Showing papers on "Local oscillator published in 2021"

Analog Coherent Detection for Energy Efficient Intra-Data Center Links at 200 Gbps Per Wavelength

Abstract: 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.

Multimode W-Band and D-Band MIMO Scalable Radar Platform

Abstract: This article demonstrates the implementation of 80- and 160-GHz four-channel radar sensors employing the modular scalable platform based on a single relaxed 40-GHz local oscillator and cascadable transceiver chips. The first two channels synthesize $2 \times 2$ multiple-input–multiple-output (MIMO) radar at 80 GHz with onboard $8 \times 1$ patch arrays for enhanced angular resolution, whereas the other two channels employ 160-GHz system-on-chip transceivers with integrated wideband 6-dBi micromachined on-chip antennas for enhanced range resolution. Configurable modulators in each transceiver offer ranging, direction-of-arrival (DoA) estimation, velocity/vibrations measurement, and data communication applications. Frequency-modulated continuous wave (FMCW) is demonstrated with 4-/8-GHz sweep bandwidth at 80/160 GHz corresponding to 3.75-/1.875-cm range resolution. Chirp-sequence FMCW is employed to measure the heartbeat rate of a human, and 78 bpm is measured with 0.06-Hz Doppler resolution. Mechanical vibration rate from a loudspeaker is measured using the CW radar technique, whereas phase-modulated continuous wave is employed for distant selective vibrations measurement. Time-division multiplexing MIMO radar is configured at 80 GHz in a multitarget scenario for DoA estimation, and the targets are distinguished with 25° effective angular resolution. Frequency-division multiplexing MIMO radar technique is demonstrated based on $\Delta \Sigma $ -modulation and binary phase shift keying (BPSK) modulators. Furthermore, the 10-Mb/s BPSK data communication link is evaluated at 80 GHz with a 20-dB signal-to-noise ratio at 1 m. The 160-GHz vector modulators offer additional modulations.

Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Abstract: In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded mixing efficiency and system performance. Here, we use a pilot-assisted self-coherent detection approach to overcome this problem. Specifically, we transmit both a Gaussian data beam and a frequency-offset Gaussian pilot tone beam such that both beams experience similar turbulence and modal coupling. Subsequently, a photodetector mixes all corresponding pairs of the beams’ modes. During mixing, a conjugate of the turbulence-induced modal coupling is generated and compensates the modal coupling experienced by the data, and thus the corresponding modes of the pilot and data mix efficiently. We demonstrate a 12 Gbit s−1 16-QAM polarization-multiplexed free-space optical link that is resistant to turbulence. A transmission scheme for free-space optical communications is shown to be highly robust against turbulence.

Heterodyne sensing of microwaves with a quantum sensor.

Abstract: Diamond quantum sensors are sensitive to weak microwave magnetic fields resonant to the spin transitions. However, the spectral resolution in such protocols is ultimately limited by the sensor lifetime. Here, we demonstrate a heterodyne detection method for microwaves (MW) leading to a lifetime independent spectral resolution in the GHz range. We reference the MW signal to a local oscillator by generating the initial superposition state from a coherent source. Experimentally, we achieve a spectral resolution below 1 Hz for a 4 GHz signal far below the sensor lifetime limit of kilohertz. Furthermore, we show control over the interaction of the MW-field with the two-level system by applying dressing fields, pulsed Mollow absorption and Floquet dynamics under strong longitudinal radio frequency drive. While pulsed Mollow absorption leads to improved sensitivity, the Floquet dynamics allow robust control, independent from the system’s resonance frequency. Our work is important for future studies in sensing weak microwave signals in a wide frequency range with high spectral resolution. High-resolution microwave detection with NV centers in diamond is currently applicable to signals with frequencies below 10 MHz, thus limiting their range of applications. Here, the authors demonstrate detection of GHz signals with sub-Hz spectral resolution, not limited by the quantum sensor lifetime.

Coherent Data Center Links

Abstract: As link bit rates within and between data centers continue to increase, it is challenging to maintain low power consumption while accommodating ever-tighter optical link budgets. Although power consumption can be reduced by co-packaging optical transceivers with electrical switches and employing optical switching, both approaches increase losses, further compressing link budgets. Local oscillator-based coherent receivers traditionally employed for long-haul systems provide a path to higher bit rates and improved link budgets, but their power consumption is excessive owing to high-speed digital signal processing (DSP). We discuss alternative designs for coherent receivers, such as DSP-free coherent receivers and Kramers–Kronig (KK) receivers. We compare them in terms of receiver sensitivity, power consumption, and complexity.

