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In this paper, we propose a digital phase noise measurement using a 10-bit digital oscilloscope MXR608A from Keysight Technologies. The digital oscilloscope’s four channel data are used for digital phase noise measurement: two channels are assigned for the equally divided SUT (source under test), while the other two are assigned for the equally divided reference signals. First, we propose a cross correlation method to identify the phase noises added by the ADCs in the digital oscilloscope from the measured phase noises. Then, we propose a novel cross correlation method to extract the SUT phase noise. The cross-correlation output of the proposed method yields only the SUT phase noise and does not contain the reference signal phase noise unlike the traditional method. The proposed method was applied to measure the phase noises of the two SUTs, Keysight’s synthesized signal generator E8257D and function generator 33600A. The measured phase noises of the two SUTs were compared and found to show remarkable agreements with those measured using Keysight’s signal source analyzer E5052B. The phase noise floor of our digital phase noise measurement system is about −160 dBc/Hz.

The biggest challenge that quantum computing and quantum machine learning are currently facing is the presence of noise in quantum devices. As a result, big efforts have been put into correcting or mitigating the induced errors. But, can these two fields benefit from noise? Surprisingly, we demonstrate that under some circumstances, quantum noise can be used to improve the performance of quantum reservoir computing, a prominent and recent quantum machine learning algorithm. Our results show that the amplitude damping noise can be beneficial to machine learning, while the depolarizing and phase damping noises should be prioritized for correction. This critical result sheds new light into the physical mechanisms underlying quantum devices, providing solid practical prescriptions for a successful implementation of quantum information processing in nowadays hardware. [ABSTRACT FROM AUTHOR]

The reduction in phase noise in electronic systems is of utmost importance in modern communication and signal processing applications and requires an understanding of the underlying physical processes. Here, we systematically study the phase noise in mutually synchronized chains of nano-constriction spin Hall nano-oscillators (SHNOs). We find that longer chains have improved phase noise figures at low offset frequencies (1/f noise), where chains of two and ten mutually synchronized SHNOs have 2.8 and 6.2 dB lower phase noise than single SHNOs. This is close to the theoretical values of 3 and 10 dB, and the deviation is ascribed to process variations between nano-constrictions. However, at higher offset frequencies (thermal noise), the phase noise unexpectedly increases with chain length, which we ascribe to process variations, a higher operating temperature in the long chains at the same drive current and phase delays in the coupling between nano-constrictions. [ABSTRACT FROM AUTHOR]

Kerr optical frequency combs are expected to play a major role in photonic technology, with applications related to spectroscopy, sensing, aerospace, and communication engineering. Most of these applications are related to the metrological performance of Kerr combs, which is ultimately limited by their noise-driven fluctuations. For this reason, it is of high importance to understand the influence of random noise on the comb dynamics. In this communication, we theoretically investigate a model where Gaussian white noise is added to the coupled-mode equations governing the comb dynamics. This stochastic model allows us to characterize the noise-induced broadening of the spectral lines. Moreover, this study permits to determine the phase noise spectra of the microwaves generated via comb photodetection. In this latter case, our analysis indicates that the low-frequency part of the spectra is dominated by pattern drift while the high-frequency part is dominated by pattern deformation. The theoretical results are found to be in excellent agreement with numerical simulations. Kerr optical frequency combs are extensively explored for their potential capabilities in fields such optical communication, spectroscopy, and sensing. This work theoretically analyses the role of phase noise in comb generation dynamics through a stochastic approach, which can impact future studies of frequency comb sources. [ABSTRACT FROM AUTHOR]

The high-order modulation format has the advantages of high spectral efficiency and large system capacity. However, the traditional frequency offset estimation and compensation algorithms, such as fast Fourier transform-based frequency offset estimation (FFT-FOE) that relies on a large number of complex FFT operations and differential frequency offset estimation (Diff-FOE) that relies on finite phase difference between adjacent symbols, are difficult to meet the frequency offset estimation requirements for any high-order modulation format. In this work, a novel FOE scheme using QPSK training symbols aided feedback structure is proposed. The performance of the proposed FOE scheme is evaluated in a polarization multiplexing QPSK-aided 32/64-quadrature amplitude modulation (QAM) simulation platforms with a symbol rate of 28 GBaud. The results show that has the technical advantages of low complexity, suitable for arbitrarily high-order modulation, tolerance for laser phase noise and wide tracking frequency offset range. [ABSTRACT FROM AUTHOR]

