Electromagnetic Band-Gap Structures With Irregular Topologies For Ultrawideband Noise Suppression

With the emerging trend of modern convergent systems that integrate with thecomputer, communications, entertainment and other functions in one portable product,the new concept of system-on-package (SOP) has become a promising solution.However, such high-density and heterogeneous integration for SOP can lead to higherlevels of electromagnetic noise. In the meanwhile, the predicted trends of faster speed,higher frequencies and lower power consumption from the open released documentsby the International Technology Roadmap of Semiconductors (ITRS) for the futureelectronic systems mean the dramatic increase of fast transient current at highfrequencies. Hence, the simultaneous switching noise (SSN) which results from a largenumber of drivers switching between “ON” and “OFF” states simultaneously isrecognized as one of the most challenging and significant issues in modern high-speedsystems. SSN can excite cavity resonance modes within the power/ground plane pairs,causing severe power or signal integrity issues as well as electromagnetic interferenceproblems or radiated emissions. These issues cannot be ignored, and can even causemalfunction of a system.The simultaneous switching noise (SSN), also referred to as the ground bouncenoise (GBN) or delta-I (△I) noise, has been studied intensively during past decades.Many strategies have been presented to suppress SSN, but most of them are efficientonly in a limited frequency range. Recently, various electromagnetic band-gap (EBG)structures that can prevent the propagation of any surface waves in their forbiddenband-gaps have been utilized in the SSN suppression. The research work carried out inthis dissertation focuses on the technique that etches EBG structures at least in oneplane of the power/ground plane pair in the power distribution network for high-speedcircuits and mixed-signal systems to suppress noise in an ultrawideband (UWB)frequency range, with emphasis on exploring novel uniplanar EBG structures withirregular topologies and developed localization design concept. The proposed designsin this dissertation are simple, effective and have shown remarkable capabilities toeither enhance the magnitude or broaden the bandwidth in SSN suppression, and theyhave been verified by both simulation and measurement. This dissertation consists ofnine chapters forming an integrated system. The presented chapters in this dissertationare independent, but they are closely linked to each other providing a systematic approach to SSN suppression.As a whole, the core original research work presented in this dissertation can besummarized as the following three major aspects.1. Firstly, some explorations on the topic of EBG structures with irregulartopologies for UWB noise suppression in high-speed circuits have been done. Severalnovel EBG structures with irregular topologies have been proposed in this dissertation,including two leafy EBG structures, two wavy EBG structures and a few EBGstructures using fractal high impedance topologies with different iterations. Then, theseEBG structures have been applied to suppress SSN in high-speed circuits. They aredone by etching EBG structures on the whole power plane of the power/ground planepair. These designs have exhibited good performance in UWB SSN suppression, andtheir effective suppression bandwidth can be ranged from several megahertzs (MHz) to20GHz. All these results have shown the potential of EBG structures with irregulartopologies in UWB SSN suppression for high-speed circuits; they provide the impetusfor us to do further research on the effectiveness of the less-known Sierpinskispace-filling curves and special fractal constructions to suppress noise in the followingaspects. For completeness, the mathematical fundamentals and applications of fractalshave been summarized.2. Secondly, the Sierpinski space-filling curves, a special type of fractalconstructions and less known to engineers, have been introduced in detail and havebeen applied to suppress SSN for high-speed circuits for the first time in the world.Good performance has been obtained. Motivated by the potential RF/microwaveapplications of Sierpinski curves and the less accuracy of formulas in the book byCundy et al., a clear derivation for the formulas showing the basic properties ofSierpinski curves is presented from a geometrical point of view. As at present there arefew publications on the Sierpinski curves, the mathematical background of Sierpinskicurves is introduced in detail. These contents play a useful supplementary role for theinterested researchers. After that, Sierpinski curves with different iterations areemployed to construct novel EBG structures. These EBG structures are also etched onthe whole power plane of the power/ground plane pair to suppress SSN in high-speedcircuits. Both simulated and measured results verify the efficiency of these designs.They also show the potential of Sierpinski curves in noise suppression. Especially forthe Sierpinski curve with one iteration, after integrating with effective bridges usingmeander lines, it exhibits remarkable capabilities in noise suppression; the-50dBnoise suppression bandwidth can be broadened from263MHz to19GHz. It is worth mentioning that the proposed EBG structures using Sierpinski curves and theirmodifications or the Sierpinski curves with different iterations and their improvementsmay be applicable to other subject areas.3. Finally, in view of practical engineering considerations, the effectiveness ofemploying localization concepts in noise suppression for high-speed mixed-signalsystems has been discussed. For the further investigation of Sierpinski curve’spotentiality in SSN suppression, the Sierpinski curve with one iteration is also utilizedin the designs of this aspect. At the beginning, the named “array” localization concepthas been investigated and two novel array designs etching EBG structures withdifferent topologies in the region of noise source and noise-sensitive devices areproposed. Both results of numerical simulation and experimental measurement haveshown the good performance of these two novel designs in SSN suppression for themixed-signal systems. After that, a more concise localization concept that etches EBGstructures only in the region of noise source on the power plane of the power/groundplane pair is proposed. To verify the efficiency of this novel concept, two localizeddesigns including the6-cell EBG localized design and4-cell EBG localized design areput forward. From the results of simulation and measurement, the two proposeddesigns can suppress noise in the UWB frequency ranges from less than200MHz to20GHz which nearly cover the whole noise band in the UWB application. It is knownthat the excessive discontinuities introduced by the method employing EBG structuresfor noise suppression usually can cause signal integrity issues, resulting in limitationsin practical engineering. Hence, to further study the feasibilities of the proposedlocalization concept in practical engineering, the signal integrity on the two proposeddesigns are measured. From the measured data, the designs cannot only satisfy thedemands of UWB noise suppression but also keep the quality of signal propagation.Especially for the proposed4-cell EBG design, from the measured eye diagrams, littledegradation on the propagation quality of high-speed signals can be observed when thesingle-ended traces pass over the power/ground plane pair with the4-cell EBGlocalized design. It is worth emphasizing that there are fewer measured eye diagramspresented in the publications while most are simulated eye diagrams. For the samedesign, the measured eye diagrams are usually worse than the simulated eye diagrams.But the measured results including the eye-diagrams in this aspect are based on theactual PCB board. Therefore, the proposed new localization concept has some practicaland instructional significance for practical engineering applications.