Showing papers on "Phase noise published in 2013"
TL;DR: Generation of highly coherent microwaves using a chip-based device that derives stability from high optical quality factor is reported, which has a record low electronic white-phase-noise floor for a microcavity-based oscillator and is used as the optical, voltage-controlled oscillator in the first demonstration of a photonic-based, microwave frequency synthesizer.
Abstract: Low-phase-noise microwave oscillators are important to a wide range of subjects, including
communications, radar and metrology. Photonic-based microwave-wave sources now provide
record, close-to-carrier phase-noise performance, and compact sources using microcavities
are available commercially. Photonics-based solutions address a challenging scaling problem
in electronics, increasing attenuation with frequency. A second scaling challenge, however, is
to maintain low phase noise in reduced form factor and even integrated systems. On this
second front, there has been remarkable progress in the area of microcavity devices with
large storage time (high optical quality factor). Here we report generation of highly coherent
microwaves using a chip-based device that derives stability from high optical quality factor.
The device has a record low electronic white-phase-noise floor for a microcavity-based
oscillator and is used as the optical, voltage-controlled oscillator in the first demonstration of
a photonic-based, microwave frequency synthesizer. The synthesizer performance is comparable
to mid-range commercial devices.
292 citations
TL;DR: The root cause of performance bottlenecks in current full-duplex systems is investigated and signal models for wideband and multiple-input-multiple-output (MIMO) full- DUplex systems are proposed, capturing all the salient design parameters, thus allowing future analytical development of advanced coding and signal design for full- duplex systems.
Abstract: Recent experimental results have shown that full-duplex communication is possible for short-range communications. However, extending full-duplex to long-range communication remains a challenge, primarily due to residual self-interference, even with a combination of passive suppression and active cancelation methods. In this paper, we investigate the root cause of performance bottlenecks in current full-duplex systems. We first classify all known full-duplex architectures based on how they compute their canceling signal and where the canceling signal is injected to cancel self-interference. Based on the classification, we analytically explain several published experimental results. The key bottleneck in current systems turns out to be the phase noise in the local oscillators in the transmit-and-receive chain of the full-duplex node. As a key by-product of our analysis, we propose signal models for wideband and multiple-input-multiple-output (MIMO) full-duplex systems, capturing all the salient design parameters, thus allowing future analytical development of advanced coding and signal design for full-duplex systems.
251 citations
TL;DR: Three iterative algorithms with different complexity vs. performance trade-offs are proposed to mitigate asynchronous impulsive noise, exploit its sparsity in the time domain, and apply sparse Bayesian learning methods to estimate and subtract the noise impulses.
Abstract: Asynchronous impulsive noise and periodic impulsive noises limit communication performance in OFDM powerline communication systems. Conventional OFDM receivers that assume additive white Gaussian noise experience degradation in communication performance in impulsive noise. Alternate designs assume a statistical noise model and use the model parameters in mitigating impulsive noise. These receivers require training overhead for parameter estimation, and degrade due to model and parameter mismatch. To mitigate asynchronous impulsive noise, we exploit its sparsity in the time domain, and apply sparse Bayesian learning methods to estimate and subtract the noise impulses. We propose three iterative algorithms with different complexity vs. performance trade-offs: (1) we utilize the noise projection onto null and pilot tones; (2) we add the information in the date tones to perform joint noise estimation and symbol detection; (3) we use decision feedback from the decoder to further enhance the accuracy of noise estimation. These algorithms are also embedded in a time-domain block interleaving OFDM system to mitigate periodic impulsive noise. Compared to conventional OFDM receivers, the proposed methods achieve SNR gains of up to 9 dB in coded and 10 dB in uncoded systems in asynchronous impulsive noise, and up to 6 dB in coded systems in periodic impulsive noise.
244 citations
TL;DR: In this article, a closed-loop echo cancellation technique is proposed to cancel high-power echoes at the receive chain as echoes with powers much higher than the desired received signal, which can be implemented purely in the analogue domain.
