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This article presents a 50–112-Gb/s current-mode four-level pulse amplitude modulation (PAM-4) transmitter with a two-tap fractional-spaced feed-forward equalizer (FFE). The principle analysis shows that the fractional-spaced FFE can provide an extended compensation range beyond the Nyquist frequency without amplifying noise. For the transmitter prototype implementation, the tap delay is adjusted by a coarse–fine capacitor array-based delay cell located in the quarter-rate clock path. Dynamic latches, pseudo-AND2s, and bandwidth-enhanced 4:1 multiplexers are employed to guarantee an adequate timing margin and a sufficient bandwidth for the data rate of 112 Gb/s. A linearity-optimized FFE driver is employed to overcome the current compression caused by the channel-length modulation. Fabricated in a 65-nm CMOS process, the measurement results show that the proposed fractional-spaced FFE can significantly improve the eye-opening in terms of expanding the eye width and optimizing the eyelid thickness. The PAM-4 transmitter can operate in both full-rate PAM-4 and half-rate NRZ modes, achieving a maximum data rate of 112 Gb/s with an energy efficiency of 2.17 pJ/bit.

A Mueller-Muller Phase Detector (MM PD) technology based on duo-binary four-level pulse amplitude modulation (DB PAM-4) with low complexity and high phase-detection density is presented. The proposed low complexity includes low phase-detection complexity and low space complexity of data processing. The waveform sifting technology simplifies 175 specific waveform changes into five fuzzy waveform change trends, reducing the complexity of subsequent phase detection. By making the data sample before the waveform sifting, the data bit width is reduced from 8 bit to 3 bit, which realizes data dimensionality reduction, greatly reduces the scale of subsequent auxiliary data, reduces the number of basic devices by 13.7%, and reduces the spatial complexity of data processing. The coherent coding of DB PAM-4 combined with waveform sifting increases the phase-detection density from 50% to 65% and improves both phase-detection density and phase-detection gain by 30%, and improves the jitter tolerance. Through the simulation of the clock and data recovery (CDR) model built by Cadence, the fast locking capability of CDR is verified.

To reduce the high bit error rate of serial transceivers under strong channel attenuation, a low-power 112 Gb/s SerDes transmitter was designed using a duo-binary PAM4 modulation technology. By adopting duo-binary PAM4 modulation technology, the problem of the low bandwidth utilization of a high-speed PAM4 (pulse amplitude modulation 4) signal was improved. The problem of high jitter caused by charge sharing and the limited bandwidth of a 4:1 high-speed MUX was improved by using precharging auxiliary transistors. The system power consumption of the transmitter was reduced by using a 7-bit weighted voltage-driven digital-to-analog converter (DAC). The transmitter was designed with a 28 nm CMOS process and powered by a voltage of 0.9 V. The simulation results showed that when the channel attenuation was 20.9 dB, the transmitter could work at 112 Gb/s, the power consumption was 2.02 pJ/bit, and the linearity was 96.7%.

This article presents a complete frequency-domain model for injection-locked oscillators (ILOs), which is applicable to all ILO topologies. Based on the essence of the phase accumulation within ILOs, an equivalent linear frequency-domain feedback loop is constructed. By introducing an injection factor that depicts the proportion of the phase shift perturbation with respect to the injection phase disturbance, the phase transfer function (PTF)/noise transfer function (NTF) and tracking bandwidth equation of ILOs are formulated. In addition, a general single transient simulation-based injection factor-extraction procedure is proposed. Theoretical analysis for the injection factor based on both traditional vector diagram and the impulse sensitivity function is also demonstrated. Based on a ring oscillator-based pulse ILO fabricated in a 65-nm CMOS process, the deduced PTF/NTF, tracking bandwidth equation, and their properties are verified using the simulated results and measured phase noise, respectively.