A 16-Element Fully Integrated 28-GHz Digital RX Beamforming Receiver

Abstract: A 16-element fully integrated 28-GHz digital beamformer combines with a custom eight-layer LTCC substrate with a 4 $\times \,\,{4}$ patch antenna array for a complete 16-element single-chip 28-GHz millimeter-wave (mm-wave)-to-digital beamforming system. Sixteen-element digital beamforming in a single integrated circuit (IC) represents an excellent tradeoff between die size, signal loss, and I/O routing complexity. Per-element RX slices with an inductor-less mm-wave front end and 4 $\times $ parallel continuous-time bandpass delta–sigma analog-to-digital conversion (ADC) arrays enable compact mm-wave-to-digital conversion. The 4 $\times $ parallel ADC array provides in-built finite-impulse response (FIR) filtering for additional harmonic suppression and anti-alias filtering. ADC sampling of a high (1 GHz) IF facilitates single-phase mm-wave local oscillator (LO) routing and moves the I/Q mixing into the digital domain. Optimum bump and RX slice placement shortens LO and mm-wave signal routing and reduces signal loss. Bit-stream processing (BSP) takes advantage of the narrow bit-width raw outputs of the RX slices to implement digital beamforming with area- and energy-efficient MUXes. The prototype 16-element beamformer generates four independent, simultaneous beams. Over-the-air measurements confirm accurate 3-D beam patterns and indicate a measured overall noise figure of 7 dB and QAM-4 error vector magnitude (EVM) of −18 dB.

Towards underwater coherent optical wireless communications using a simplified detection scheme

Abstract: In this paper, an effective method of underwater coherent optical wireless communication (UCOWC) with a simplified detection scheme is proposed. The proof-of-concept experiments with M-ary PSK have been conducted with a common laser used for the signal source and local oscillator (LO). The BER performance has been evaluated at different underwater channel attenuations and the maximum achievable attenuation length (AL) with a BER below the forward error correction (FEC) limit of 3.8×10-3 is investigated. The tested system offers data rates of 500 Mbps, 1 Gbps, and 1.5 Gbps with the BPSK, QPSK and 8PSK modulated signals, respectively. The corresponding maximum achievable attenuation lengths are measured as 13.4 AL 12.5 AL, and 10.7 AL. In addition, the performance degradation of the practical system with separate free running lasers for the signal and LO is also estimated. To the best of our knowledge, the UCOWC system is proposed and experimentally studied for the first time. This work provides a simple and effective approach to take advantages of coherent detection in underwater wireless optical communication, opening a promising path toward the development of practical UCOWC with next-generation underwater data transmission requirements on the capacity and transmission distance.

A low-noise photonic heterodyne synthesizer and its application to millimeter-wave radar.

Abstract: Microwave photonics offers transformative capabilities for ultra-wideband electronic signal processing and frequency synthesis with record-low phase noise levels. Despite the intrinsic bandwidth of optical systems operating at ~200 THz carrier frequencies, many schemes for high-performance photonics-based microwave generation lack broadband tunability, and experience tradeoffs between noise level, complexity, and frequency. An alternative approach uses direct frequency down-mixing of two tunable semiconductor lasers on a fast photodiode. This form of optical heterodyning is frequency-agile, but experimental realizations have been hindered by the relatively high noise of free-running lasers. Here, we demonstrate a heterodyne synthesizer based on ultralow-noise self-injection-locked lasers, enabling highly-coherent, photonics-based microwave and millimeter-wave generation. Continuously-tunable operation is realized from 1-104 GHz, with constant phase noise of -109 dBc/Hz at 100 kHz offset from carrier. To explore its practical utility, we leverage this photonic source as the local oscillator within a 95-GHz frequency-modulated continuous wave (FMCW) radar. Through field testing, we observe dramatic reduction in phase-noise-related Doppler and ranging artifacts as compared to the radar’s existing electronic synthesizer. These results establish strong potential for coherent heterodyne millimeter-wave generation, opening the door to a variety of future applications including high-dynamic range remote sensing, wideband wireless communications, and THz spectroscopy. Photonics-based radars offer intriguing potential but face tradeoffs in tunability, complexity, and noise. Here the authors present microwave generation in a photonics platform by heterodyning of two low-noise, self-injection-locked lasers, and demonstrate its advantages in an FMCW radar system.

