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This article comprehensively reviews and studies CMOS transformer tank voltage‐controlled oscillators (VCOs) designed to improve the frequency tuning range (FTR) and minimize phase noise (PN) across a broad frequency range, particularly for mm‐wave and fifth‐generation applications. The study focuses on enhancing the performance of the oscillators to meet the demanding requirements of these advanced applications. This study thoroughly investigates and compares various strategies to increase the FTR, minimize PN, and reduce power dissipation in transformer tank VCOs. The aim is to establish fundamental guidelines for implementing transformer‐based tank VCOs. The study comprehensively reviews and analyzes the overall architecture of transformer‐based tank VCOs, presenting a detailed examination of the methods employed to enhance VCO performance. Additionally, the study illustrates the impact of the coupling factor on the VCO's performance parameters, detailing and demonstrating the overall tank circuit quality factor (Q) and resonator coupling factor (κ). A thorough understanding of PN methodology and the limitations of FTR has led to the development of innovative architectures. These include transformer‐based capacitive feedback (FB) oscillators with resistively adjusted variable inductors, as well as class‐F and inverse class‐F VCOs. These novel architectures contribute significantly to the improvement of oscillator performance. [ABSTRACT FROM AUTHOR]

Summary: This paper presents more compatible three‐stage inverter‐based ring voltage controlled oscillators (VCOs) by modifying the current‐starved delay cell to oscillate with high tuning range. Unlike some ring structures in which extra transistors are used as current boosting to enhance the frequency tuning range, no extra elements are used in the proposed three‐stage VCOs for increasing the tuning range. Besides, a new method is introduced to couple two proposed ring VCOs for designing a six‐phase ring VCO. The coupling method can be generalized to some other ring VCOs to generate multiphase signals. The proposed circuits have wide frequency tuning ranges and show good noise performances. The proposed six‐phase VCO can oscillate from 1.62 GHz to 3.45 GHz, which illustrates 72.2% tuning range. The phase noise of the proposed VCO is −97.5 dBc/Hz at 1 MHz offset frequency. The circuit figure of merit is −181.5 dBc/Hz. The post‐layout simulation results of the proposed six‐phase VCO are provided based on the TSMC 0.18 μm CMOS process. [ABSTRACT FROM AUTHOR]

Optical frequency combs have revolutionized frequency metrology and spectroscopic measurements, enabling the most precise measurements of all physical quantities. However, precision frequency metrology heavily relies on mode‐locked laser combs, which are only directly available for a few selected near‐infrared wavelength ranges. Recently, a strong tendency emerged for combs in the mid‐infrared molecular fingerprint region. To this end, several methods for wavelength conversion have been proposed and demonstrated, which nevertheless cost a degradation of coherence properties. Here a first approach is presented toward measuring resulting phase noise fluctuations, exploiting the temporal resolution of the dispersive temporal interferometry (DTI) technique for experimentally unveiling the carrier‐envelope phase dynamics of a cw‐seeded femtosecond optical parametric amplifier (OPA). Particularly, it is experimentally demonstrated for the first time that unexpectedly low seed power levels suffice to exceed vacuum fluctuations by more than an order of magnitude, resulting in pulse‐to‐pulse phase fluctuations of 82 mrad at rather moderate cw seed levels of 8 mW. Additionally, a formula is provided that allows exact prediction of the experimentally observed noise levels. This study therefore provides new insight into the role of vacuum fluctuations in OPAs, which open up an avenue for coherent dual‐comb systems in the mid‐infrared and beyond. [ABSTRACT FROM AUTHOR]

In this paper, to analyze the tuning range (TR) of transistors, we introduced two streamlined modeling approaches that can precisely predict the extent and direction of the TR. The first approach, known as the average DC (Id) method, employed a simplified circuit model to dissect transistor characteristics, enabling us to understand the general trajectory of the TR. The second approach involved the transient current Id (tc) method, which offers a nuanced portrayal of the transistor's real‐world performance. By analyzing the current fluctuations within the transistor during transient states, its tuning capabilities could be more accurately ascertained. Further, this paper presents several designs for ultra‐wide‐tuning‐range complementary metal–oxide–semiconductor (CMOS) voltage‐controlled oscillators (VCOs) that employ a novel two‐mode current‐starved delay cell, featuring a tunable transistor‐based current source for coarse frequency adjustment operating in synergy with a varactor for precise tuning. Using the 65‐nm CMOS process, three prototype VCOs (Designs 2/3/4) based on the new cell and targeting different numbers of phases and performance were fabricated, thoroughly characterized, and compared with their traditional inverter‐based counterpart (Design 1). Design 1 featured an inverter‐based four‐phase structure, with an output frequency range of 3.14–9.82 GHz, i.e., a radio frequency (RF) TR of 103%, with phase noise (PN) ranging from 137.7 to 132.1 dBc/Hz at an offset of 100 MHz, figure of merit with tuning range and area (FoMTA) varying from 200.7 to 205.1 dBc/Hz, and area of 0.0036 mm2. In contrast, Designs 2/3/4, based on the new delay cell, featured 8/3/4 phases, with output frequencies in the ranges of 1.14–9.17, 1.26–16.53, and 1.15–18.32 GHz, respectively, resulting in increased RF TRs of 155.8%, 171.7% and 176.4%, as well as PN at an offset of 100 MHz in the ranges of 142.1–138, 130.5–131.3, and 131.9–129.6 dBc/Hz, respectively. This yielded better FoMTAs in the ranges of 201.2–209.9, 205.3–217.9, and 194.1–209.9 dBc/Hz, thus allowing the VCOs to maintain consistent performance across the frequency band and occupy comparable or smaller silicon areas of 0.00425, 0.000972, and 0.00348 mm2 in the same 65 nm technology. These designs showcase the versatility and efficiency of the two‐mode current‐starved delay architecture, which offers wide TRs, tiny areas, and competitive performance metrics for various applications in RF integrated circuits. [ABSTRACT FROM AUTHOR]

