This dissertation investigates adaptive decision feedback equalizers for high-speed
serial data links.
An adaptive data-transition decision feedback equalizer (DT-DFE) was developed. The DT-DFE boosts the eye-opening of the high-frequency components
of data without attenuating their low-frequency counterparts. Reference voltages
were obtained by transmitting consecutive 1s and 0s and measuring the output
of the continuous-time linear equalizer using a pair of successive approximation
register analog-to-digital converters in a training phase. It uses loop unrolling
to detect data transitions, activate tap-tuning, launch DFE, and combat timing
constraints. The performance of the DT-DFE and its advantages over commonly
used data-state DFE were validated using the schematic-level simulation results
of 5 Gbps backplane links.
A new adaptive DT-DFE with edge-emphasis (EE) taps and raised references
was developed. Loop-unrolling was further developed for DT-DFE with EE-taps.
The reference voltages were raised beyond that set by the low-frequency components of data to increase vertical eye-opening. Clock and data recovery was performed using 4x oversampling. The DT-DFE was validated using the schematiclevel simulation results of 10 Gbps backplane links.
A pre-skewed bi-directional gated delay line (BDGDL) bang-bang frequency
difference-to-digital converter and a BDGDL integrating frequency difference-todigital converter (iFDDC) were proposed for clock and data recovery. Both frequency difference detectors feature all-digital realization, low power consumption,
and high-speed operation. The built-in integration of iFDDC results in a zero
static frequency error and the first-order noise-shaping of the quantization errors
of the BDGDL and digitally-controlled oscillators. Their effectiveness was validated using schematic-level simulation results of 5-GHz frequency-locked loops.
All systems validating the proposed adaptive DFE and frequency-difference
detectors were designed in TSMC’s 65 nm CMOS technology and analyzed using
Spectre from Cadence Design Systems.