dB Variation Research Articles

Developing guidelines for a reproducible method for low-frequency impact measurements in buildings

The impact noise performance in buildings is evaluated using the measured radiated sound pressure level when impacted by a standard tapping machine. Recent work has shown that there can be 4 - 5 dB variation in the sound pressure levels at different measurement locations in the room. This can lead to a high reproducibility error for field tests. In this work, the authors have developed a novel reciprocity-based measurement method that shows approximately 1 - 1 .25 dB standard deviation in low-frequencies. Additionally, this method provides output/input ratio-based measurements, which can be useful in design predictions. The method was developed using a simulation model and verified using testing in three structures.

Research on the Calculation Method and Influence Law of High-speed Railway Line Sound Source Propagation Attenuation Caused by Building Sheltering

Abstract In recent years, China’s rail transit system, particularly the high-speed railway network, has experienced rapid development. However, the issue of noise pollution along these railways has become increasingly severe. The accurate prediction of sound levels at specific points near buildings is challenging due to complex factors such as differences in line height, distance, and angle relative to the building. To address this challenge and improve predictions of sound propagation attenuation caused by building shelter from high-speed railway line sources, this study derives an integral expression for diffraction attenuation based on Curze and Meakawa’s point source acoustic diffraction theory. Numerical calculations are conducted to investigate the sound propagation attenuation patterns under different position relationships between buildings and railway lines. Field tests are also carried out along a high-speed railway in China. The findings are as follows: (1) The calculated results show a difference of less than 0.5 dB compared to measured values, indicating that they accurately reflect sound attenuation caused by building shelter. (2) The angle between the building and the railway as well as the distance between the sound point and the edge of the building significantly influence building shelter attenuation; with angle being most prominent among them within a frequency band of 500~2000 Hz resulting in an attenuation range of 0.6~15 dB variation should be considered when predicting noise levels at sensitive points or designing vibration and noise reduction measures accordingly. (3) Different distances between buildings and railway lines result in additional effects on attenuations.

A high-performance sub-THz planar antenna array for THz sensing and imaging applications

Terahertz (THz) spectral region from 0.1 to 3 THz is envisaged to hold immense potential in the next generation of wireless technologies. Recently, research has focused on this terahertz gap, because of its unprecedented channel capacities. At the physical layer, the design complexities and fabrication of THz devices, especially antennas are the prime bottlenecks to realize its full potential. This article introduces a cost-effective, easy-to-fabricate, and reproducible sub-THz antenna design based on a single-layer planar printed circuit board technology. The antenna incorporates carefully designed quasi-cross slots and applied machine learning-assisted global optimization techniques to achieve the desired performance metrics. The antenna performance is elucidated through numerical simulations and verified through a rigorous in-house THz experimental framework around 100–110 GHz. The proposed antenna offers a peak gain of 13.90 dBi with less than 1 dB variation within the entire band of 100–110 GHz. The antenna holds the potential to achieve terabits per second data rates and futuristic high-resolution short-range THz imaging applications.

Low windage dual‐band omnidirectional antenna for high‐speed aircraft communication application

AbstractThe letter presents a low‐windage omnidirectional antenna for high‐speed aircraft in the UHF and L bands. It combines a planar biconical antenna with a printed tape parasitic branch monopole antenna. Upgrading the traditional restricted‐length biconical antenna to a double‐layer planar design meets the compact, lightweight, and low windage requirements of airborne use. To enhance bandwidth and meet the lightweight, compact criteria of high‐speed aircraft, the planar‐printed monopole antenna integrates parasitic stubs and loop antenna concepts. Experimental results exhibit excellent isolation between antenna elements, with over 15 dB segregation and operational spectrum return loss of 27% and 18% at 10 dB. The voltage standing wave ratio is below 2, with less than 5 dB variation in the horizontal radiation pattern across frequency bands. The antenna, measuring 20 mm × 190 mm × 270 mm and weighing around 0.5 kg, holds great promise for high‐speed aircraft applications.

Horn array antenna with high aperture efficiency and suppressed grating lobes

AbstractIn the design of horn array antennas, usually there is a challenge with the grating lobe problem and consequently quite low aperture efficiency. A new configuration for horn array antennas is presented which introduces high aperture efficiency with suppressed grating lobes in both E‐& H‐plane radiation patterns. The proposed array unit cell is a dual‐mode horn loaded by two corrugations in E‐plane. A sample 4 ⨯ 4 array of the proposed unit cell is designed to operate at Ku band. The simulation and measurement results show 13.3% operating bandwidth over which the grating lobes are totally suppressed and the aperture efficiency is above 70%. The antenna measured gain is also 27 dBi with 2 dB variation over the bandwidth. The results show that the aperture efficiency of 98% is achievable making use of the proposed topology.

