In recent year, the single-end transmission line is instead by differential transmission line . Differential signaling has been generally used in the high speed digital interconnection on the PCBs. The advantages of the differential signal with a low noise and high common-mode noise suppression, but the differential mode transmission signal is a very high quality requirements of circuit, the two line should have same length and symmetry, but in the practical package the circuit is not this case, In the limit space ,the differential signal should through the bend, it would lead to the phase skew and produce the differential to common mode conversion noise on the signal integrity and electromagnetic interference(EMI) problem. In this paper a new type of bend is proposed that reduces differential -to-common mode conversion noise for high speed digital circuit. This novel structure can reduce the mode conversion over 20dB at DC to 10GHz, and the differential insertion loss remains low. Also time domain the TDT common mode noise from 0.09V to 0.008V as compared with the bended differential transmission line using the edge couple bend. Moreover, the measurement on proposed structure show a close match with the full-wave simulation result. However, this structure does not have a reference plane, the return path is not complete, the current is easy to radiate out, so I design a guard trace to reduce the radiation in this structure.

The main focus of this thesis is placed on high frequency PCB signal Integrity Is-sues and RF/Microwave filters using EBG structures. From the signal Integrity aspect, two topics were mainly discussed. On one hand, the effect of increasing frequency on classical design rules for crosstalk reduction in PCBs was investigated experimentally and by full-wave simulations. An emphasis was placed on the 3×W spacing rule and the use of guard traces. Single-ended and differential transmission lines were considered. S-parameter measurements and simu-lations were carried out at high-frequency (up to 20 GHz). The results emphasize the necessity to reevaluate traditional design rules for their suitability in high frequency applications. Also, the impacts of using guard traces for high frequency crosstalk re-duction were clearly pointed out. On the other hand, the effect of high loss PCB ma-terials on the signal transmission characteristics of microstrip lines at high frequency (up to 20 GHz) was treated. Comparative studies were carried out on different micro-strip configurations using standard FR4 substrate and a high frequency dielectric ma-terial from Rogers, Corporation. The experimental results highlight the dramatic im-pact of high dielectric loss materials (FR4 and solder mask) and magnetic plating metal (nickel) on the high frequency signal attenuation and loss of microstrip trans-mission lines. Besides, the epoxy-based SU8 photoresist was characterized at high frequency (up to 50 GHz) using on-wafer conductor-backed coplanar waveguide transmission lines. A relative dielectric constant of 3.2 was obtained at 30 GHz. Some issues related to the processing of this material, such as cracks, hard-skin, etc, were also discussed. Regarding RF/Microwave filters, the concept of Electromagnetic Band Gap (EBG) was used to design and fabricate novel microstrip bandstop filters using periodically modified substrate. The proposed EBG structures, which don’t suffer conductor backing issues, exhibit interesting frequency response characteristics. The limitations of modeling and simulation tools in terms of speed and accuracy are also examined in this thesis. Experiments and simulations were carried out show-ing the inadequacies of the Spice diode model for the simulations in power electronics. Also, an Artificial Neural Network (ANN) model was proposed as an alternative and a complement to full-wave solvers, for a quick and sufficiently accurate simulation of interconnects. A software implementation of this model using Matlab’s ANN toolbox was shown to considerably reduce (by over 800 times) the simulation time of microstrip lines using full-wave solvers such as Ansoft’s HFSS and CST’s MWS. Finally, a novel cooling structure using a double heatsink for high performance electronics was presented. Methods for optimizing this structure were also discussed. / QC 20100809