TEMPEST-D Radiometer: Instrument Description and Prelaunch Calibration

Abstract: The Temporal Experiment for Storms and Tropical Systems Technology Demonstration (TEMPEST-D) instrument is a five-frequency millimeter-wave radiometer operating from 87 to 181 GHz. The cross-track scanning radiometer has been operating on a 6U CubeSat in low Earth orbit since September 5, 2018. The direct-detection architecture of the radiometer reduces its mass and power consumption by eliminating the need for a local oscillator and mixer, also reducing system complexity. The instrument includes a scanning reflector and ambient calibration target. The reflector rotates continuously to scan the antenna beams in the cross-track direction, first across the blackbody calibration target, then toward the Earth over the full range of incidence angles, and finally to cosmic microwave background radiation at 2.73 K. This enables precision end-to-end calibration of the millimeter-wave receivers during every 2-s scan period. The TEMPEST-D millimeter-wave radiometers are based on 35-nm indium phosphide (InP) high-electron-mobility transistor (HEMT) low-noise amplifiers. This article describes the instrument and its characterization prior to launch.

A Compact Harmonic Radar System With Active Tags at 61/122 GHz ISM Band in SiGe BiCMOS for Precise Localization

Abstract: This article presents a frequency-modulated continuous wave (FMCW) harmonic radar in the 61-/122-GHz industrial, scientific, and medical (ISM) frequency bands. The radar is based on two self-designed monolithic microwave wave integrated circuits (MMICs) for the transceiver (TRX) and tag which are fabricated in a 130-nm SiGe BiCMOS technology. The presented TRX-MMIC consists of a fundamental voltage-controlled oscillator (VCO), a power amplifier (PA), Wilkinson power dividers, and a static divide-by-16 chain for stabilization within a phase-locked loop (PLL) in the transmitter (TX) part. The receiver (RX) part has two channels with a low noise amplifier (LNA), a Gilbert cell mixer, and an intermediate frequency (IF)-amplifier each. The fundamental of the VCO is converted by a frequency doubler and distributed to the local oscillator (LO) input of the RX-mixers. With such a TRX architecture the active nonlinear tag which consists of antennas, pre-amplifiers, and a frequency doubler can be detected. For a sweep from 60 to 64 GHz, a spatial resolution of 4 cm at 1-m distance and a range of 23.3 m is achieved. With these characteristics, the tag enables harmonic radar applications in the millimeter-wave (mm-wave) range for medium range with high accuracy and resolution with a small form factor.

Towards Energy Efficient Mobile Wireless Receivers Above 100 GHz

Abstract: Wireless communication above 100 GHz offers the potential for massive data rates and has attracted considerable attention for Beyond 5G and 6G systems. A key challenge in the receiver design in these bands is power consumption, particularly for mobile and portable devices. This paper provides a general methodology for understanding the trade-offs of power consumption and end-to-end performance of a large class of potential receivers for these frequencies. The framework is applied to the design of a fully digital 140 GHz receiver with a 2 GHz sample rate, targeted for likely 6G cellular applications. Design options are developed for key RF components including the low noise amplifier (LNA), mixer, local oscillator (LO) and analog-digital converter (ADC) in 90 nm SiGe BiCMOS. The proposed framework, combined with detailed circuit and system simulations, is then used to select among the design options for the overall optimal end-to-end performance and power tradeoff. The analysis reveals critical design choices and bottlenecks. It is shown that optimizing these critical components can enable a dramatic 70 to 80% power reduction relative to a standard baseline design enabling fully-digital 140 GHz receivers with RF power consumption less than 2 W.

Demonstration of high-speed and low-complexity continuous variable quantum key distribution system with local local oscillator.

