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A generalized design procedure for Doherty power amplifier (DPA) with arbitrary output back-off power level (OBO) is proposed in this study. This method which covers many of previously reported configurations is employed to derive analytical formulas for a specific output combiner which is capable for absorbing parasitic elements of the main and auxiliary transistors. Combiner parameters can be adjusted to control operational frequency bandwidth at back-off and saturation. By considering parasitic elements in the design procedure, the needs for additional offset lines and CAD optimization are eliminated and efficiency does not degrade significantly at back-off. According to the proposed design methodology, a wide band DPA is designed, simulated and implemented with commercial packaged GaN transistor. Drain efficiency (DE) between 50 and 77% at 6 dB OBO and 57.5–80.4% at saturation in the frequency band of 1.05–2.35 (GHz) (76.4% fractional bandwidth) are achieved corresponding to the maximum output power and gain within 43–45.3 dBm and 11–13.3 dB, respectively. Gain fluctuation is lower than 0.6 dB for frequencies higher than 1.4 GHz. Combination of high efficiency, excellent power utilization factor and flat gain through an analytical design strategy introduces this method as a promising way to design wide band DPAs.

We report here on initial results from the Thousand Pulsar Array (TPA) programme, part of the Large Survey Project "MeerTime" on the MeerKAT telescope. The interferometer is used in tied-array mode in the band from 856 to 1712~MHz, and the wide band coupled with the large collecting area and low receiver temperature make it an excellent telescope for the study of radio pulsars. The TPA is a 5 year project which aims to observe (a) more than 1000 pulsars to obtain high-fidelity pulse profiles, (b) some 500 of these pulsars over multiple epochs, (c) long sequences of single-pulse trains from several hundred pulsars. The scientific outcomes from the programme will include determination of pulsar geometries, the location of the radio emission within the pulsar magnetosphere, the connection between the magnetosphere and the crust and core of the star, tighter constraints on the nature of the radio emission itself as well as interstellar medium studies. First results presented here include updated dispersion measures, 26 pulsars with Faraday rotation measures derived for the first time and a description of interesting emission phenomena observed thus far., Accepted by MNRAS

OBJECTIVE Determine if changes in middle ear absorbance measured with wide-band tympanometry (WBT) occur following hearing-preservation cochlear implantation (CI). Such measures may provide insight into the mechanisms of acoustic hearing loss postimplantation. STUDY DESIGN Clinical capsule report. SETTING Tertiary academic referral center. DESIGN WBT absorbance was measured bilaterally during pre- and postoperative clinical office visits in five unilaterally-implanted cochlear implant recipients. Pre- and postoperative WBT measures were compared within each subject in the implanted and contralateral, unimplanted ears. RESULTS In general, WBT absorbance measurements show a broad spectral pattern including two or three distinct peaks measured over a frequency range of 226 to 8000 Hz. Grand average and linear mixed model comparisons between the pre- and postoperative WBT patterns show significantly reduced (p

A technique is proposed for designing multiband and/or wide band printed quadritilar helical antennas. This technique uses a microstrip line tuning section in the vicinity of the feeding ports. This section contains an elongated body and a tail member extending away from the body. A geometry of the tail member is selected for modifying an impedance of the radiating element and broadening the antenna resonance bandwidth. A four port antenna is designed for operating in wide band (24%, Sll

The main goal of this article is to design a low-profile wide band Rectangular Dielectric Resonator Antenna (RDRA). The proposed “S” shaped rectangular DRA is excited by means of a popular microstr...

A laboratory setup for the study of wide-range piezo-sorption sensitive elements in the measurement of gas humidity using nitrogen as an example was assembled. It is determined that all sensitive elements have a variation of statistical parameters, which leads to an error. To reduce the error, it was pro-posed to introduce a correction factor. To determine the nominal static characteristics, the results of the experiments were approximated by a polynomial of the 6th degree. In connection with the difficulty of identifying the model parameters, it was proposed to use 3rd degree polynomials in various parts of the humidity concentration.

Several noise propagation models used to calculate the noise produced by wind turbines have been reported. However, these models do not accurately predict sound pressure levels. Most of them have been developed to estimate the noise produced by industries, in which wind speeds are less than 5 m/s, and conditions favor its spread. To date, very few models can be applied to evaluate the propagation of sound from wind turbines and most of these yield inaccurate results. This study presents a comparison between noise levels that were estimated using the prediction method established in ISO 9613 Part 2 and measured levels of noise from wind turbines that are part of a wind farm currently in operation. Differences of up to 56.5 dBZ, with a median of 29.6 dBZ, were found between the estimated sound pressure levels and measured levels. The residual sound pressure levels given by standard ISO 9613 Part 2 for the wind turbines is larger for high frequencies than those for low frequencies. When the wide band equivalent continuous sound pressure level is expressed in dBA, the residual varies between −4.4 dBA and 37.7 dBA, with a median of 20.5 dBA.

