulations,as in chapter V, has been done, in order to investigate thefrequency behaviors of this new structure in the bothfrequency domains, as the Figure 11 shows. 7. FABRICATION OF FILTERS ANDMEASUREMENT The following multilayer cascaded low-pass filters havebeen fabricated and measured in order to compare theirperformance:1)   Conventional microstrip cascaded-LPF.2)   Microstrip open-stub-cascaded LPF.3)   Microstrip Mutilayer without open-stub LPF.The structural details with physical dimensions of thefabricated Low-pass filters are shown in Table I. and inFigures 12 and 13 show the fabricated filter and thesimulation and measurement results respectively. As canbe seen from the results, the insertion loss from DC to 4.8GHz is less than 0.4 dB and the return loss is better than30 dB in the entire pass-band, which represent. The majorimprovements offered by these LPFs.As we said before, in order to reduce the size of theproposed structure, a simple multilayer technique wasused, as shown in Figures 12 and 14. The method isdetermined as following: The centered DGS resonator isshifted to upper layer and the both DGS-resonators willbe placed as cascaded side by side [8-10]. The advantageof this topology is that the size will be reduced up to 35%in comparison to the conventional filter (structure 3 inFigure 8). The combination of the DGS-, multilayer- andexponential method allows a realization of a LPFstructure with sharp cutoff dropping from less than 3 dBto almost 33 dB within a range of 3 GHz and a stop-band of almost 5 GHz . The proposed LPF structures 4, 5are up to 50% more compact than the conventionalcascaded LPF (structures 1, 2 and 3). The Figures 14 and15 and Figures 2 and 3 shown the comparison betweenthe improved und conventional structures. 8. CONCLUSION A new type of compact LPF using only two DGS andone top π   -arrowhead resonator has been proposed. Toverify the performance, the filter has been fabricated,simulated and measured. The measurements show goodconsistency with the simulation. Additional to compactsize, the low-pass filter also has low insertion loss in thepass-band and very high rejection in the stop-band. The35% compact size, sharp cutoff frequency response andhigh harmonic suppressions would make the introducedDGS meet the requirements of modern wirelesscommunication systems. ACKNOWLEDGEMENT The authors are grateful to administrator Mr. D.Winkler for his computer assitance and Rodieck andDempewolf, the lab managers of the Institute forElectronics, Signal Processing and Communication(IESK) at the University of Magdeburg, Germany. REFERENCES [1] Ahmed Boutejdar; Batmanov, Anatoliy; Omar, Abbas;Burte, Edmund P., (  Book Chapter  ) A miniature 3.1 GHzmicrostrip bandpass filter with suppression of spuriousharmonics using multilayer technique and defected groundstructure open-loop ring" In: Ultra-wideband, short-pulseelectromagnetics 9 . - New York, NY : Springer, ISBN978-0-387-77844-0, S. 191-200, 2010 Kongress:Conference on Ultra-Wideband Short-PulseElectromagnetics; 9 (Lusanne).[2] D. Ahn, J. S. Park, C.S. Kim, J. Kim, Y. Qian and T. Itoh,“A design of the low-pass filter using the novel microstripdefected ground structure”,  IEEE Trans. MicrowaveTheory Tech. , vol.49, n.1, pp. 86-93, Jan. 01.[3] Ahmed Boutejdar, Abbas Omar and Edmund Burte,Miniaturized Low-pass and Bandstop Filters UsingControlled Coupling of Open-Loop-Ring Defected GroundStructure (DGS),  Microwave and Optical Technology Letters , Vol. 52, No. 11, November 2010 2575.[4] V. Radisic, Y. Qian, R. Coccioli, and T. Itoh, “Novel 2- Dphotonic bandgap structure for microstrip lines,”  IEEE  Microw. Guided Wave Lett  ., vol. 8, no. 2, pp. 69–71, Feb.1998.