This paper presents a 20 GHz subharmonic injection-locked clock multiplier (SILCM), which adopts a mixer based self-align injection timing control loop to guarantee the optimal injection point. In addition, to further improve the injection time accuracy and reduce the super, a V/I mismatch cancellation are utilized. Furthermore, a frequency-locked loop with a frequency-lock detection and enable control switch is employed to expand the injection-locked range and save power. Fabricated in a 65 nm CMOS technology, the SILCM can lock from 19.2 GHz to 23.2 GHz. It exhibits − 125.5 dBc/Hz phase noise at 1 MHz offset and consumes 8 mW under 1.2 V power supply. The measured root-mean-square jitter integrating from 0.1 kHz to 100 MHz is 106 fs and the reference spur is − 43 dB.

This paper presents a 32 Gb/s low power little area re-timer with Phase Interpolator (PI) based Clock and Data Recovery (CDR). To further ensure signal integrity, both a Continuous Time Linear Equalizer (CTLE) and Feed Forward Equalizer (FFE) are adapted. To save power dissipation, a quarter-rate based 3-tap FFE is proposed. To reduce the chip area, a Band-Band Phase Discriminator (BBPD) based PI CDR is employed. In addition, a 2-order digital filter is adopted to improve the jitter performance in the CDR loop. This re-timer is achieved in 65 nm CMOS technology and supplied with 1.1 V. The simulation results show that the proposed re-timer can work at 32 Gb/s and consumes 91 mW. And it can equalize >−12 dB channel attenuation, tolerate the frequency difference of 200 ppm.

This paper presents a 20 GS/s four-channel time-interleaved sample-and-hold amplifier (SHA), which aims to improve the harmonic distortion performance, eliminate the common-mode voltage fall in track-to-hold transition, and solve the difficulty of timing mismatch calibration among different sampling channels. In data path, the harmonic distortion of the track-hold switch is optimized by introducing a distortion-improving resistor into the switched emitter follower. The common-mode voltage fall is eliminated by an inserted delay-regulating resistor. Additionally, broadband data buffers are utilized to further guarantee a wide bandwidth. In clock path, an interpolator-based phase regulator in analog domain is implemented to calibrate the timing mismatch, hence avoiding the large area cost and complicated algorithm in the digital domain. Fabricated in a 0.18 &mu, m SiGe BiCMOS process, the experimental results show that the SHA achieves a bandwidth of 16 GHz and a total harmonic distortion of &minus, 39.6 to approximately &minus, 51.8 dB with a &minus, 3 dBm input. By applying the proposed sampling phase regulator, the timing mismatch can be optimized to satisfy the requirement of 6-bit resolution at a 4 &times, 5 GS/s sampling rate. The proposed SHA shows prominent performance on both bandwidth and linearity, which makes it suitable for ultra-high-speed communication networks.

This paper presents a 2-40 Gb/s dual-mode wireline transmitter supporting the four-level pulse amplitude modulation (PAM4) and non-return-to-zero (NRZ) modulation with a multiplexer (MUX)-based two-tap feed-forward equalizer (FFE). An edge-acceleration technique is proposed for the 4:1 MUX to increase the bandwidth. By utilizing a dedicated cascode current source, the output swing can achieve 900 mV with a level deviation of only 0.12% for PAM4. Fabricated in a 65-nm CMOS process, the transmitter consumes 117 mW and 89 mW at 40 Gb/s in PAM4 and NRZ at 1.2 V supply. © 2018, Institute of Electronics Engineers of Korea. All rights reserved.

This paper presents a 40-Gb/s transmitter (TX) and receiver (RX) chipset for chip-to-chip communications in a 65-nm CMOS process. The TX implements a quarter-rate multi-multiplexer (MUX)-based four-tap feed-forward equalizer (FFE), where a charge-sharing-effect elimination technique is introduced into the 4:1 MUX to optimize its jitter performance and power efficiency. The RX employs a two-stage continuous-time linear equalizer as the analog front end and integrates a low-cost sign-based zero-forcing engine relying on edge-data correlation to automatically adjust the tap weights of the TX-FFE. By embedding low-pass filters with an adaptively adjusting bandwidth into the data-sampling path and adopting high-linearity compensating phase interpolators, the clock data recovery achieves both high jitter tolerance and low jitter generation. The fabricated TX and RX chipset delivers 40-Gb/s PRBS data at BER 16-dB loss at half-baud frequency, while consuming a total power of 370 mW.

