- 标题
- 摘要
- 关键词
- 实验方案
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Dynamic Behavioral Modeling of RF Power Amplifier Based on Time-Delay Support Vector Regression
摘要： A new, dynamic behavioral modeling technique, based on a time-delay support vector regression (SVR) method, is presented in this paper. As an advanced machine learning algorithm, the SVR method provides an effective option for behavioral modeling of radio frequency (RF) power amplifiers (PAs), taking into account the effects of both device nonlinearity and memory. The basic theory of the proposed modeling technique is given, along with a detailed model extraction procedure. Unlike traditional artificial neural network (ANN) techniques, which take time to determine the best configuration of the model, the SVR method can obtain the optimal model in short time, using the grid-search technique. An example of an optimal SVR model selection applied to an RF PA is also given; the performance of the selected model presents a big improvement when compared with the default SVR model. Experimental validation is performed using an LDMOS PA, a single device gallium nitride (GaN) PA, and a Doherty GaN PA, revealing that the new modeling methodology provides very efficient and extremely accurate prediction. Compared with traditional Volterra models, canonical piecewise linear models, and ANN-based models, the proposed SVR model gives improved performance with reasonable complexity. In addition, it is shown that the model can predict accurately the behavior of the PA under input power levels that are different from those under which it is extracted.
关键词： time delay,radio frequency (RF) power amplifiers (PAs),machine learning,Dynamic behavioral model,support vector regression (SVR)
更新于2025-09-23 15:23:52
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A Square-Root-Based Memory Polynomial Model for Concurrent Dual-Band Digital Predistortion
摘要： In this letter, a novel 2-D square-root-based memory polynomial behavioral model is proposed. A new set of square-root-based basic functions is adopted to describe the characteristic of the predistorter. Since the proposed model has only two nested summations, the number of coefficients of the proposed model is greatly reduced compared with models which have three nested summations. The experimental results show that the proposed model can reduce the coefficients by more than 66.7% compared with the 2-D digital predistortion (2D-DPD) model. Moreover, the proposed model can achieve better adjacent channel power ratio (ACPR) performance. Compared with the 2D-DPD model and the simple online coefficient update model, the proposed model can improve the normalized mean-square error by 11 dB. Compared with the 2-D modified memory polynomial model, the proposed model can obtain similar ACPR performance with a shorter running time.
关键词： power amplifiers (PAs),Digital predistortion (DPD),dual band
更新于2025-09-23 15:22:29
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Passive Sampling of Gaseous Elemental Mercury Based on a Composite TiO2NP/AuNP Layer
摘要： Passive sampling systems (PASs) are a low cost strategy to quantify Hg levels in air over both different environmental locations and time periods of few hours to weeks/months. For this reason, novel nanostructured materials have been designed and developed. They consist of an adsorbent layer made of titania nanoparticles (TiO2NPs, ≤25 nm diameter) ?nely decorated with gold nanoparticles. The TiO2NPs functionalization occurred for the photocatalytic properties of titania-anatase when UV-irradiated in an aqueous solution containing HAuCl4. The resulting nanostructured suspension was deposited by drop-casting on a thin quartz slices, dried and then incorporated into a common axial sampler to be investigated as a potential PAS device. The morphological characteristics of the sample were studied by High-Resolution Transmission Electron Microscopy, Atomic Force Microscopy, and Optical Microscopy. UV-Vis spectra showed a blue shift of the membrane when exposed to Hg0 vapors. The adsorbed mercury was thermally desorbed for a few minutes, and then quanti?ed by a mercury vapor analyzer. Such a sampling system reported an ef?ciency of adsorption that was equal to ≈95%. Temperature and relative humidity only mildly affected the membrane performances. These structures seem to be promising candidates for mercury samplers, due to both the strong af?nity of gold with Hg, and the wide adsorbing surface.