Abstract: Full Duplex or Simultaneous transmission and reception (STR) in the same frequency at the same time can potentially double the physical layer capacity. However, high power transmit signal will appear at receive chain as echoes with powers much higher than the desired received signal. Therefore, in order to achieve the potential gain, it is imperative to cancel these echoes. As these high power echoes can saturate low noise amplifier (LNA) and also digital domain echo cancellation requires unrealistically high resolution analog-to-digital converter (ADC), the echoes should be cancelled or suppressed sufficiently before LNA. In this paper we present a closed-loop echo cancellation technique which can be implemented purely in analogue domain. The advantages of our method are multiple-fold: it is robust to phase noise, does not require additional set of antennas, can be applied to wideband signals and the performance is irrelevant to radio frequency (RF) impairments in transmit chain. Next, we study a few protocols for STR systems in carrier sense multiple access (CSMA) network and investigate MAC level throughput with realistic assumptions in both single cell and multiple cells. We show that STR can reduce hidden node problem in CSMA network and produce gains of up to 279% in maximum throughput in such networks. Moreover, at high traffic load, the gain of STR system can be tremendously large since the throughput of non-STR system is close to zero at heavy traffic due to severe collisions. Finally, we investigate the application of STR in cellular systems and study two new unique interferences introduced to the system due to STR, namely BS-BS interference and UE-UE interference. We show that these two new interferences will hugely degrade system performance if not treated appropriately. We propose novel methods to reduce both interferences and investigate the performances in system level. We show that BS-BS interference can be suppressed sufficiently enough to be less than thermal noise power, and with favorable UE-UE channel model, capacities close to double are observed both in downlink (DL) and uplink (UL). When UE-UE interference is larger than DL co-channel interferences, we propose a simple and "non-cooperative" technique in order to reduce UE-UE interference.
208 citations
TL;DR: A comprehensive study of circuit-to-phase-noise conversion mechanisms of different oscillators' structures shows the proposed class-F exhibits the lowest phase noise at the same tank's quality factor and supply voltage.
Abstract: An oscillator topology demonstrating an improved phase noise performance is proposed in this paper. It exploits the time-variant phase noise model with insights into the phase noise conversion mechanisms. The proposed oscillator is based on enforcing a pseudo-square voltage waveform around the LC tank by increasing the third-harmonic of the fundamental oscillation voltage through an additional impedance peak. This auxiliary impedance peak is realized by a transformer with moderately coupled resonating windings. As a result, the effective impulse sensitivity function (ISF) decreases thus reducing the oscillator's effective noise factor such that a significant improvement in the oscillator phase noise and power efficiency are achieved. A comprehensive study of circuit-to-phase-noise conversion mechanisms of different oscillators' structures shows the proposed class-F exhibits the lowest phase noise at the same tank's quality factor and supply voltage. The prototype of the class-F oscillator is implemented in TSMC 65-nm standard CMOS. It exhibits average phase noise of -136 dBc/Hz at 3 MHz offset from the carrier over 5.9-7.6 GHz tuning range with figure-of-merit of 192 dBc/Hz. The oscillator occupies 0.12 mm2 while drawing 12 mA from 1.25 V supply.
196 citations
TL;DR: A closed-loop echo cancellation technique which can be implemented purely in analogue domain is presented and is robust to phase noise, does not require additional set of antennas, can be applied to wideband signals and the performance is irrelevant to radio frequency (RF) impairments in transmit chain.
Abstract: Full Duplex or Simultaneous transmission and reception (STR) in the same frequency at the same time can potentially double the physical layer capacity. However, high power transmit signal will appear at receive chain as echoes with powers much higher than the desired received signal. Therefore, in order to achieve the potential gain, it is imperative to cancel these echoes. As these high power echoes can saturate low noise amplifier (LNA) and also digital domain echo cancellation requires unrealistically high resolution analog-to-digital converter (ADC), the echoes should be cancelled or suppressed sufficiently before LNA. In this paper we present a closed-loop echo cancellation technique which can be implemented purely in analogue domain. The advantages of our method are multiple-fold: it is robust to phase noise, does not require additional set of antennas, can be applied to wideband signals and the performance is irrelevant to radio frequency (RF) impairments in transmit chain. Next, we study a few protocols for STR systems in carrier sense multiple access (CSMA) network and investigate MAC level throughput with realistic assumptions in both single cell and multiple cells. We show that STR can reduce hidden node problem in CSMA network and produce gains of up to 279% in maximum throughput in such networks. Finally, we investigate the application of STR in cellular systems and study two new unique interferences introduced to the system due to STR, namely BS-BS interference and UE-UE interference. We show that these two new interferences will hugely degrade system performance if not treated appropriately. We propose novel methods to reduce both interferences and investigate the performances in system level.
