Timothy De Keulenaer

A Wide-Band, 5-Tap Transversal Filter With Improved Testability for Equalization up to 84 Gb/s

A millimeter wave integrated transversal filter operating at up to 84 Gb/s is presented. The implemented topology offers improved testability, which allows for filter characterization in both the time and frequency domain. The filter has an input and output return loss better than 10 dB up to 67 GHz. Using this filter, frequency equalization of an NRZ input to either an NRZ or a duobinary output is demonstrated at 84 Gb/s across a channel consisting of a 5 cm differential grounded coplanar waveguide trace and a pair of 80 cm coaxial cables. The filter is implemented in 130 nm SiGe BiCMOS process, has a die area of 2.5 mm × 1.4 mm and consumes 210 mW from a 2.5 V power supply.

Silicon-organic hybrid (SOH) modulators for intensity-modulation / direct-detection links with line rates of up to 120 Gbit/s

High-speed interconnects in data-center and campus-area networks crucially rely on efficient and technically simple transmission techniques that use intensity modulation and direct detection (IM/DD) to bridge distances of up to a few kilometers. This requires electro-optic modulators that combine low operation voltages with large modulation bandwidth and that can be operated at high symbol rates using integrated drive circuits. Here we explore the potential of silicon-organic hybrid (SOH) Mach-Zehnder modulators (MZM) for generating high-speed IM/DD signals at line rates of up to 120 Gbit/s. Using a SiGe BiCMOS signal-conditioning chip, we demonstrate that intensity-modulated duobinary (IDB) signaling allows to efficiently use the electrical bandwidth, thereby enabling line rates of up to 100 Gbit/s at bit error ratios (BER) of 8.5 × 10-5. This is the highest data rate achieved so far using a silicon-based MZM in combination with a dedicated signal-conditioning integrated circuit (IC). We further show four-level pulse-amplitude modulation (PAM4) at lines rates of up to 120 Gbit/s (BER = 3.2 × 10-3) using a high-speed arbitrary-waveform generator and a 0.5 mm long MZM. This is the highest data rate hitherto achieved with a sub-millimeter MZM on the silicon photonic platform.

Real-time 100 Gbps/lambda/core NRZ and EDB IM/DD transmission over multicore fiber for intra-datacenter communication networks

A BiCMOS chip-based real-time intensity modulation/direct detection spatial division multiplexing system is experimentally demonstrated for both optical interconnects. 100 Gbps/λ/core electrical duobinary (EDB) transmission over 1 km 7-core multicore fiber (MCF) is carried out, achieving KP4 forward error correction (FEC) limit (BER < 2E-4). Using optical dispersion compensation, 7 × 100 Gbps/λ/core transmission of both non-return-to-zero (NRZ) and EDB signals over 10 km MCF transmission is achieved with BER lower than 7% overhead hard-decision FEC limit (BER < 3.8E-3). The integrated low complexity transceiver IC and analog signal processing approach make such a system highly attractive for the high-speed intra-datacenter interconnects.

Adaptive Transmit-Side Equalization for Serial Electrical Interconnects at 100 Gb/s Using Duobinary

The ever-increasing demand for more efficient data communication calls for new, advanced techniques for high speed serial communication. Although newly developed systems are setting records, off-line determination of the optimal equalizer settings is often needed. Well-known adaptive algorithms are mainly applied for receive-side equalization. However, transmit-side equalization is desirable for its reduced linearity requirements. In this paper, an adaptive sign–sign least mean square equalizer algorithm is developed applicable for an analog transmit-side feed-forward equalizer (FFE) capable of transforming non-return-to-zero modulation to duobinary (DB) modulation at the output of the channel. In addition to the derivation of the update strategy, extra algorithms are developed to cope with the difficult transmit–receive synchronization. Using an analog six tap bit-spaced equalizer, the algorithm is capable of optimizing DB communication of 100Gb/s over 1.5-m Twin-Ax cable. Both simulations and experimental results are presented to prove the capabilities of the algorithm demonstrating automated determination of FFE parameters, such that error-free communication is obtained (BER

A digitally controlled threshold adjustment circuit in a 0.13µm SiGe BiCMOS technology for receiving multilevel signals up to 80Gbps

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Analysis and design of a high power, high gain SiGe BiCMOS output stage for Use in a millimeter-wave power amplifier

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Capacitance sensor measurements of upward and downward two-phase flow in vertical return bends

In this paper, a high bandwidth digitally controlled threshold adjustment circuit is proposed which can be used for demodulating high-speed multi-level signals. Simulations of the bandwidth are presented together with measurements of the control currents to indicate the threshold adjustment capability. A bandwidth above 80GHz in a 0.13μm SiGe BiCMOS technology and a threshold tunable between ±160mV in steps of 0.6mV is achieved, allowing very precise control of the threshold level. This allows the circuit to accurately position the threshold on the eye-crossing of a high speed multi-level signals. By applying this circuit to demodulate a duobinary signal over a 40GHz channel, a data rate of up to 80Gbps can be achieved.

First demonstration of real-time 100 Gbit/s 3-Level duobinary transmission for optical interconnects

In this paper a high gain, high power output stage designed in a 250nm SiGe BiCMOS technology is presented. The used topology together with a discussion on the stability of the output stage is explained in detail. In order to increase the gain of the output stage and thus increases the attainable power added efficiency (PAE), positive feedback is used. Furthermore a formula predicting the input impedance of a common base transistor at high frequencies is deducted which explains and predicts the magnitude of the feedback mechanism. The output stage achieves a peak gain of 14.4dB at 31GHz with a maximum output power of 22dBm.