We propose a novel phase shifter for beam scanning in phased arrays using a cascaded injection-locked voltage-controlled oscillator (VCO) array with weak reverse coupling. We analyze the phase noise performance of a multi-signal injection-locked oscillator and establish a phase output model for the array, studying the effects of forward and reverse injection ratios on phase and phase noise at each stage. By decoupling and cascade locking VCO array elements through controlled injection ratios, we design a 2.45 GHz one-dimensional linear array of four VCOs that achieves a continuous fixed phase difference between adjacent oscillators from −180° to 180°, enabling electronic tuning of phase shift and beam scanning. Finally, the beam scanning of the antenna array is realized by using the VCO array. Our theoretical and experimental results demonstrate the effectiveness of our proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a Class-D voltage-controlled oscillator (VCO) with a hybrid switch capacitor array. In order to reduce the phase noise of the oscillator, an implicit common-mode resonance technique is used, effectively suppressing the conversion of power supply noise to VCO phase noise. At the same time, due to the use of a transformer in implicit common-mode resonance technology, the core area of the oscillator is not significantly increased compared with the traditional Class-D VCO. Based on the proposed technology, the proposed VCO exhibits lower phase noise compared to the original Class-D VCO, and also has many different advantages compared to low-voltage VCOs produced by similar technological processes. The proposed VCO was designed in a 55 nm CMOS process. Simulation results show that this VCO has an operating range from 4.36 to 6.43 GHz, resulting in the frequency tuning range (FTR) of 38.5%. In addition, its power consumption was 3.46 mW, the phase noise at 4.36 GHz was −124.2 dBc/Hz@1 MHz, and the figure of merit (FoM) was −191.6 dBc/Hz@1 MHz. The core area is 0.15 mm2. [ABSTRACT FROM AUTHOR]

The increasing demand for data and the rapid increase in the number of wireless connected devices make the shortage of energy and spectrum resources more serious. This paper considers a wireless powered communication network (WPCN) composed of N wireless devices (WDs) installed with single-antenna and a hybrid access point (HAP) equipped with multi-antenna, where HAP sends wireless energy to WDs in the downlink and receives information transmission from WDs in the uplink. To overcome "double near and far" problem, this paper adopts a clustering cooperative transmission method to enhance some WDs' throughput performance far from the HAP, i.e., one of N WDs is selected as a cluster head (CH) and the remaining (N - 1) WDs as cluster members (CMs), and the CH helps relay CMs' information to transmit. However, because the CH needs to transmit N WDs' information, its energy consumed during information transmission will be the bottleneck of the system performance. To achieve a tradeoff between energy and data rate, this paper adopts multi-antenna energy beamforming technology to concentrate more energy to transmit the CH, so as to balance the energy consumption among all WDs. Considering the influence of in-phase/orthogonal imbalance,nonlinear amplification amplitude and phase noise on those physical transceivers of low-cost sensor nodes, nonlinear energy harvesting technology is employed to improve throughput performance of the WPCN system. Particularly, the proposed scheme's throughput performance is derived, and simulation results demonstrate that this scheme can be effective to increase the WPCN system's throughput fairness and spectral efficiency. [ABSTRACT FROM AUTHOR]

The frequency stability of nanomechanical resonators (NMRs) dictates the performance level of many state-of-the-art sensors (e.g., mass, force, temperature, radiation) that relate an external physical perturbation to a resonance frequency shift. While this is obviously of fundamental importance, accurate models and understandings of sources of frequency instability are not always available. The contribution of thermomechanical noise to frequency stability has been well studied in recent years and is often the fundamental performance limitation. Frequency stability limited by thermal fluctuation noise has attracted less interest but is nevertheless of fundamental importance notably in temperature sensing applications. In particular, temperature-sensitive NMR have become promising candidates for replacing traditional bolometers in infrared radiation sensing. However, reaching the ultimate detectivity limit of thermal radiation sensors requires their noise to be dominated by fundamental thermal fluctuation, which has not been demonstrated to date. In this work, we first develop a theoretical model for computing the frequency stability of NMR by considering the effect of both additive phase noise (i.e., thermomechanical and experimental detection noise) and thermal fluctuation noise in a close-loop frequency tracking scheme. We thereafter validate this model experimentally and observe thermal fluctuation noise in SiN drum resonators of various sizes at room temperature. Our work shows that by using resonators of specific characteristics—such as high temperature sensitivity, high mechanical quality factors, and high mass-to-thermal-conductance ratio—one can minimize additive phase noise below thermal fluctuation noise. This paves the way for uncooled NMR-based radiation sensors that can reach the fundamental detectivity limit of thermal radiation sensing and outperform existing technologies. [ABSTRACT FROM AUTHOR]

Optimizing the bias modulation of a fiber-optic gyroscope is crucial to improving its precision. In this study, we propose and demonstrate the use of multiple harmonics of sinusoidal modulation as an intermediate alternative to the widely used modulation methods: sinusoidal and square-wave modulation. We show that this alternative integrates the advantages of each modulation method by providing a smooth modulation that produces a clean, spike-free output and a satisfactory signal-to-noise ratio. By using three harmonics of modulation in combination with a high frequency to reduce thermal phase noise, we obtained an angular random walk of 5.2 (2) μ deg / h and a bias instability of ∼ 10 μ deg / h . This is the highest performance ever reported for fiber-optic gyroscopes. [ABSTRACT FROM AUTHOR]