176 citations
TL;DR: A fully phase-locked frequency comb that can operate outside the well-controlled optical laboratory and should enable metrological measurements outside the laboratory with the precision and accuracy that are the hallmarks of comb-based systems is demonstrated.
Abstract: We demonstrate a self-referenced fiber frequency comb that can operate outside the well-controlled optical laboratory. The frequency comb has residual optical linewidths of < 1 Hz, sub-radian residual optical phase noise, and residual pulse-to-pulse timing jitter of 2.4 - 5 fs, when locked to an optical reference. This fully phase-locked frequency comb has been successfully operated in a moving vehicle with 0.5 g peak accelerations and on a shaker table with a sustained 0.5 g rms integrated acceleration, while retaining its optical coherence and 5-fs-level timing jitter. This frequency comb should enable metrological measurements outside the laboratory with the precision and accuracy that are the hallmarks of comb-based systems. Work of the U.S. government, not subject to copyright
164 citations
TL;DR: The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo-optic effect, leading to transverse mode instability in high-power rare-earth doped fiber amplifiers.
Abstract: We present a simple theoretical model of transverse mode instability in high-power rare-earth doped fiber amplifiers. The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo-optic effect, leading to transverse mode instability. The temporal and spectral characteristics of the instability dynamics are investigated, and it is shown that the instability can be seeded by both quantum noise and signal intensity noise, while pure phase noise of the signal does not induce instability. It is also shown that the presence of a small harmonic amplitude modulation of the signal can lead to generation of higher harmonics in the output intensity when operating near the instability threshold.
163 citations
TL;DR: Multidimensional Coherent Optical Photocurrent Spectroscopy (MD-COPS) is implemented using unstabilized interferometers, achieving sufficient phase stability without the need for active stabilization.
Abstract: Multidimensional Coherent Optical Photocurrent Spectroscopy (MD-COPS) is implemented using unstabilized interferometers. Photocurrent from a semiconductor sample is generated using a sequence of four excitation pulses in a collinear geometry. Each pulse is frequency shifted by a unique radio frequency through acousto-optical modulation; the Four-Wave Mixing (FWM) signal is then selected in the frequency domain. The interference of an auxiliary continuous wave laser, which is sent through the same interferometers as the excitation pulses, is used to synthesize reference frequencies for lock-in detection of the photocurrent FWM signal. This scheme enables the partial compensation of mechanical fluctuations in the setup, achieving sufficient phase stability without the need for active stabilization. The method intrinsically provides both the real and imaginary parts of the FWM signal as a function of inter-pulse delays. This signal is subsequently Fourier transformed to create a multi-dimensional spectrum. Measurements made on the excitonic resonance in a double InGaAs quantum well embedded in a p-i-n diode demonstrate the technique.
159 citations
TL;DR: It is shown that by operating the oscillator at special points in the resonator's anharmonic regime the authors can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit.
Abstract: In its most basic form an oscillator consists of a resonator driven on resonance, through feedback, to create a periodic signal sustained by a static energy source. The generation of a stable frequency, the basic function of oscillators, is typically achieved by increasing the amplitude of motion of the resonator while remaining within its linear, harmonic regime. Contrary to this conventional paradigm, in this Letter we show that by operating the oscillator at special points in the resonator’s anharmonic regime we can overcome fundamental limitations of oscillator performance due to thermodynamic noise as well as practical limitations due to noise from the sustaining circuit. We develop a comprehensive model that accounts for the major contributions to the phase noise of the nonlinear oscillator. Using a nanoelectromechanical system based oscillator, we experimentally verify the existence of a special region in the operational parameter space that enables suppressing the most significant contributions to the oscillator’s phase noise, as predicted by our model.
154 citations
TL;DR: The analysis shows that when phase noise dominates mixer and quantization noise, full-duplex systems can use either active analog cancellation or baseband digital cancellation to achieve near-identical rate gain regions.