Injection‐locked dividers feature ultrahigh operating frequency, low power consumption, and low phase noise, making them suitable for Q‐band phase‐locked loop. This paper presents a transformer‐based divide‐by‐4 injection locking frequency divider with a high third harmonic rejection buffer based on 40‐nm CMOS technology. Employing a fourth‐order transformer resonator enhances the third‐order harmonic amplitude, increasing the injection efficiency and expanding the locking range. The proposed high third harmonic rejection buffer using a source degeneration inductor can effectively suppress the output of the third harmonic caused by the resonator, ultimately yielding a clean fundamental frequency signal. Simulation results demonstrate that the proposed divide‐by‐4 injection‐locked frequency divider (ILFD) achieves a locking range of 10.2 GHz (from 40.3 to 50.5 GHz) with 0 dBm input signal. The core divide‐by‐4 ILFD circuit consumes 4.6 mW power with a 0.9 V supply and occupies an area of 0.026 mm2. [ABSTRACT FROM AUTHOR]

A differential ring voltage‐controlled oscillator (DRVCO) is proposed in this paper as one of the critical blocks in communication systems. It consists of four stages of delay cells connected in a chain, creating a ring structure with auxiliary path interconnections. The oscillation frequency of the DRVCO can be controlled by adjusting the tuning voltage that controls the charging current. To achieve the desired performance for wireless applications, the Wu active inductor, which is a low‐noise and high‐quality factor active inductor, is employed in each delay cell for the first time. Using an active inductor provides a wide tuning range and also allows for proper phase noise and low power consumption. The proposed circuit is designed and simulated using standard 180‐nm CMOS technology with a 1.8‐V voltage source (VDD). The circuit is designed to achieve a tuning range of 2.15 GHz with a center frequency oscillation of 2.745 GHz, over the control voltage variation of 1.4 V (0 to 1.4 V). To achieve the desired performance, the circuit consumes an average power of 1.99 mW. It achieves a phase noise of − 91.2 dBc/Hz at 1 MHz offset frequency, indicating effective noise suppression. The figure of merit (FoM) for the circuit is − 156.9 dBc/Hz, representing its overall performance. The final layout of the circuit estimates an area of 0.00072 mm2. Various analyses, including Monte–Carlo simulations, PVT (process, voltage, temperature) variation analysis, and other relevant analyses, have been performed to ensure the reliable performance of the proposed circuit. [ABSTRACT FROM AUTHOR]

This article proposed a technique for a low‐power and fast start‐up voltage‐controlled oscillator (VCO) for a high data rate 5 G New Radio (5G‐NR) application. The 5G‐NR high data rate signals require a fast start‐up VCO to accommodate the short pulse width. In this proposed work, a cross‐coupled pair (XCP) is integrated with a center‐tapped orthogonal symmetry inductor placed at the gates of the XCP, forming an inductive booster VCO (IBVCO). The inductive impedance at the gate of the XCP preserve the symmetry signal profile of the output voltage swing while alleviating the intrinsic parasitic capacitance effect and flicker noise effect of the transistor under the absence of the tail current source. The concept proves with the improvement on the phase noise performance and generating a fast start‐up without affecting the VCO bandwidth. The VCO also provides the enhancement of the output voltage swing under low power consumption. The IBVCO has been fabricated in 180 nm complementary metal oxide semiconductor technology and consumes a minimum area of only 0.7 mm2. The IBVCO achieved a 13% tuning range from 3.3 to 3.75 GHz bandwidth with a supply voltage, VDD of 0.7 V. The total power consumption is 1 mW with a corresponding phase noise of −122.60 dBc/Hz and a Figure of Merit (FoM) of 193.48 dBc/Hz at 3.52 GHz carrier center frequency at 1 MHz offset. The start‐up time of the VCO achieved is 5 ns. [ABSTRACT FROM AUTHOR]

Robustness against Electronic Warfare/Electronic Defence attacks represents an important advantage of Noise Radar Technology (NRT). An evaluation of the related Low Probability of Detection (LPD) and of Intercept (LPI) is presented for Continuous Emission Noise Radar (CE‐NR) waveforms with different operational parameters, that is, "tailored", and with various "degrees of randomness". In this frame, three different noise radar waveforms, a phase Noise (APCN) and two "tailored" noise waveforms (FMeth and COSPAR), are compared by time–frequency analysis. Using a correlator (i.e. a two antennas) receiver, assuming a complete knowledge of the band (B) and duration (T) of the coherent emission of these waveforms, it will be shown that the LPD features of a CE‐NR do not significantly differ from those of any CE radar transmitting deterministic waveforms. However, in real operations, B and T are unknown; hence, assuming an instantaneous bandwidth estimation will show that the duration T can be estimated only for some specific "tailored" waveforms (of course, not to be operationally used). The effect of "tailoring" is analysed with prospects for future work. Finally, some limitations in the classification of these radar signals are analysed. [ABSTRACT FROM AUTHOR]

Coherent light beams play an important role in the development of opto‐electronic microwave and terahertz technologies, serving as a source for generating RF carrier signals with very high quality. The authors explore in this work an approach to enhance the coherence between two incoherent lasers so as to provide coherent light beams, and proof‐of‐concept demonstrates a terahertz signal generation with low phase noise. Based on the proposed passive phase compensation technique, the phase noise between two independent lasers can be well suppressed and the carrier to noise ratio in the terahertz regime remains high. In the experiment, the beating phase noise between two independent lasers is reduced from −60.68 dBc/Hz@10kHz to −90.05 dBc/Hz@10kHz at about 280 GHz, which is promisingly applicable in the terahertz photonics community. [ABSTRACT FROM AUTHOR]

The impact of noise sources in real‐world implementations of twin‐field quantum key distribution (TF‐QKD) protocols is investigated, focusing on phase noise from photon sources and connecting fibers. This work emphasizes the role of laser quality, network topology, fiber length, arm balance, and detector performance in determining key rates. Remarkably, it reveals that the leading TF‐QKD protocols are similarly affected by phase noise despite different mechanisms. This study demonstrates duty cycle improvements of over a factor of two through narrow‐linewidth lasers and phase‐control techniques, highlighting the potential synergy with high‐precision time and frequency distribution services. Ultrastable lasers, evolving toward integration and miniaturization, offer promising solutions for agile TF‐QKD implementations on existing networks. Properly addressing phase noise and practical constraints allows for consistent key rate predictions, protocol selection, and layout design, crucial for establishing secure long‐haul links for the quantum communication infrastructures under development in several countries. [ABSTRACT FROM AUTHOR]