As humans intensify their activity on landscapes, it is important to consider anthropogenic noise when managing habitat for wildlife. Wetlands along rural to urban gradients are subject to road noise pollution, and the waterbirds that live there could be at risk for behavioral disturbance. We tested the positional response of wintering waterbirds to road traffic noise (i.e., sound pressure level) in a playback study in wetlands of Arkansas, USA, from January through March 2018. Each trial consisted of 3, 20‐minute phases of road noise playback designated as pre, during, and post. We repeated instantaneous scan sampling every minute during each phase to collect the number, species, and distance of each bird relative to the playback speaker. Distance bins were designated as 0–25, 26–50, 51–75, and 76–100 m from the speaker. Birds approached the speaker at closer distances during the pre phase compared to during and post phases. There was an increase in the probability of a bird occurring in the distance bin farthest from the speaker over the course of the trial. Our results suggest waterbirds might avoid noisier areas within a habitat; however, more study is needed to assess species‐specific responses, determine thresholds for disturbance, and examine downstream effects of habitat avoidance. If these results persist at larger scales, the soundscape of a wetland could be an important consideration in conservation planning. [ABSTRACT FROM AUTHOR]

Photonic‐based low‐phase‐noise microwave generation with real‐time frequency tuning is crucial for a broad spectrum of subjects, including next‐generation wireless communications, radar, metrology, and modern instrumentation. Here, for the first time to the best of the authors' knowledge, narrow‐bandwidth dual‐wavelength microlasers are generated from nearly‐degenerate polygon modes in a high‐Q active lithium niobate microdisk. The record‐high‐Q (≈107) nearly‐degenerate polygon modes formation with independently controllable resonant wavelengths and free spectral ranges is enabled by the weak perturbation of the microdisks using a tapered fiber. Moreover, because a high spatial overlap factor between the pump and the dual‐wavelength laser modes is achieved, the gain competition between the two lasing modes spatially separated with a π‐phase difference is suppressed, leading to stable dual‐wavelength laser generation with low threshold, and in turn, the low noise microwave source. The stable beating signal confirms the low phase‐noise achieved in the tunable laser. Without the need of external phase stabilizers, the measured microwave signal shows a phase noise of −123 dBc Hz−1 and an electro‐optic tuning efficiency of −1.66 MHz V−1. The linewidth of the microwave signal is measured as 6.87 kHz, which is more than three orders of magnitude narrower than current records based on integrated dual‐lasers. [ABSTRACT FROM AUTHOR]

Starting with the single-loop optoelectronic oscillator (OEO), an analysis of the effects of a radio frequency (RF) injected signal on the phase-locked loop OEO is done. After obtaining the injection locking equation of the oscillator, the generalized locking equation is derived and a time-domain model of a phase-locked loop OEO under RF signal injection is shown. Assuming the OEO is phase-locked to the reference signal and is injection-pulled by an independent RF signal, the behavior of the OEO is discussed. The frequency response of the spurious outputs due to RF injection signal in terms of the injection transfer function discussion is presented. An equivalent dual loop model of phase locked loop OEO under RF signal injection is presented for phase noise analysis. The presented analysis is partially supported by experimental results shown at the end. [ABSTRACT FROM AUTHOR]

In this study, a C~K band frequency synthesizer used in broadband electronic warfare equipment was designed, developed, and the meas- urement results were presented. The structure of the designed frequency synthesizer generates a signal up to 6 GHz using only direct digital synthesizer (DDS) without a mixer or multiplier. For signals above 6 GHz frequency, the structure uses a multiplier. In addition, a variable sampling frequency structure and a DDS circuit were designed to improve signal quality by reducing spurious signals, harmonic signals, and phase noise. The developed frequency synthesizer has different signal quality performance depending on the use of the multiplier, and the C∼G band has output power flatness ±1.7 dB, spurious signal less than −55 dBc, and phase noise less than −95 dBc/Hz (@1 kHz). The H~K band using multiplier has characteristics of output power flatness ±2.0 dB, spurious signal less than −35 dBc, and phase noise less than −80 dBc/Hz (@1 kHz). The results of this study confirmed the miniaturization of the signal generation module in the C∼K band. [ABSTRACT FROM AUTHOR]

This article presents the design and implementation of a 40 MHz crystal oscillator (XO) with low phase noise, based on the 55 nm CMOS process, for wireless transceiver systems, particularly those used in Wireless Local Area Network (WLAN). The proposed design employs a bandgap reference circuit that includes a start-up circuit and a low-voltage common-source common-gate current mirror, which ensures that the bandgap reference circuit is powered up effectively across all temperatures and process corners. A low-pass filter is also incorporated at the low dropout regulator (LDO) input to reduce the phase noise of the XO circuit. The experimental results demonstrate that the proposed design achieves a final phase noise of −164.36 dBc/Hz at 100 kHz offset frequency, with a power consumption of 0.444 mW. The test of start-up time is 0.718 ms and the compact chip area is 0.088 mm2. According to the simulation and test results, the final FOM value calculated in this paper is 209.93 dBc/Hz at 100 kHz offset. [ABSTRACT FROM AUTHOR]

