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We present an interpretation of conventional figure-of-merit (FOM) and average input-referred noise current density (IRNCD) that characterizes optical receivers to determine how technologies and circuits best address energy efficiency. A design methodology is presented for differential optical receivers based on Cherry-Hooper Emitter Follower (CHEF) front-end designs targeting 56-Gbps applications is realized in a 130-nm SiGe BiCMOS process. The electrical measurements in a 50- $\Omega$ environment demonstrate data rates up to 112 Gbps and 84 Gbps for two design variants. In an open input and maximum gain configuration, the rms input referred noise currents are 3.59 $\mu$ $A_{RMS}$ and 2.41 $\mu$ $A_{RMS}$ and the corresponding average input referred noise current densities are 17.25 $pA/\sqrt{Hz}$ and 12.86 $pA/\sqrt{Hz}$. The packaged electro-optical measurements of the receiver variants is carried out with a single commercial off-the-shelf (COTS) photodetector demonstrate open eyes at data rates up to 64 Gbps. At 60 Gbps, the receiver variants achieve a $BER < 10^{-10}$ and $BER < 10^{-9}$. The total power consumption for the variants are 162 mW and 138 mW for overall energy efficiencies (with respect to electro-optical performance) of 2.53 $pJ/bit$ and 2.3 $pJ/bit$. [ABSTRACT FROM AUTHOR]

This article presents a full-duplex (FD) rake receiver (RX) that uses the orthogonality properties of pseudo-noise (PN) codes to reject transmitter (TX) self-interference (SI) in the RF domain, allowing simultaneous transmit and receive (STAR) operation in the same frequency channel. The rake RX also exploits multipath propagation in wireless channels and PN code orthogonality to gather signals across multipath components to increase the signal-to-noise ratio (SNR) while avoiding the fading effects of multipath channels. The rake RX shares a low-noise amplifier (LNA) between the three rake fingers and a high-linearity baseband (BB) section with the second-order filtering to improve the rejection with low power consumption. Measurements indicate that TX SI rejection is 41.2 dB in the RF domain with 9-dB SNR improvement in a multipath channel. The rake RX is implemented in a 45-nm RFSOI CMOS process and occupies an active area of 1.6 mm2 while consuming 45.8 mW per finger, including clock power consumption. [ABSTRACT FROM AUTHOR]

RF photonic components suffer from poor spurious-free dynamic range (SFDR) due to the high noise and distortion generated by a silicon photonic (SiP) Mach–Zehnder modulator (MZM). This work demonstrates a distributed silicon–germanium (SiGe) heterojunction bipolar transistor (HBT)-based low-noise amplifier (LNA) co-designed for linearization with a SiP MZM for a broadband radio-over-fiber (RoF) link. The SiGe LNA incorporates a distributed, tunable predistortion scheme that is inherently wideband and improves the third-order intercept point over an 18-GHz range. The assembled SiGe LNA and SiP MZM prototype demonstrates an SFDR as high as 120 dB ⋅ Hz2/3 at 9 GHz, a 14-dB improvement over previous SiP RF components or RoF links. [ABSTRACT FROM AUTHOR]

As datacenters continue to scale in size, energy efficiency for short reach (<2 km) links is a major factor for networks that may connect hundreds of thousands of servers. We demonstrate that links based on analog coherent detection (ACD) offer a promising path to simultaneously achieving significantly larger link budgets and improved link energy efficiency. A complete analysis is presented that considers the power consumption of all the photonic and electronic components necessary to realize an ACD link architecture based on 50 Gbaud (GBd) quadrature phase-shift keying (QPSK) signaling combined with polarization multiplexing to achieve 200 Gb/s/λ. These links utilize receivers that incorporate an optical phase-locked loop (OPLL) to frequency- and phase-lock the local oscillator (LO) laser to the incoming signal. QPSK modulation offers compelling advantages both in achievable link budget and in energy efficiency. Indeed, low-complexity electronics based on limiting amplifiers can be used as opposed to the linear front-ends, A/D converters, and digital signal processing (DSP) required for higher-order QAM or PAM formats. Our analysis indicates that links with 13 dB of unallocated budget operating at error rates of <10−12 can be achieved and is compatible with higher error rates that require forward error correction (FEC). We present a comparison of silicon and InP platforms and evaluate both traveling-wave and segmented modulator designs, providing an illustration of the wide design space before converging on the most promising architectures that maximize energy efficiency and minimize laser power. We establish the theoretical potential to achieve picojoule-per-bit energy efficiency targets. [ABSTRACT FROM AUTHOR]

We present a comparison of design trade-offs for transimpedance, sensitivity, DC voltage offset cancellation, group-delay variation (GDV), common-mode rejection, and overload for transimpedance amplifiers (TIA) based on balanced, unbalanced, and pseudodifferential topologies. The TIAs are implemented monolithically in the IHP 250-nm SiGe BiCMOS EPIC process (fT = 190 GHz). Measurement results shown here support data rates to 50 Gb/s with BER better than 10−10. The power consumption of the TIAs is 54 mW for TIA designs that approach 1 pJ/b. [ABSTRACT FROM AUTHOR]

Collective pulse oscillators (CPOs) are novel designs constructed using pulse regenerative amplifiers that exhibit time-variant gate delay based on the residual charge from past state. This property makes it possible to achieve precise phase resolutions smaller than a pulse gate delay and/or provide identical phase taps at multiple physical locations. CPOs exhibit temporal phase error correction that results in an improvement in frequency stability $\propto -10\log p$ for power $\propto p$ across all timescales beyond the correction settling time. While CPOs result in device noise-based figure of merits (FoMs) comparable to that of ring oscillators, they are more resilient to power-coupled and impulse noise. This article presents a systematic time-domain analysis of the properties of CPOs based on an abstract model that captures the time-variant delay of pulse gates. Closed-form analytic solutions for CPOs disturbed by impulse noise are derived, and higher order CPOs with continuous noise injection are analyzed using behavioral simulations and characterized using Allan deviation. Hspice simulation results are presented to validate the model and compare CPOs with ring oscillators. Allan deviation and phase noise measurements on CPOs of 8 and 40 gates fabricated in GFUS8RF (130-nm) technology corroborate the theory and simulation results. [ABSTRACT FROM AUTHOR]

Though GaN HEMTs have primarily been used for power amplification, they are also well suited for receiver applications. In the front-end of receivers, non-linearities, in particular third-order intermodulation products lead to in-band signal distortion. The intermodulation distortion is primarily dominated by transconductance and its derivatives. In this paper, we report on N-polar GaN MIS-HEMTs able to simultaneously achieve high gain (12.7 dB) and excellent linearity performance (OIP3/PDC of 15 dB) for low-power receiver application at 30 GHz. With a two-tone load-pull input-bias sweep, we demonstrate that the linearity of high performance HEMTs is sensitive to bias, and we present our measurement methodology to accommodate this. [ABSTRACT FROM AUTHOR]