关键词： TiO2NPs,PAS device,mercury vapors adsorbing layer,AuNPs,photocatalysis
更新于2025-09-23 15:21:01
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EXPRESS: A Study of the Surface of Fe <sub/>3</sub> O <sub/>4</sub> @SiO <sub/>2</sub> Nanoparticles Functionalized with Different Groups Using a Photoacoustic Infrared Spectroscopic Method
摘要： A permanent development of hybrid materials based on the highly absorptive or opaque materials has prompted a need of analytical tools, which are able to overcome obstacles connected with their physicochemical features. Iron oxide (II, III) (Fe3O4) nanoparticles gained a huge attention as supporters, as they are not only easily accessible using various synthetic approaches, but they also exhibit homogeneity and paramagnetic properties, which make them easily separable materials. Nevertheless, the classic infrared spectroscopic studies might meet several problems with characterization of such systems. Therefore, infrared spectroscopy in photoacoustic mode using Fourier transform infrared–photoacoustic infrared spectroscopy (FT-IR PAS) can be an extremely sensitive and exact analytical tool for investigation of the magnetite-based hybrid materials surface. Herein, we present a synthesis of Fe3O4 nanoparticles using co-precipitation method with their subsequent encapsulation within silica matrix decorated with different silanes containing various terminal functional groups. The proper syntheses of core/shell structures were confirmed using the FT-IR PAS method. Each spectrum exhibited specific bands corresponding to vibrations of magnetite particles, silica lattice and particular surface functional groups, which strictly indicated successful grafting of silanes onto Fe3O4 surface.
关键词： PAS,Magnetite nanoparticles,Fourier transform infrared,core/shell structures,surface analysis,photoacoustic infrared spectroscopy,FT-IR PAS,FT-IR
更新于2025-09-19 17:13:59
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Radiology, Lasers, Nanoparticles and Prosthetics || 7. Positron emission tomography
摘要： Positron emission tomography (PET) is a nuclear imaging modality used in clinics for cardiologic, neurologic, and oncologic studies. The PET method is based on the annihilation of positrons and electrons via converting their rest mass into two γ-photons flying in opposite directions. These two γ-photons are detected in a fashion similar to SPE or SPECT. Positron annihilation spectroscopy (PAS) is also used in condensed matter physics for determining the density and diffusivity of defects in solids. PAS is the opposite effect to pair production, which occurs when photons interact with nuclei at photon energies beyond 1 MeV. Pair production is important for cancer treatment with very hard x-rays, discussed in Chapter 9. However in this chapter we consider PET as an analytic tool.
关键词： nuclear imaging,PET,positron annihilation spectroscopy,γ-photons,Positron emission tomography,PAS
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Signal and noise analysis in resonant photoacoustic spectroscopy using fast Fourier transform
摘要： A simple method based on fast Fourier transform (FFT) is used to analyze the signal and noise in resonant photoacoustic spectroscopy. Varying the sampling time, the photoacoustic signal and noise are analyzed using FFT method, and compared with lock-in amplifier method. A detection limit of 1 ppm of methane has been achieved in pure nitrogen using a 1653 nm laser with an average power of 3.6 mW.
关键词： climate control,research,gas absorption,methane,FFT,PAS
更新于2025-09-16 10:30:52
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Quantitative Evaluation of Broadband Photoacoustic Spectroscopy in the Infrared with an Optical Parametric Oscillator
摘要： We evaluate the spectral resolution and the detection thresholds achievable for a photoacoustic spectroscopy (PAS) system in the broadband infrared wavelength region 3270 nm to 3530 nm driven by a continuous wave optical parametric oscillator (OPO) with P ≈ 1.26 W. The absorption spectra, IPAS(λi), for diluted propane, ethane and methane test gases at low concentrations (c ～ 100 ppm) were measured for ～1350 discrete wavelengths λi. The IPAS(λi) spectra were then compared to the high resolution cross section data, σFTIR, obtained by Fourier Transform Infrared Spectroscopy published in the HITRAN database. Deviations of 7.1(6)% for propane, 8.7(11)% for ethane and 15.0(14)% for methane with regard to the average uncertainty between IPAS(λi) and the expected reference values based on σFTIR were recorded. The characteristic absorption wavelengths λres can be resolved with an average resolution of δλres ～ 0.08 nm. Detection limits range between 7.1 ppb (ethane) to 13.6 ppb (methane). In an additional step, EUREQA, an artificial intelligence (AI) program, was successfully applied to deconvolute simulated PAS spectra of mixed gas samples at low limits of detection. The results justify a further development of PAS technology to support e.g., biomedical research.
关键词： photoacoustic spectroscopy,optical-parametric oscillator,PAS,gas sampling,hydrocarbons,spectral deconvolution,EUREQA,OPO
更新于2025-09-04 15:30:14