In this paper, an accurate linear model of the Mueller–Muller phase detector (MMPD)-based clock and data recovery circuit (MM-CDR) is proposed, which analyzes several critical points of the MM-CDR including the linearization of the MMPD and the gain of the voter. Using our technique, the jitter between the recovery clock and the input data can be estimated with a sub-picosecond accuracy, as demonstrated in the simulation results of a 56 Gb/s quarter-rate MM-CDR implemented in 28 nm CMOS.

This letter presents a 112-Gb/s four-level pulse amplitude modulation (PAM-4) transmitter with a 2-tap fractional-spaced feed-forward equalizer (FFE) implemented in a 65-nm CMOS process. The tap delay is adjusted by a coarse-fine capacitor array-based delay cell located in the clock path. Dynamic latches, pseudo-AND2s, and bandwidth-enhanced 4:1 MUXs are employed to guarantee an adequate timing margin and a sufficient bandwidth for the 112-Gb/s design. The measurement results show that the fractional-spaced FFE can significantly optimize the eye opening. The fabricated PAM-4 transmitter achieves a maximum data rate of 112 Gb/s with an energy efficiency of 2.17 pJ/bit.

This paper presents a 4-40 Gb/s PAM-4 transmitter using a novel hybrid driver. Different from conventional current-mode (CM) drivers with poor linearity and source-series terminated (SST) drivers with limited differential output swing, the proposed hybrid driver delivers a differential output swing exceeding the supply voltage with high linearity using a combination structure of the CM and SST driver. In addition, a 4-40 Gb/s quarter-rate transmitter with one-tap feedforward equalization is designed in 65nm CMOS technology using the hybrid driver, yielding a 1.8V differential peak-to-peak output swing at 1.2 V supply voltage with a 96.4% ratio of level mismatch.

A 10 GHz 4-phase ring-VCO based injection-locked clock multiplier (RILCM) for 40 Gb/s SerDes application is presented in this paper. The RILCM adopts two loops which share common part circuit to realize the injection lock. The first loop which is the frequency lock loop (FLL), drags the VCO's free-running frequency to the injection lock-in range. Another loop which is the injection timing control loop (ITCL), controls the injection timing of the pulse to reduce the race condition and improve the phase noise. The RILCM is designed in a 65nm CMOS technology and supplied with 1.1V. The simulation results show that the proposed RILCM can provide 4-phase 10 GHz clocks with 3.61ps total jitter, at this time the total consumption is 17 mW.

This paper describes the design of a serial-link transceiver that supports various communication standards from 1.25 to 12.5Gb/s, implemented in 40nm CMOS technology. Both DC and AC coupling mode can be provided by the receiver, in which a wide range PI-based CDR is also proposed. The transceiver utilizes a 3-tap FFE, a 2-stage CTLE and an adaptive 2-tap DFE to achieve the compensation for a Nyquist channel loss of 32.4dB, and consumes 66mW from a 1.1V supply when operating at 12.5Gb/s.

This paper presents a 28Gbps voltage controlled oscillator (VCO) based clock and data recovery (CDR) with a separate proportional path technology. It employs a quarter rate ternary Bang-Bang phase detector to extract the phase error between the local clock and input data. The circuit designed in a 65nm CMOS process achieves ±1000 ppm lock-in rang, ±6000 ppm tracking range. The simulation results show that the total jitter of the recovered clock is 4.7ps when the CDR locked at 28 Gb/s. In addition, this CDR can track a 500 KHz sinusoidal phase jitter with 2UI amplitude.

An 80 Gb/s 4-level pulse amplitude modulation (PAM4) wireline receiver is presented in this paper. This receiver adopts quarter rate architecture to improve data rate and reduce power consumption. In order to reduce the complexity of the clock and data recovery (CDR) design, a voltage control oscillator (VCO) based CDR without reference clock is used. Furthermore, four BBPDs are used to sample the edge and data information generated by the middle slicer for extraction the phase error between the data and clock. The receiver is designed in 65nm CMOS technology and supplied with 1.2V. The simulation results show that the proposed PAM4 receiver can work at 80 Gb/s with 235mW consumption.