The authors deal with the problem of the design and manufacture of a high‐resolution FMCW radar for drone detection and classification. The difficulties of the problem are discrete clutter reduction and spurious phase noise mitigation. The discrete clutter is due to the reflected signals from land vehicles, birds etc., while the spurious phase noise is inherent in the radar signal due to the phase‐locked loop component and leakage between the transmitting and receiving paths. Both spurious phase noise and clutter will increase the system noise level and hence reduce the probability of detection of small targets such as drones and induce false alarms on the radar screen. In order to reduce discrete clutter, the authors propose a method to separate a drone from discrete clutter based on the design of the radar system parameters for a drone and its propeller detection, target's Doppler dispersion and moving characteristics. For spur mitigation, a method that focuses on the design of the isolation coefficient between transmitting and receiving paths to decrease the power of spurs below the minimum power requirement at the input of the analogue‐to‐digital converter is introduced. The results were applied by the authors to the development and manufacture of a radar with the given specifications for drone detection and classification. Different laboratory and field tests show that the spurs are mitigated and the drones are separated from discrete clutter with a range and accuracy better than the one recently published. [ABSTRACT FROM AUTHOR]

In this paper, a genetic‐based synthesis approach for an impedance matching section based on a composite right‐/left‐handed (CRLH) transmission line model called CRLH transmission line impedance matching section (CRLHTLIMS) in viewpoint of transmission phase shift and noise figure is newly presented. To find the unknown values of right‐/left‐handed inductances and capacitances of a CRLHTLIMS, a type of global optimization algorithm called continuous parameter genetic algorithm is used. The length, transmission phase shift, and noise figure of the CRLHTLIMS are computed by using simple equations. Different examples for a uniform CRLHTLIMS are given. According to the results, this approach is an easy and effective way for the synthesis of transmission line impedance matching sections in viewpoint of transmission phase shift and noise figure. [ABSTRACT FROM AUTHOR]

Chip‐based optical frequency combs address the demand for compact, bright, coherent light sources of equidistant phase‐locked lines. Traditionally, the Fourier Transform Spectroscopy (FTS) technique is considered a suboptimal choice for resolving comb lines in chip‐based sensing applications due to the requirement of long optical delays, and spectral distortion from the instrumental line shape. Here, a sub‐nominal resolution FTS technique is developed that extracts the comb's offset frequency in any spectral region directly from the measured interferogram without resorting to nonlinear f$f$‐to‐2f$2f$ interferometry. This in turn enables 10's of MHz resolution spectrometry with millimeter optical retardations currently limited by the emission linewidth and phase noise of the used lasers. Low‐pressure Doppler‐broadened absorption lines probed by widely‐tunable chip‐scale mid‐infrared optical frequen with electrical pumping are fully resolved over a span of tens of nanometers. This versatile technique paves the way for compact, electrostatically‐actuated, or even all‐on‐chip high‐fidelity FTS, and can be readily applied to boost the resolution of existing commercial instruments with compact interferometers several hundred times. [ABSTRACT FROM AUTHOR]

Summary In the first part of this paper, we closely examine well‐known methods for balancing the output power level of the pseudo‐differential current‐reuse voltage‐controlled oscillator. We scrutinize their effectiveness in terms of canceling output mismatches, insensitivity to process, voltage, and temperature variations, and their capability of not degrading phase noise performance. Through analyses and simulations, it is shown that contrary to common belief, some techniques are not as effective as previously thought and should be employed only under specific circumstances. The best conventional approach is proven to be the use of a common‐mode shunting capacitor at the inductor's center tap node to create a virtual ground. In the second part, it is demonstrated that the current‐reuse voltage‐controlled oscillator can intrinsically produce balanced outputs without using any additional techniques or extra passive or active components. Using single‐ended tank capacitors instead of differential ones, the common‐mode voltage of the outputs is shunted to the real ground. This technique reintroduces a reference voltage to the tank circuit, forcing the oscillator to achieve equilibrium between positive and negative swings. The proposed current‐reuse oscillator is designed and post‐layout simulated in a 65‐nm CMOS process, covering a frequency range of 4.84–6.38 GHz with an average power consumption of 0.65 mW. It produces balanced outputs with an amplitude error of less than ±0.2% and achieves a phase noise of −126.7 dBc/Hz and FoMT of 201.8 dB at a 3‐MHz offset frequency. [ABSTRACT FROM AUTHOR]

A high‐linearity LC‐voltage‐controlled oscillator (LC‐VCO) with combined metal‐oxide semiconductor varactors and bulk‐biased P‐channel metal‐oxide semiconductor varactors in parallel is proposed to reduce the VCO‐gain (KVCO) variation and extend the linear range of the control voltage. Fabricated in a 180‐nm complementary metal‐oxide semiconductor process, the proposed topology achieves a low gain variation of less than 6.3% and a tuning range of ~28% operating from 2.31 to 3.06 GHz, corresponding to a linear control voltage range from 0.6 to 1.4 V. The phase noise is measured to be −115.3 dBc/Hz at 1 MHz offset at 3.06 GHz and the figure of merit (FoM) is −181.2 dBc/Hz. The oscillator occupies an area of 0.93 × 0.54 mm and consumes 1.8 mW from mixed 1.2/1.8 V supply voltage. [ABSTRACT FROM AUTHOR]