Abstract: In this paper, we analytically study the regime in which practical full-duplex systems can achieve larger rates than an equivalent half-duplex systems. The key challenge in practical full-duplex systems is uncancelled self-interference signal, which is caused by a combination of hardware and implementation imperfections. Thus, we first present a signal model which captures the effect of significant impairments such as oscillator phase noise, low-noise amplifier noise figure, mixer noise, and analog-to-digital converter quantization noise. Using the detailed signal model, we study the rate gain region, which is defined as the region of received signal-of-interest strength where full-duplex systems outperform half-duplex systems in terms of achievable rate. The rate gain region is derived as a piecewise linear approximation in log-domain, and numerical results show that the approximation closely matches the exact region. Our analysis shows that when phase noise dominates mixer and quantization noise, full-duplex systems can use either active analog cancellation or baseband digital cancellation to achieve near-identical rate gain regions. Finally, as a design example, we numerically investigate the full-duplex system performance and rate gain region in typical indoor environments for practical wireless applications.
TL;DR: In this paper, the effect of phase noise in frequency-selective massive MIMO systems with imperfect channel state information (CSI) was studied and a linear and low-complexity time-reversal maximum ratio combining (TR-MRC) reception strategy was proposed.
Abstract: Multi-user multiple-input multiple-output (MU-MIMO) cellular systems with an excess of base station (BS) antennas (Massive MIMO) offer unprecedented multiplexing gains and radiated energy efficiency. Oscillator phase noise is introduced in the transmitter and receiver radio frequency chains and severely degrades the performance of communication systems. We study the effect of oscillator phase noise in frequency-selective Massive MIMO systems with imperfect channel state information (CSI). In particular, we consider two distinct operation modes, namely when the phase noise processes at the $M$ BS antennas are identical (synchronous operation) and when they are independent (non-synchronous operation). We analyze a linear and low-complexity time-reversal maximum-ratio combining (TR-MRC) reception strategy. For both operation modes we derive a lower bound on the sum-capacity and we compare their performance. Based on the derived achievable sum-rates, we show that with the proposed receive processing an $O(\sqrt{M})$ array gain is achievable. Due to the phase noise drift the estimated effective channel becomes progressively outdated. Therefore, phase noise effectively limits the length of the interval used for data transmission and the number of scheduled users. The derived achievable rates provide insights into the optimum choice of the data interval length and the number of scheduled users.
TL;DR: Compared with the commonly used class-B/C architectures, the optimal class-D oscillator produces less phase noise for the same power consumption, at the expense of a higher power supply pushing.
Abstract: This paper presents class-D CMOS oscillators capable of an excellent phase noise performance from a very low power supply voltage. Starting from the recognition of the time-variant nature of the class-D LC tank, accurate expressions of the oscillation frequency, oscillation amplitude, current consumption, phase noise, and figure-of-merit (FoM) have been derived. Compared with the commonly used class-B/C architectures, the optimal class-D oscillator produces less phase noise for the same power consumption, at the expense of a higher power supply pushing. A prototype of a class-D voltage-controlled oscillator (VCO) targeted for mobile applications, implemented in a standard 65-nm CMOS process, covers a 46% tuning range between 3.0 and 4.8 GHz; drawing 10 mA from 0.4 V, the phase noise at 10-MHz offset from 4.8 GHz is -143.5 dBc/Hz, for an FoM of 191 dBc/Hz with less than 1-dB variation across the tuning range. A version of the same VCO with a resonant tail filter displays a lower 1/f3 phase-noise corner and improves the FoM by 1 dB.
TL;DR: In this paper, a 32-element symmetrical TX/RX 60 GHz RF integrated circuit (RFIC) with built-in self-test is presented, which achieves record size and power consumption.
