Investigations On Signal Integrity Of High-Speed Interconnects And Systems

With the increase of clock frequency and edge rates in high-speed digital systems, high-speed signal experience delay, reflection, attenuation, crosstalk, dispersion in high-speed interconnect, which get more critical and become domain in signal integrity design. The signal integrity problems are electromagnetic(EM) problems in nature. In order to take complex electromagnetic effects into account, full-wave EM analysis based on EM theory must be resorted. Around the topic of EM modeling and simulation, high-speed interconnects and 500Mbps high-speed system have been analyzed for signal integrity issues in frequency and time domain, which incorporated circuit and system analysis methods and experiment measures. They mostly study how the transmission of high-speed signal is effected in interconnects circuit. Then design guidelines for improved signal integrity are derived from the results obtained. Thereby, the design of high-speed circuits can be guided to solve signal integrity issues. The goal of signal integrity analysis is to ensure reliable high-speed data transmission. The main fruit of this dissertation on both theory and applications are listed as follows:1. The expressions of mixed-mode S-parameters for various topologies differential circuits are developed and the corresponding transformation between standard S-parameters and mixed-mode S-parameters is developed. The cascade formulas for mixed-mode S-parameters of these differential circuits are theoretically deduced. The concept of mixed-mode S-parameters are applied into high-speed differential interconnects and 500Mbps high-speed system for signal integrity analysis.2. The microstrip lines and other kinds of transmission lines will be analyzed and their effects on signal integrity will be discussed, which commonly found on high-speed interconnects. The used microstrip interconnects have the following characteristics: various characteristic impedance, length, dielectric thickness and relative dielectric permittivity. The used other kinds of transmission lines are chosen to achieve the comparison: grounded co-planar waveguides (GCPW), striplines, coated-microstriplines. The analysis is mainly based on experiment measures which incorporated 3D full-wave EM simulation in frequency and time domain. Then the differential microstrip line and stripline will be analyzed on signal integrity by used mixed-mode S-parameters based on 3D EM simulation in frequency domain.3. Various discontinuities in high-speed interconnects will be analyzed on signal integrity. The discontinuities in high-speed interconnects are chosen: bends, steps, terminated by mismatching loads and vias. The analysis is mainly based on experiment measures which incorporated 3D full-wave EM and circuit and system simulation in frequency and time domain. Then various discontinuities in high-speed differential interconnections will be analyzed on signal integrity by used mixed-mode S-parameters which are included: bends, steps and vias. Therefore, all kinds of operation behavior are understood which high-speed signal propagation along the discontinuities in differential interconnects.4. The adaptive domain decomposition FDTD method (ADD-FDTD) is presented for solving signal integrity issues of high-speed interconnects. ADD-FDTD is more efficient in both computational time and computational complexity. In ADD-FDTD, the problem domain is broken into several independent FDTD sub-regions. The sub-regions are terminated using a single boundary condition applied simultaneously to all sub-regions providing adaptive tests between the sub-regions. When the wave is tested to propagate on the testing boundary, the corresponding sub-region along wave propagation direction is active in the iteration procedure of FDTD. Otherwise, the sub-region is sleep without involving in the field iteration. As a validation of the method, the analysis of the two-dimensional waveguide systems and 3D high-speed interconnects has been presented.5. High-speed interconnects crossing imperfect reference planes will be analyzed on signal integrity. The used imperfect reference planes are chosen: various widths and lengths of gaps, stitching capacitors crossing split reference planes, interconnections on meshed ground and differential interconnects crossing split reference planes. Then the effect of the imperfect reference planes on the couple and crosstalk between interconnections are analyzed by experiment measures. In addition, crosstalk characterization of high-speed interconnects will be analyzed based on experiment measures and simulation, taking five kinds of crosstalk as examples: various spaces between interconnections, ground trace between adjacent interconnections, terminated by various loads, discontinuities in transmission lines impedance and differential interconnects.6. Design of the backplane is presented in 500Mbps high-speed digital circuit demo system. The responses in time domain and eye patterns were measured for the high-speed system. 500Mbps high-speed digital system is systematic modeled and simulated using 3D full-wave EM solver HFSS. A complete operation characterization of the differential system includes the differential-mode, common-mode, and any mode conversion responses. The theory of mixed-mode S-parameters is applied into analyzing all those responses of the system in frequency domain. Then the system is systematic simulated in time domain for signal integrity issues, which incorporated ADS software. The design guidelines of backplane for guaranteed reliable high-speed data transmission are derived from the results obtained.