Design of a 2–18 GHz low noise amplifier MMIC with current reused topology

AbstractA 2–18 GHz ultra wideband low noise amplifier (LNA) is illustrated in this letter. The proposed LNA adopts a two‐stage structure, which is composed of a common source amplifying stage and a cascode amplifying stage. By combining band extension matching technique, current reused topology and active bias circuit, the LNA performs excellent in gain, noise figure, power consumption, and immunization against the fluctuation of voltage supply. The LNA is implemented with a 0.18‐μm GaAs pseudomorphic high electron mobility transistor process and has a compact chip area of 1.75 × 1 mm2. The dedicated LNA achieves a measured average gain of 20.7 dB with ±1.5 dB variation all over the ultra‐wide bandwidth of 2–18 GHz. It also has a measured noise figure of lower than 1.7 dB and a measured output 1 dB compression point of higher than 5 dBm in the operating frequency band. The LNA has a low direct current power dissipation of 100 mW under a 5 V voltage supply.

High-fidelity optical fiber microphone based on graphene oxide and Au nanocoating

Abstract A high-fidelity optical fiber microphone (HF-OFM) with hybrid frequency and fast response is theoretically and experimentally demonstrated by the nanofabrication techniques for real-time communication, which consists of a graphene oxide (GO) film, an Au nanocoating, and an air cavity. The internal stress of the film is increased by the method of mechanical tensile preparation, and the microphone response flatness is improved. Meanwhile, the structural design of the 3 nm Au nanocoating improves the acoustic pressure detection sensitivity by 2.5 times by increasing the reflectivity. The experimental result shows that single, dual, and triple frequency acoustic signal detection in the frequency range of 0.1 kHz–20 kHz are achieved with acoustic pressure sensitivities of 9.64, 9.66, and 8.9 V/Pa, as well as flat frequency response (<2 dB variation). The minimum detectable pressure (MDP) at 1 kHz is 63.25 μPa/Hz1/2. In addition, the high-fidelity real-time transmission of audio signals over an angle range of −90° to 90° is verified by a self-made acoustic pressure detection device. Such a compact, high sensitivity, and large measurement range HF-OFM is very promising for applications of oil leakage exploration, acoustic source location, and real-time communication.

Advanced Noise Indicator Mapping Relying on a City Microphone Network.

In this work, a methodology is presented for city-wide road traffic noise indicator mapping. The need for direct access to traffic data is bypassed by relying on street categorization and a city microphone network. The starting point for the deterministic modeling is a previously developed but simplified dynamic traffic model, the latter necessary to predict statistical and dynamic noise indicators and to estimate the number of noise events. The sound propagation module combines aspects of the CNOSSOS and QSIDE models. In the next step, a machine learning technique-an artificial neural network in this work-is used to weigh the outcomes of the deterministic predictions of various traffic parameter scenarios (linked to street categories) to approach the measured indicators from the microphone network. Application to the city of Barcelona showed that the differences between predictions and measurements typically lie within 2-3 dB, which should be positioned relative to the 3 dB variation in street-side measurements when microphone positioning relative to the façade is not fixed. The number of events is predicted with 30% accuracy. Indicators can be predicted as averages over day, evening and night periods, but also at an hourly scale; shorter time periods do not seem to negatively affect modeling accuracy. The current methodology opens the way to include a broad set of noise indicators in city-wide environmental noise impact assessment.

Compact E-Band Sheet Beam Folded Waveguide Traveling Wave Tube for High Data Rate Communication

The design of a compact <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band (71–76 GHz) sheet beam (SB) folded waveguide (FWG) traveling wave tube (TWT) for high data rate communications is presented in this article. The round beam tunnel for a pencil FWG slow wave structure (SWS) has been redesigned with a rectangular beam tunnel to be suitable for the SB with increased beam current. A novel periodic permanent magnet (PPM)–periodic quadrupolar magnet (PQM) focusing system has been developed to reduce the beam ripple and improve the transmission ratio. A multistep side-out coupler is designed to import and extract the RF power from the SWSs and be compatible with the planar periodic magnetic focusing system. Particle-in-cell (PIC) simulations are employed to evaluate the performance of the high-frequency circuit. Driven by a 1 W signal, the 30-period circuit is estimated to produce more than 100 W power and achieve a 21 dB gain with a less than 0.4 dB variation over 71–76 GHz. Moreover, phase and linearity analysis show a less than 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> in-band phase distortion and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 30 dB third-order intermodulation distortion (C/3IM) at 30 W of output power, meeting the requirements of a communications-focused TWT. Over 5% circuit efficiency and 40% overall efficiency when equipped with a single-stage collector can be achieved by the compact TWT over the target band.

