MODELING OF HIGH FREQUENCY AMPLIFIERS FOR MODERN RADIO SYSTEMS

2019 ◽  
Author(s):  
Sergey Chumarov
Keyword(s):  
High Frequency ◽  
Radio Systems

The modeling features of high-frequency amplifiers are considered. The urgency of the development of such amplifiers is justified and the application areas are indicated. The stages of design of amplifiers are described in detail.

scholarly journals Using of New Narrowband Waveforms to Ensure Proper Operation of Command and Communication Systems

2018 ◽  
Vol 215 (4) ◽  
pp. 47-61
Author(s):  
Robert Matyszkiel ◽  
Bogusław Grochowina ◽  
Adam Dobkowski ◽  
Marcin Wiśniewski ◽  
Paweł Domaros
Keyword(s):  
High Frequency ◽  
Communication Systems ◽  
Radio Communication ◽  
Very High Frequency ◽  
Communication Devices ◽  
Working Groups ◽  
Basic Services ◽  
Radio Systems ◽  
Services Implementation ◽  
Proper Operation

Abstract Accomplishment of basic services implementation with specific quality is one of the main challenges of the command and communication systems for modern maritime safety and defense. The specificity of the marine environment imposes the use of narrowband HF (High Frequency) and VHF (Very High Frequency) radio communication devices which are capable to implement IP transmission. This paper presents the requirements for the HF and VHF radio systems according to the IP protocol requirements. At the beginning basic properties of narrowband HF and VHF waveforms in context of their operational scenarios has been described. Then results of experimental research (implementation of narrowband services — voice and data) has been presented. Finally further research directions with contribution of the authors, in NATO working groups related to the development of NBWF (Narrowband Waveform) for coalition communication has been presented.

scholarly journals Solar eclipse effects of 22 July 2009 on Sporadic-E

2010 ◽  
Vol 28 (2) ◽  
pp. 353-357 ◽  
Author(s):  
G. Chen ◽  
Z. Zhao ◽  
C. Zhou ◽  
G. Yang ◽  
Y. Zhang
Keyword(s):  
Solar Eclipse ◽  
High Frequency ◽  
Oblique Incidence ◽  
Critical Frequency ◽  
Eastern China ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Radio Systems ◽  
Sporadic E ◽  
The One

Abstract. The total solar eclipse of 22 July 2009, was visible from some regions of China and the intense sporadic-E (Es) that broke out during the solar eclipse period over the eastern China provided a unique chance to study solar eclipse effects on the Es-layer. The ground based high-frequency (HF) vertical-incidence and oblique-incidence backscatter radio systems in Wuhan and an HF oblique receivers located in Suzhou were operated to detect the Es-layer. The vertical, oblique and backscatter ionograms of 22 and 23 July were recorded, processed and analyzed. The analyzing results show that the critical frequency of Es, the hop number and power of the rays transmitted from Wuhan to Suzhou as well as the Doppler frequency shift of the one-hop oblique-incidence waves reflected by the Es-layer all increased during the solar eclipse period. These variations are displayed in the paper and explained to be induced by the wind-field, which is produced by the powerful meridional air flows from the sunshine region to the moon's shadow.

scholarly journals Application of Asymptotic and Rigorous Techniques for the Characterization of Interferences Caused by a Wind Turbine in Its Neighborhood

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Maria Jesús Algar ◽  
Lorena Lozano ◽  
Javier Moreno ◽  
Iván González ◽  
Felipe Cátedra
Keyword(s):  
Wind Turbine ◽  
Method Of Moments ◽  
Scattered Field ◽  
High Frequency ◽  
Wind Farms ◽  
Uniform Theory Of Diffraction ◽  
Spline Surfaces ◽  
Radio Systems ◽  
Geometrical Theory Of Diffraction

This paper presents a complete assessment to the interferences caused in the nearby radio systems by wind turbines. Three different parameters have been considered: the scattered field of a wind turbine, its radar cross-section (RCS), and the Doppler shift generated by the rotating movements of the blades. These predictions are very useful for the study of the influence of wind farms in radio systems. To achieve this, both high-frequency techniques, such as Geometrical Theory of Diffraction/Uniform Theory of Diffraction (GTD/UTD) and Physical Optics (PO), and rigorous techniques, like Method of Moments (MoM), have been used. In the analysis of the scattered field, conductor and dielectric models of the wind turbine have been analyzed. In this way, realistic results can be obtained. For all cases under analysis, the wind turbine has been modeled with NURBS (Non-Uniform Rational B-Spline) surfaces since they allow the real shape of the object to be accurately replicated with very little information.

The Microstructure of Steatite (Protoenstatite)

1985 ◽  
Vol 43 ◽  
pp. 236-237
Author(s):  
W. E. Lee ◽  
A. H. Heuer
Keyword(s):  
High Frequency ◽  
Glass Ceramics ◽  
Magnesium Silicate ◽  
Beam Current ◽  
Glassy Matrix ◽  
Angle Of Incidence ◽  
X Ray ◽  
Mechanical And Electrical Properties ◽  
Argon Ions ◽  
High Temperature Polymorph

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

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