Analog Equalizer In High Speed Communication System

High-rate data communication over cable suffers from inter-symbol-interference introduced by the cable's transmission loss which limits the date rate and distance. The inter-symbol-interference can be greatly reduced if the receiver includes a cable equalizer. Receiver equalization refers to a method of restoring a signal's high-frequency components that the media preferentially attenuates. Located at the receive end of the cable, the equalizer compensates the channel loss by boosting the higher frequency components of the signal, thereby minimizing the amplitude difference between the low and high frequency components of the bit stream.This paper is focus on the receiver equalization in high speed SATA communication system. The paper discusses the causes of the signal degradations when high speed data traveling through a cable, simulates the actual attenuation characteristic of SATA cable, and then explains the principle of the equalization and two type of equalization technology, pre-emphasis and equalization. Finally the paper proposes a high-speed CMOS cable equalizer with adjustable gains, the equalizer can compensate the loss of different cable length. The variable gain boost is achieved by selecting the capacitor array on chip. The equalizer is fabricated in SMIC 0.13μm CMOS process, can equalize the differential signal with 3Gbps data rate. The equalizer effectively compensates the high frequency components of the signal, improves the quality of the signal, so that the high frequency signal can travel further with higher data rate, and the clock and data recovery becomes easier.