Comparison of low-dropout voltage regulators designed with line and nanowire tunnel-FET experimental data including a simple process variability analysis

This work presents the comparison between Nanowire Tunnel Field-Effect Transistor (NW-TFET) and Line-TFET applied on the design of Low-Dropout Voltage Regulator (LDO). Both devices have a SiGe source composition in order to enhance the current drive. The transistors were modeled using lookup tables (LUTs) approach based on experimental data using Verilog-A language. The LDOs were designed for two conditions, considering different gm/ID, load currents and load capacitances. In order to compare the TFET LDOs with an established technology, a MOSFET LDO was designed with TSMC 0.18 µm process design kit. Both TFET LDOs reach stability without the presence of a compensation capacitor. For gm/ID = 10.5 V−1 the current consumption of NW-TFET LDO (1.5nA) is near two orders of magnitude lower than Line-TFET LDO (68nA) and three orders of magnitude lower than MOSFET LDO (9 µA). The Line-TFET LDO exhibits better results in almost all parameters despite of the gain-bandwidth product (GBW) that is in the same order of magnitude of the MOSFET LDO, 171 kHz compared to 250 kHz for gm/ID = 10.5 V−1. The comparison between TFET LDOs for gm/ID = 7 V−1 was also performed regarding the transient and process variability analysis. The transient response revealed that the Line-TFET LDO has a pronounced lower settling time, 71 µs compared to 5 ms for a load step, but with a damped oscillatory response, the NW-TFET LDO presented lower undershoot for the load step. The process variability analysis was performed for devices within the wafer and was observed that the Line-TFET LDO suffers a higher impact with a 20 dB variation on the loop gain in comparison to 10 dB in the NW-TFET LDO.

Area-Efficient 28-GHz Four-Element Phased-Array Transceiver Front-End Achieving 25.2% Tx Efficiency at 15.68-dBm Output Power

An area-efficient 28-GHz four-element phased-array transceiver front-end (TRx FE) is proposed in this article. Transmitter/receiver (T/R) switch, phase shifter (PS), and power combining/splitting network all use customized coupler-based structures to replace area-consuming quarter-wavelength ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4) transmission line (T-line) structures. In Tx mode, a three-stage power amplifier (PA) is designed by cascading a class-AB predriver amplifier, a deep class-AB driver amplifier, and a class-A output amplifier for high output power. In Rx mode, a two-stage low noise amplifier (LNA) is designed with a 3-bit resistive adjusting load for high dynamic range of input power. A coupler is adopted in the variable gain amplifier (VGA) to achieve constant phase during gain adjustment. The proposed TRx FE is fabricated in a 40-nm CMOS process. Measurement results show that output 1-dB compression point (OP1dB) of 14.99 dBm and saturated output power (OPsat) of 15.68 dBm with 25.2% power efficiency are achieved in each Tx element. In each Rx element, noise figure (NF) of 4.54 dB, input 1-dB compression point (IP1dB) of −10.15 dBm, and maximum gain of 26.3 dB with 56.1-mW power consumption are realized. The gain range of Rx/Tx mode is 9.9–26.3 dB/24.2–44.6 dB with a resolution of 0.3 dB and phase variation less than 2° at 28 GHz. Thanks to the area-efficient coupler-based structures, the phased-array TRx FE occupies an area of 0.42 mm2 for each element and 0.084 mm2 for total area of combiner/splitter, achieving high area efficiency for Ka-band phased-array TRx FEs.