[5] A. Boutejdar, A. Adel Rahman, A. Batmanov, A. S. Omarand E. Burte Miniaturized Band-Stop Filter Based onMultilayer- Technique and New Coupled OctagonalDefected Ground Structure (DGS) With InterdigitalCapacitor  Microwave and Optical Technology Letters ,Volume 52, Issue 3, pp: 510-514, March 2010[6] A. Abdel-Rahman, A. K. Verma, A. Boutejdar and A. S.Omar Control of bandstop response of Hi-Lo microstripLow-pass filter using slot in ground plane  IEEE Trans. Microwave Theory Tech ., vol. 52, pp. 1008-1013, 2004[7] J. S. Park and M. S. Jung, “A novel defected groundstructure for an active device mounting and it applicationto a microwave oscillator”  IEEE Microwave WirlessComp. Lett. , vol. 14, pp. 198-200, May. 2004.[8] A. Boutejdar, G. Nadim, S. Amari and A.S. Omar,”Controlof bandstop response of cascaded microstrip Low-passbandstop filters using arrowhead slots in backside metallicground plane,“  IEEE AP-S Symp. (Washington DC),2005.[9] Ahmed Boutejdar “Design of A New Compact Dual-ModeMulti-Band Bandpass Filter Using Multi-Armed Ring-Open-Loop Resonators Without Coupling Gaps”,  Microwave and Optical Technology Letters , Volume 52,Issue 12, pages 2668-2672, December 2010.[10] J. S. Lim, C. S. Kim, Y. T. Lee, D. Ahn, and S. Nam “Anew type of Low-pass filter with defected groundstructure,” in Proc. 32 nd  Eur. Microwave Conf  ., Sep. 2002,pp. 32–36.[11] E. Yablonovitch, “Photonic band-gap structures, “J. Opt.Soc. Amer. B, Opt. Phys ., vol. 10, pp. 283-295,Feb.1993.[12] A. Boutejdar, S. Amari and A. S. Omar A Novel CompactJ-Admittance Inverter-Coupled Microstrip Bandpass FilterTable I. Dimensions of the proposed filters   Item Dimensions in mm & in mm 2 Conventional LPF w = 1.9 , a = 4.8,  p   = 5.2Open-stub-cascaded LPF F  0   = 6, F  1   = 9, g = 0.6,  L 1   = 3.6  L 2   = 2.4Mutilayer-without open-stub LPF r  = 6.9 , n = 2 Page 3 of 9John Wiley & SonsMicrowave and Optical Technology Letters 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960  F    o  r    P    e  e  r    R   e  v   i    e  w    Using Arrowhead-Shape As Defected Ground Structure(DGS)  Microwave and Optical Technology Letters ,Volume 52, Issue 1, pp: 34- 38, January 2010[13] Ahmed Boutejdar, Adel Rahman, and Anatoliy Batmanov,Abbas Omar and Edmund Burte, Miniaturized Band-StopFilter Based on Multilayer-Technique and New CoupledOctagonal Defected Ground Structure (DGS) WithInterdigital Capacitor,  Microwave and Optical Technology Letters , Volume 52, Issue 3, pp: 510-514, March 2010.[14] Ahmed Boutejdar, Anatoliy Batmanov, Edmund Burte andAbbas Omar, Design of a New Bandpass Filter with SharpTransition Band Using U-Defected Ground Structure(DGS) and Multilayer-Technique,  IET Microwave, Antennas and Propagation , Volume 4, Issue 9, pp: 1415-1420, September 2010 Figure captions Fig.1. The proposed DGS unit section. (a) Three-dimensional view of the π   -arrowhead Slot, (b) lumped-element circuit model of theslot. resonator.Fig. 2. Simulated S 12 -parameters for different values of a.Fig. 3. Schematic views of the cascaded DGS-filter (structure1).Fig. 4. Simulated S -parameters of the cascaded DGS-filter (structure1).Fig. 5. Schematic views of the cascaded DGS-filter (structure2). Fig. 6. Comparison between the S -parameters of structure 1, 2 , 3 . Fig. 7. Magnetic field distribution results: (a) The pass-band at 1.5 GHzand (b) the stop-band at 8 GHz.Fig. 8. Schematic view of the cascaded DGS-filter (structure 3). Fig. 9. Schematic views of cascaded DGS-filter. (a) Structure 4 and (b)structure 5.Fig. 10. Simulated S-parameters for (a) structure 4 and (b) structure 5.Fig. 11. Magnetic field distribution results: (a) The pass-band at 1.5GHz, (b) the stop-band at 8 GHz.Fig. 12. Fabricated DGS-LPF with open-stubs. (a) Top view, (b) bottomview.Fig. 13. Measured and simulated S -parameters of the multilayer-LPFwith open-stubs.Fig. 14. Fabricated DGS-LPF without open-stubs. (a) Top view, (b)bottom view.Fig. 15. Measured and simulated S -parameters of the multilayer-LPFwithout open-stubs. Page 4 of 9John Wiley & SonsMicrowave and Optical Technology Letters 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960
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