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A reconfigurable wearable textile antenna with wide frequency tuning range is demonstrated in this work. The frequency agility is realized by adding a coplanar reconfiguration module to a planar inverted-F antenna (PIFA) constructed in textile technology. The reconfiguration module consists of a small flexible printed circuit board (PCB) which integrates a tuning circuitry with commercial snap-on buttons as electronic-to-textile connectors. Using this module equipped with a varactor diode, the frequency reconfigurability of the PIFA is investigated and optimized parametrically for maximum tuning range, exploiting a smooth transition from a quarter-wave to a half-wave patch resonant mode. A fabricated prototype demonstrates a very wide tuning range of approximately 70% (or one octave) with stable directive radiation characteristics, as predicted by simulations. The robust performance and mechanical stability of the reconfigurable antenna in various on-body and bending configurations validates the viability of the antenna tuning concept and the practicality of the proposed coplanar reconfiguration module.

The study addresses the benefit of tuning single harmonics with vocal tract resonances to increase vocal loudness. The loudness of theoretically constructed vocal sounds with variable levels of sound energy in the first, second, and third harmonics is computed on the basis of ISO standard 226:2003. In comparison to increased loudness with changes in overall spectral slope, it is shown that single harmonic tuning requires a greater range of SPL to produce a similar range of loudness. For example, a 10-40 dB increase in the level of a single harmonic produces less than two doublings of loudness, whereas a spectral slope change from -12 dB/octave to -3 dB/octave can produce a similar doubling of loudness with only a 5 dB SPL increase.

Optical isolators today are exclusively built on magneto-optic principles but are not readily implemented within photonic integrated circuits. So far, no magnetless alternative1–22 has managed to simultaneously combine linearity (that is, no frequency shift), linear response (that is, input–output scaling), ultralow insertion loss and large directional contrast on-chip. Here we demonstrate an electrically driven optical isolator design that leverages the unbeatable transparency of a short, high-quality dielectric waveguide, with the strong attenuation from a critically coupled absorber. Our concept is implemented using a lithium niobate racetrack resonator in which phonon-mediated13 photonic Autler–Townes splitting10,16,23,24 breaks the chiral symmetry of the resonant modes. We demonstrate isolators at wavelengths one octave apart near 1,550 nm and 780 nm, fabricated from the same lithium-niobate-on-insulator wafer. Linear isolation is demonstrated with simultaneously 39 dB contrast and 10 dB bandwidth up to ~200 MHz. Non-magnetic optical isolators are demonstrated using phonon-mediated photonic Autler–Townes splitting. The on-chip lithium niobate devices simultaneously achieve ultralow insertion loss and high contrast.

An investigation of the optic spectral components beating at the photodetector to recover the RF signal at the output of a sub-octave microwave photonic link is presented, by a theoretical and experimental approach. It is demonstrated the best efficiency is achieved when the carrier to sideband ratio (CSR) is 0 dB at a low bias voltage condition on Mach-Zehnder (MZM) intensity modulator. A RF power link gain improvement of 9.7 dB is demonstrated for a same photodetector incident optic power, compared with a link operating at quadrature bias voltage condition on the MZM.

Recently, machine learning and its applications have gained a large attraction in different fields. Accurate predictions in building acoustics is vital especially in the design stage. This paper presents a sound insulation prediction model based on Artificial Neural Networks (ANNs) to estimate acoustic performance for airborne and impact sound insulation of floor structures. At an initial stage, the prediction model was developed and tested for a small amount of data, specifically 67 measurement curves in one third octave bands. The results indicate that the model can predict the weighted airborne sound insulation for various floors with an error around 1 dB, while the accuracy decreases for the impact sound especially for complex floor configurations due to large error deviations in high frequency bands between the real and estimated values. The model also shows a very good accuracy in predicting the airborne and impact sound insulation curves in the low frequencies, which are of higher interest usually in building acoustics. Keywords: building acoustics, airborne sound, impact sound, prediction model, neural networks

This brief presents a design space analysis for optimum load trajectory selection in multi-octave continuous class power amplifiers using nonlinear embedding model. The proposed approach solves the major problem associated with the synthesis of a broadband matching network due to the non-foster behavior of load at the device package terminal. The nonlinear embedding model allows the designer direct access at the current generator plane for applying any load apparently creating desired waveforms for any class of operations. These loads are then projected to the package plane using the model for designing the required matching network. For demonstration, a nonlinear embedding model of 25 W GaN HEMT device from Wolfspeed is extracted and utilized to develop multi-octave continuous class F PA operating in 0.5-2.2 GHz band with 60%-73.8% drain efficiency in measurement.

The COVID-19 pandemic has led to a global trend in mask wearing. This study investigates how wearing face masks attenuate sound in the human speech range. Masks were equipped onto a test fixture to evaluate acoustic insertion loss over whole-octave bands important for vocal transmission. With the exception of face shield, tested masks showed less than 2 dB of insertion loss at frequencies less than 2 kHz and up to 5 dB of attenuation at frequencies above 2 kHz. The face shield showed insertion loss of more than 10 dB in the 4 and 8 kHz octave bands. © INTER-NOISE 2021 .All right reserved.

Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements. While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance for low frequencies (below 600 Hz) leads to a rather narrowband absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiplecavity perforated panels have been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed. © 2021 Institute of Noise Control Engineering.