A metal-dielectric-metal (MDM) waveguide coupled with fixed height to length (bi/ai = 0.8) stubs is proposed in our work. Then, an obvious band-stop filtering phenomenon can be observed in MDM waveguide coupled with single fixed height to length stub. Interestingly, the MDM waveguide coupled with two fixed height to length stubs exhibits better band-stop filtering performance than that in a single fixed height to length stub coupled waveguide structures. The phase difference analysis and transmission line theory are established to discuss the transmission spectrum and the wide band-stop filtering phenomenon of our proposed structure. Inconceivably, the bandwidth of band-stop filtering can reach to 1750 nm through tuning structure parameters and the number of the fixed height to length stub. These results may provide great potential applications for plasmonic filtering devices.

In this paper, the design of a graded honeycomb radar absorbing structure (RAS) is presented to realize both a wide bandwidth and absorption over a wide range of angles. For both transverse-electric and transverse-magnetic polarization, a fractional bandwidth of more than 118.6% is achieved for at least a 10 dB reflectivity reduction when the incident angle is

This work develops a new CMOS wide-band low-voltage low-noise amplifier (LNA). The proposed LNA uses negative feedback and gain boosted technique to increase its high-frequency gain to achieve high...

A new thin and wideband RCS reduction metasurface is designed and fabricated by using two different AMC unit cell tiles arranged in chessboard like configuration. One of these tiles is formed by saltire arrow unit cells, whereas the other one is formed by Jerusalem unit cells which are designed to achieve out phase difference at broad frequency range. This metasurface reduces the RCS more than 10-dB from 15.75 GHz to 41.3 GHz (90% bandwidth). The designed metasurface works properly at both TE and TM propagation modes, also. Moreover, it has stable 10-dB RCS reduction bandwidth for TM propagation mode up to 50° oblique incident angle and 30° for TE ones. These good specifications prove the designed metasurface capability compared with the state of the art references.

This correspondence proposes a new technique for signal classification and jamming detection in wide-band (WB) radios. Theory of compressed sensing is exploited to recover the sparsely populated WB spectrum from sub-Nyquist samples, thus reducing the very high-rate sampling requirements at the receiver analog to digital converter. From the recovered WB, key spectral features of each narrow-band (NB) signal are extracted. These spectral features are then used to train a simple yet powerful classifier, the naive Bayes classifier (NBC). The trained NBC is then used not only to classify various NB signals into their respective modulations but also to detect the jamming on different NB signals, which are the main contributions of this letter. The proposed algorithm is then evaluated under different empirical setups and is shown to perform better when compared to a recently proposed feature-based jamming detection algorithm.

In this paper, a reconfigurable receiver front‐end for the frequency range of 800 MHz to 2.5 GHz is presented. The radio frequency front‐end is realized in wideband form with reconfigurable baseband filter. The proposed front‐end targets the GSM, WLAN, WCDMA, and GPS standards residing in the aimed frequency range. The necessary specifications for each individual standard have been revisited and recalculated. The interaction of the different standards and their interoperability has been thoroughly investigated and extra specifications derived for the multistandard receiver. The multistandard receiver has been designed, layouted, and simulated in RFCMOS 0.18‐μm process.

A $2 \times 2$2×2 circularly polarised (CP) antenna array with four square radiating patch elements has been introduced here. The array elements are sequentially rotated and have been fed by a simple single-layer feeding network with sequential phase structure. This feeding network generates successive phase difference at its four outputs. To have a wide CP bandwidth, the proposed method of feeding network has been combined with new simple tuning stubs which are embedded in radiating patch elements. The common reflection coefficient bandwidth ($S_{11} \lt - 10\, {\rm dB}$S11

The wide-band limit is a commonly used approximation to analyze transport through nanoscale devices. In this work we investigate its applicability to the study of charge and heat transport through molecular break junctions exposed to voltage biases and temperature gradients. We find that while this approximation faithfully describes the long-time charge and heat transport, it fails to characterize the short-time behavior of the junction. In particular, we find that the charge current flowing through the device shows a discontinuity when a temperature gradient is applied, while the energy flow is discontinuous when a voltage bias is switched on and even diverges when the junction is exposed to both a temperature gradient and a voltage bias. We provide an explanation for this pathological behavior and propose two possible solutions to this problem., Comment: 11 pages, 9 figures