A complementary metal oxide semiconductor (CMOS) voltage‐controlled oscillator (VCO) using a tail current source modulated with the output frequency is presented to achieve low phase noise with low power consumption at the K‐band. Differentially modulated current sources, which reduce flicker noise by the feedback of the VCO outputs, contribute to an overall reduction in the phase noise of the VCO using the electromagnetic‐based fully symmetrical design. The proposed LC VCO with a 3‐bit switched capacitor bank for a wide tuning range was fabricated on the size of 0.4 × 0.57 mm2 using a 65‐nm CMOS process. The measurement results of the proposed VCO showed a frequency tuning range from 22.57 to 25.3 GHz, and a phase noise of −108.48 dBc/Hz at a 1‐MHz offset frequency with a power consumption of 8.27 mW at a supply voltage of 1.2 V. The calculated figure of merit (FoM) and FoM with the tuning range were −186.48 and −187.67 dBc/Hz, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel ultra low jitter phase‐locked loop (PLL) circuit architecture for RF Sampling Transceiver. The programmable frequency divider with duty cycle expansion and the new phase frequency detector and charge pump circuit are used to solve the problem of voltage domain conversion of narrow pulses in the traditional high‐performance charge pump PLL structure. The traditional structure degrades charge pump linearity and noise, thus deteriorating overall jitter performance. Furthermore, voltage‐controlled oscillator uses the dual core structure and the second harmonic suppression technology, combined with the proposed new switching capacitor structure, and achieves −139.3 dBc/Hz phase noise at the 1 MHz frequency offset of the 5.2 GHz carrier under the open loop state. The PLL implemented in a standard Taiwan Semiconductor Manufacturing Company 28 nm process occupies a core area of 0.4 mm2 and generates a frequency ranging from 4 to 5.2 GHz using 50 MHz oscillator input, the power consumption is 40 mW. It achieves 74.8 fs root‐mean‐square jitter integrated from 10 KHz to 30 MHz. When the PLL output is divided by 2, the output phase noise at 1 MHz frequency offset is −125.75 dBc/Hz, and the PLL FoM is −246. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a new low phase noise (PN) quadrature voltage controller oscillator (QVCO), which includes four class C LC‐VCOs oscillated at 13 GHz operating frequency with 45‐degree phase differences from each other. By combining the second harmonics (super‐harmonic) of the LC‐VCOs, the quadrature outputs with low PN at 26 GHz are generated. To assess the performance of the proposed QVCO, post‐layout simulations are performed in 65‐nm CMOS technology with a 0.6 V supply voltage. The post‐layout results represent that the proposed circuit has 26 GHz quadrature outputs with the PN of −116.4 at 1 MHz offset frequency. Also, the proposed QVCO occupies an area of 0.366 mm2 and consumes 10.4 mW of power. Therefore, the proposed QVCO is a good candidate for 5G applications. [ABSTRACT FROM AUTHOR]

Summary: The research and development on solid‐state source generators have been making progress on chip, aiming to generate low noise, high output power, and high DC‐to‐RF energy efficiency in the millimeter‐wave (mmW) and terahertz (THz) domains. In particular, their full integration in silicon technologies, such as advanced complementary‐metal‐oxide‐semiconductor processes, has motivated the design of low cost, high performance, and miniature integrated circuits (ICs). This manuscript focuses on providing a general overview of recent progress on solid‐state signal source operating beyond 60 GHz till the THz region, from the perspective of operating principle, design metrics, state‐of‐the‐art performance, testing results, and their applications in emerging mmW/THz systems. Finally, with the use of fully integrated source generators, several design arts are highlighted to showcase the recent advances of ICs toward millimeter‐wave and THz radiation, imaging, coupled oscillator network (CON), and communication. Potential future research directions enabled by mmW/THz signal sources will be envisioned. [ABSTRACT FROM AUTHOR]

This work demonstrates an actively driven ultra‐low phase noise mode‐locked laser built with all polarization‐maintaining components. The output of the laser is an optical pulse train at 4‐GHz repetition rate and 1.63‐ps pulse width. The absolute phase noise and timing jitter of the photo detected signal is measured and found to be –140 dBc/Hz at 10‐kHz offset frequency and 10.21 fs (integrated from 100 Hz to 10 MHz). [ABSTRACT FROM AUTHOR]

A 0.5‐V low‐power VCO by using TSMC 0.18‐μm CMOS process has been proposed. For achieving low phase noise and low power consumption, several techniques have been utilized. The forward body biasing technique can lower the supply voltage and power consumption. The noise filtering, feedback capacitors, and switched biasing technique can reduce the phase noise and power consumption. The PMOS transistors, which has lower flicker noise than the NMOS transistors, are used for further lowering the phase noise. The body‐controlled cross‐coupled pair is proposed for choosing the oscillation frequencies without using additional varactors, which lower the oscillation signal loss and phase noise. The measured results show the phase noise at 1 MHz offset frequency from the carrier signal is −118.6 dBc/Hz with 1/f3 corner frequency of 230 kHz while the control voltage is 0 V. The frequency tuning range is from 2.4 to 2.46 GHz under power consumption from 0.5 to 0.8 mW. The figure of merit at 1 MHz offset frequency from the carrier signal is −189 dBc/Hz. [ABSTRACT FROM AUTHOR]

Summary: An innovative, high‐quality factor, and small‐area V‐shaped inductor is presented in this article to improve the performance of voltage‐controlled oscillators (VCOs). The differential inductance of the suggested V‐shaped inductor in the resonator and the buffer is 280 pH and 630 pH, respectively. The inductor area is compacted by 42% and 76% compared to the conventional inductor with the same inductance value. Using 0.18‐ μm CMOS technology, the proposed V‐shaped inductor is employed to design a compact VCO operating at Ku‐band. The proposed VCO has a simulated phase noise range of −114 to −114.6 dBc/Hz, which is relatively constant. Also, its simulated frequency tuning range (FTR) is 5.6 % from 14.03 to 14.74 GHz. The power consumption is 2.2 mW. The simulated figure of merit (FoM) ranges from −193.5 to −194.2 dBc/Hz, which is enhanced by 6%. The designed VCO core area is 0.034 mm2, which is compacted by 35% compared to using a conventional spiral inductor. The achieved area‐included figure of merit (FoMA) is −208.7 dBc/Hz. The VCO has an output power of −6.8 dBm and a good harmonic suppression of 29.4 dB between the fundamental and the second harmonic. [ABSTRACT FROM AUTHOR]

Summary: A high frequency resolution digitally controlled oscillator (DCO) is proposed for wireless transceivers, in which the scheme adopts an optimized cascaded differential switched‐capacitor (SC) ladder and a low‐coupled eight‐shaped transformer. The frequency resolution is further improved by the low electromagnetic coupling effect between the primary and secondary coils of the on‐chip transformer, thus reducing quantization noise and phase noise. An eight‐shaped transformer designed using two coils cross‐connected each other is adopted to reduce the magnetic coupling and frequency pulling. The proposed DCO is implemented in a TSMC 180‐nm CMOS process, and a tuning range of 36.7% from 3.83 to 5.55 GHz with a frequency resolution of 17 kHz is achieved. The phase noise is −120.29 dBc/Hz at 1 MHz offset from the 3.83 GHz carrier frequency. The DCO consumes 9.26 mA from a 1.8 V supply, while the figure of merit with tuning range is −191 dBc/Hz. The chip size is 0.294 mm2. [ABSTRACT FROM AUTHOR]