Low-phase noise and wideband phased-locked loops (PLLs) are crucial for high-data rate communication and imaging systems. Sub-millimeter-wave (sub-mm-wave) PLLs typically exhibit poor performance in terms of noise and bandwidth due to higher device parasitic capacitances, among other reasons. In this regard, a low-phase-noise, wideband, integer-N, type-II phase-locked loop was implemented in the 22 nm FD-SOI CMOS process. The proposed wideband linear differential tuning I/Q voltage-controlled oscillator (VCO) achieves an overall frequency range of 157.5–167.5 GHz with 8 GHz linear tuning and a phase noise of −113 dBc/Hz @ 100 KHz. Moreover, the fabricated PLL produces a phase noise less than −103 dBc/Hz @ 1 KHz and −128 dBc/Hz @ 100 KHz, corresponding to the lowest phase noise generated by a sub-millimeter-wave PLL to date. The measured RF output saturated power and DC power consumption of the PLL are 2 dBm and 120.75 mW, respectively, whereas the fabricated chip comprising a power amplifier and an integrated antenna occupies an area of 1.25 × 0.9 mm2. [ABSTRACT FROM AUTHOR]

Broadcast and multicast protocols are two branches of multi-party quantum communication. Implementing these protocols based on partial entanglement is of great practical importance since maximally entangled channels are not robust due to noise applied by the surrounding environment. Previous research has used global operators (i.e. operators which are applied on the qubits owned by different parties), which contradicts the concept of multi-party communication protocols. In this research, broadcast protocol and multicast protocol with two receivers are proposed using partially entangled channels. Then the protocols are extended to the case with an arbitrary number of receivers. In the proposed protocol, Alice shares a two-qubit maximally entangled state with each receiver, therefore the whole channel is a partially entangled state. Then, the proposed protocol is modified to be secure against eavesdroppers. Also, the effects of phase damping, bit flip, and phase damping noise on the broadcast protocol are examined and compared. [ABSTRACT FROM AUTHOR]

In this paper, the origin of disentanglement for two specific sub-classes of X -states namely maximally nonlocal mixed states (MNMSs) and maximally entangled mixed states (MEMSs) is investigated analytically for a physical system consisting of two spatially separated qubits interacting with a common vacuum bath. The phenomena of entanglement sudden death (ESD) and the entanglement sudden birth (ESB) are observed, but the characteristics of ESD and ESB are found to be different for the case of two-photon coherence and single photon coherence states. The role played by initial coherence for the underlying entanglement dynamics is investigated. Further, the entanglement dynamics of MNMSs and MEMSs under different environmental noises namely phase damping, amplitude damping and random telegraph noise (RTN) noise with respect to the decay and revival of entanglement is analyzed. It is observed that the single photon coherence states are more robust against the sudden death of entanglement, indicating the usability of such states in the development of technologies for the practical implementation of quantum information processing tasks. [ABSTRACT FROM AUTHOR]

Temperature variation degrades the performance of fiber-optic gyroscopes. In terms of a noise mechanism, we report that thermal phase noise contributes to the dominant effect of temperature variation in large fiber-optic gyroscopes when the conventional Shupe effect is basically suppressed. High-order frequency modulation is introduced to reduce the corresponding effect of temperature variation. A time-varying temperature variation experiment has been carried out for verification. Compared with the conventional eigen frequency modulation, the temperature sensitivity is reduced by 32 times, which effectively enhances the temperature adaptability of the fiber-optic gyroscope. [ABSTRACT FROM AUTHOR]

Objectives: Interferogram filtering is the key to the subsequent processing steps of interferometric synthetic aperture radar, such as phase unwrapping and geocoding. However, the existing filtering methods can't retain features in dense fringes and accurately estimate phase in low-coherence regions. The convolutional neural networks (CNN) is introduced to learn noise features and solve this problem. Methods: First, we selected a certain number of interferograms as samples, and divided them into training set, test set, and validation set. Second,we preprocessed the training set samples, and cut the preprocessed training set interferograms into small fixed-size block and randomly extract it as a model training sample, used the above steps to train the autoencoder filter model, after a certain number of iterations, the model was fitted. Results: Experiments were carried out on spaceborne imaging radar-C-band synthetic aperture radar data and Sentinel-1A data. Our proposed method was compared with Goldstein filter, mean filter, Lee filter, Frost filter, and improved denoising convolutional neural network (DnCNN). Goldstein filter can remove most of the noise while maintaining fringes edge, has good denoising ability. Mean filter performs well in high-coherence areas, but performs poorly in low-coherence areas, and can't filter noise well. Lee filter maintains it well image resolution, but the denoising effect is weak, and it can be seen from the filtering results that there is still a lot of noise. Frost filtering is weak in low-coherence areas and there is a lot of noise, but the fringe edges are well maintained in high-coherence areas. The improved DnCNN filter can significantly eliminate the noise, but it can't distinguish the fringe edge and the noise well. Our proposed method can suppress the noise very well, and it can maintain the fringe edge well in the low-coherence area and the high-coherence area. Conclusions: This proposed method can greatly improve the phase quality of the interferogram, suppress the noise to a greater extent, and restore more image details and maintain the edge continuity of the interference fringe. [ABSTRACT FROM AUTHOR]