Abstract: We present an experimental demonstration of the feasibility of the first 20 + Mb/s Gaussian modulated coherent state continuous variable quantum key distribution system with a locally generated local oscillator at the receiver (LLO-CVQKD). To increase the signal repetition rate, and hence the potential secure key rate, we equip our system with high-performance, wideband devices and design the components to support high repetition rate operation. We have successfully trialed the signal repetition rate as high as 500 MHz. To reduce the system complexity and correct for any phase shift during transmission, reference pulses are interleaved with quantum signals at Alice. Customized monitoring software has been developed, allowing all parameters to be controlled in real-time without any physical setup modification. We introduce a system-level noise model analysis at high bandwidth and propose a new ‘combined-optimization’ technique to optimize system parameters simultaneously to high precision. We use the measured excess noise, to predict that the system is capable of realizing a record 26.9 Mb/s key generation in the asymptotic regime over a 15 km signal mode fibre. We further demonstrate the potential for an even faster implementation.

A 43–97-GHz Mixer-First Front-End With Quadrature Input Matching and On-Chip Image Rejection

Abstract: This article presents a wideband millimeter-wave (mmWave) receiver front-end that covers the frequency range from 43 to 97 GHz, supporting the operation in the major parts of the V-, E-, and W-bands. The front-end incorporates a passive mixer-first topology to achieve high linearity and wideband performance. The front-end adopts I/Q generation at the RF port, using a coupled-line coupler (CLC), rather than at the local oscillator (LO) port to mitigate the crosstalk of the overlapping I/Q LO signals especially present at high frequencies. The CLC at the RF input facilitates ultrawide band input matching. The front-end implements the multi-gate gm3 cancellation technique at the IF amplifiers to preserve the linearity and provide gain at the IF section. Image rejection capabilities using a current mode transformer-based IF 90° coupler are implemented on chip and demonstrated with measurements. The front-end prototype is fabricated on the GlobalFoundries 22-nm FD-SOI CMOS process and it demonstrates an ultra-wideband performance across the frequency range 43–97 GHz (2.25:1 bandwidth) with image rejection of up to 32 dB, IIP3 of 1.6–5.2 dBm, and gain of 15 dB. The implementation used is low-IF topology with 3.8-GHz IF frequency and 1-GHz bandwidth. Furthermore, the measurement results show that the front-end supports high-speed modulated signals of up to 6-Gbps 64QAM modulation data.

A 28-GHz Bidirectional Active Gilbert-Cell Mixer in 90-nm CMOS

Abstract: A bidirectional active mixer based on Gilbert-cell topology is proposed and realized in 90-nm CMOS at 28 GHz. The offered mixer can achieve both the up- and down-conversion under 1-dBm local oscillator (LO) power by adjusting the Gilbert quad switch’s gate bias. An IF bidirectional amplifier (IFBDA) is adapted to compensate for the conversion loss (CL) of the Gilbert quad switch. The measured peak conversion gain (CG) is −2.14/−3.28 dB at 28-GHz, and the 3-dB bandwidth is 7/6 GHz in transmit (Tx)/receive (Rx) mode. Total dc power consumption is only 8.4/6.4 mW for Tx/Rx mode under 1.2-V supply voltage. Compared with the traditional bidirectional passive mixers, this mixer demonstrates a low CL with a low LO power.

Frequency comb distillation for optical superchannel transmission

Abstract: Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical noise can degrade performance in optical systems. To overcome this, we demonstrate wideband noise reduction for comb lines using a high-Q microring resonator whose resonances align with the comb lines, providing tight optical filtering of multiple combs lines at the same time. By distilling an optical frequency comb in this way, we are able to reduce the required comb line OSNR when these lines are used in a coherent optical communications system. Through performance tests on a 19.45-GHz-spaced comb generating 71 lines, using 18 Gbaud, 64-QAM sub-channels at a spectral efficiency of 10.6 b/s/Hz, we find that noise-corrupted comb lines can reduce the optical signal-to-noise ratio required for the comb by ~ 9 dB when used as optical carriers at the transmitter side, and by ~ 12 dB when used as a local oscillator at the receiver side. This demonstration provides a method to enable low power optical frequency combs to be able to support high bandwidth and high-capacity communications.