Electrical signals derived from optical sources have achieved record‐low levels of phase noise, and have demonstrated the highest frequency stability yet achieved in the microwave domain. Attaining such ultrastable phase and frequency performance requires high‐fidelity optical‐to‐electrical conversion, typically performed via a high‐speed photodiode. This paper reviews characteristics of the direct photodetection of optical pulses for the intent of generating high power, low phase noise microwave signals from optical sources. The two most popular types of photodiode detectors used for low noise microwave generation are discussed in terms of electrical pulse characteristics, achievable microwave power, and photodetector nonlinearities. Noise sources inherent to photodetection, such as shot noise, flicker noise, and photocarrier scattering are reviewed, and their impact on microwave phase fidelity is discussed. General guidelines for attaining the lowest noise possible from photodetection that balances power saturation, optical amplification, and amplitude‐to‐phase conversion are also presented. [ABSTRACT FROM AUTHOR]

Low‐frequency noise, generated inherently by the number or mobility fluctuation of carriers, is a crucial concern for the design of analog and digital circuits. Unified modelling based on experimental validation of near‐DC noise in amplifiers is a long‐standing open problem. This article develops a model for low‐frequency noise by deriving new bounds for carrier capturing and releasing. According to the proposed model, a measurement system is suggested that operates in a wide frequency range and even at very low frequencies. The system is noise‐tolerant, since the amplifier is selected based on acceptable noise levels. Among the advantages are the independence from specialized structural noise models for each component and the low cost of the measurement system. The evaluation results show that the proposed method leads to a promising improvement in the low‐frequency noise measuring and is superior to conventional models in the normalized root mean square error indicator. Findings reveal that the proposed measurement method can estimate the flicker noise around the DC frequency, and the proposed model agrees reasonably with the proposed measurement circuit. [ABSTRACT FROM AUTHOR]

The field of optical‐frequency‐combs (OFCs) has seen significant progress in recent years due to the advance of mode‐locked fiber lasers with low‐noise performance and long‐term reliability. With the emergence of applications, OFCs with repetition rates close to GHz have become highly sought after. However, generating GHz fiber‐based combs with low noise remains a significant challenge. In this study, a GHz figure‐9 Er‐doped OFC based on a nested fiber ring resonator is presented. By matching the free‐spectral range (FSR) of external and internal optical resonators, an 11‐fold increase in repetition rate from 82 MHz to 907 MHz is achieved. Notably, it is demonstrated that a single pulse operation with long‐term FSR matching can be achieved without any active feedback control. The comb offset frequency is detected using f‐to‐2f technique to ensure high coherence between pulses, which is distinguished from harmonic mode‐locking. The results show that the nested resonators are capable of generating GHz ultrafast OFC pulses with low phase noise via a more flexible cavity design than conventional short‐cavity solutions. This work provides a valuable contribution to the field of ultrafast laser and optical metrology, which demonstrates the potential of nested‐resonators for generating low noise OFCs with boosted repetition rate. [ABSTRACT FROM AUTHOR]

This paper presents a differential complementary metal oxide semiconductor inductor‐capacitor voltage controlled oscillator (LC‐VCO). The VCO is adopted from the gate‐to‐source capacitor feedback Colpitts VCO which has the advantage of large value of negative conductance. Due to the large negative conductance, the VCO has a more reliable startup oscillation at the lower currents. The main characteristics of the VCO such as negative conductance, oscillation frequency and phase noise are discussed and analysed. The value of parameters in this circuit have been determined using Non‐dominated Sorting Genetic Algorithm (NSGA‐II) to have the optimum performance. The designed VCO oscillates at 2.76 GHz under a supply voltage of 1.4 V. Power dissipation of the proposed VCO is 873 μW which is significantly lower than that of some other VCOs. The post‐layout simulation results of the proposed VCO are presented and compared with the performance of some other VCOs. [ABSTRACT FROM AUTHOR]

A dual‐core voltage‐controlled oscillator (VCO) using harmonic resonance is presented in this letter. Without an additional switch capacitor bank, harmonic resonance implemented in VCO is realized by only a single control voltage, satisfying the requirement of frequency‐modulated continuous‐wave radar. Two pairs of varactors are added to the transformer‐based tank, which ensures a constant ratio between the two resonant frequencies of the tank in the entire tuning range. Robustly single‐frequency oscillation is obtained by increasing the coupling coefficient of the transformer and the coupling capacitor's capacitance. Implemented in a 28‐nm complementary metal–oxide–semiconductor, the VCO shows a 14.75% frequency tuning range covering 34.16–39.6 GHz. The measured results show it exhibits −102.13 dBc/Hz phase noise at a 1 MHz offset from the 34.16 GHz. The oscillator core draws 21–28 mA from a 0.9 V supply. [ABSTRACT FROM AUTHOR]

This article presents a low‐phase noise negative resistance oscillator using the dual‐cavity resonator (DCR) based on substrate integrated suspended line (SISL) technology. Two air cavities are stacked without increasing the footprint areas of the oscillator. A coupling hole is introduced to realize weak coupling between the two air cavities. The DCR can enhance the roll‐off of the equivalent resonator. The measured Q factor of the DCR is increased by 15% compared with the single cavity resonator. The measured phase noise of the designed oscillator is −135.32 dBc/Hz at 1 MHz offset from the carrier frequency of 12.44 GHz, and the measured FOM at 1 MHz offset is −204 dBc/Hz. Besides, the designed oscillator based on SISL technology has the advantages of low cost, compact size, and self‐packaging properties. [ABSTRACT FROM AUTHOR]

Atomic spin‐wave (SW) memory is a building block for quantum repeater. However, due to decoherence caused by atomic motions and magnetic‐field gradients, SW retrieval efficiency decays with storage time. Slow magnetic‐field fluctuations (SMFFs) lead to shot‐to‐shot phase noises of SWs, but have not been considered in previous repeater protocols. Here, a SW model including a homogeneous phase noise caused by SMFFs is developed, and then revealed that such phase noise induces decoherence of single‐excitation entanglement between two atomic ensembles in a repeater link. For verifying this conclusion, single‐excitation entanglement between two SWs in a cold atomic ensemble is experimentally prepared and observed entanglement decoherence induced by SMFFs. Limited by SMFFs, the evaluated lifetime of the single‐excitation entanglement over a repeater link is ≈135 ms, even if the link uses optical‐lattice atoms as nodes. Then an approach that may overcome such limitations and extend this lifetime to ≈1.7 s is presented. [ABSTRACT FROM AUTHOR]

