Low Noise Performance Research Articles

Friction in Oil-Lubricated Rolling–Sliding Contacts with Technical and High-Performance Thermoplastics

Thermoplastics show great potential due to their lightweight design, low-noise operation, and cost-effective manufacturing. Oil lubrication allows for their usage in high-power-transmission applications, such as gears. The current design guidelines for thermoplastic gears lack reliable estimates for the coefficient of friction of oil-lubricated rolling–sliding contacts. This work characterizes the friction of elastohydrodynamic rolling–sliding contacts with technical and high-performance thermoplastics with oil lubrication. The influence of polyoxymethylene (POM), polyamide 46 (PA46), polyamide 12 (PA12), and polyetheretherketone (PEEK), as well as mineral oil (MIN), polyalphaolefin (PAO), and water-containing polyalkylene glycol (PAGW), was studied. Experiments were carried out on a ball-on-disk tribometer, considering different loads, speeds, temperatures, and surface roughness. The results show that, for fluid film lubrication, there is very low friction in the superlubricity regime, with a coefficient of friction lower than 0.01. Both sliding and rolling friction account for a significant portion of the total friction, depending on the contact configuration and operating conditions. In the mixed to boundary lubrication regime, the sliding friction depends on the thermoplastic and rises sharply, thus increasing the total friction.

Bionic microstructure design of cross flow fan for high aerodynamic and low noise performances

In this paper, a novel approach was introduced for cross flow fan design by incorporating bionic microstructures on the blade surface. Two types of bionic microstructures, riblet and convex hull, were constructed and studied to achieve high aerodynamic efficiency and low noise design. Numerical simulations were conducted to understand the influence of bionic microstructures on the fan’s aerodynamic and acoustic performance, and the impact of design parameters on these performances was investigated. After printing the bionic microstructure fan samples, the experimental tests were carried out. The flow field and sound field data of the fans with bionic microstructures and the original fan were compared. The results demonstrated that both riblet and convex hull microstructures effectively improved the fan’s aerodynamic performance by reducing turbulent kinetic energy on the blade surface. Additionally, the microstructures inhibited boundary layer separation on the suction surface of adjacent blades, which contributed to reducing vortex noise. However, the pressure gradient formed near the convex hull and the edge of the small-diameter riblet resulted in deterioration in the noise of the corresponding fan. By optimizing the diameter and spacing of the riblet microstructure, the best noise reduction performance was achieved for the riblet fan. The optimized fan showed a 5.3% increase in maximum air volume flow rate and a 2.4 dB(A) reduction in noise. Overall, the cross flow fan design method based on bionic microstructures has valuable application potential in improving the aerodynamic and acoustic performance of various rotating machinery.

Investigating the Performance Optimization of Three‐Quantum‐Well High Electron Mobility Transistor Device: Analyzing Operational Characteristics and Gate Voltage Influence

Quantum well AlGaN/AlN/GaN high electron mobility transistor (HEMT) devices are a unique kind of semiconductor device that make use of a heterostructure made up of layers of different materials. In this study, the operational characteristics and performance optimization of HEMT devices, with a specific emphasis on the behavior of three‐quantum‐well (3QW) HEMT devices, are explored. The impact of gate voltage is explored and is observed that higher gate voltages result in lower pinch‐off voltages and higher saturation drain currents. In these findings, valuable insights for optimizing circuit designs and ensuring dependable operation across a range of electronic applications are offered. In addition, In this study, the device's ability to detect changes in gate voltage and its nonlinear characteristics is emphasized, providing valuable information for improving the device's performance. Additionally, the benefits of HEMT devices with negative threshold voltages are explored. Devices utilizing AlGaN/AlN/GaN structures demonstrate exceptional performance characteristics, such as rapid switching capabilities, high energy efficiency, and low noise performance, making them well suited for a wide range of scientific and technological applications. Finally, when comparing a QW HEMT device at different drain bias conditions (Vd = 1 V and Vd = 5 V), noticeable variations suggesting improved performance with higher drain bias.

A rapid aerodynamic noise prediction model for multi-rotor unmanned aircraft systems with inclusion of wake effect

In this work, the effect of wake on the rotor aerodynamics and aeroacosutics is studied based on an efficient rapid prediction model, which incorporates the induced effects of tip vortex on the blades into the blade element momentum theory. The tip vortex model is estimated using the free vortex wake method. The aerodynamic flow variables, as well as the unsteady loadings due to the radial flow and induction of tip vortices, are employed to model to equivalent sources and, therefore, noise emission, using Goldstein's acoustic analogy. The comparison between the hybrid algorithm and blade element momentum theory shows that the wake effect is not significant in the case of axial flow only. During forward flight conditions, the wake vortex correction greatly affects high frequency harmonics. In addition, a preliminary case study of a quad-rotor vehicle is also discussed, demonstrating the proposed low-fidelity computational framework is helpful for low-noise design and operation of the multi-rotor UAS vehicles.

