174 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 15, NO. 3, MARCH 2005

A Novel Power Plane With Super-WidebandElimination of Ground Bounce Noise

on High Speed CircuitsTzong-Lin Wu, Senior Member, IEEE, Chien-Chung Wang, Yen-Hui Lin, Ting-Kuang Wang, and George Chang

Abstract—A novel L-bridged electromagnetic bandgap (EBG)power/ground planes is proposed with super-wideband suppres-sion of the ground bounce noise (GBN) from 600 Mz to 4.6 GHz.The L-shaped bridge design on the EBG power plane not onlybroadens the stopband bandwidth, but also can increase the mu-tual coupling between the adjacent EBG cells by significantly de-creasing the gap between the cells. It is found the small gap designcan prevent from the severe degradation of the signal quality forthe high-speed signal referring to the perforated EBG power plane.The excellent GBN suppression performance with keeping reason-ably good signal integrity for the proposed structure is validatedboth experimentally and numerically. Good agreement is seen.

Index Terms—Electromagnetic bandgap (EBG), ground bouncenoise (GBN), high-speed digital circuits, power integrity, signalintegrity, simultaneously switching noises.

I. INTRODUCTION

GROUND bounce noise (GBN), also known as simulta-neous switching noise (SSN), on the power/ground planes

is becoming one of the major concerns for the high-speed digitalcomputer systems with fast edge rates, high clock frequencies,and low voltage levels. The resonance modes between the powerand ground planes excited by the GBN causes significant signalintegrity (SI) problems and electromagnetic interference (EMI)issues for the high-speed circuits [1]–[3]. With fast increase ofthe clock speed of the high-speed digital circuits, the elimina-tion of this noise is essential.

Adding decoupling capacitors to create a low impedancepath between power and ground planes is a typical way tosuppress the GBN. However, in general, these capacitors arenot effective at frequencies higher than 600 MHz due to theirfinite lead inductance. Recently, a new idea for eliminating theGBN is proposed by designing electromagnetic bandgap (EBG)structure on the ground or power plane [4]–[7]. The first EBGpower/ground plane design was demonstrated with 1.7 GHzstop-band bandwidth centered at 3.77 GHz [4]. Because theGBN is dominantly distributed at the low frequency rangebelow 6 GHz [4], several researches focus on the EBG powerplane design to either lower the stop-band center frequencyor broaden the stopband bandwidth for more efficiently sup-pressing the low frequency GBN. Although a design of the

Manuscript received June 8, 2004; revised September 27, 2004. This workwas supported by the National Science Council, Taiwan, R.O.C., under GrandNSC91–2213-E-110-034. The review of this letter was arranged by AssociateEditor J.-G. Ma.

The authors are with the Department of Electrical of Engineering, Na-tional Sun Yat-Sen University, Kaohsiung 80424, Taiwan, R.O.C. (e-mail:wtl@mail.ee.nsysu.edu.tw)

Digital Object Identifier 10.1109/LMWC.2005.844216

inductance-enhanced high impedance surface (HIS) and theconcept of cascading EBG structures with different stop-bandswere proposed to achieve wider bandgap bandwidth [5], [6],there are some drawbacks. One is the substantial increase infabrication cost because three or four layers metal are neededfor implementing the HIS and much more power/ground planesarea are occupied to cascade different stop-band EBG. Theother is the performance is degraded at the transition frequencyrange between the two stop-bands for the cascading design.Furthermore, to our best knowledge, the stop-bands in theprevious designs are all distributed above 1 GHz and wouldnot cover the hundred MHz ranges, where the GBN energy isdominant.

A novel power plane designed with a coplanar EBG struc-ture is proposed in this work with 4-GHz stop-band coveringfrom 600 MHz to 4.6 GHz. Without needing three or four layersmetal, the proposed structure is based on the two-layer con-cept with designing a novel periodic EBG patterns on the powerplane and still keeping continuous for the ground plane. The unitcell of the EBG power plane is consisted of one square pad andfour L-shaped bridges on each side of the pad. The L-shapedbridges connecting between pads not only significantly broadenthe stop-band, but also keep the signal quality not degraded forthe signal traces referring to the EBG-patterned power plane dueto the increase of the mutual coupling between the neighboringpads. The distinctive behavior of the new EBG power plane bothin super-wideband suppression of the GBN and keeping good SIis validated by measurement and simulation.

