IC Interconnects Modeling using X-parameters

-The performance of IC interconnects has been stretched tremendously recently years by high speed integrated circuit systems. Even though S-parameters are popularly used for the characterization of IC interconnects, their modeling has to consider the existence of active devices, such as buffers and drivers. The I/O model is difficult to obtain due to the IP protection and limited information. In this paper, we propose to use the X-parameter to model the IC interconnect system. Based on the PHD formalism, X-parameter models provide an accurate frequency-domain method under large-signal operating points to characterize their nonlinear behaviors. Another challenge is that in the digital IC system, the digital signal is best represented in the time domain while S-parameter and X-parameter are both in the frequency domain. Hence, a proper control of the harmonic contents inside the input signal to drivers and buffers are needed. Starting from modeling the CMOS inverter, we present the whole link modeling primarily based on X-parameter for the pulsed digital signal. According to our knowledge, this is the first time X-parameter is applied for this type of applications.