In order to widen the absorbing band, an equivalent gradient structure absorber was designed based on the particle distribution. Firstly, the electromagnetic parameter of the absorbent with uniform dispersion was tested using the vector network analyzer in 8–18 GHz. Three different equivalent materials of the spherical, square and hexagon empty shape were designed. The scattering parameters and the monostatic reflection loss (RL) of the periodic structural materials were simulated in the commercial software. Then the effective permittivity and the permeability was derived by the Nicolson-Ross-Weir algorithm and fitted by Maxwell-Garnett mixing rule. The results showed that the simulated reflectance and transmission parameters of equivalent composites with the different shapes were very close. The derived effective permittivity and permeability of the composite with different absorbent content was also close, and the average deviation was about 0.52 + j0.15 and 0.15 + j0.01 respectively. Finally, the wide band absorbing material was designed using the genetic algorithm. The optimized RL result showed that the absorbing composites with thickness 3 mm had an excellent absorbing property (RL

The Tiangong-II space lab was launched at the Jiuquan Satellite Launch Center of China on September 15, 2016. The Wide Band Spectral Imager (WBSI) onboard the Tiangong-II has 14 visible and near-infrared (VNIR) spectral bands covering the range from 403–990 nm and two shortwave infrared (SWIR) bands covering the range from 1230–1250 nm and 1628–1652 nm respectively. In this paper the selected bands are proposed which aims at considering the closest spectral similarities between the VNIR with 100 m spatial resolution and SWIR bands with 200 m spatial resolution. The evaluation of Gram-Schmidt transform (GS) sharpening techniques embedded in ENVI software is presented based on four types of the different low resolution pan band. The experimental results indicated that the VNIR band with higher CC value with the raw SWIR Band was selected, more texture information was injected the corresponding sharpened SWIR band image, and at that time another sharpened SWIR band image preserve the similar spectral and texture characteristics to the raw SWIR band image.

Electronic structure calculations of five crystallography-imitated structures of CsMI3 perovskites with M = Ge, Sn, Pb, Mg, Ca, Sr, and Ba were performed. The formation energy of different perovskite phases, their relative stability, and structural and electronic properties were explored. The sensitivity of the calculations to the choice of the density functional was investigated, and the predictions were compared with experimental results. The outcome of this study is that Mg and Ba perovskites are unlikely to form in the cubic, tetragonal, or orthorhombic phases because they have positive formation energies. Although Ca and Sr perovskites have negative formation energies with respect to the metal-iodide precursors, they exhibit wide band gaps and high hygroscopicity, making these unlikely candidates for applications in photovoltaic devices. Our results suggest that the performance of a local density functional with a nonseparable gradient approximation (NGA) is similar to that of hybrid functionals in t...

The as-prepared Ca 3-x-y Ga 2 Ge 3 O 12 (CGGO): xTb 3+ , yTm 3+ phosphors exhibit a color-tunable long persistent luminescence (LPL) after the near-ultraviolet irradiation. Our results indicate that the shallow traps act as not only the trapping centers but also the bridge that contributes to the release of the carriers from deeper traps at room-temperature (RT), improving the LPL properties significantly. Moreover, the CGGO: xTb 3+ , yTm 3+ phosphors exhibit an advantageous LPL performance at high-temperature because of the existence of deeper defect states.

A wideband polarisation-insensitive metasurface (MS) has been proposed for tunable near-field scattering focusing. The MS is composed of dual-polarised unit cells with tunable reflection phases covering a range of 360°. Designed with the optical path method, the proposed MS demonstrates precise tunable and polarisation-insensitive near-field focusing in a wide band from 11 to 13 GHz in both simulation and experimental results.

Competitive interaction of orthogonally polarized modes in a two-mode laser operating in a regime of wide-band frequency modulation has been numerically simulated. This modulation was implemented by means of the corresponding variation of the laser cavity length. Parameters of the active medium adopted in the numerical model were characteristic of He–Ne lasers with an inhomogeneously broadened gain line. It is established that negative consequences of the mode competition can be significantly reduced at certain values of the modulation frequency and frequency deviation.

The current diamond-wire-sawed multi-crystalline silicon wafer lacks an effective light trapping structure, which results in high reflectivity and hinders the improvement of efficiency. In this work, we proposed an enhanced light trapping structure outside the junction of multi-crystalline silicon solar cells, that is, constructing a ZnO nano-needle array on the surface of the textured multi-crystalline silicon to minimize the reflection in the visible-near infrared band to achieve light trapping effect. Solar cells with ZnO nano-needle structure exhibit excellent light trapping performance over a wide band (350–1100 nm). The low-cost and simple preparation method makes this enhanced light trapping structure has broad application prospects.

This paper presented a novel design of thin and wide-band electromagnetic absorber. The proposed structure was composed of a bottom metal plate, a homogeneous resistance layer (HRL), a dielectric spacer, and a periodic resistance layer (PRL) at the top made of the Jerusalem cross structure, and the overall thickness of the absorber was only 5.055 mm. The simulation result exhibited that more than 90% absorption has been achieved in 2–40 GHz, corresponding to the fractional bandwidth of 181% under the normal incidence. The measured and the simulated results showed an agreement. The absorber had a good potential application in the field of microwave absorption.