High Rate CV-QKD Secured Mobile WDM Fronthaul for Dense 5G Radio Networks

Abstract: A coherent transmission methodology for a continuous-variable quantum key distribution (CV-QKD) system based on quantum-heterodyne measurement through a coherent intradyne receiver is experimentally demonstrated in the framework of 5G mobile fronthaul links Continuous optical carrier synchronization is obtained through training information, which is multiplexing to the quantum signal as pilot tone in both, frequency and polarization Spectral tailoring by means of optical carrier suppression and single-sideband modulation is adopted to simultaneously mitigate crosstalk into the quantum channel and self-interference for the pilot tone, thus allowing for a high signal-to-noise ratio for this training signal Frequency offset correction and optical phase estimation for the free-running local oscillator of the receiver is accurately performed and guarantees low-noise quantum signal reception at high symbol rates of 250 MHz and 500 MHz with additional Nyquist pulse shaping A low excess noise in the order of 01% to 05% of shot-noise units is obtained for fiber-based transmission over a fronthaul link reach of 132 km Moreover, co-existence with 11 carrier-grade classical signals is experimentally investigated Joint signal transmission in the C-band of both, quantum signal and classical signals, is successfully demonstrated Secure-key rates of 18 and 10 Mb/s are obtained under strict security assumptions, where Eve has control of the receiver noise, for a dark and a lit fiber link, respectively Moreover, rates of 85 and 72 Mb/s are resulting for a trusted receiver scenario These secure-key rates are well addressing the requirements for time-shared CV-QKD system in densified 5G radio access networks with cloud-based processing

An 8.2-to-21.5 GHz Dual-Core Quad-Mode Orthogonal-Coupled VCO with Concurrently Dual-Output using Parallel 8-Shaped Resonator

Abstract: Software-defined radio transceivers, wireless infrastructure equipment, and test equipment require the local oscillator (LO) to cover a very wide range of the output frequencies while meet the phase noise performance. The most straightforward method for a wide tuning range is to adopt multiple separated oscillators. However, this method suffers from the bulky area and relatively complicated multiplexing functions. The authors in [1] introduces triple-coupled inductors that create multiple resonant frequency in a high-order resonator. Nevertheless, the impedance magnitude looking into either port of the high-order resonator shows higher peak value at the lower resonant frequency, which makes it difficult to sustain stable oscillation at higher resonant frequency when the coupling factor is large. The VCO in [2] exploits series 8-shaped coils to generate two oscillation modes without coupling between each other while occupying compact area. However, the quality factor of the 8-shaped inductor is considerably lower than a typical octagonal inductor thereby degrading the oscillator phase noise. In order to solve the above-mentioned issues, a dual-core quad-mode orthogonal-coupled VCO using parallel 8-shaped resonator is proposed. Each core in the proposed VCO have two modes, with one mode being equivalent to the 8-shaped inductor, which allows both cores to be orthogonal to each other by proper configurations.

An 84.48 Gb/s CMOS D-band Multi-Channel TX System-in-Package

Abstract: This paper presents an in-package D-band wireless module co-integrating an innovative channel bonding transmitter IC in 45 nm CMOS PDSOI technology and a patch antenna fabricated using a low-cost printed circuit board process. The transmitter is composed of two up-conversion chains with dedicated millimeter-wave local oscillator generators and operates over contiguous sub-bands around 147.96 GHz. The two sub-band signals are combined off-chip using a substrate integrated waveguide diplexer and radiated by a four-patch antenna array realized on the same laminate substrate. The total output band spans from 139.3 to 156.6 GHz. A data rate of 84.48 Gb/s is demonstrated using 64-QAM. The radiated power is 3.8 dBm at the output 1 dB compression point. The chip consumes 600 mW from a 1-V voltage supply and occupies a compact area of 4.8mm2.

Photonic approach to flexible multi-band linearly frequency modulated microwave signals generation

Abstract: In this paper, a flexible multi-band linearly frequency modulated (LFM) signal generator based on a dual-polarization binary phase-shift keying (DP-BPSK) modulator is proposed and demonstrated by experiment. Two dual-drive Mach-Zehnder modulators of the DP-BPSK modulator are driven by a local oscillator (LO) signal and an LFM signal, respectively. By appropriately changing the phase difference introduced by a polarization controller, flexible multi-band LFM signals can be obtained after photoelectric conversion. The LO signal is phase modulated to eliminate self-heterodyne, which will affect the quality of the resulting signal.