Slot waveguides based on silicon-rich materials are proposed and experimentally demonstrated, which consist of a silicon-rich oxide (SRO) slot layer sandwiched by two silicon-rich nitride (SRN) layers. Measurements show the waveguides have a low propagation loss of $\sim$2.2 dB/cm and a 50-$\mu \text{m}$-radius micro-ring resonator can achieve a loaded quality factor ($Q_{load}$) of $\sim 10^5$. Four-wave mixing experiments in the slot waveguides reveal a high nonlinearity $\gamma$ of 16 W$^{-1}$m$^{-1}$ of the waveguide and an averaged nonlinear index $n_2$ of 2.5 x 10$^{-18}$ m $^2$/W of the silicon-rich materials, 10 times larger than that of stoichiometric silicon nitride (Si$_3$N$_4$). Supercontinuum generation (SCG) experiments have shown a large fabrication tolerance of such slot waveguides that 1.2 octave spectral broadening in a 1510-nm-wide slot waveguide can be achieved while that is 0.9 octave in a slot waveguide with a width shrinking as large as 220 nm.

To satisfy the requirements for multi-standard frequency generation, mode-switching oscillators are developed to increase the frequency tuning range without incurring considerable phase noise penalty. However, this improvement in the tuning range is often limited by the parasitics of the circuitry for mode selection and tuning. To address this challenge, this work presents a dual-core octave-tuning VCO using a switch-less tertiary magnetic coupling loop. The design employs the benefits of transformer-switching without incurring switch loss and quality factor degradation and also the benefits of mode switching without the parasitics from the mode selection and tuning network. The VCO employs a non-constant $RC$ scaling for the capacitors’ bank, across the tuning bits, and positive feedback dc-coupled inductive-degenerated output buffer to maximize the tuning range. Implemented in 22 nm fully depleted silicon-on-insulator (FDSOI), the dual-core VCO achieves a 72% tuning at 8–17 GHz and a figure-of-merit-tuning ( $\text {FoM}_{T}$ ) of 208.8 dBc/Hz at 11 GHz. The chip operates from a 0.45 V supply with a power consumption of 17–33 mW and a core area of 0.39 mm2. To the best of our knowledge, the VCO achieves the highest $\text {FoM}_{T}$ and lowest supply for designs over 10 GHz.

In this paper, we describe the design, layout, and performance of a 6-bit TTD (true time delay) chip operating over the entire band of 2–18 GHz. The 1.15 mm2 chip is implemented using TSMC foundry 65 nm technology. The least significant bit is 1 ps. The design is based on the concept of all-pass network with some modifications intended to reduce the number of unit cells. Thus, the first three bits are implemented in a single delay cell. A peaking buffer amplifier between bit 4 and bit 5 is used for impedance matching and partial compensation of the insertion loss slope. The rms delay error of the TTD is

Field measurements of the ground vibrations due to subway moving load are carried out in two distinct geological conditions (soft soil ground, granite ground) in China. Vibration measurements are performed on the tunnel ground after the vibration generated by another running subway transmitting in the medium. Vibration accelerations, frequency spectrum and 1/3 octave curves are obtained and the effects of geological conditions of the measured ground vibrations are well considered. It is found that vibration acceleration of the granite ground is approximately 5 times higher than soft soil ground under the subway trains moving load. In addition, much higher frequency vibrations is observed in the granite ground, which is absent in the soft soil ground. Furthermore, the maximum vibration level in granite ground is nearly 90 dB that seriously affects adjacent structures, sensitive machineries, and even passengers.

This letter presents a new approach for reconfiguring substrate integrated waveguide (SIW) devices. It involves allowing or prohibiting the wave propagation by using a removable wall which is built from a series of drill holes. When the wall is required, the holes are filled with gallium-based liquid metal (LM), thus forming vias. When the wall is no longer required, the holes are emptied of LM. The method has been applied to a single-pole single-throw (SPST) SIW switch as well as a single-pole double-throw (SPDT) switch. Both switches perform well over a wide frequency bandwidth, approaching one octave. The SPST switch performs well from 2.4 to 4.3 GHz. In the ON-state (i.e., wall removed), the insertion loss (IL) is ≤0.5 dB. In the OFF-state (i.e., wall inserted), the isolation is 30 dB. The SPDT switch operates effectively from 4.7 to 7.2 GHz. The IL, between two connected ports, is 0.7 dB. The isolation between unconnected ports is 40 dB. The proposed approach will be applicable within a wide range of different reconfigurable microwave devices.

This paper presents a switched-power-combining RF power amplifier (PA) architecture, using evanescent-mode resonators as input splitters and output combiners. The input resonator also provides proper input matching to the transistor, eliminating the need for an input matching network, which reduces the overall size of the PA. The external couplings into the resonators are switchable to allow for activating one, two, or all three sub-PAs, depending on the power requirement. This results in a higher Output Backoff (OBO) efficiency, compared to a single PA. The presented concepts for the proposed architecture are supported by theoretical analysis and experimental validation. The implemented PA is based on Class-E sub-PAs, operates in the 1.2-2.4 GHz range, provides 36-40 dBm output power, and occupies an area of 41 × 82 mm2. Compared to the state-of-the-art amplifiers operating at this frequency range, this resembles an average of 80% reduction in size.