A 19‐GHz low‐phase‐noise PLL‐frequency synthesizer is presented in this letter that is intended to be used in a K‐band FMCW radar which requires strict phase noise for detecting a small unmanned aerial vehicle. The 17.9 to 19.5‐GHz PLL includes a Darlington cross‐coupled capacitive‐degeneration VCO which presents higher maximum attainable oscillation frequency (ƒtrans) and larger negative transconductance (gm), thus resulting in low phase noise. Manufactured using the SiGe BiCMOS process, the K‐band synthesizer demonstrates −114 dBc/Hz at 1 MHz offset and −138 dBc/Hz at 10 MHz offset from 19.456 GHz locking carrier frequency. [ABSTRACT FROM AUTHOR]

This paper develops a calculus around a new β‐Pochhammer symbol of two variables, (a,b)m,n based on the Beta weighting ta−11−tb−1. The approach is a natural rising factorial formulation that offers a new way to express hypergeometric functions of two variables. The results are implemented to solve the problem of finding the phase error probability of a vector perturbed by Gaussian noise with an arbitrary phase threshold in closed form for the first time, in terms of the incomplete confluent hypergeometric function 1ℱ1. This has been an unresolved problem in angle modulation dating back to the 1950s. Closed‐form solutions are developed around the lower and upper incomplete Humbert second Φ2 confluent hypergeometric function of two variables using the new incomplete β‐Pochhammer calculus. [ABSTRACT FROM AUTHOR]

Proofs of sharp phase transition and noise sensitivity in percolation have been significantly simplified by the use of randomized algorithms, via the OSSS inequality (proved by O'Donnell et al. and the Schramm–Steif inequality for the Fourier‐Walsh coefficients of functions defined on the Boolean hypercube. In this article, we prove intrinsic versions of the OSSS and Schramm–Steif inequalities for functionals of a general Poisson process, and apply these new estimates to deduce sufficient conditions—expressed in terms of randomized stopping sets—yielding sharp phase transitions, quantitative noise sensitivity, exceptional times and bounds on critical windows for monotonic Boolean Poisson functions. Our analysis is based on a new general definition of "stopping set", not requiring any topological property for the underlying measurable space, as well as on the new concept of a "continuous‐time decision tree", for which we establish several fundamental properties. We apply our findings to the k$$ k $$‐percolation of the Poisson Boolean model and to the Poisson‐based confetti percolation with bounded random grains. In these two models, we reduce the proof of sharp phase transitions for percolation, and of noise sensitivity for crossing events, to the construction of suitable randomized stopping sets and the computation of one‐arm probabilities at criticality. This enables us to settle an open problem suggested by Ahlberg et al. (a special case of which was conjectured earlier by Ahlberg et al. on noise sensitivity of crossing events for the planar Poisson Boolean model with random balls whose radius distribution has finite (2+α)$$ \left(2+\alpha \right) $$‐moments and also show the same for planar confetti percolation model with bounded random balls. We also prove that critical probability is 1/2$$ 1/2 $$ for the planar confetti percolation model with bounded, π/2$$ \pi /2 $$‐rotation invariant and reflection invariant random grains. Such a result was conjectured by Benjamini and Schramm in the case of fixed balls and proved by Müller, Hirsch and Ghosh and Roy in the case of balls, boxes and random boxes, respectively; our results contain all previous findings as special cases. [ABSTRACT FROM AUTHOR]

Coupled microwave oscillators could be potentially considered a good replacement for the feed network of frequency‐diverse arrays. However, previous studies showed that the stability region for a mutually weak‐coupled oscillator array in the Mode Lock State (MLS) is too small to be practical. Besides, by increasing the coupling strength or reducing the initial natural frequency of the oscillators, the current analytical methods lose their accuracy. The final steady‐state and dynamic of a non‐linear Van‐der‐Pol medium‐coupled oscillator array in the MLS is investigated. By using the Kuramoto Model results in analysing the biological cells, an alternative approach is suggested and investigated in the entrainment region for the mode‐locked microwave oscillator array. This approach is accurate even for medium‐coupled oscillator arrays, where the locking range to the beat frequency ratio is greater than 0.1. The stability of the oscillator in this region is investigated by imposing some perturbations in the form of phase noise on the initial signals. Also, the optimum initial condition to design large arrays is investigated using the analysis results. In the described initial conditions for small beat frequencies, the simulation results show that the stability region is much greater than the large beat frequency region. This capability initiates a new practical approach for implementing Frequency Diverse Arrays. [ABSTRACT FROM AUTHOR]

This paper presents a wide‐band charge‐pump phase‐locked loop (CPPLL) with reference spur reduction techniques. To broaden the frequency range without deteriorating phase noise, a 6‐bit capacitor array‐based VCO and an automatic frequency calibrator (AFC) are used. A compact loop filter technique saves the capacitor area and maintains the bandwidth. Also, a novel charge pump with dynamic current matching circuit is proposed to reduce the reference spur of the PLL. The current mismatch is less than 0.22 μA (0.16%) over the voltage range from 0.75 to 1.55 V. Fabricated in 0.13 μm CMOS technology, the proposed PLL achieves a locking range of 7.6–12.3 GHz (47.2%), with a 25 MHz frequency interval. The PLL consumes 23.3 mA from a 2.5 V supply voltage and occupies a core area of 0.92 mm × 0.72 mm. The reference spur of the proposed PLL is measured to be −81.1 dBc, and in‐band phase noise reaches −110.8 dBc/Hz at 1 MHz offset frequency from the 9.5 GHz carrier frequency. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a comprehensive analysis of oscillation frequency, oscillation amplitude, and phase noise is conducted for an LC cross‐coupled oscillator with unequal inductors, active and passive transconductance amplification structure, and very low phase noise. In this study, for the first time, a complete analysis of the phase noise of this oscillator is presented using a novel method that does not require complex simulations to calculate the Impact Sensitivity Function (ISF) and phase noise, and as a result, a closed‐form equation is extracted for the phase noise. The calculated results are compared with the corresponding simulations to evaluate the validity of the extracted equations. Using the closed‐form phase noise equation as well as the oscillation frequency, designers can comprehend the design trade‐offs and design an oscillator for specific phase noise and oscillation frequency. The proposed method of calculating the ISF is also applicable and valid for other second‐order oscillators. In the following, the structure of the proposed oscillator is designed and simulated using the standard 0.18‐μm CMOS technology with a 1.8‐ V power supply and 575.2‐MHz oscillation frequency to have the optimal coupling coefficient in terms of the phase noise and oscillation amplitude. The simulation results as well as the analyses performed based on the phase noise and oscillation amplitude parameters show that the structure proposed in this study provides a better performance with a much lower phase noise comparing with the structure of a conventional cross‐coupled oscillator as well as the proposed cross‐coupled oscillator with equal inductors. [ABSTRACT FROM AUTHOR]