A low‐noise fully‐integrated charge‐pump phase‐locked loop (CPPLL) for 5G applications is presented in this letter. The PLL architecture includes a phase and frequency detector (PFD), a charge pump (CP), a low‐pass filter (LPF), a voltage‐controlled oscillator (VCO), and a programmable divider. To achieve low phase noise, class‐C VCO, TSPC logic, and other methods are employed in the PLL circuit design. Fabricated in 65 nm technology, the PLL measures a tuning range of 5.91–8.94 GHz. The minimum and maximum measured phase noise are −125 dBc/Hz and −116.6 dBc/Hz @1 MHz. The size of CPPLL core area is 0.8 mm by 0.95 mm without the pads while having a 50‐mW power consumption. [ABSTRACT FROM AUTHOR]

This study develops a multiphase voltage-controlled oscillator (VCO) by using the subfeedback loop technique. The proposed N-stage ring oscillator with k-stage subfeedback loops (where N is not a multiple of k) has N output phases, and its operating frequency is as high as that of the k-stage subfeedback loops. Circuit analysis and simulation processes for design optimization are presented herein. The first-order linear inverter model of the proposed ring oscillator defines the relationship between its operating frequency and phase number. In the topology of the proposed oscillator, the operating frequency does not decrease as the number of stages of the ring oscillator increases. The proposed multiphase VCO is verified in a 5-GHz 12-phase phase-locked loop. The test chip is implemented in a 0.18-μm complementary metal–oxide–semiconductor process, and its core area is determined to be 260 × 355 μm2. The root mean square jitter and peak-to-peak jitter are 1.03 and 8.85 ps, respectively. The phase noise of the output signal is − 91.44 dBc/Hz at 1-MHz. [ABSTRACT FROM AUTHOR]

Summary: A coupled complementary split‐ring resonator (CSRR) has been proposed. The proposed resonator consists of two coupled 50‐Ω transmission lines and complementary split rings in the ground plane (bottom layer) as defected ground structure (DGS). The proposed bandpass filter (BPF) has a measured stopband attenuation loss of less than −20 dB in the frequency band between 2.3 and 2.9 GHz and a low insertion loss of 1.15 dB. The measurement is carried by a VNA (vector network analyzer) meter of model ZVA67. Then, the proposed resonator (BPF) is utilized with an active device (SiGe BFP 640) as an output matching network of a class‐F oscillator. Fundamentally, this research aims to design and model an optimum achievement of BPF for optimum oscillator performance. The design simulation of the CSRR oscillator has been obtained by ADS and CST programs. The proposed band pass filter is designed and fabricated on a Rogers (RO4003C) micro‐strip material printed with a dielectric constant epsilon of 3.38 and a thickness of 0.813 mm. Depending on this study, the oscillator displays a minimum phase noise of −109.3 dBc/Hz at 1 MHz offset frequency and maximum dBm output power equals 13.4 dBm at 2.45 GHz oscillation frequency. The power dispassion of the proposed oscillator equals 8.3 mW from a 2 V supply voltage. The obtained maximum dBm output power and minimum phase noise is a benefit for power charger wireless applications, sub‐6 GHz fifth generation applications, and multistandard applications. [ABSTRACT FROM AUTHOR]

Soliton frequency combs generated in microresonators offer powerful tools for optical metrology, due to the high time-frequency resolution. Here, via exciting the intracavity Brillouin laser in a high Q monolithic fiber resonator, a pair of orthogonal Kerr soliton combs is generated, which share the same repetition (frep ≈ 1.001 GHz) due to the soliton trapping but different central wavelengths (≈ 9.278 GHz). They offer rich dual-comb beat notes with minimum phase noise down to -166.5 dBc Hz-1@1 MHz. Thanks to the geometric flexibility of the monolithic fiber resonator, the orthogonal soliton pair is found to be mechanically controllable with high precision. Specifically, by applying external stress on the microcavity in a range of ≈ 0-7.33 mN, the difference of their carrier-envelope-offset frequencies (Δfceo) is linearly tunable with a response of 0.3 kHz µN-1, meanwhile, tunability of the frep reaches 0.4 kHz µN-1. Such an orthogonally polarized dual soliton with stress controllability combining Brillouin excitation and parametric oscillation can offer a miniature all-in-fiber tool for wide applications ranging from frequency-adjustable photonic microwave sources to highly sensitive gyroscopes. [ABSTRACT FROM AUTHOR]