This paper reports on the design of frequency-dependent feed networks for linear antenna arrays with minimum half-power beamwidth (HPBW) variation in more than one octave of the frequency spectrum. The proposed approach is based on: i) frequency-dependent power dividers that gradually shift the RF power from the outer elements of the array to the inner ones with the increase of frequency and ii) uniformly or non-uniformly-spaced directive antenna elements. The operating principles and design trade-offs of the concept are presented through ideal simulations of four- and six-element antenna arrays shaped by isotropic or directive radiators. It is shown that by employing directive antenna elements and non-uniform spacing, minimum HPBW variation can be obtained in a broad bandwidth (BW, e.g., 3:1). For physical verification purposes, two frequency-dependent feed networks and Vivaldi antenna elements were designed, manufactured, and measured. The first network feeds a uniformly-spaced four-element array of Vivaldi antennas and demonstrates a 58% HPBW variation in a 3:1 of BW. The second network feeds a non-uniformly-spaced six-element Vivaldi array and results in a 67% HPBW variation in a 2.5:1 of BW.

This study aims to develop a novel acoustic panel that constitutes more natural fiber rather than a resin matrix, and the effect of perforation depth in the composite panel is investigated. Jute fiber-reinforced composite panels undergo partial perforation using a tapping machine of depth 7.5 mm, 15 mm, and 22.5 mm to the total thickness of 30 mm. The samples are tested experimentally in an impedance tube and sound transmission loss test setup to evaluate the acoustic capabilities for the frequency range of 100–1600 Hz. For validation, the intrinsic parameters are predicted from experimental sound absorption data using the inverse characterization technique. Insight of application aspect, the panel is modeled to be present in a rectangular acoustical cavity and analyzed numerically in COMSOL Multiphysics. The impedance tube test results indicate that the peak of the sound absorption coefficient increases with increases of perforation depth. Similarly, perforation depth influences the transmission loss of the panel, and significant results noticed. The use of a jute panel in rectangular enclosure results in a 3–6 dB reduction in the overall sound pressure level of one-third octave frequencies.

This paper reports on the design and practical validation of monopole antenna arrays with reduced half-power beamwidth (HPBW) variation in a bandwidth (BW) greater than one octave of the RF spectrum. The HPBW variation is reduced by feeding the antenna elements with frequency-dependent feed networks. The feed networks are designed in such a way that the element power is gradually shifted from the outer elements at low frequencies to the inner elements at high frequencies. The operating principles of the proposed concept are explored through simulated examples of four-element arrays made of isotropic elements and then realistic monopole elements. Scalability of the concept to eight-element arrays is also explored using ideal simulations. For practical validation purposes, a four-element monopole antenna array and its corresponding feed network are designed and measured. The prototype resulted in a HPBW variation of 78% in a 2.6:1 BW, which is significantly reduced compared to the uniformly fed array, having a 216% variation.

Noise generated by trains running on elevated lines creates many disturbances to the normal lives of surrounding residents. Investigations have shown that people living along elevated lines complain that the noise is sometimes unbearable. To better control the noise and optimize the acoustic environment, noise spectrum characteristics were analyzed and compared with a field test and a numerical simulation. Through an energy analysis of the noise on the bridge side, the energy distribution characteristics of the noise at specific measuring points in different frequency bands were obtained. The influence of the Doppler effect on frequency shift was analyzed. Based on the partial coherence theory, a multi-input and single-output program was compiled to calculate the correlation and contribution degree of the bridge structure-borne noise and wheel/rail noise at the one-third octave center frequency. The results show that the peak noises of the bridge and the wheel/rail are concentrated at 31.5`-63 Hz and 400`-800 Hz, respectively. For environmental noise on the bridge side, the frequency band above 250 Hz is mainly affected by the wheel/rail noise. In areas of noise source strength, the relative ratio of noise energy above 250 Hz can reach 83.4%. Noise in the near ground and far bridge area is mainly low-frequency, and the relative energy ratio is about 8.9%. The Doppler effect has an influence of less than 6% on the frequency shift with a speed of 67.9 km/h. In the low-frequency band below 250 Hz, the noise in the acoustic shadow area near the bridge and the ground is mainly contributed to by the vibration-radiated noise of the bridge, of which the contribution of the bottom panel is the most prominent. The noise in the comprehensive noise area of the far bridge is mainly caused by the structure-borne noise of the bridge, and the contribution of each bridge panel is different. This study can provide a reference for finding the source of elevated rail noise in some challenging frequency ranges and for then determining optimal designs and measures for noise reduction.

A handclap is a convenient and easily available source for room acoustic measurements. If used correctly (e.g., application of optimal hand configuration) it can provide usable results for the measurement of acoustic parameters, within an expected deviation. Its biggest drawbacks are the low sound pressure level (especially in the low frequency range) as well as its low repeatability. With this in mind, this paper explores the idea of testing a handclap with a glove in order to assess the effect on its source characteristics. For this purpose, measurements were performed with 12 participants wearing leather gloves. Sound levels were compared with simple handclaps without gloves, and between grouped results (overall A-weighted SPL, octave bands, 1/3 octave bands). Measurements were also performed several times to evaluate the effect on repeatability. Results indicate that the use of leather gloves can increase the sound levels of a handclap by 10 dB and 15 dB in the low frequency ranges (63 Hz and 125 Hz octave bands, respectively). Handclaps with leather gloves also point toward improved repeatability, particularly in the low-frequency part of the frequency spectrum. In conclusion, compared to simple handclaps without gloves, evidence from this study supports the concept that handclaps with leather gloves can be used in engineering practices for improved room acoustic measurements of room impulse response.