Femtosecond frequency combs are among the most precise measurement tools in existence. They have applications ranging from high‐precision spectroscopy and metrology to time‐domain quantum physics. Maximizing the passive stability of these instruments is essential to achieve their full potential in fundamental science and high‐tech industry. However, the noise mechanisms across the entire operating space of these devices have not been fully characterized. Here the noise properties of fiber‐based frequency combs are studied as a function of intracavity dispersion, pump power, and repetition rate. Distinct minima are discovered in this parameter space where the free‐running linewidth of the carrier‐envelope offset (CEO) frequency fCEO drops below 1 kHz. The individual comb lines are analyzed spread over a wide spectral range producing a complete understanding of the particular contributions to the phase noise and their interplay. Exploiting these findings, combs featuring sharp teeth at specific frequency positions and over the entire spectrum from fCEO to 300 THz are demonstrated. The ultrabroadband stability offered by these compact systems provides a new level of quality for front‐end measurement tasks in both time and frequency domains. [ABSTRACT FROM AUTHOR]

Due to their perfect periodic autocorrelation property, Zadoff–Chu sequences are often used as stimulus signals in the measurement of radio channel responses. In this letter, the cross‐correlation of a linear shift‐invariant system's response to a Zadoff–Chu sequence is derived for the case that a multiplicative perturbation such as phase noise is present at its output. The perturbation signal is shown to incur a spurious discrete Fourier transform, thus degrading the correlation's peak to sidelobe ratio. The implications for the performance limits of channel measurement systems are discussed. [ABSTRACT FROM AUTHOR]

The ever‐expanding horizon of radar applications demands solutions with high‐end radar functionalities and technologies and is often limited by the available radar equipment, cost and time. A practical method to tackle the situation is to rely on the modelling and simulation of radar systems based on the user requirements. The comprehensive system‐level modelling of a pulsed Doppler radar in MATLAB/Simulink consisting of all the fundamental blocks in the transmit chain, the environment, the receive chain, and the data processing chain is presented in this article. The first half of the article discusses the high‐fidelity simulation of each building block in the radar model. In the second half of the article, the range‐Doppler plot generated from the high‐fidelity radar model is compared and validated using the range‐Doppler plot from a real radar trial. The radar phase noise plays a crucial role in the detection of slowly moving, low radar cross‐section targets in the presence of strong clutter. The article also briefly discusses the effects of radar oscillator phase noise in the range‐Doppler plot. The validated, fully flexible radar model has the advantage of supporting the addition of further building blocks and optimising the parameters based on user requirements. [ABSTRACT FROM AUTHOR]

Ionospheric scintillation could seriously disrupt the signal tracking of the global navigation satellite systems (GNSS), further causing positioning accuracy degradation or unavailability. BeiDou navigation satellite system (BDS), a newly developed GNSS by China, has begun to provide global positioning, navigation, and timing service. The objective of the present study is to investigate the effects of ionospheric scintillation on BDS‐2 and BDS‐3 multi‐frequency signals. Ionospheric scintillation monitor receiver data from four monitors in Brazil were collected from October 2021 to May 2022. The results illustrate that S4(B2) and S4(B3) linearly increase with S4(B1) for S4(B1) ≤ 0.6, which is consistent with weak scattering theories, and average experimental ratios of S4(B2)/S4(B1), S4(B3)/S4(B1), and S4(B2)/S4(B3) are less than corresponding theoretical ones by 6.1%, 4.4%, and 1.9%, respectively. Meanwhile, as S4 values increase, lower‐frequency scintillation saturates earlier than higher ones, and the probability of ionospheric scintillation events on B2 and B3 signals is approximately twice (S4 ≥ 0.7) as B1 signals in the equatorial ionization anomaly (EIA) regions. To alleviate the undesirable effects of missing data on GNSS positioning, we first investigate the inter‐frequency relationship and distribution probability of two significant spectral parameters, that is, T (the spectral strength of the phase noise at 1 Hz) and p (the spectral slope of the phase power spectral density) in the tracking jitter model among three BDS frequencies. Results show that the performances among B1, B2, and B3 frequencies have a higher correlation respectively, and their values for B2 and B3 signals are more susceptible to be impacted by ionospheric scintillation. Plain Language Summary: Ionospheric scintillation seriously affects the precision and continuity of the global navigation satellite systems (GNSS) signals and causes positioning accuracy degradation or unavailability. Therefore, it is essential to study the impacts of ionospheric scintillation on the GNSS receiver performance. This study first investigates the inter‐frequency relation of the amplitude scintillation index S4 for B1, B2, and B3 signals from BDS‐2 and BDS‐3 satellites based on the Ionospheric scintillation monitor receiver data at four geomagnetic latitudes in the Brazilian territory. Furthermore, the distribution probability and inter‐frequency relationship of two significant phase spectral parameters of the tracking jitter model, which are widely applied in GNSS positioning solutions, are also presented among three BDS frequencies. All investigations conducted within this contribution show agreement with earlier work in ionospheric scintillation and provide supportive and detailed numerical statements and comparisons. Key Points: The inter‐frequency relation of the amplitude scintillation index for multi‐frequency signals from BDS‐2 and BDS‐3 satellites is displayedThe probability of the ionospheric scintillation events on B2 and B3 signals is approximately twice (S4 ≥ 0.6) as B1 signals in EIA regionsThe spectral parameters p and T of B2 and B3 signals are more susceptible to be affected by ionospheric scintillation [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]