Abstract: Fully integrated 32-element symmetrical TX/RX 60-GHz RF integrated circuit (RFIC) with built-in self-test is presented. The RF bidirectional power-combining architecture with shared blocks and less than 1-dB millimeter-wave transmit/receive (T/R) switch loss achieves record size and power consumption. The RFIC features an 8-dB noise figure and - 28-dBm IP1 dB in RX mode, 10-dB power gain, and Psat of +3.5 dBm per chain in TX mode. Further included are a 2-bit phase shifter, an IF converter to/from 12 GHz, and an integrated frac-N synthesizer with push-push voltage-controlled oscillator having a-93 dBc@1-MHz phase noise at 48-GHz local oscillator port. A novel high dynamic range phase and power detector is presented with 2° and ±1-dB accuracy over PVT in phase and power. A detailed analysis of both phase quantization and power distribution is presented. Array impairments such as mismatch and coupling were compared for different topologies. The RFIC is packaged on alumina for testing and on low-temperature co-fired ceramic (LTCC) for antenna integration. The 6 × 6 patch antenna on LTCC including four dummies achieves a gain of 19 dBi with scanning of ± 30°. The total root mean square amplitude and phase error of the array is 0.8 dB and 6° , respectively, resulting in a maximum array beam degradation of 1.4 dB for 2-bit quantization. The RFIC area is 29 mm2 and it consumes 1.2 W/0.85 W at TX/RX, with a 29-dBm effective isotropic radiated power at -19-dB error vector magnitude.
TL;DR: The narrow linewidth of optomechanical oscillation combined with harmonic optical modulation generated by nonlinear optical transfer function, can result in sub-pg mass sensitivity in large silica microtoroid OMOs and the analysis shows that femtogram level resolution is within reach even with relatively large O MOs.
Abstract: Mass sensing based on mechanical oscillation frequency shift in micro/nano scale mechanical oscillators is a well-known and widely used technique. Piezo-electric, electronic excitation/detection and free-space optical detection are the most common techniques used for monitoring the minute frequency shifts induced by added mass. The advent of optomechanical oscillator (OMO), enabled by strong interaction between circulating optical power and mechanical deformation in high quality factor optical microresonators, has created new possibilities for excitation and interrogation of micro/nanomechanical resonators. In particular, radiation pressure driven optomechanical oscillators (OMOs) are excellent candidates for mass detection/measurement due to their simplicity, sensitivity and all-optical operation. In an OMO, a high quality factor optical mode simultaneously serves as an efficient actuator and a sensitive probe for precise monitoring of the mechanical eigen-frequencies of the cavity structure. Here, we show the narrow linewidth of optomechanical oscillation combined with harmonic optical modulation generated by nonlinear optical transfer function, can result in sub-pg mass sensitivity in large silica microtoroid OMOs. Moreover by carefully studying the impact of mechanical mode selection, device dimensions, mass position and noise mechanisms we explore the performance limits of OMO both as a mass detector and a high resolution mass measurement system. Our analysis shows that femtogram level resolution is within reach even with relatively large OMOs.
TL;DR: An analysis of several different oscillators, starting with the common class-B architecture and arriving to the proposed class-C design, shows that the latter exhibits a figure-of-merit (FoM) that is closest to the ideal FoM allowed by the integration technology.
Abstract: This paper presents two class-C CMOS VCOs with a dynamic bias of the core transistors, which maximizes the oscillation amplitude without compromising the robustness of the oscillation start-up, thereby breaking the most severe trade-off in the original class-C topology. An analysis of several different oscillators, starting with the common class-B architecture and arriving to the proposed class-C design, shows that the latter exhibits a figure-of-merit (FoM) that is closest to the ideal FoM allowed by the integration technology. The class-C VCOs have been implemented in a 90 nm CMOS process with a thick top metal layer. They are tunable between 3.4 GHz and 4.5 GHz, covering a tuning range of 28%. Drawing 5.5 mA from 1.2 V, the phase noise is lower than -152 dBc/Hz at a 20 MHz offset from a 4 GHz carrier. The resulting FoM is 191 dBc/Hz, and varies less than 1 dB across the tuning range.
TL;DR: It was concluded that the differential cascode buffer placed between the VCO and doubler was instrumental in achieving the best phase noise and output power with good efficiency and without compromising tuning range.