We report the generation of an infrared (IR) supercontinuum spanning over an octave using a centimeter (6 cm) length of photonic crystal fiber (PCF) filled with MoS2, which has a considerably large nonlinear refractive index. The fiber is pumped with a femto-second laser pulse with an infrared wavelength of 2080 nm, pumping intensity of 336.76 GW/cm2, peak power of 0.75 GW, and pulse width of 150 fs. With the assistance of highly nonlinear MoS2, a supercontinuum bandwidth that remarkably extends from 1400 to 2700 nm below 20 dB is achieved. This supercontinuum bandwidth significantly exceeds the previously reported spectra for other nonlinear glass-based optical fibers, even with a fairly short fiber length. Furthermore, this short fiber length allows PCF to be more efficiently utilized, and is expected to be suitable for various applications, such as broadband light source through liquid-based fibers and waveguide-based optical communications, especially in the IR region.

Conventional broadband couplers use multi-sectioning techniques and consist of multiple coupled lines. In this study, in contrast to traditional methods, one pair of coupled lines is used to design multi-octave broadband couplers. In the proposed microstrip couplers, the coupled lines are weakly coupled and are of one-eighth wavelength at the highest operating frequency. The weakly coupled lines exhibit a linear coupling response with a slope of 6 dB/octave. To compensate the coupling response, one-pole low-pass networks with a slope of −6 dB/octave are cascaded with the microstrip coupled lines. To validate the design concept, two broadband microstrip couplers for the frequency range of 30–500 MHz and 1–3 GHz have been designed and fabricated. The couplers exhibit a coupling of 52 and 39 dB, respectively. The broadband couplers provide a ripple of 0.5 dB in the coupling response. The proposed weakly coupled couplers are adequate for high-power measurements. The weak coupling permits lumped-element surface mount devices to be used as the compensating network. The multi-octave couplers are realised in small areas.

Purpose: Given the increased levels of fine and ultrafine dust, as well as the spread of COVID-19, current opinion is that most people will wear a face mask such a KF94 mask for a long time To test speech transmission through the face masks, various types of masks including dust masks available in the market at the time of the study were tested under laboratory conditions Methods: Fourteen types of masks worn on a head and torso simulator (HATS) and test signals were played on a speaker installed in the mouse position of the HATS Speech Transmission Index (STI) and the speech level in the octave band were measured at distances of 1 m and 2 m Results: STI at a distance of 2 m was decreased to 3 4-5 7% and speech levels in the octave band at 4 kHz or higher were also decreased when wearing disposable masks and a cotton mask KF80 and KF94 masks showed decreased STI similar to those of disposable masks;however, a decrease in the speech level was observed at the octave bands of above 2 kHz Dust masks and single-cartridge half-face respirators showed approximately 11 2% and 33 7% to 39 3% decreases in STI levels, respectively Conclusion: When wearing masks, STI and the speech level was decreased in the high-frequency bands However, speech level differences at high frequencies may be related to the increased voice level of the speaker and the understanding of consonants with the masks for several hours in living and working environments © 2020 Korean Academy of Audiology

A family of aperiodic Mo/Be multilayer mirrors was designed for maximum uniform reflectivity in the ranges 111 – 138, 111 – 150, 111 – 200 and 111 – 222 Å at normal radiation incidence. The simulations took into account the existence of Mo-on-Be and Be-on-Mo transition layers. It was shown that the reflectivity may be as high as 10% in an octave wavelength range of 111 – 222 Å. We demonstrate the operation of an imaging transmission-grating spectrograph with a broadband Mo/Be multilayer mirror with a uniform reflectivity in the wavelength range 111 – 138 Å synthesised at the Institute for the Physics of Microstructures, RAS. The spectrograph was used to record the line spectra of multiply charged fluorine and magnesium ions from a laser-produced plasma. The role of the grating support structure in the formation of spectral source images is discussed. The spatial resolution of 50 μm is demonstrated.

The gravity method is a geophysical exploration method to measure variations in the acceleration of gravity on the surface of the earth in response to variations in rocks that exist beneath the surface. In gravity exploration requires a preliminary picture as a reference for measurement. This study aims to make forward modeling synthetic OCTAVE based using synthetic data on subsurface rock structures, so as to produce intrusion and fracture models based on differences in the value of the acceleration of gravity from one point to another on the surface of the earth. Synthetic modeling with the geological parameter approach of the study area is based on variations in the price of rock density. The model parameters used in intrusion modeling are the density value of 2.7 g/cm3 and the depth of 850 meters while the fracture modeling uses a density value of 2.7 g/cm3 with a depth of 350 meters and 360 meters and a thickness of 500 meters. From intrusion modeling, the gravity vertical component of attraction force is 0.03 mGal and in the fracture modeling the gravity vertical component of attraction force is 0.0565 mGal. Based on the results of this modeling, distance curve vs. gravity anomaly response is obtained for both cases. In the intrusion rock model obtained by the profile model with an open type down. While the fracture modeling is obtained anomalous profile curve variation which states that in the fracture area with a significant change in the direction of the curve.