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]

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]

Separating the climate response to external forcing from internal climate variability is a key challenge. While most previous studies have focused on surface responses, here we examine zonal‐mean patterns of North Pacific subsurface temperature responses. In particular, the changes since 1950 driven by anthropogenic aerosol emissions are found by using a pattern recognition method. Based on the single‐forcing large‐ensemble simulations from two models, we show that aerosol forcing caused a nonmonotonic temporal response and a characteristic zonal‐mean pattern within North Pacific, which is distinct from the pattern associated with internal variability. The aerosol‐forced pattern with the nonmonotonic temporal feature shows a substantial temperature change in subpolar regions and a reversed change on the southern flank of the subtropical gyre. A similar characteristic pattern and nonmonotonic time evolution are extracted from the subsurface observations, which likely reflect the subsurface responses to the aerosol forcing, although differences exist with the simulated responses. Plain Language Summary: Pacific climate has long been of interest as considerable evidence has emerged of a decades‐long change. As the background noise, such as Interdecadal Pacific Oscillation and El Niño‐Southern Oscillation, is very strong in the Pacific, it remains a major challenge to detect and understand the changes due to human activities. In this study, we take advantage of a pattern recognition method to investigate the North Pacific subsurface temperature response to aerosol emissions, a suspension of fine particles in air, due to industrial development. The results are primarily based on two sets of model simulations with different phases of background noise and identical external forcing, which stems from anthropogenic aerosol emissions only. We find that the aerosol emissions from North America and Europe cause a clear nonmonotonic time evolution (increased during 1950–1985 and then decreased afterward) and a characteristic zonal mean pattern of the subsurface ocean temperature within the North Pacific. The extracted temporal and spatial features from ocean observations are broadly consistent with those from models, although there are some differences. Key Points: A pattern recognition method is applied to extract aerosol‐induced subsurface temperature pattern from internal variability in North PacificBased on two large‐ensemble simulations, aerosols govern a nonmonotonic feature in temperature change with a characteristic patternThis spatiotemporal feature can be obtained from observations since 1950, although there are some differences with the modeled results [ABSTRACT FROM AUTHOR]

This study denotes a procedure of a small phase noise (SPN) oscillator employing three different substrate integrated waveguide (SIW) resonators as a frequency stabilization‐component. The SIW resonator as modifying phase noise (PN) is investigated and branchline coupler in the feedback loop is presented. The design technique to attain SPN usage for optimized efficiency is proposed. Then, three different X‐band SIW oscillators using a packaged GaAs FET transistor are planned. Due to the PN and compacting, the miniaturized conventional SIW (MCSIW) oscillator is selected. This MCSIW oscillator operates at 8.15 GHz, mentions a PN of −169 dBc/Hz at 1‐MHz frequency‐offset. [ABSTRACT FROM AUTHOR]

A noise circulating voltage‐controlled oscillator (VCO) with an intrinsic injection locking tripler is introduced. Based on the conventional frequency tripling scheme, by integrating the injection transistor pair into the fundamental VCO core, the current of the fundamental VCO core is reused by the injection transistor pair, and the phase noise is reduced due to the noise circulating behavior. The proposed VCO may achieve the fundamental and 3rd harmonic outputs, simultaneously. A protype design is implemented in a standard 65 nm CMOS process, with a tuning range of 33.68–40.11 GHz (17.4%). The phase noise at 1‐MHz offset varies between −101.2 and −97.9 dBc/Hz among the tuning range. The FoMT is in the range of 190.4 and 187.9 dBc/Hz, at 1‐MHz offset. [ABSTRACT FROM AUTHOR]

The traditional sub‐sampling phase‐locked loop faces the tradeoffs between phase noise and spur, in that low in‐band phase noise requires large sampling capacitor size but at the sacrifice of spur performance. This paper presents a sub‐sampling PLL aimed at minimizing in‐band phase noise via sampling thermal noise cancellation technique. It enables the substantial reduction of in‐band phase noise while reducing the sampling capacitor size. In addition, due to the reduction of the sampling capacitance, the reference spur performance of the PLL is improved, and the power consumption of the isolation buffer is reduced. Implemented in a 65 nm CMOS process, the in‐band phase noise at 200 kHz offset is −133.4 dBc/Hz at 2.2 GHz and integrated jitter is 80 fsrms. The reference spur is −67 dBc. It consumes 5.5 mA from 1.2 V supply and occupies 0.72 mm2. [ABSTRACT FROM AUTHOR]

For this task, an improved phase locked loop (PLL) was developed using a more sophisticated phase‐frequency detector with multiband flexible dividers that provide enhanced frequency resolution, a better spectrum, and a better output signal. Great timing jitter was the problem for the old PLL designs because of the unbalanced frequency transfer function caused by the voltage‐controlled oscillator and noise introduced by increases in supply voltage. A new design was suggested for the phase‐frequency detector (PFD) such that PLL lock times are reduced while maintaining a low level of phase jitter. This way, they used fewer transistors, used less power, and had lower propagation holdup and smaller size compared to static PFDs. Additionally, forward ring voltage‐controlled oscillator may improve the resolution of frequency and phase variation errors owing to supply noise by balancing driving force ratios in the feed‐forward and feedback paths. Additionally, there is a dynamic sense flexible divider with several bands for separating special divisions (divide‐by‐47 and divide‐by‐48) that lacks a few extra flip‐flops which save considerable power and improves the frequency difficulties of the multi‐band divider. The advanced phase locked loop (ADPLL) has integrated phase and frequency errors, where the ADPLL excels. The supply noise is decreased by three reference clock cycles and the effect is that the measurement of jitter is better. Advanced Phase Locked Loop oscillates at frequencies ranging from 500 MHz to 4 GHz. A root mean square jitter of 1.29 ps is observed at 1 GHz. Our PLL is rated at 92.1‐μW, with power used at 0.31 mW/GHz. The aim of this article is to design a 180 mm CMOS‐based PLL circuit with a 400 MHz clock and a 0.65 V supply at a fast, dynamic phase frequency detector for resolution and stability. [ABSTRACT FROM AUTHOR]