To improve the accuracy of phase recovery in quantitative phase imaging, a novel two-stage synthetic denoising method is proposed in this paper. In this method, to avoid the loss of effective detail information, the mode of fixed attenuation parameter setting is changed into two stages of self-adaptation setting: the first attenuation parameter is defined as the convolution of filtered pixels in the window of interest, the second attenuation parameter is defined as the noise standard deviation of each pixel after filtering in the first stage. Moreover, the Pearson coefficient expression is redefined to get a more accurate similarity evaluation, and the algorithm's operational efficiency has been improved using cross-correlation functions and fast Fourier transform. The comparative results of simulations and experiments show that this method is more effective in reducing speckle noise in quantitative phase imaging and enhancing phase recovery accuracy, providing a new digital image denoizing method for efficient and accurate imaging. [ABSTRACT FROM AUTHOR]

Phase noise is one of the most important criteria for evaluating the performance quality of the oscillators. Some of the effective methods to reduce phase noise and improve transconductance at low power consumption are coupled inductors and positive feedback, respectively. The coupling process between the inductors can reduce the volume of the inductor, and in turn, increase its amount. However, the modeled parallel resistor of the inductor remains constant and will eventually reduce the phase noise because of improving the quality factor of the LC tank. In this paper, we perform a comprehensive study and analysis of the LC cross-coupled oscillator in order to improve the transconductance and phase noise of the oscillator. First, we analyze the oscillation frequency, oscillation amplitude, and phase noise of the proposed oscillator using the averaging method and calculating the Impulse Sensitivity Function through a novel method without a need for complicated simulations. Then, we design an experimental oscillator via the 0.18 μ m CMOS technology, which works at 520.5 MHz , and consumes 2.7 mA from a 1.8 v power supply. The simulation results as well as the analyses show that the designed oscillator has better performance than a conventional cross-coupled oscillator at the same power consumptions. [ABSTRACT FROM AUTHOR]

This study proposes a frequency synthesizer with fast frequency modulation using a 28-nm CMOS process. The synthesizer used a two-point modulation technique that divides the frequency range into high- and low-pass regions to lock the frequency. In the high-pass region, continuous frequency modulation was achieved using a charge-digital-to-analog converter, while in the low-pass region, the synthesizer was set to the desired frequency using a divider and a delta-sigma modulator. The manufactured signal generator is capable of oscillating at frequencies between 14.1 GHz and 16.2 GHz, with a phase noise of −100.14 dBc/Hz at 1 MHz offset frequency. For chip signal generation, the generator had a chip time of 42.8 s and a bandwidth of 860 MHz. The chip area was 1,070×700 μm². [ABSTRACT FROM AUTHOR]

In this work, a prior-training-free and low-complexity modulation format identification (MFI) scheme, based on amplitude histogram distributions, was proposed and demonstrated, both numerically and experimentally, for autonomous digital coherent receivers. In the proposed scheme, after having performed power normalization, incoming polarization division multiplexed (PDM) signals were classified into QPSK, 8QAM, 16QAM, 32QAM and 64QAM signals, according to their ratios. Ratios were defined according to specific features of their amplitude histograms. The proposed MFI scheme used only amplitude information. As such, it was insensitive to carrier phase noise. Furthermore, the proposed scheme did not require any prior information, such as optical signal-to-noise ratio (OSNR). The performance of the proposed MFI scheme was numerically verified using 28GBaud PDM-QPSK/-8QAM/-16QAM/-32QAM/-64QAM signals. The numerical simulation results showed that the proposed scheme was able achieve a 100% correct identification rate for all five modulation formats when their OSNR values were higher than the thresholds corresponding to the 20% FEC correcting bit error rate (BER) of 2.4 × 10−2. To further explore the effectiveness of the proposed MFI scheme, proof-of-concept experiments in 28GBaud PDM-QPSK/-8QAM/-16QAM, and 21.5GBaud PDM-32QAM transmission systems were also undertaken, which showed that the proposed scheme as robust against fiber nonlinearities. To explore the scheme's feasibility for use in practical transmission systems, the computational complexity analysis of the proposed scheme was conducted. It showed that, compared with relevant MFI schemes, the proposed MFI scheme was able to significantly reduce the computational complexity. [ABSTRACT FROM AUTHOR]

This paper presents a K-band CMOS cross-coupled pair voltage-controlled oscillator (VCO) that utilizes the varactor-only capacitor network. The proposed circuit features low parasitics and a compact capacitor network, such that the varactor in the analog tuning path directly affects the oscillation frequency with a large gain of the VCO, and the varactor in the digital tuning path results in minimal noise sources, thus achieving low phase noise for the automotive FMCW radar application. This VCO was designed using TSMC 65 nm technology, and the post-layout simulation results show a stable oscillation across 18–19.2 GHz, a minimum phase noise of −105.9 and −128 dBc/Hz at 1- and 10-MHz offset frequencies while dissipating 21 mW of power from a 1 V supply. Furthermore, no notable variations in phase noise are observed across the oscillation frequency tuning range. It reveals a figure of merit (FOM) of −178.3 dBc/Hz while using a varactor-only capacitor array and occupying a small chip area. [ABSTRACT FROM AUTHOR]