Optical filters used specifically for special functions to block a particular wavelength or range of wavelength and transmit the rest of the spectrum have received research attention for the past few eras. Recently, optical filter based on multilayer coating are more focused due to potential to manipulate filter properties by changing layer thickness in order to apply in various fields. This Quarter wave stack (QWS) model design is one of the approaches to design optical filter such as edge filter. However, to obtain desire minimum specification need an optimization. Therefore, in this study aims to design optical edge filter based QWS model by optical matrix method in Octave software. In this design, MoS2 and Si are being choose for high (H) and low (L) refractive index materials respectively. The optimum twenty-four (24) number of layers are determined by calculating maximum transmittance obtained. The Rayleigh wavelength ( λex ) of 405 nm ,532 nm and 633 nm are selected and ‘glass|12HL|air’ configuration is set for the design simulation. Then, the cut-on wavelength (λcut-on) and cut-off wavelength ((λcut-off) of successful designed optical edge filter are measured. The result shows that the cut-on wavelength of 408.11 nm, 536 nm and 640.25 nm with minimum effective transmission (MET) of 32.3%, 31.3% and 32% respectively are obtained. In conclusion, this present study shows the deviation between the calculated value and simulation of about 0.2 nm,1.7 nm and 1.15 nm for each λex of 405 nm, 532 nm and 633 nm is determined. But for λcut-off, the value obtained are much higher than the calculated value. The MET of each filter is 32.3% ,31.3% and 32% for Rayleigh wavelength respectively.

We present the results of a theoretical calculation and an experimental study of double-sided antireflective processing of a dielectric plate by creating a specially profiled corrugated structure on its surface. Such a structure allows one to minimize the reflection coefficient of an electromagnetic wave to a level of about −30 dB within a range of at least one octave. This antireflective effect can be used in energy output windows of frequency-tunable generators operated in the millimeter- and submillimeter-wave bands. It can also be applied in windows of wideband spectroscopy devices used to diagnose a broad range of materials including both gases and condensed media, as well as in medical devices, in which the studied sample/object is placed in a vacuum-tight box. Theoretical calculations are based on solving numerically the complete equations of the electromagnetic field. Reflections from double-sided corrugated plates were studied experimentally using a Michelson interferometer. It is shown that the reflection coefficient is equal to no more than −23 dB in the 50–220 GHz frequency range. The antireflective profile was manufactured using a plate of radiation-processed fluorine F-4 (Raflon). This new material allowed us to manufacture an antireflective structure with a required accuracy.

Since its invention, optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy. The recent development of microresonator-based frequency combs (microcombs) provides a unique pathway to create frequency comb systems on a chip. Indeed, microcomb-based spectroscopy, ranging, optical synthesizer, telecommunications and astronomical calibrations have been reported recently. Critical to many of the integrated comb systems is the broad coverage of comb spectra. Here, microcombs of more than two-octave span (450 nm to 2,008 nm) is demonstrated through χ(2) and χ(3) nonlinearities in a deformed silica microcavity. The deformation lifts the circular symmetry and creates chaotic tunneling channels that enable broadband collection of intracavity emission with a single waveguide. Our demonstration introduces a new degree of freedom, cavity deformation, to the microcomb studies, and our microcomb spectral range is useful for applications in optical clock, astronomical calibration and biological imaging., Here, the authors demonstrate the use of chaos to obtain 2-octave comb generation. The deformation lifts the circular symmetry and creates chaotic tunneling channels that enable broadband collection of intracavity emission with a single waveguide, introducing a new degree of freedom to microcomb studies.

A synthesis problem is solved for low-order windows with the sidelobe spectrum falloff rate equal to 12n decibel per octave (dB/oct), where n is an integer, that are optimal by the criterion of the minimum highest spectrum sidelobe level over a given frequency region outside the main lobe. To obtain this sidelobe falloff rate, it is proposed to synthesize the windows in the form of a portion of the Fourier series in terms of cosine functions with an odd number of half-waves along the observation interval. A synthesis method for the optimal functions with verification of the solution is developed. Order 3 to 6 windows with sidelobe falloff rates 12, 24, and 36 dB/oct are synthesized and their parameters are presented.

Two female harbor seals were exposed for 60 min to a continuous one-sixth-octave noise band centered at 32 kHz at sound pressure levels of 92 to 152 dB re 1 mu Pa, resulting in sound exposure levels (SELs) of 128 to 188 dB re 1 mu Pa(2)s. This was part of a larger project determining frequency-dependent susceptibility to temporary threshold shift (TTS) in harbor seals over their entire hearing range. After exposure, TTSs were quantified at 32, 45, and 63 kHz with a psychoacoustic technique. At 32 kHz, only small TTSs (up to 5.9 dB) were measured 1-4 min (TTS1-4) after exposure, and recovery was within 1 h. The higher the SEL, the higher the TTS induced at 45 kHz. Below similar to 176 dB re 1 mu Pa(2)s, the maximum TTS1-4 was at 32 kHz; above similar to 176 dB re 1 mu Pa(2)s, the maximum TTS1-4 (up to 33.8 dB) was at 45 kHz. During one particular session, a seal was inadvertently exposed to an SEL of similar to 191 dB re 1 mu Pa(2)s and at 45 kHz, her TTS1-4 was >45 dB; her hearing recovered over 4 days. Harbor seals appear to be equally susceptible to TTS caused by sounds in the 2.5-32 kHz range.