155 GHz FMCW and Stepped-Frequency Carrier OFDM Radar Sensor Transceiver IC Featuring a PLL With <30 ns Settling Time and 40 fs rms Jitter

Abstract: A radar transceiver with two transmitters (TXs) and two receivers (RXs) is reported in 22 nm fully depleted silicon-on-insulator (FDSOI) CMOS. It includes a novel 200 MHz bandwidth 80 GHz phase-locked loop (PLL) based on a single-sideband (SSB) upconverter and an 11 GHz bandwidth phase-frequency detector to achieve >8 GHz locking range with record phase noise of −97, −103, and −113 dBc/Hz at 100 kHz, 1 MHz, and 10 MHz offset, respectively, and rms jitter $P_{\mathrm {SAT}}$ of the power amplifier (PA) in each TX are 5 and 9 dBm, respectively. The IQ amplitude mismatch and phase error of each RX are $P_{\mathbf {out}}$ mismatch between the TXs is < 1 dB. The sensor consumes 1.13 W, with 300 mW by the PLL, 275 mW by the 160 GHz local oscillator (LO)-tree, 190 mW by each TX, and 87.5 mW by each RX.

A 10-Gb/s 180-GHz Phase-Locked-Loop Minimum Shift Keying Receiver

Abstract: A 180-GHz minimum shift keying (MSK) receiver (RX) using a phase-locked loop (PLL), which self-synchronizes the carrier frequency, is demonstrated. The mixer-first RX is fabricated in a 65-nm CMOS process. A double-balanced anti-parallel-diode-pair sub-harmonic mixer performs the phase detection, reducing the frequency of local oscillator (LO) by half. Tunable zeros realized by series inductors are used to improve the stability and to increase the data rate handling capability. Without external LO synchronization, the RX demodulates MSK signals at 10 Gb/s with a bit error rate (BER) $\times $ 10−5. The BER at 10 Gb/s is the lowest and the data rate of 12.5 Gb/s is the highest for PLL RXs.

Frequency-Domain-Multiplexing Single-Wire Interface and Harmonic-Rejection-Based IF Data De-Multiplexing in Millimeter-Wave MIMO Arrays

Abstract: Recently, mm-wave multi-in multi-out (MIMO) arrays are garnering significant attention because of their ability to form multiple spatial beams, achieving significantly higher data rates compared to traditional phased array-based approaches. Furthermore, scalable MIMO arrays can provide many other functionalities, such as full digital beamforming and per-power amplifier (PA) digital pre-distortion. In this work, an MIMO four-element TX array architecture is presented with a frequency-domain multiplexing-based single-wire interface (SWI), breaking the tradeoff between channel-to-channel isolation and single wire (SW) bandwidth (BW). The concept of harmonic-rejection mixing (HRM) is used to de-multiplex the four modulated signals simultaneously from the SW using a single passive mixer driven by a multi-phase local oscillator (LO). The two-stage harmonic recombination circuits are implemented in baseband and, hence, achieve high channel-to-channel isolation with a low power overhead. A 60-GHz four-element TX prototype demonstrates the proposed architecture in 45-nm RF silicon-on-insulator (RFSOI) CMOS. The frequency-division-multiplexed (FDM)-based SWI can support 8-GHz total intermediate frequency (IF) BW across the four channels with 30–40-dB channel-to-channel isolation. Each TX element in the array achieves 20–35-dB conversion gain and +8.8–10.9-dBm OP1dB while consuming 225 mW/element.

Photonics-based Simultaneous Angle of Arrival and Frequency Measurement System with Multiple-Target Detection Capability

Abstract: A photonics-based system for simultaneous angle of arrival (AOA) and frequency measurement is proposed and demonstrated. In the proposed system, an acousto-optic modulator (AOM) based optical frequency shift loop (OFSL) is used to generate an optical frequency-stepped local oscillator (LO). After balanced in-phase and quadrature (I/Q) down-conversion with the frequency-stepped LO, the frequency to be measured is obtained. Thanks to the balanced I/Q down-conversion, the image frequencies and undesired frequency-mixing components can be suppressed, making the system have better adaptability to multiple-target scenarios. In addition, the AOA from different RF sources can also be estimated based on the Van CittertZernike theorem, even if the working bands of these targets overlap with each other. In the proof-of-concept experiment, the measurement of multiple targets with different frequencies is achieved by frequency detection with 0.179 MHz resolution. Moreover, incoherent microwave sources at the same frequency band can also be distinguished in the angular direction, achieving the capacity of simultaneous frequency and AOA measurement of multiple-target.