II. STRUCTURE DESIGN AND GBN SUPPRESSION

A. Design Concept

Fig. 1(a) shows the proposed L-bridged EBG power/groundplanes design. The ground plane is kept continuous and ninecells EBG with L-shaped bridges are etched on the power plane.The unit cell of the L-bridged EBG and its corresponding pa-rameter notations is shown in Fig. 1(b). Compared with thetraditional coplanar EBG structure with straight bridges [7], [8],the L-shaped bridge significantly increase the effective induc-tance between adjacent cells and thus increase the stop-bandbandwidth. However, it is known that the signal quality willbe degraded as the high-speed signal refers to the perforatedreference plane such as the proposed EBG power plane. TheL-bridged EBG plane could significantly ease the damage ofthe imperfect power plane to the signal quality because themutual capacitance between adjacent cells can be increased bydecreasing the gap . Decreasing will narrow the stop-band

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WU et al.: NOVEL POWER PLANE 175

Fig. 1. Nine-cell EBG board. (a) 3-D view and the locations of three ports.(b) Parameters of a square unit cell.

Fig. 2. Comparison of jS j between the nine-cell PBG board and thereference board by the HFSS simulation and the measurement.

bandwidth for the traditional EBG structure with straight bridgedue to the decrease of the bridge length (inductance), but itseffect is relatively small for the L-shaped bridge design becausethe bridge is parallel to the edge of the cell. Fig. 1 showsan example design on a two-layer PCB with the dimension90 mm 90 mm 0.4 mm. Nine square unit cells are etchedon the power plane with their corresponding parameters30 mm, 7.5 mm, 15.2 mm, 0.1 mm, 0.2 mm,and 0.65 mm. As shown in Fig. 1(a), three ports from 1to 3 for the boards are located at (46 mm, 45 mm), (74 mm,74 mm) and (74 mm, 45 mm), respectively, for measurementof the insertion loss of the structure. The original point (0, 0) ison the left corner of the PCB board as shown in Fig. 1(a).

B. Broadband GBN Suppression

Fig. 2 shows the measured and simulated for the de-signed L-bridged EBG power/ground planes. The insertion loss

Fig. 3. Measured GBN suppression behavior for the noise excitation locatedat different locations, port2 and port3, respectively.

Fig. 4. Four layer structure with transmission line transit between theL-bridged EBG power and solid ground plane.

of the reference board with both power and ground planes beingsolid is also presented in this figure for comparison. The EM toolHFSS is used to simulate the GBN behavior of the structure.Excellent agreement between the measurement and simulationfrom dc to 6 GHz is seen. Because the dispersion property of theFR4 substrate is not considered in the modeling, slight differ-ence between them is seen at higher frequencies above 4 GHz.Compared with the reference board, it is clearly seen that theL-bridged EBG power plane behaves highly efficient GBN elim-ination with averagely 60 dB suppression in a wide-band rangefrom about 600 MHz to 4.6 GHz (4 GHz bandwidth). The band-width is defined by the insertion loss lower than 30 dB.

Fig. 3 shows the measured GBN suppression behavior for thenoise excitation located at different locations, port2 and port3,respectively. The receiving port is all at port1. It is seen thatthe broadband GBN suppression behavior is almost the samefor different excitation location of excitation. It implies that thelow-period EBG power planes can omni-directionally eliminatethe GBN on the power/ground planes.