Flyover auralization of a blended wing body aircraft considering atmospheric turbulence effects

In the ARTEM project a novel blended wing body (BWB) long-range aircraft was designed and optimized for low-noise operation. Virtual flyovers of different BWB vehicle variants were synthesized and auralized in the AuraLab using a loudspeaker array. Prior to auralizing the novel aircraft, the applied methods were hierarchically validated by comparison with field recordings of existing jet aircraft, assessing acoustical indices, time-frequency features, perceived plausibility, and induced noise annoyance. To achieve convincing syntheses, the focus was on developing new auralization models for a realistic representation of atmospheric turbulence effects. The syntheses of the BWB obtained with the successfully validated methods were then used in psychoacoustic laboratory experiments for perception-based evaluation regarding (minimized) noise annoyance. The evaluation revealed that, while the BWB may initially be perceived as somewhat more unfamiliar, it is substantially less annoying than current tube-and-wing long-range aircraft of similar range and mission for take-offs as well as for landings.

A Comparative Study on Picoammeter Designs as Alternatives for Nuclear Reactor Power Measurement Systems

Abstract The study investigates the picoammeter, a highly sensitive current measurement device capable of measuring currents in the picoampere (pA) range. It discusses the typical amplification technique in picoammeters, utilizing an Op-Amp in a trans-impedance amplifier (TIA) circuit to convert the current into a voltage signal. The paper explores the impact of different IC Op-Amps on the picoammeter’s performance, evaluating AD549, MAX4230, LMC662, TLV272, and MCP6001. The result reveals that AD549 Op-Amp ICs are more suitable for picoammeter design due to their low noise performance and low input bias current. Noise output and AC stability are assessed through numerical analysis and simulations using a circuit simulator. The resulting picoammeter exhibits low noise, high sensitivity, and precise measurement accuracy, making it an optimal choice for precise low-current measurements in CIC detectors.

Research on flow-induced radiated noise of twin-screw pumps based on the Lighthill acoustic analogue theory

Abstract To optimize the control of twin-screw pumps (TSP), it is essential to ensure performance while simultaneously preventing noise levels from exceeding specified limits. In order to investigate the flow characteristics and the mechanism of flow-induced radiated noise under various operating conditions, a coupled numerical simulation approach using Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) was employed, and the findings were validated through experiments. The study reveals that the highest sound pressure levels of radiated noise occur near the rotor outlet surface, and the dynamic-static interference at the rotor-boundary interface is the primary cause of flow-induced noise in TSP. The flow-induced noise in TSP exhibits dipole characteristics, with the overall sound pressure level gradually increasing and then sharply rising with the increase in rotational speed (or flow rate). It stabilizes near the design operating point and continues to increase steadily with further increases in rotational speed (or flow rate). Modal testing using a dual-distributed measurement technique highlights significant interference effects between the rotor inlet and the dynamic rotor for the first two Blade Passing Frequencies (BPF) in TSP. The results of this study provide a theoretical foundation for the low-vibration and low-noise design and operation of TSP.

Effective Low Noise Rumble Strip Design and Performance

The purpose of the NCHRP 15-68 Effective Low Noise Rumble Strips project research was to develop and recommend a rumble strip design to achieve somewhat conflicting goals. The design was to minimize the exterior noise that can affect residences along a roadway while producing sufficient interior noise and vibration inside the vehicle to alert the operator of a lane departure. Review of the previous research indicated that this could best be accomplished with a rumble strip of a sinusoidal profile. The first portion of this research was to develop a recommended test procedure which was presented at the 2022 TRB Annual Winter Meeting. Using this procedure, sinusoidal strips were tested in three different states, which included four different wavelengths, 12, 14, 18, and 24 in. The smallest of these produced sufficient interior noise and vibration; however, it produced higher levels of pass-by noise. The largest of these produced the lowest pass-by levels but insufficient interior noise and vibration relative to existing criteria. To explore the intermediate dimensions, 20 different designs of sinusoidal rumble strips were constructed and tested in Washington State. In addition to wavelength, the peak-to-peak dimension of the sinusoidal shape, and the amount that the shape was recessed relative to the existing pavement surface were tested. From the results of the testing of strips, a wavelength of 14 to 15 in., a peak-to-peak amplitude of 7/16 in., and no recess are recommended.

Fast photodiode arrays for high frequency fluctuation measurements of reconnecting flux ropes.