A 20–42-GHz IQ Receiver in 22-nm CMOS FD-SOI With 2.7–4.2-dB NF and −25-dBm IP1dB for Wideband 5G Systems

Abstract: This article presents a 20–42-GHz in-phase and quadrature (IQ) receiver in 22-nm CMOS fully depleted silicon on insulator (FD-SOI). The receiver includes a wideband low noise variable-gain amplifier (LN-VGA), double-balanced IQ mixers, wideband I/Q generation network and wideband local oscillator (LO) driver, low-pass filters, and wideband intermediate frequency (IF) amplifiers. The measured receiver has a peak conversion gain of 25.3 dB with a 3-dB bandwidth of 19.8–42 GHz and an I and Q bandwidth of 5.7 GHz and covers the 5G millimeter-wave (mm-wave) band. The measured single-sideband noise figure (NF) is 2.7–4.2 dB at 24–42 GHz with an IP1dB of −26 to −23 dBm. The I/Q downconverter consumes a total of 102 mW from 0.8- and 1.6-V supplies. The IP1dB can be improved by 5 dB with an NF degradation by only 1.2 dB using RF VGA gain control. At peak gain and −8-dB VGA setting, the receiver dynamic range is 64–68 dB for a 100-MHz bandwidth, which is very high for low power consumption. The gain and phase mismatch between the I and Q channels is < 0.6 dB and <6°, respectively. To the best of the authors’ knowledge, this is the first wideband I/Q receiver that covers the entire mm-wave 5G band based on GF 22-nm CMOS FD-SOI. The application area is multistandard multigigabit per second communication systems.

A 300-GHz Transmitter Front End With −4.1-dBm Peak Output Power for Sub-THz Communication Using 130-nm SiGe BiCMOS Technology

Abstract: This article presents a compact 300-GHz transmitter front end manufactured in a 130-nm SiGe BiCMOS process. The transmitter consists of a 240-GHz amplifier multiplier chain (AMC) and a modified 300-GHz Gilbert mixer. Limited by the space between top two thick metal layers of the SiGe process, the coupling coefficient between the coils, which form a transformer-based balun, is usually small at subterahertz (THz). Therefore, the vertical or horizontal coupling single-turn transformer-based balun will exhibit large insertion loss at around 300 GHz. In this work, a self-shielded Marchand balun (SSMB) with an enhancement to the coupling coefficient is proposed, which is realized by a novel multilayer metal topology with self-shielded coupling (SSC). The AMC is composed of a 120-GHz frequency doubler, a 120-GHz two-stage power amplifier (PA), and a two-way power synthesis balanced frequency doubler. This AMC exhibits a measured peak output power of 5.5 dBm at 252 GHz, with 48-GHz 3-dB bandwidth from 212 to 260 GHz. The transmitter chip achieves a maximum output power of −4.1 dBm at 300 GHz and delivers an output power better than −10 dBm from 270 to 315 GHz. Over the 30-GHz 3-dB bandwidth from 280 to 310 GHz, the transmitter shows a maximum OP1dB of −6.5 dBm at 296 GHz, a peak conversion gain of −11.2 dB at 298 GHz, and a local oscillator (LO)-to-RF leakage rejection better than 40 dB, with only 300-mW dc power consumption. Compared with other state of the arts, the transmitter exhibits a comparable output power among silicon-based transmitters near 300 GHz.

System-on-chip upgrade of millimeter-wave imaging diagnostics for fusion plasma

Abstract: Monolithic, millimeter wave “system-on-chip” technology has been employed in chip heterodyne radiometers in a newly developed Electron Cyclotron Emission Imaging (ECEI) system on the DIII-D tokamak for 2D electron temperature and fluctuation diagnostics. The system employs 20 horn-waveguide receiver modules each with customized W-band (75–110 GHz) monolithic microwave integrated circuit chips comprising a W-band low noise amplifier, a balanced mixer, a ×2 local oscillator (LO) frequency doubler, and two intermediate frequency amplifier stages in each module. Compared to previous quasi-optical ECEI arrays with Schottky mixer diodes mounted on planar antennas, the upgraded W-band array exhibits >30 dB additional gain and 20× improvement in noise temperature; an internal eight times multiplier chain is used to provide LO coupling, thereby eliminating the need for quasi-optical coupling. The horn-waveguide shielding housing avoids out-of-band noise interference on each module. The upgraded ECEI system plays an important role for absolute electron temperature and fluctuation measurements for edge and core region transport physics studies. An F-band receiver chip (up to 140 GHz) is under development for additional fusion facilities with a higher toroidal magnetic field. Visualization diagnostics provide multi-scale and multi-dimensional data in plasma profile evolution. A significant aspect of imaging measurement is focusing on artificial intelligence for science applications.