III. SIGNAL INTEGRITY FOR THE EBG POWER PLANE

Although the novel EBG power plane demonstrates superwideband suppression of the GBN with a cost effective designof using only two layers metal, the degradation of the perforatedpower plane to the signal quality is needed to be evaluated.As shown in Fig. 4, we consider a signal trace of 80 mmpassing from the first layer to the fourth layer and back tothe first layer with two via transitions along the path. Thesecond and third layer is the L-bridged EBG power and solid

176 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 15, NO. 3, MARCH 2005

Fig. 5. Simulated eye patterns for (a) the reference board and (b) the proposedEBG board.

ground planes, respectively. The eye patterns at the outputport (port 2) are simulated. The of the signal path isnumerically calculated. The SPICE-compatible models are thenextracted from the -parameter by a commercial tool SIDEA.According to the broadband SPICE models, the eye patternsare generated in the HSPICE environment with launching apattern source of PRBS, nonreturn to zero (NRZ), codedat 2.5 GHz. The bit sequence swing is 500 mV and the nominalrise/fall time is 120 ps. Fig. 5(a) and (b) show the simulatedeye patterns for the reference board and the proposed EBGboard, respectively. Compared with the reference board, thereis no severe degradation of the signal quality for the proposedEBG board. Two parameters, maximum eye open (MEO) andmaximum eye width (MEW), are used to be metrics of the eyepattern quality. It is seen that for the reference board435 mVand 358 ps, and for the EBG board402 mV and 345 ps. The degradation of the MEO

and MEW for the proposed EBG board is about 7.5% and3.6%. The SI performance will be better if the signal trace isshorter or the data transmission rate is slower than 2.5 Gbps.

IV. CONCLUSION

A novel L-bridged EBG power plane is proposed in this paperwith super-wideband suppression of the GBN from 600 Mz to4.6 GHz. Compared with previous designs, this novel structureprovides three advantages. First, the L-bridged power plane sig-nificantly broadens the stop band bandwidth to 4 GHz and cancover to the low frequency range of 600 MHz. Second, the signalquality is still kept acceptably good for the signal referring tothe perforated EBG power plane. Third, it is cost effective be-cause only two layer metals are needed to design this novelpower/ground planes structure. The excellent performance ofthe low-period PBG power planes is investigated both by mea-surement and simulation.

REFERENCES

[1] S. Van den Berghe, F. Olyslager, D. De Zutter, J. De Moerloose, and W.Temmerman, “Study of the ground bounce caused by power plane reso-nances,” IEEE Trans. Electromagn. Compat., vol. 40, no. 2, pp. 111–119,May 1998.

[2] G.-T. Lei, R. W. Techentin, and B. K. Gilbert, “High frequency char-acterization of power/ground-plane structures,” IEEE Trans. Microw.Theory Tech., vol. 47, no. 5, pp. 562–569, May 1999.

[3] T. L. Wu, S. T. Chen, J. N. Huang, and Y. H. Lin, “Numerical and exper-imental investigation of radiation caused by the switching noise on thepartitioned dc reference planes of high speed digital PCB,” IEEE Trans.Electromagn. Compat., vol. 46, no. 1, pp. 33–45, Feb. 2004.

[4] R. Abhari and G. V. Eleftheriades, “Metallo-dielectric electromagneticbandgap structures for suppression and isolation of the parallel-platenoise in high-speed circuits,” IEEE Trans. Microw. Theory Tech., vol.51, no. 6, pp. 1629–1639, Jun. 2003.

[5] T. Kamgaing and O. M. Ramahi, “A novel power plane with inte-grated simultaneous switching noise mitigation capability using highimpedance surface,” IEEE Microw. Wireless Compon. Lett., vol. 13, no.1, pp. 21–23, Jan. 2003.

[6] S. Shahparnia and O. M. Ramahi, “Simultaneous switching noise miti-gation in PCB using cascaded high-impedance surfaces,” Electron. Lett.,vol. 40, no. 2, Jan. 2004.

[7] T. L. Wu, Y. H. Lin, and S. T. Chen, “A novel power planes with lowradiation and broadband suppression of ground bounce noise using pho-tonic bandgap structures,” IEEE Microw. Wireless Compon. Lett., vol.14, no. 7, pp. 337–339, Jul. 2004.

[8] F. R. Yang, K. P. Ma, Y. Q., and T. Itoh, “A uniplanar compact photonic-bandgap (UC-PBG) structure and its applications for microwave circuit,”IEEE Trans. Microw. Theory Tech., vol. 47, no. 8, pp. 1509–1514, Aug.1999.