An array of compact, high-bandwidth (>200MHz) and low-cost optical photodiodes has been developed and implemented on the PHASe MApping (PHASMA) experiment. Using purpose-built electronics, an array of 16 photodetectors was constructed and used to monitor broadband (1-5MHz) fluctuations in light intensity emitted by flux ropes undergoing electron-only magnetic reconnection. These measurements reveal a swath of oscillatory behavior, including wave propagation inward toward the diffusion region at approximately the local electron Alfvén speed. Custom 3D-printed collection optics and mounting hardware allow quick reconfiguration of the array for radial or axial measurements. The electronics design is flexible enough to be used with other current-sourcing transducers, such as avalanche photodiodes; silicon photomultipliers; and infrared, x-ray, and UV photodiodes. A noise-rejecting electrical layout allows for low-noise operation close to pulsed plasma discharges. A 16-channel, 64-pixel tomographic array was constructed and initial reconstructions are presented.

Effective low noise rumble strip design and performance

The purpose of the NCHRP 15-68 Effective Low Noise Rumble Strips project was to develop and recommend a rumble strip design capable of minimizing the exterior noise that can impact residences along a roadway while producing sufficient noise and vibration inside the vehicle to alert the operator of lane departure. A review of the previous research indicated that this could best be accomplished with a rumble strip of a sinusoidal profile. Twenty sinusoidal test sites were installed in Washington State, varying the wavelength from 12 to 24 inches, the peak-to-peak amplitude from 5/16 to 1/2 inch, and the recess from 0 to 1/8 inch. Each of the test sites were evaluated using the recommended test procedure developed during Phase I of the NCHRP project, which included a primary interior noise measurement, a primary interior vibration measurement, and an exterior pass-by measurement. Based on the accepted interior noise and vibration standard of 10 dB or more difference on and off the strips and the design goal used in this research of 5 dB or less at the pass-by location, the recommended rumble strip design is a sinusoidal profile with a 15-inch wavelength, a 7/16- to 1/2-inch peak-to-peak amplitude, and a 0-inch recess.

A novel programmable gain control low noise amplifier (PGCLNA) design for automatic gain control loop in BLE applications

Bluetooth low energy (BLE) is a widely used short-range communication protocol and BLE receivers frequently encounter transient high-power RF (radio frequency) signals from antennas, leading to receiver saturation. To address this issue, this work proposes a 2.4 GHz programmable gain control low-noise amplifier (PGCLNA), which is a key element in an automatic gain control (AGC) system for BLE receiver applications. The proposed PGCLNA achieves discrete levels of gain using the g m -boosting technique by splitting the negative feedback. The proposed circuit is simulated in UMC 180 nm technology and the maximum gain achieved is 41.4 dB, with a step decrease of 15 dB in discrete levels. The gain variations do not degrade the performance of S11, which is always less than -16 dB. The noise figure (NF) is always minimum of 5.5 dB and in high gain mode, the minimum value of NF is 1.82 dB. The third-order intercept point (IIP3) is −7.621 dBm in the best circumstances and always remains above −10.69 dBm. These results are achieved by utilising 5.4 mW power at 1.8 V of supply voltage. The circuit occupies an area of 732 μm × 771 μm. The proposed PGCLNA design offers a solution to accommodate a wide range of input signals in BLE receivers, excellent gain control, low noise and robust performance characteristics, making it an essential component in an AGC system for BLE receiver applications.

Low noise operation of an all polarization-maintaining figure-9 Er:fiber laser with near-zero cavity dispersion

We demonstrate the low noise operation of a figure-9 1.5-μm Er:fiber laser constructed by all polarization-maintaining (PM) fiber and fiber components. Starting from the original rate equations and nonlinear Schrödinger equation, the cavity roundtrip evolution toward stable mode locking state is present. The radio frequency spectrum shows a 94.6-MHz fundamental repetition rate with up to 100 dB high signal-to-noise ratio. The net dispersion is tailored to near zero by incorporating and optimizing the length of PM dispersion-compensating fiber in the cavity. As a result, an integrated root-mean-square relative intensity noise of 0.0026 % [1 Hz, 1 MHz] and 10.8-fs timing jitter [100 Hz, 1 MHz] at the fundamental repetition rate are measured. We also lock the fundamental repetition frequency to a stable radio frequency reference and an in-loop relative stability of 2.1 × 10−12 at 1-s gate time is obtained.