Abstract: The paper presents design optimization strategies and a comparison of the performance of SiGe HBT fundamental and push-push Colpitts and Colpitts-Clapp voltage-controlled oscillators (VCOs), with and without doublers and buffers, as possible solutions for efficient milliwatt-level, low-noise signal sources at submillimeter-wave frequencies. The fundamental frequency Colpitts VCO covers a 12% tuning range between 218 and 246 GHz (the highest for SiGe HBTs) with up to -3.6-dBm output power and 0.8% efficiency. The 300-GHz signal source, consisting of a Colpitts-Clapp VCO followed by a buffer amplifier and a doubler, shows -1.7-dBm output power around 290 GHz, -101-dBc/Hz phase noise at 10-MHz offset, 7.5% tuning range, and 0.4% efficiency. Finally, the push-push Colpitts-Clapp VCO exhibits the highest operation frequency, from 309 to 325 GHz, but with reduced efficiency of only 0.07% and 5% tuning range. It was concluded that the differential cascode buffer placed between the VCO and doubler was instrumental in achieving the best phase noise and output power with good efficiency and without compromising tuning range.
TL;DR: By combining the technique with the short-term stability provided by a remote, high-quality quartz oscillator, this system is potentially applicable to transcontinental optical-fiber time and frequency dissemination where the optical round-trip propagation time is significant.
Abstract: We demonstrate long-distance (≥100-km) synchronization of the phase of a radio-frequency reference over an optical-fiber network without needing to actively stabilize the optical path length Frequency mixing is used to achieve passive phase-conjugate cancellation of fiber-length fluctuations, ensuring that the phase difference between the reference and synchronized oscillators is independent of the link length The fractional radio-frequency-transfer stability through a 100-km "real-world" urban optical-fiber network is 6 × 10(-17) with an averaging time of 10(4) s Our compensation technique is robust, providing long-term stability superior to that of a hydrogen maser By combining our technique with the short-term stability provided by a remote, high-quality quartz oscillator, this system is potentially applicable to transcontinental optical-fiber time and frequency dissemination where the optical round-trip propagation time is significant
TL;DR: A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated, achieving the widest fundamental frequency tunable range ever achieved by an OEO.
Abstract: A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated. A tunable range from 4.74 to 38.38 GHz is realized by directly tuning the bandwidth of the optical bandpass filter. To the best of our knowledge, this is the widest fundamental frequency tunable range ever achieved by an OEO. The phase noise performance of the generated signal is also investigated. The single-sideband phase noise is below -120 dBc/Hz at an offset of 10 KHz within the whole tunable range.
TL;DR: A feedback class-C voltage-controlled oscillator that has robust start-up and a large oscillation amplitude and transforms automatically into an amplitude-enhanced class- C VCO when it reaches steady-state to give improved noise performance is proposed.
Abstract: We propose a feedback class-C voltage-controlled oscillator (VCO) that has robust start-up and a large oscillation amplitude. It initially starts oscillating as a conventional cross-coupled LC-VCO for robust start-up and subsequently transforms automatically into an amplitude-enhanced class-C VCO when it reaches steady-state to give improved noise performance. Detailed analysis of the start-up conditions, enhanced oscillation swing, and amplitude stability provides valuable insight into oscillator design considerations. The proposed VCO is implemented in a 0.18-μm CMOS process. The measured phase noise at room temperature is - 125 dBc/Hz at 1 MHz offset with a power dissipation of 3.4 mW at an oscillation frequency of 4.84 GHz. The figure-of-merit is -193 dBc/Hz.
TL;DR: Both reduction in jitter accumulation down to sub-picosecond levels and improved supply noise rejection over conventional PLL architectures is demonstrated with low power consumption.
Abstract: A highly-digital clock multiplication architecture that achieves excellent jitter and mitigates supply noise is presented. The proposed architecture utilizes a calibration-free digital multiplying delay-locked loop (MDLL) to decouple the tradeoff between time-to-digital converter (TDC) resolution and oscillator phase noise in digital phase-locked loops (PLLs). Both reduction in jitter accumulation down to sub-picosecond levels and improved supply noise rejection over conventional PLL architectures is demonstrated with low power consumption. A digital PLL that employs a 1-bit TDC and a low power regulator that seeks to improve supply noise immunity without increasing loop delay is presented and used to compare with the proposed MDLL. The prototype MDLL and DPLL chips are fabricated in a 0.13 μm CMOS technology and operate from a nominal 1.1 V supply. The proposed MDLL achieves an integrated jitter of 400 fs rms at 1.5 GHz output frequency from a 375 MHz reference clock, while consuming 890 μ W. The worst-case supply noise sensitivity of the MDLL is 20 fspp/mVpp which translates to a jitter degradation of 3.8 ps in the presence of 200 mV supply noise. The proposed clock multipliers occupy active die areas of 0.25 mm2 and 0.2 mm2 for the MDLL and DPLL, respectively.