Passive continuous-variable quantum key distribution using a locally generated local oscillator

Abstract: We proposed a passive continuous-variable quantum key distribution (CVQKD) using a locally generated local oscillator (LLO) at reception. Different from the LLO-based Gaussian-modulated coherent-state quantum key distribution, our protocol is implemented by taking advantage of a multimode thermal source, beam splitters, optical attenuators, and homodyne detectors rather than the amplitude and phase modulators, which could be a cost-effective solution for LLO-based CVQKD. We adopt a general LLO noise model to analyze the performance of our protocol. That is to say, our consideration for noise in the proposed scheme contains the excess noise caused by passive state preparation, the phase noise, and the photon-leakage noise from the reference path. Because our protocol waives the necessity of the use of amplitude and phase modulators, there is no need to bear the effect of modulation noise caused by finite dynamics. Simulation results show that the improvement of the mode-overlap coefficient can suppress the excess noise caused by passive state preparation and thus enhance the performance of our protocol. Because lower relative phase drift and the photon-leakage noise can be obtained by using the multiplexing technique, we can still achieve reasonable performance of our protocol with the mode-overlap coefficient values which are very close to the experimental reference. Furthermore, we perform the finite-size analysis for the proposed protocol, which is more practical than that achieved in the asymptotic limit. This work confirms the feasibility of passive CVQKD implemented in the LLO configuration within the metropolitan area.

Frequency comb distillation for optical superchannel transmission

Abstract: Optical frequency combs can potentially provide an efficient light source for multi-terabit-per-second optical superchannels. However, as the bandwidth of these multi-wavelength light sources is increased, it can result in low per-line power. Optical amplifiers can be used to overcome power limitations, but the accompanying spontaneous optical noise can degrade performance in optical systems. To overcome this, we demonstrate wideband noise reduction for comb lines using a high-Q microring resonator whose resonances align with the comb lines, providing tight optical filtering of multiple combs lines at the same time. By distilling an optical frequency comb in this way, we are able to reduce the required comb line OSNR when these lines are used in a coherent optical communications system. Through performance tests on a 19.45-GHz-spaced comb generating 71 lines, using 18 Gbaud, 64-QAM sub-channels at a spectral efficiency of 10.6 b/s/Hz, we find that noise-corrupted comb lines can reduce the optical signal-to-noise ratio required for the comb by ~ 9 dB when used as optical carriers at the transmitter side, and by ~ 12 dB when used as a local oscillator at the receiver side. This demonstration provides a method to enable low power optical frequency combs to be able to support high bandwidth and high-capacity communications.

High Rate CV-QKD Secured Mobile WDM Fronthaul for Dense 5G Radio Networks

Abstract: A coherent transmission methodology for a continuous-variable quantum key distribution (CV-QKD) system based on quantum-heterodyne measurement through a coherent intradyne receiver is experimentally demonstrated in the framework of 5G mobile fronthaul links. Continuous optical carrier synchronization is obtained through training information, which is multiplexing to the quantum signal as pilot tone in both, frequency and polarization. Spectral tailoring by means of optical carrier suppression and single-sideband modulation is adopted to simultaneously mitigate crosstalk into the quantum channel and self-interference for the pilot tone, thus allowing for a high signal-to-noise ratio for this training signal. Frequency offset correction and optical phase estimation for the free-running local oscillator of the receiver is accurately performed and guarantees low-noise quantum signal reception at high symbol rates of 250 MHz and 500 MHz with additional Nyquist pulse shaping. A low excess noise in the order of 0.1% to 0.5% of shot-noise units is obtained for fiber-based transmission over a fronthaul link reach of 13.2 km. Moreover, co-existence with 11 carrier-grade classical signals is experimentally investigated. Joint signal transmission in the C-band of both, quantum signal and classical signals, is successfully demonstrated. Secure-key rates of 18 and 10 Mb/s are obtained under strict security assumptions, where Eve has control of the receiver noise, for a dark and a lit fiber link, respectively. Moreover, rates of 85 and 72 Mb/s are resulting for a trusted receiver scenario. These secure-key rates are well addressing the requirements for time-shared CV-QKD system in densified 5G radio access networks with cloud-based processing.