Research And Design Of Passive Equalization Technology For High-Speed Digital Circuit

Nowadays,the rapid development of digital communication systems he data rate of highspeed digital I/O interfaces has been greatly increased from Mbps to Gbps,which brings some challenges that whether signals can be transmitted stably.Some undesired factors will affect the transmission of the signal,such as attenuation,impedance discontinuities,radiation and crosstalk noise.The edge of the high-speed signals passed the interconnect channels is declined and the amplitude is reduced because the frequency dependent loss of transmission line that the attenuation of high frequency components is much greater than the attenuation of low frequency components,which will increase the timing jitter and bit-errorrate(BER)of the receiver.In order to solve this problem,it is necessary to use equalization technology to ensure the relative balance of attenuation in the entire bandwidth of the interconnect channel.In this paper,a new type of compact boradband passive equalization design is proposed based on continuous time linear equalization technology,which can compensate for intersymbol interference caused by long transmission line losses on the PCB and has better compensation capability in a compact area.Firstly,the low-frequency de-emphasis process is analyzed by studying the signal transmission mechanism in the time domain on the basis of the T-type passive equalizer,and then the parameter selection guidelines of the structure are given through simulation analysis.In order to further optimize the equalization effect of the structure,the optimal parameters of the structure are obtained under the neural network fitting.Second,In order to enhance compensation capability in a compact area,a new passive equalization structure is proposed,which use a high impedance spiral line embedded in ground plane.The equalizer is mainly composed of lumped resistance for DC attention and sprial line for low frequency attenuation and using its reflection gain to achieve low frequency de-emphasis.Its advantages are:1)The high-impedance branch line is embedded in the ground plane,which reduces the influence of the routing on the PCB signal layer.2)The proposed equalization structure occupies a smaller area on the board level.Third,the passive equalization structure is simulated and measured on the transmission line of FR-4 PCB board to compensate the frequency dependent loss of 10Gbps data transmission over a 40-inch trace.Compared with the traditional T-type passive equalization structure,the frequency domain amplitude attenuation is more flatter,and the eye height and eye width are increased by 52%and 20%respectively.