TL;DR: In this article, the authors show that the current generation of aperture masking observations of young solar-type stars, taken carefully in excellent observing conditions, are consistent with being limited by temporal phase noise and photon noise.
Abstract: Bispectrum phase, closure phase and their generalisation to kernel-phase are all independent of pupil-plane phase errors to first-order. This property, when used with Sparse Aperture Masking (SAM) behind adaptive optics, has been used recently in high-contrast observations at or inside the formal diffraction limit of large telescopes. Finding the limitations to these techniques requires an understanding of spatial and temporal third-order phase effects, as well as effects such as time-variable dispersion when coupled with the non-zero bandwidths in real observations. In this paper, formulae describing many of these errors are developed, so that a comparison can be made to fundamental noise processes of photon- and background-noise. I show that the current generation of aperture-masking observations of young solar-type stars, taken carefully in excellent observing conditions, are consistent with being limited by temporal phase noise and photon noise. This has relevance for plans to combine pupil-remapping with spatial filtering. Finally, I describe calibration strategies for kernel-phase, including the optimised calibrator weighting as used for LkCa 15, and the restricted kernel-phase POISE technique that avoids explicit dependence on calibrators.
28 Mar 2013
TL;DR: This paper presents a 10 Gbps millimeter wave OFDM experimental system using a highly efficient modulation and coding scheme where iterative phase noise compensation can drastically alleviate performance degradation due to phase noise.
Abstract: This paper presents a 10 Gbps millimeter wave OFDM experimental system using a highly efficient modulation and coding scheme where iterative phase noise compensation can drastically alleviate performance degradation due to phase noise. 60 GHz frequency synthesizer in a silicon RF-CMOS IC suffers from relatively large phase noise, which severely degrades the performance of the 10 Gbps OFDM using 64QAM and LDPC code with coding rate of 14/15. In order to alleviate this impairment, the experimental system applies combination of decision-directed phase noise compensation (DD-PNC), decision-directed channel estimation (DDCE) and packet interleaving (P-IL) to OFDM reception processing. The sophisticated combination of iterative processing provides a synergistic effect on coping with the influence of the phase noise by exploiting outputs of the LDPC decoder. Experimental results of the 10 Gbps OFDM with 60 GHz cable connection demonstrate that the combination can achieve 10 Gbps throughput at SNR of 25.8 dB when the phase noise level is -89 dBc/Hz at 1 MHz offset.
TL;DR: Fundamental timing jitter in repetition rate of a mode locked Kerr frequency comb generated in an externally pumped nonlinear ring resonator results in the increase of low frequency noise, and a decrease in high frequency noise.
Abstract: We study fundamental timing jitter in repetition rate of a mode locked Kerr frequency comb generated in an externally pumped nonlinear ring resonator. We show that the increase in the integrated power of the comb harmonics, and the corresponding decrease of the duration of the associated pulse, results in the increase of low frequency noise, and a decrease in high frequency noise.
TL;DR: In this paper, invariant-based inverse engineering is used to drive fields that invert the population of a two-level atom in a given time, robustly with respect to dephasing noise and/or systematic frequency shifts.
Abstract: We design, by invariant-based inverse engineering, driving fields that invert the population of a two-level atom in a given time, robustly with respect to dephasing noise and/or systematic frequency shifts. Without imposing constraints, optimal protocols are insensitive to the perturbations but need an infinite energy. For a constrained value of the Rabi frequency, a flat $\ensuremath{\pi}$ pulse is the least sensitive protocol to phase noise but not to systematic frequency shifts, for which we describe and optimize a family of protocols.
TL;DR: A MEMS-based programmable oscillator is presented which achieves better than ±0.5-ppm frequency stability from -40°C to 85°C and less than 1-ps (rms) integrated phase noise.