Low excess noise HgCdTe e-SWIR avalanche photodiode operating at high gain and temperature

The Hg1−xCdxTe material can exhibit a pure electron avalanche when the composition of the Cd is below 0.6. This hole-to-electron impact ionization ratio close to zero results in noiseless gain. In this paper, we present the results on the gain and noise characteristics of the extended short wavelength infrared (e-SWIR) HgCdTe electron-initialed avalanche photodiodes (e-APDs). The e-APD has a Cd composition of 0.4 and a cutoff wavelength of 3.1μm. At 80 K with a bias voltage of −18.5 V, the device achieves a remarkable gain of 1080, with an excess noise factor below 1.6. Furthermore, the device maintains a gain of 550 and an excess noise below 1.6 at 220 K. Notably, this work reports for the first time the low noise performance of the device at high temperatures and high gain. Moreover, we investigate the responsivity and detectivity of the device when operating at the unit gain point.

Proton beam spot size and position measurements using a multi-strip ionization chamber

PurposeTo develop and characterize a large-area multi-strip ionization chamber (MSIC) for efficient measurement of proton beam spot size and position at a synchrotron-based proton therapy facility. Methods and MaterialsA 420 mm x 320 mm MSIC was designed with 240 vertical strips and 180 horizontal strips at 1.75 mm pitch. The MSIC was characterized by irradiating a grid of proton spots across 17 energies from 73.5 MeV to 235 MeV and comparing to simultaneous measurements made with a reference Gafchromic EBT3 film. Beam profiles, spot sizes, and positions were analyzed. Short term measurement stability and sensitivity were evaluated. ResultsExcellent agreement was demonstrated between the MSIC and EBT3 film for both spot size and position measurements. Spot sizes agreed within ± 0.18 mm for all energies tested. Measured beam spot positions agreed within ± 0.17 mm. The detector showed good short term measurement stability and low noise performance. ConclusionThe large-area MSIC enables efficient and accurate proton beam spot characterization across the clinical energy range. The results indicate the MSIC is suitable for pencil beam scanning proton therapy commissioning and quality assurance applications requiring fast spot size and position quantification.

Assessment of 180 nm double SOI technology for analog front-end design with back-gate voltage

This paper provides an assessment of the electrical and noise performance in the 180 nm double silicon-on-insulator (DSOI) technology, which shows advantages for analog front-end radiation detectors. For the first time, the impact of the back-gate voltage on the electrical and noise performance of DSOI MOSFETs is investigated. The transconductance-to-current (gm /ID ) ratio and low-frequency (1/f) noise were measured as a function of the MOS device types (NMOS/PMOS), gate length, and bias condition of front- and back-gates. Experimental results show that positive back-gate voltage deteriorates the gm /ID ratio of the MOSFETs in weak inversion region. The DSOI NMOS devices overwhelm the PMOS with better gm /ID and 1/f performance. The DSOI devices have a comparable 1/f noise with the 180 nm SOI counterparts. With negative back-gate voltage applied, the low frequency noise performance of NMOS is improved. This assessment of DSOI technology gives a guideline for the readout circuit design in detector front-end systems.

Design and Simulation of VCO for RF Transceivers with Low Power, Low Phase Noise and Wider Tuning Range using Silterra 130nm CMOS Technology

The performance of low-power transceivers is required to meet stringent specifications for an advanced wireless radio frequency (RF) application. The design topology in this paper is simulated to meet the specifications and operation of VCO for low power, low phase noise and wide tuning range in complementary metal oxide semiconductor (CMOS) 130nm technology for RF transceivers. The relationship between the phase noise, power consumption and frequency turning range is fully analyzed to further improve the performance of the voltage-controlled oscillator (VCO). The architecture of the VCO employs two sets of symmetrical cross-couple split NMOS and PMOS with biased current sources operating in the triode region, and a resonator tank that achieves the desired low phase noise performance of about -110 dB/Hz at a tuning range of 4.1 to 4.5 GHz with a supply of 0.9 V. The control of the DC bias point reduces the conduction angle, which improves the current efficiency, power consumption and phase noise. The topology generates sufficient –gm for the oscillator incorporation to mitigate the start-up issue of the VCO. At the center frequency of 4.38 GHz, the VCO serves as a promising solution for improving low power and low phase for wireless communication systems and RF transceiver applications. The design consumes a very low power of 0.138 mW, achieves a phase noise of -110.53 dBc/Hz at 1 MHz offset, and a figure of merit (FoM) of -191.90 dBc/Hz.