In this paper, a two-loop photoelectric oscillator based on chirped fiber Bragg grating (CFBG) is used to construct a swept source, which acts on the frequency scanning array antenna to realise multibeamforming. The simulation results of the designed beamforming system have shown that it can realise wide-range beam scanning and has ultralow phase noise. [ABSTRACT FROM AUTHOR]

Delay line oscillators based on photonic components, offer the potential for realization of phase noise levels up to 3 orders of magnitude lower than achievable by conventional microwave sources. Fibreoptic-based delay lines can realize the large delay required for low phase noise systems whilst simultaneously achieving insertion loss levels that can be compensated with available microwave and photonic amplification technologies. Multimode operation is an artefact of the delay line oscillator and introduces modulational instability into phase-locked control loops. An optoelectronic oscillator (OEO) with large delay under proportional integral control by a phase-locked loop (PLL) is modelled, providing the first report of the location of all the infinity of poles of the PLL-OEO system function. The first experimental observation of giant phase modulated oscillation of a free OEO and spontaneous giant phase modulated oscillation of a PLL-OEO are also reported and explained respectively as a source and manifestation of modulational instability. Nevertheless, the analysis and experimental observations, including a prototype 10 GHz PLL-OEO phase noise spectral density achieving - 80 d B c / H z at 10 H z and - 145 d B c / H z at 10 k H z , demonstrate that stable phase lock operation and optimum phase noise performance is achievable provided full account of the multimode nature of the OEO is taken in the phase lock analysis. [ABSTRACT FROM AUTHOR]

Injection-locked frequency divider (ILFD) is an essential component of a phase-locked loop (PLL) used in a communication transceiver. Due to the rapid growth of virtual reality and artificial intelligence technologies, high-speed communication has become a crucial factor. As a result, highly efficient ILFDs must be engineered to ensure accurate high-speed communication. An optimized ILFD is anticipated to have a large locking range, a low power consumption, a low phase noise, and a low injection power for better functioning of a high speed PLL. However, there are inevitable trade-offs of frequency, phase noise, division ratio, and power consumption, making it more challenging to design an ILFD with a high division ratio at higher frequencies. Choosing an appropriate topology for different operational frequencies is also a challenging task for RFIC designers. This study exemplified different design architectures available for CMOS ILFDs in different super high frequency (SHF) and extremely high frequency (EHF) frequency ranges. The performance parameters of these architectures are analyzed, and a detailed discussion on the device's performance is presented. This review will serve as a comparative study and reference for the RFIC designer's future ILFD designs. [ABSTRACT FROM AUTHOR]

This paper presents a fast lock-in time clock frequency multiplier without using traditional clock generation circuits such as PLLs and DLLs. We propose a novel technique based on capacitive finite impulse response (FIR) filters to generate clock phases while reducing the input clock phase noise at the same time. A new delay line circuit is also proposed for improving power supply rejection. In addition, to improve the matching quality as well as the end-effects tolerance of the on-chip capacitors, a single-value series/parallel algorithm is proposed. Designed in a 0.18 μ m digital CMOS process, with a 20 MHz input clock frequency, the multiplier achieves a multiplication factor of 5 with a lock-in time of less than 4 clock cycles. The input clock jitter is reduced from 7ns RMS to 153 ps RMS after frequency multiplication. [ABSTRACT FROM AUTHOR]

In this study, we designed an MOS varactor for application in the differential voltage-controlled oscillator (VCO). To improve the quality factor of the MOS varactor, we proposed a symmetric layout technique of the MOS varactor with reduced parasitic components. Compared with the typical MOS varactor layout, the metal line for the interconnection of the MOS varactors that is inevitable in the typical MOS varactors for the cross-coupled VCO was minimized to reduce the parasitic resistance. In addition, with the reduced interconnection metal line, the overall size of the proposed MOS varactor was also reduced compared with the typical one. To verify the feasibility of the proposed MOS varactor structure, the typical and proposed MOS varactors were designed using a 180 nm RFCMOS process. Compared to the typical MOS varactor, the measured quality factor of the proposed MOS varactor was improved by approximately 32% at the operating frequency of 5.0 GHz. Additionally, we successfully verified that the parasitic capacitance induced by the lossy silicon substrate was reduced in the proposed MOS varactor structure. [ABSTRACT FROM AUTHOR]

We study the effect of additive noise to the inversion of FIOs associated to a diffeomorphic canonical relation. We use the microlocal defect measures to measure the power spectrum of the noise in the phase space and analyze how that power spectrum is transformed under the inversion. In general, white noise, for example, is mapped to noise depending on the position and on the direction. In particular, we compute the standard deviation, locally, of the noise added to the inversion as a function of the standard deviation of the noise added to the data. As an example, we study the Radon transform in the plane in parallel and fan-beam coordinates, and present numerical examples. [ABSTRACT FROM AUTHOR]