A generalized Lugiato-Lefever equation in frequency domain for the modeling of Kerr frequency combs, including full-order frequency dependence of all parameters, is derived and solved without sacrifice of computational time. The proposed model shows high accuracy and efficiency in simulations, agreeing well with previous reports. Based on the proposed model, the influence of parametric frequency dependence is systemically investigated by generating octave-spanning combs in a silicon-nitride micro-ring-resonator with an air slot. The device is dispersion-tailored for broadband comb generation, and its parameters are strongly dependent on frequency. When considering three kinds of parametric influence separately, we reach the following conclusions. The frequency dependent propagation constant determines whether the dispersive wave is generated, matching well with the phase-matching condition. Besides, the frequency dependence of effective area and nonlinear refractive index can both introduce spectral blue-shift. Combining full-order frequency dependence of the three parameters together, a dispersive wave sideband emerges and this phenomenon has never been reported. Our work reveals that full-order frequency dependence of all parameters can be considered with high computational efficiency, which enables precise prediction of dispersive wave frequency for f-2f self-referencing and opens up more reliable avenues for the understanding of Kerr frequency comb generation, especially octave-spanning cases.

In this work, we design and simulate an air-core As 2 S 3 ring fiber for high-order orbital angular momentum (OAM) supercontinuum generation. We show that the chromatic dispersion of the ring fiber can be substantially tailored by proper optimization of the air-core radius. Two-octave supercontinuum carrying OAM 17,1 mode, spanning from 1560 to 6250 nm, is obtained by pumping a 50-fs 100-kW secant hyperbolic pulse centered at the wavelength of 3800 nm into the designed fiber with 50-μm air-core radius and 1-μm ring width. We further engineer the chromatic dispersion of some other OAM modes and perform simulations of supercontinuum spectra using different kilowatt-level peak power, which indicates that the fiber we design represents a promising avenue for supercontinuum generation of all the OAM l,1 modes (|l| ≤17). The proposed fiber is suitable for the transmission of OAM beams in infrared wavelength range and it could promote the development and application of high-order OAM beams.

Implementing flexible, software-defined duplexing transceivers remains challenging due to the inherent self-interference from TX to RX that requires cancellation in the RF/analog domain. Previously, we presented a novel, duplexing, integrated, single antenna transceiver architecture that used an M-stage distributed amplifier combined with an artificial transmission line to achieve high transmit-receive isolation across more than an octave in center frequency. In this paper, we explain and explore the trade-offs and limits on this class of distributed, duplexing transceivers as a function of system and sub-circuit parameters.

This letter presents a new tuning method for coaxial cavity resonator-based bandpass filters (BPFs). The proposed tuning mechanism lays its foundations on pneumatically-actuated Galinstan that functionalizes the inner conductor of a capacitively-loaded coaxial cavity resonator. By altering the volume of Galinstan (i.e., height of inner conductor), ultrawide (>octave) and low loss RF tuning can be obtained without the need for small capacitive gaps that typically limit the RF performance of coaxial BPFs. To validate the concept, a coaxial cavity resonator with frequency tuning between 2.9 and 9.9 GHz (3.4:1 tuning range), and unloaded quality factor between 120 and 625 was manufactured and measured. Furthermore, the RF performance of a two-pole BPF with: 1) tunable frequency between 3.4 and 7.5 GHz (2.2:1); 2) an intrinsically switched-off state; 3) insertion loss

The sound insulation performance of extruded panels used in railway vehicles is critical to control the interior noise, especially in the case of floor panels. To reduce the mass of floating floors and increase its sound insulation performance, a lightweight design instruction approach has been proposed based on the vibration response of each component of the floating floor structures. The total height, length, thickness of the top layer, thickness of the ribs, and thickness of the bottom layer in the typical cross section of the exterior floor are used as variables; the mass of the typical cross section and the averaged sound transmission loss (STL) results in 1/3 octave bands centred from 400 to 3150 Hz are used as the optimisation targets; the optimal result of the smallest mass and the largest averaged STL are achieved in commercial software VA One and Isight. The effect of this optimisation scheme on the sound insulation performance of the floating floor is analysed based on the verified STL prediction model. After this optimisation, the results indicate that the mass of the exterior floor structure is reduced by 15.2% compared with the original exterior floor structure, and the averaged STL in 1/3 octave bands centred from 400 to 3150 Hz and the weighted STL of the floating floor are increased by 0.8 dB and 1 dB, respectively.

Introduction. The resolution of the problem of radio polarimetry in multiposition microwave screening systems (MMSS) with aperture synthesis requires the use of antennas with a high level of cross-polarization discrimination (XPD) in a wide spatial angle. The radio images are reconstructed in MMSS at distances commensurate with the aperture of the antenna structures. Therefore, the value of the spatial angle, at which high XPD is required, can reach 30°. This leads to a new problem of creating an antenna configuration of the X and Ku band, the application of which in MMSS will resolve the problem of constructing a radio image of depolarized microwave radiation scattered on the human body in the form of hidden dangerous objects.Aim. To develop a double-ridged receiving antenna for long-term operation in MMSS with an XPD level of 28 dB at a spatial angle of 30° and operating frequencies of 8…20 GHz.Materials and methods. The requirements for the receiving antenna in MMSS were determined. Theoretical justifications were proposed for the choice of antenna design. Aperture synthesis was used to construct microwave images in MMSS. The stages and results of modelling broadband double-ridge antennas were presented using the CST Studio software broadly applied for three-dimensional electro-magnetic field modelling. The results of modelling pyramidal and conical double-ridged antennas, as well as those in circular and elliptical waveguides, were analyzed. The designed antenna was tested in an anechoic chamber. The measurement results were compared with those obtained during simulation.Results. An elliptical double-ridged horn antenna with a VSWR of no more than 2 and cross-polarization discrimination in a spatial angle of 30° of no less than 28 dB for the frequency range that covers an octave was designed and constructed.Conclusion. The developed antenna can be used in MMSS for the purpose of detecting the effect of micro-wave radiation depolarization as hidden dangerous objects on a human body. Such characteristics of the antenna as its high XPD value in a wide spatial angle will allow the future introduction of microwave polarimetry in MMSS.

