In recent years, the data rates of serial chip-to-chip digital I/O communication channels have increased considerably and are now over 10 Gb/s. Due to these increasing data rates, high-speed digital I/O signals are seriously suffering from frequency-dependent losses on printed circuit boards (PCBs) and at cables, consequently resulting in inter-symbol interference (ISI) problems and the subsequent degradation of receiver eye-opening, timing jitter, and voltage margin with declined system sensitivity and bit-error-rate (BER). In order to compensate for the frequency-dependent losses in a high-speed I/O channel, equalization methods have received significant attention as practical loss-compensation techniques for transmitter and receiver designs. Among various equalization methods, on-chip active equalization is a beneficial approach for applications that require active gain. However, on-chip active equalization inevitably sacrifices active power consumption and suffers from bandwidth limitation with current IC technology. On the other hand, passive equalization techniques are preferred for applications with low power consumption or with a wide bandwidth requirement. However, to achieve wide band in passive equalization, costly materials and manufacturing processes are required for wide-band passive component implementation. Even though wide band is achieved, it still has a DC attenuation problem, which is an inherent drawback of passive equalizers.
In this thesis, a sophisticated wide-band passive equalization technique using microwave effects is proposed, which can be easily integrated on a planar package and PCB with conventional manufacturing processes. The newly proposed passive equalizer consists of coupled microstrip line structures with different characteristic impedances, which intentionally cause near-end crosstalk (NEXT) and reflections as the main mechanisms for pre-emphasis and de-emphasis, respectively. An analytic model and an equivalent circuit model for the proposed passive equalizer are then proposed. Based on the analytic model, a design optimization procedure is proposed, in which the design parameters are recursively determined so as to converge to the optimal values that maximize eye-opening and minimize negative ISIs. With the optimized design parameters, the proposed passive equalization technique using NEXT and reflections was experimentally verified with a data rate of up to 16 Gb/s, achieving a normalized eye-opening and eye-width of 11.4% and 64.8%, respectively. To achieve a wide band and active gain at the same time, which are the primary benefits of passive and active equalizers, a novel hybrid equalization technique is proposed by combining the proposed passive equalizer with an active equalizer. The proposed design optimization process for passive equalization is modified for the proposed hybrid equalization to optimize the design parameters of the passive equalizer when it is combined with a given active equalizer. The proposed hybrid equalizer was demonstrated by measurement with a data rate of 3.4 Gb/s and a channel of 10-meter-long high-definition multimedia interface (HDMI) cable assembly. With the proposed hybrid equalization technique, the figure of merit (FOM), which is proposed to evaluate a link in this thesis, is significantly improved by 400% and 280% compared with those of active and passive equalization, respectively.
본 논문에서는 기존의 수동소자를 사용한 수동이퀄라이저의 대역폭한계를 극복하기 위해 새롭게 Near-end crosstalk과 Reflection이라는 전자파 현상을 이용하여 16Gb/s 광대역 수동이퀄라이저 설계방법을 제안하였다. 더불어 Impulse response anslysis를 통한 분석적모델과 SPICE simulation에 적용할수 있도록 등가회로 모델을 제안하였고, 제안한 모델을 바탕으로 한 설계 최적화 방법을 제안하였다. 제안한 설계 최적화 방법은 Peak Distortion Analysis (PDA) 를 이용하여 최대의 Eye-opening 를 보장하는 디자인을 찾고, Negative ISI cancellation technique을 사용하여 디지털 심볼간 간섭인 Inter-symbol Interference (ISI) 를 최소화 하는 과정을 수행한다.
또한 능동이퀄라이저와 수동이퀄라이저를 결합한 혼성 이퀄라이저를 새롭게 제안하였으며, 능동게인과 광대역의 장점을 한꺼번에 가져올수 있도록 하였다. 혼성 이퀄라이저의 구현을 위해 사용된 능동 이퀄라이저는 삼성 0.18um CMOS 공정을 사용하여 제작된 2nd-order Equalizer 로써 실제 측정을 통해 기능성을 검증하였다. 제작된 능동 이퀄라이저의 특성을 포함한 설계 최적화 과정을 제안함으로써 혼성 이퀄라이저의 성능을 최대화 하였다. 측정결과, 현재 디지털영상전송에 많이 쓰이고 있는 10M 길이의 HDMI cable을 지난 3.4 Gb/s신호를 성공적으로 복원함으로써 그 효용성을 검증하였다.