A new scheme on the realisation of voltage-tunable immittance function (VTIF) is proposed. Here two types of grounded, high-quality (Q) resonant filters and voltage-controlled quadrature oscillators (VCQO) with a linear tuning law are presented. Analysis indicates that the filter/QO parameters are impervious to the ABB parasitic components. Experimental results exhibit a VCQO-linear tuning range of fo~14 MHz with a satisfactory phase-noise margin of immittances, viz., inductance (L) and frequency-dependent negative resistance (D) are derived using the Current Feedback Amplifier (CFA) combined with analog voltage-multiplier elements as the active building block (ABB). Subsequently, implementation of LC-bandpass and rD-band-reject selective filters, along with QO designs, is presented with low THD and phase noise of (─)104 dBc/Hz at 30 kHz offset. Experimental results of the proposed circuits had been satisfactorily verified using standard commercially available IC modules. [ABSTRACT FROM AUTHOR]

Cascaded multilevel three-phase inverters are commonly used in industrial applications and the quality of these inverters is highly dependent on the modulation techniques. The common mode voltage is one of the factors affecting the quality of the three-phase inverter output voltage. This paper proposes a carrier phase modulation method for cascade multilevel inverters to reduce the magnitude of common-mode voltage magnitude and harmonics. In the proposed method, the carrier phase modulator is considered as an adaptive controller and the phase of carrier is completely controlled by the magnitude of control signal. The phase modulation has a high immunity to the noises compared with the modulations of frequency and amplitude because it is difficult for noises to intrude into the phase of carrier. In addition, the algorithm of carrier phase modulation is simple and requires little memory. Moreover, the number of switching commutations of the proposed method also reduces significantly. Simulation and experiment results based on a cascaded five-level three-phase inverter system have confirmed the effectiveness of the proposed method compared with that of the popular methods using unmodulated carriers such as phase disposition (PD) and phase opposite disposition (POD). [ABSTRACT FROM AUTHOR]

This work presents a complementary PMOS NMOS voltage-controlled power oscillator (VCO) based on a high quality (Q) factor off-chip inductor in 130 nm CMOS process. The proposed VCO achieves a frequency tuning range of 166% from 393 MHz to 4.17 GHz and this wide tuning range is divided into six bands where each band is also sub-divided into three bands using a single switching voltage. The proposed design takes into consideration the effect of the bond wire that is used to connect the off-chip inductor with the VCO core moreover, the measured SNP files of the off-chip inductors are utilized to ensure accurate results. This technique improves the figure of merit (FoM) by 4–25 dB compared to the conventional inductor VCO. Using six different values of the off-chip inductors, the proposed VCO works in six bands with a tuning range of 166%, and a minimum phase noise of − 127 dBc/Hz @ 1 MHz offset frequency 2.2 GHz carrier. Furthermore, the proposed VCO draws 1.37 mA from 1.1 V supply voltage and has a minimum achieved Figure-of-Merit (FOM) equal to -193 dBc/Hz with a maximum output power of 4.25 dBm. The VCO core area equals 0.07 mm 2 , while the total chip area including RF pads and output buffers is 0.437 mm 2 . [ABSTRACT FROM AUTHOR]

A static frequency-modulated continuous-wave (FMCW) radar imaging system uses different local oscillator (LO) and clock signals owing to the spatial separation of the transmitter and receiver, resulting in asynchronization problems of various factors that can deteriorate the quality of radar images. In this study, we defined signal models for bistatic FMCW asynchronization factors:1) the time difference between reference signals in the transmitter and receiver, 2) LO phase noise difference, 3) pulse repetition frequency mismatch, and 4) center frequency difference. We generated ISAR images of the point scatterer for each asynchronization factor to analyze the influence of asynchronization through the ISAR image in terms of quality parameters. [ABSTRACT FROM AUTHOR]

In this paper, we report on our simulation and design of a photonic integrated circuits (PIC)-based heterodyne optical phase-locked loop (OPLL). Our simulation reveals that the OPLL operation can be in one of three states, i.e., absolutely stable, metastable, and unstable states, depending on the relative position of the initial phase reversal point to the loop bandwidth. By systematically optimizing all of the loop parameters involved, the loop bandwidth of 247.8 MHz and the residual phase noise variance of 0.012 rad2 are theoretically obtained in such a PIC-OPLL system, which are better than any reported counterparts. In addition, the lowest required power of the master laser is also evaluated, assuming that the largest acceptable residual phase noise variance is 0.02 rad2, and it is found that the lowest master laser power is −54 dBm in our current OPLL system, and this value can be reduced to −56 dBm, providing that the summed linewidth is reduced to 10 kHz. [ABSTRACT FROM AUTHOR]