Abstract: MEMS-based oscillators offer a silicon-based alternative to quartz-based frequency references. Here, a MEMS-based programmable oscillator is presented which achieves better than ±0.5-ppm frequency stability from -40°C to 85°C and less than 1-ps (rms) integrated phase noise (12 kHz to 20 MHz). A key component of this system is a thermistor-based temperature-to-digital converter (TDC) which enables accurate and low noise compensation of temperature-induced variation of the MEMS resonant frequency. The TDC utilizes several circuit techniques including a high-resolution tunable reference resistor based on a switched-capacitor network and fractional-N frequency division, a switched resistor measurement approach which allows a pulsed bias technique for reduced noise, and a VCO-based quantizer for digitization of the temperature signal. The TDC achieves 0.1-mK (rms) resolution within a 5-Hz bandwidth while consuming only 3.97 mA for all analog and digital circuits at 3.3-V supply in 180-nm CMOS.
TL;DR: A prototype 25 GHz VCO based on transconductance linearization of the active devices is integrated in a dual-path PLL and achieves superior performance compared to the state of the art.
Abstract: This paper describes a new approach to low-phase-noise LC VCO design based on transconductance linearization of the active devices. A prototype 25 GHz VCO based on this linearization approach is integrated in a dual-path PLL and achieves superior performance compared to the state of the art. The design is implemented in 32 nm SOI CMOS technology and achieves a phase noise of $-$ 130 dBc/Hz at a 10 MHz offset from a 22 GHz carrier. Additionally, the paper introduces a new layout approach for switched capacitor arrays that enables a wide tuning range of 23%. More than 1500 measurements of the PLL across PVT variations were taken, further validating the proposed design. Phase noise variation across 55 dies for four different frequencies is $\sigma . Also, phase noise variation across supply voltages of 0.7–1.5 V is 2 dB and across 60 $^{\circ}{\rm C}$ temperature variation is 3 dB. At the 25 GHz center frequency, the VCO $FOM_{T}$ is 188 dBc/Hz. Additionally, a digitally assisted autonomic biasing technique is implemented in the PLL to provide a phase noise and power optimized VCO bias across frequency and process. Measurement results indicate the efficacy of the autonomic biasing scheme.
02 Jun 2013
TL;DR: In this article, a closed-form expression for the ranging uncertainty of a primary frequency-modulated continuous-wave (FMCW) radar is introduced, where the phase noise profile of the transceiver serves as an input for this novel approach.
Abstract: In this paper, a closed-form expression for the ranging uncertainty of a primary frequency-modulated continuous-wave (FMCW) radar is introduced. In addition to basic system parameters also the phase noise profile of the transceiver serves as an input for this novel approach. On the signal processing side, phase noise range correlation effects are taken into account and an estimate for the ranging uncertainty is deduced. Thus, the influence of phase noise on the system performance in terms of precision can be directly predicted. For support of the theory, Monte-Carlo simulations were conducted. Measurement results acquired with a 77 GHz radar system are in good agreement with the theory.
28 Mar 2013
TL;DR: Relaxation oscillators are suitable candidates to generate on-chip reference clock generators for low-cost low-power area-efficient SoCs, such as implantable biomedical devices and microcomputers but the poor phase noise performance and large long-term variation limit their application.
Abstract: There is a growing interest in implementing on-chip reference clock generators for low-cost low-power area-efficient SoCs, such as implantable biomedical devices and microcomputers. Relaxation oscillators are suitable candidates to generate such reference clocks due to their compact size, low power consumption and wide frequency tuning range. However, the poor phase noise performance and large long-term variation are two major problems that limit their application.
TL;DR: In this paper, high-power, high-linearity modified unitraveling carrier (MUTC) photodiodes were used for low-phase-noise photonic microwave generation based on optical frequency division (OFD).
Abstract: We utilized and characterized high-power, high-linearity modified unitraveling carrier (MUTC) photodiodes for low-phase-noise photonic microwave generation based on optical frequency division (OFD). When illuminated with picosecond pulses from a repetition-rate-multiplied gigahertz Ti:sapphire modelocked laser, the photodiodes can achieve a 10 GHz signal power of +14 dBm. Using these diodes, we generated a 10 GHz microwave tone with less than 500 attoseconds absolute integrated timing jitter (1 Hz–10 MHz) and a phase noise floor of −177 dBc/Hz.We also characterized the electrical response, amplitude-to-phase conversion, saturation, and residual noise of the MUTC photodiodes.