Investigating the effects of base oil type on microstructure and tribological properties of polyurea grease

The soaring prices and physiological toxicity of lithium-based grease make polyurea grease a promising alternative due to its balanced cost and performance. Employing preformed thickeners to avoid toxic raw materials has become a preferred method for eco-friendly preparation of polyurea grease. However, the underlying mechanism of base oil modulates the microstructure of polyurea greases prepared with preformed thickeners, subsequently influencing their macroscopic performance remains unclear. Herein, three polyurea greases were synthesized by regulating the base oil types ((poly(α-olefin) oil (PAO40), alkyl naphthalene oil (AN30), and polyether oil (OSP320)) with the same preformed thickener. The real-time polarizing microscope observation of the grease structure evolution process revealed that the preformed thickeners gradually expanded in the base oil and formed a fiber structure. An increased polarity disparity between thickener and base oil leads to a reduced swelling rate and increased fiber length. As a result, compared with high polarity OSP320 and low polarity AN30, non-polar PAO40 induces a more interconnected 3D network composed of long fiber in obtained grease (PG). Low field nuclear magnetic resonance characterization and molecular simulations reveal this network exhibits significant binding ability towards base oil, reducing the movement ability of the base oil, endowing PG with the highest structural strength, achieving effective lubrication and low noise performance. These in-depth understandings will help promote the research and development of polyurea greases.

Systematic analysis of the principles and application scenarios of Low-Noise Amplifier

As society advances, new ideas and products are increasingly integrated into our daily lives. 5th generation mobile networks tech enables faster, lag-free connectivity, raising performance standards for components like Low-Noise Amplifiers. Summarizing Low-Noise Amplifier tech and applications helps researchers and firms leverage past knowledge and explore innovations. This paper analyzes Low-Noise Amplifier development and application, discussing types, principles, key performance indicators, and circuit structures of basic amplifiers. Five vital Low-Noise Amplifier characteristicsnoise figure, impedance matching, linearity, stability, and gainare examined. The author introduces design and application cases in radio astronomy, navigation systems, and 5th generation mobile networks communications based on Low-Noise Amplifier characteristics and performance requirements. The author concludes that advancing radio frequency tech requires improved Low-Noise Amplifiers, especially for high-frequency signals in 5th generation mobile networks. Promising noise performance enhancements come from technologies like modified high electron mobility transistors on GaAs and InP substrates. Monolithic Microwave Integrated Circuit integration reduces size while maintaining cost-effective performance. Future advancements in these areas could further boost Low-Noise Amplifier performance.

Low phase noise microwave oscillator based on gain driven polariton

Low phase noise oscillators are key building blocks of many high-end microwave systems. This work introduces a phase noise reduction mechanism through a gain driven polariton platform, where coherent coupling is used to suppress frequency distribution around the carrier, effectively reducing the phase noise. The design process for achieving low phase noise performance is outlined, and three prototypes are constructed, all of which feature key components, such as gain-embedded planar microwave cavity, yttrium iron garnet, and magnets. In particular, the first prototype is used to showcase the phase noise reduction mechanism, while the second prototype, a fixed-frequency oscillator working at 3.544 GHz, exhibits phase noise levels of −117 and −132 dBc/Hz at 10 and 100 kHz offset frequencies, respectively. The third prototype offers a tuning range from 2.1 to 2.7 GHz, while maintaining phase noise levels comparable to the second prototype.

Ultrafast electro-optic time-frequency fractional Fourier imaging at the single-photon level.

The Fractional Fourier Transform (FRT) corresponds to an arbitrary-angle rotation in the phase space, e.g., the time-frequency (TF) space, and generalizes the fundamentally important Fourier Transform. FRT applications range from classical signal processing (e.g., time-correlated noise optimal filtering) to emerging quantum technologies (e.g., super-resolution TF sensing) which rely on or benefit from coherent low-noise TF operations. Here a versatile low-noise single-photon-compatible implementation of the FRT is presented. Optical TF FRT can be synthesized as a series of a spectral disperser, a time-lens, and another spectral disperser. Relying on the state-of-the-art electro-optic modulators (EOM) for the time-lens, our method avoids added noise inherent to the alternatives based on non-linear optical interactions (such as wave-mixing, cross-phase modulation, or parametric processes). Precise control of the EOM-driving radio-frequency signal enables fast all-electronic control of the FRT angle. In the experiment, we demonstrate FRT angles of up to 1.63 rad for pairs of coherent temporally separated 11.5 ps-wide pulses in the near-infrared (800 nm). We observe a good agreement between the simulated and measured output spectra in the bright-light and single-photon-level regimes, and for a range of pulse separations (20 ps to 26.7 ps). Furthermore, a tradeoff is established between the maximal FRT angle and optical bandwidth, with the current setup accommodating up to 248 GHz of bandwidth. With the ongoing progress in EOM on-chip integration, we envisage excellent scalability and vast applications in all-optical TF processing both in the classical and quantum regimes.