Summary The gain bandwidth of a single-mode fiber is limited by the atomic transitions of one rare earth gain element. Here we overcome this long-standing challenge by designing a new single-mode fiber with multi-section core, where each section is doped with different gain element. We theoretically propose and experimentally demonstrate that this configuration provides a gain bandwidth well beyond the capability of conventional design, whereas the inclusion of multiple sections does not compromise single-mode operation or the quality of the transverse modal profile. This new fiber will be beneficial in realizing all fiber laser systems with few-cycle pulse duration or octave tunability., Graphical Abstract, Highlights • A theoretical study of the fiber with asymmetric gain profile is presented • A multi-section core fiber is demonstrated with unique manufacturing strategy • This fiber greatly extends gain bandwidth while maintaining a good beam quality, Optics; Fiber Optics; Optical Materials

In this article, a novel nested-mode power amplifier (NMPA) is proposed for highly efficient multi-octave applications. By introducing a group of nested guaranteed regions (GRs) at the fundamental and harmonic frequencies as the target design space, the difficulties caused by frequency overlapping in harmonically tuned multi-octave power amplifiers (PAs) can be overcome, leading to a self-consistent theory of multi-octave PAs. Furthermore, the methodology of constructing the proposed nested GRs is demonstrated based on a simplified numerical model. According to the methodology, the desired nested GRs can be constructed by following several well-defined closed-form steps. In addition, a feasible design methodology of the NMPA is established based on a simplified deembedding technique of packaged devices. Based on the proposed theory and design method, a 1–3100-MHz NMPA is designed and measured. According to the measured results, the designed PA exhibits 57.5–73.9% drain efficiency and 39–42.6-dBm output power across the band. Moreover, the linearity and linearizability of the designed NMPA are verified using up to 20-MHz-bandwidth-modulated signals across the designed band accompanied with a digital predistortion (DPD) procedure. To the best of our knowledge, this is the state-of-the-art performance of multi-octave broadband PAs.

The analyses of more than 2000 spectro-temporal receptive fields (STRFs) obtained from the ferret primary auditory cortex revealed their dominant encoding properties along time and frequency domains. Results showed that the peak responses of the STRFs were roughly aligned along the time axis, and enhanced low modulation components of the signal around 3 Hz. On the contrary, the peaks of the STRF population along the frequency axis varied and were distributed widely. Further analyses revealed that there were some general properties along the frequency axis around the best frequency of each STRF. The STRFs enhanced modulation frequencies around 0.25 cycles/octave. These findings are consistent with techniques that have been reported in the literature to result in improvements in speech recognition performance, highlighting the significant potential of biological insights into the design of better machines.

SPM-enabled spectral selection (SESS) constitutes a powerful fiber-optic technique to generate wavelength broadly tunable femtosecond pulses. In the current demonstration, the maximum tuning range is 400 nm and the energy conversion efficiency from the pump source to the outmost spectral lobes is ∼25%. In this submission, we apply the particle swarm optimization method to the generalized nonlinear Schrödinger equation to identify the optimal parameters that maximize both the tuning range and the conversion efficiency. We show that SESS in an optical fiber with the optimized dispersion can deliver SESS pulses tunable in one octave wavelength range and the conversion efficiency can be as high as 80%. We further show the feasibility of experimental implementation based on specially designed fibers or on-chip waveguides.

The scattering phenomenon is known to be of great importance for the acoustic quality of a performance arts space. The scattering of sound can be achieved in different ways: it can be obtained by the presence of architectural and/or decorating elements inside a room (e.g., columns, statues), by the geometry and roughness of a surface (e.g., Quadratic Residue Diffuser (QRD)) and by the diffraction effect occurring when a sound wave hits the edges of an obstacle. This article deals with the surface scattering effects and the diffusion phenomenon only related to MDF and plywood panels tested by disposing the wells both horizontally and vertically. The test results undertaken inside a semi-reverberant room and inside a large reverberant room have been compared to highlight the success and the failure of the measuring methodologies. In detail, according to the existing standards and regulations (i.e., ISO 17497—Part 2), diffusion measurements have been undertaken on a few selected types of panel: two QRD panels (made of Medium Density Fiberboard (MDF) and plywood) with and without a smooth painted solid wood placed behind the QRD. The panels have been tested inside two rooms of different characteristics: a semi-anechoic chamber (Room A) and a large reverberant room (Room B). The volume size influenced the results that have been analyzed for both chambers, showing an overlap of reflections on panels tested inside Room A and a clear diffusion response for the panels tested inside Room B. In terms of the diffusion coefficient in all the octave bands between 125 Hz and 8 kHz, results should not be considered valid for panels tested in Room A because they were negatively impacted by extraneous reflections, while they are reliable for panels tested in Room B.

