Passive Equalization For High-speed Data Transmission

With the development of digital communication technologies in the recent years, data rates increase continuously. Nevertheless, the ever increasing data rates bring inevitable challenges to the transmission of high-speed circuit, and lead to signal integrity problems. Non-ideal characteristics of the channel: such as frequency-dependent loss, discontinuities, crosstalk noise and ground bounce, lead to the magnitude loss and the timing jitter of received signals and induce the degradation of transmission function and eye diagram in addition to an increase in the bit error rate.In this paper, we concentrated on the frequency-dependent loss of digital signal transmission and carried out a study on the passive equalization for high-speed data transmission. Initially, this paper focused on the equalization techniques, de-emphasis of low frequency and pre-emphasis of high frequency; analyzed the operating mechanisms in time domain; concluded the way to get the physical parameters for better performance; and verified the conclusion by the performance of the eye diagram in time domain and insertion loss in frequency domain. Lastly, this paper proposed a novel passive equalizer based on the reflection of stub and broadside coupling of lines : pre-emphasis by reflection and de-emphasis by coupling. Compared with the passive equalizer based on edge coupling, this design got high coupling coeffic ients, overcame the fabrication difficulty, and was helpful in practical applications. To further verify the effectiveness of the equalization, this design was fabricated and tested. It was observed that the transmission function in frequency domain became flatter, and the eye height and the timing jitter were improved noticeably, when compared with those of the un-equalized cases. Meanwhile, the proposed equalizer also provided better performance than the conventional T-shaped counterpart, and gave valuable ideas for study in the design of passive equalizer.