An Aperture-Coupled Stepped Dielectric Resonator UWB MIMO Antenna With AMC

In this letter, an aperture-coupled stepped dielectric resonator (DR) ultrawideband (UWB) multiple-input–multiple-output (MIMO) antenna (UMA) is presented. The proposed stepped DR resonates with quasi TE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ11</sub> at 5.4 GHz and quasi TE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sup> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1δ1</sub> mode at 6.4 GHz and merges with aperture resonating bands to achieve UWB. In the proposed orthogonal MIMO configuration, the stepped DR is able to improve the isolation in the higher frequency region and a modified neutralization line via a quarter wavelength square patch improves the isolation in the desired lower frequency region. The broadside radiating modes of the stepped DR and the dual artificial magnetic conductor (AMC) and PEC bands of the AMC reflector improves the gain and radiation characteristics. An improvement of 37.84% in gain stability within 2.3 dB variation (i.e., 4.2–6.5 dB) is achieved. The group delay of the UMA is more stable than the UWB antenna (UA). Thus, the problem of phase linearity is managed by multipath of the proposed UMA.

Analysis and design of a 1.7‐ to 27.1‐GHz low‐noise amplifier

AbstractThis letter illustrates a 1.7‐ to 27.1‐GHz single‐stage cascode low‐noise amplifier (LNA) with high and flat gain response. In the presented LNA, to obtain high and flat gain response in the broad bandwidth, the Micro‐strip type pHEMT is utilized as the common‐source stage so as to alleviate the gain bandwidth degradation caused by parasitic parameters. Meanwhile, multiple inductive‐peaking inductors are employed to enhance the gain. By optimizing the combination of several bandwidth extension techniques, the experimental results indicate that the exhibited LNA achieves high average gain up to 14.6 dB with ±1.5 dB variation, 2.4 dB typical noise figure, and 14‐dBm OP1dB in the frequency range from 1.7 to 27.1 GHz. Fabricated by using 0.15‐μm GaAs pHEMT process, the presented LNA occupies a chip area of 0.96 mm2.

A Hybrid-Element Approach to Design Wideband ME-Dipole Transmitarray With Improved Aperture Efficiency

In this letter, a wideband efficiency-enhanced transmitarray is proposed using a variety of phasing elements based on the magneto-electric (ME) dipole structure. Several different ME-dipole geometries and excitation mechanisms are investigated to realize the receive-and-transmit type elements that have same multilayer configuration, wide common bandwidth, and stable transmission phase differences. A number of different phase adjustments can be provided within a wide bandwidth by the proposed elements. A 16×16 transmitarray antenna working from 21.5 to 33 GHz (42%, defined according to 3 dB variation in aperture efficiency) is designed, fabricated, and tested, which confirms a peak gain of 26.8 dBi and a peak aperture efficiency of 41%. Comparing to the original 1-bit ME-dipole transmitarray, where only two transmission phases can be used, the presented hybrid-element design demonstrates a pronounced improvement in aperture efficiency with nearly the same bandwidth and element thickness.

Mode-locked erbium-doped fiber laser based on a mechanically exfoliated ReS2 saturable absorber onto D-shaped optical fiber

In this work, we report a femtosecond mode-locking Erbium-doped fiber laser using mechanically exfoliated rhenium disulfide (ReS2) deposited onto the polished surface of a D-shaped optical fiber. By performing the polarization and saturable absorption measurements, the sample exhibited a polarization extinction ratio of 10 dB (90%) and nonlinear transmittance variation of 3.40%. When incorporated into the cavity as a saturable absorber (SA), the passive mode-locking performance of 220 fs was achieved. This is the best mode-locking performance ever reported in literature achieved with all-fiber based ReS2 SA. By using density functional theory (DFT) calculations, we obtained the electronic states and the optical absorption spectrum at 1550 nm attributed by defects in the ReS2 structures, which is consistent with its linear and nonlinear optical absorption in the laser mode-locking mechanism.

Experimental Modal Analysis of Radiator Fan Module to Predict its Influence of Structural Characteristics on Vibration and Noise Contribution

Among many accessories of a passenger car, engine cooling Radiator Fan Module (RFM) is an important source of noise and vibration. Modal parameters provide the basis for the noise generation mechanism and noise propagation phenomena. The objective of the current research work is to characterize RFM through its modal behavior to investigate the contribution of structural vibration to noise radiation during its operating state. Hence, the experimental modal analysis and the noise measurement of RFM were carried out. Additionally a finite element modal analysis of RFM was performed to validate the finite element model that can be used for vibro-acoustic and computational fluid dynamic studies. Below 500 Hz total of eight critical modal frequencies, three for fan and five for shroud are determined and between 500 Hz to 2000Hz seven modes for fan and fifteen modes for shroud were dedermined. From the correlation study, it is witnessed that the contribution of modal behaviour for noise radiation is observed with 20 dB(A) variation below 500 Hz, along the diagonal grid points whereas beyond 500 Hz the variation was negligible. Importantly, blade passing frequencies corresponding to the fan speeds between 500 to 3000 rpm were compared with resonance frequencies obtained and they do not conicide with modal frequencies.