Optical thin films multilayer coating has been driving the advancement of ultrashort laser technology towards ever shorter pulses and broader bandwidth. Deposition and sputtering of dozens of thin film layers with sub-nanometer accuracy. It permits controlling of the spectral phase and amplitude of optical radiation over an optical octave and beyond. We give overview on non-linear effects in multilayer ultrafast coating shortly before damage threshold appear as well as damages. We describe ways how to use or post-pone these effects and damages to higher fluences.

Recent advances on supercontinuum generation of optical vortices in ring-core photonic crystal fiber is reviewed. Beyond octave-spanning supercontinuum generation of TE 01 , TM 01 , OAM 1,1 modes in the As 2 S 3 photonic crystal fiber will be discussed.

The effectiveness of ultrashort pulse compression depends on the coatings group delay dispersion (GDD) characteristics in chirped mirror (CM)-based optical systems. Current porous-layer-based CMs with low GDD oscillations are limited to less than half optical octave spectral bandwidth and the stability of their spectral parameters is still unknown. In order to address these limitations, a broadband CM (covering 400 nm bandwidth) with a porous top layer was deposited and spectral parameters were measured at different environmental conditions. The modeled refractive index of the porous layer varied by approximately 1% due to the changes in humidity. Deposited coatings exhibited low sensitivity of GDD oscillations to deposition errors of porous layer and humidity in the surrounding environment.

Photonic time-stretch (PTS) has been extensively studied due to its great potential in analog-to-digital converters. Here, we propose and demonstrate a PTS system based on phase modulation for sub-octave applications. Different from the PTS system using a Mach–Zehnder modulator (MZM), the PTS system, which uses a phase modulator (PM), has an operation bandwidth within an octave and is more suitable for preprocessing of sub-octave signals. Within the sub-octave band, the system is free of all second-order spurious signals. Because there is no direct current bias in a PM, the problem of bias drift, as well as the nonlinear distortion caused by it, can be thoroughly avoided. In addition, based on phase modulation and direct detection, the proposed PTS system has higher stability and a more simplified structure than that based on coherent detection. An exact analytical model has been established, and some compact expressions have been derived to fully characterize all frequency components of the PM-based PTS system. System properties, including the power transfer function, 3-dB bandwidth, and nonlinear distortion have been discussed, and numerical and experimental results on the performance of the PM-based PTS have been presented. In addition, a dual-channel PTS that employs a PM and a push-pull MZM has been proposed to extend the operation bandwidth to multi-octave.

Sensory systems adjust to the environment to maintain sensitivity to change. In the auditory system, the medial olivocochlear reflex (MOCR) is a known physiological mechanism capable of such adjustment. The MOCR provides efferent feedback between the brainstem and cochlea, reducing cochlear gain in response to sound. The perceptual effects of the MOCR are not well understood, such as how gain reduction depends on elicitor characteristics in human listeners. Physiological and behavioral data suggest that ipsilateral MOCR tuning is only slightly broader than it is for afferent fibers, and that the fibers feed back to the frequency region of the cochlea that stimulated them. However, some otoacoustic emission (OAE) data suggest that noise is a more effective elicitor than would be consistent with sharp tuning, and that a broad region of the cochlea may be involved in elicitation. If the elicitor is processed in a cochlear channel centered at the signal frequency, the growth of gain reduction with elicitor level would be expected to depend on the frequency content of the elicitor. In the current study, the effects of the frequency content and level of a preceding sound (called a precursor) on signal threshold was examined. The results show that signal threshold increased with increasing precursor level at a shallower slope for a tonal precursor at the signal frequency than for a tonal precursor nearly an octave below the signal frequency. A broadband noise was only slightly more effective than a tone at the signal frequency, with a relatively shallow slope similar to that of the tonal precursor at the signal frequency. Overall, these results suggest that the excitation at the signal cochlear place, regardless of elicitor frequency, determines the magnitude of ipsilateral cochlear gain reduction, and that it increases with elicitor level.

Acoustic masking reduces the efficiency of communication, prey detection, and predator avoidance in marine mammals. Most underwater sounds fluctuate in amplitude. The ability of harbor porpoises (Phocoena phocoena) to detect sounds in amplitude-varying masking noise was examined. A psychophysical technique evaluated hearing thresholds of three harbor porpoises for 500–2000 ms tonal sweeps (3.9–4.1 kHz), presented concurrently with sinusoidal amplitude-modulated (SAM) or unmodulated Gaussian noise bands centered at 4 kHz. Masking was assessed in relation to signal duration and masker level, amplitude modulation rate (1, 2, 5, 10, 20, 40, 80, and 90 Hz), modulation depth (50%, 75%, and 100%) and bandwidth (1/3 or 1 octave). Masking release (MR) due to SAM was assessed by comparing thresholds in modulated and unmodulated maskers. Masked thresholds were affected by SAM rate with the lowest thresholds (i.e., largest MR was 14.5 dB) being observed for SAM rates between 1 and 5 Hz at higher masker levels. Increasing the signal duration from 500–2000 ms increased MR by 3.3 dB. Masker bandwidth and depth of modulation had no substantial effect on MR. The results are discussed with respect to MR resulting from envelope variation and the impact of noise in the environment.