A Grooved Half-Mode Waveguide Leaky-Wave Antenna for Vertically-Polarized Endfire Radiation

A high-gain low-profile leaky-wave antenna (LWA) for vertically-polarized (VP) fixed-beam endfire radiation is proposed in this article. The LWA is composed of two back-to-back half-mode waveguides with grooves etched at the margins of both radiation edges. By etching grooves, the phase velocity of the traveling wave can be tailored to slower than the wave velocity in free space for fitting the Hansen–Woodyard condition. Compared with periodic LWAs, the proposed antenna continuously radiates at two symmetric apertures, contributing to a high endfire gain. A prototype is fabricated and tested to validate the concept. The measured and simulated results are in good agreement. A simulated gain of 14.29 dBi and a measured gain of 13.37 dBi are achieved within an antenna length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.05\lambda _{0}$ </tex-math></inline-formula> . Moreover, a measured overlapping bandwidth of 2.74–3.17 GHz (14.3%) is realized with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11} &lt; - 10$ </tex-math></inline-formula> dB and gain variation less than 3 dB. To the best of the authors’ knowledge, the proposed VP endfire LWA realizes the highest aperture efficiency and shows great advantages in high gain, low profile, and wide bandwidth.

Orientation-Insensitive Multi-Antenna Reader for Wireless Biomedical Applications.

This paper presents a multi-antenna external reader system that enables orientation insensitive communication with implantable medical devices (IMDs) for wireless biomedical applications. The proposed system consists of a circular array with six loop antennas. The antenna placement and orientations are determined by analyzing the near-field magnetic field variations of the loop antenna. The proposed system is first simulated using HFSS electromagnetic simulation software. Our simulations show that the received power at the proposed external reader with six antennas only varies about 5 dB for any given orientation of the implanted antenna, which is highly significant compared to the 20-35 dB variation with a single external antenna. Here, we select the antenna which provides the largest coupling between the IMD to receive/transmit signals. A prototype of the proposed multi-antenna external reader is then implemented using custom-designed PCBs that interconnect loop antennas, transceiver ICs, and commercially-available circuit components. A custom PCB with a miniaturized loop antenna is used to emulate an implantable device. Based on measurement results, the received power in the external reader only varies about 3 dB when the miniaturized antenna rotates with respect to the x-axis. These measurements show good agreement with the simulated reader.

2-D Beam-Steerable Generalized Mikaelian Lens With Unique Flat-Shape Characteristic

A novel two-dimensional (2-D) beam-steerable generalized Mikaelian lens is presented in this letter. The main difference of proposed lens with respect to conventional Luneburg, Maxwell fish-eye and Eaton lens is its unique flat-shape characteristic, which provides great advantages in designing the low-profile flat-shape lens antenna, avoiding using extremely complex conformal mapping methods. The all-dielectric low-cost lens prototype presenting desired graded permittivity profile is fabricated by 3-D printing. The measurement results at 10 GHz show 2-D beam-steering capabilities from −20° to 20° in both the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -plane with around 18.9 dBi of realized gain with less than ∼1.2 dB variation and low-side lobe can be achieved, revealing great potentials for developing the low-profile and cost-effective lens antenna for microwave applications.

Design of a Broadband High-Gain End-Fed Coaxial Collinear Antenna

Omnidirectional antennas are widely used for mobile communications in the base transceiver station. This letter introduces a high-gain coaxial collinear (CoCo) antenna with a stable radiation pattern. To design a wideband end-fed CoCo antenna, we modify the classic center-fed CoCo antenna structure with an appending wire-mesh structure. The proposed CoCo antenna's $-$10 dB impedance bandwidth and gain bandwidth (1 dB variation of maximum gain versus frequency) at a center frequency of 900 MHz is three times higher than the classical center-fed CoCo's equivalent bandwidth, thus retaining 9 dB gain. The unique feeding configuration is designed to create the broadband end-fed antenna and minimize the feeding cable effect on the omnidirectional radiation pattern. We prototype an antenna to evaluate the design performance and confirm the simulation results. The measured results show 8.5 dBi directivity and 125.5 MHz bandwidth at 900 MHz center frequency.