Анализ подавления нелинейных искажений в усилителях сигналом огибающей
The suppression of the nonlinear distortions in amplifier using the effect of the envelope signal of the amplified HF oscillations on the amplifier parameters is analyzed. A slow (on the time scale of the HF oscillations) variation in the parameters gives rise to additional frequency components of oscillations that compensate for the nonlinear distortions of the original signal. Several variants to employ the compensating signal using the feedback circuits in the transistor amplifiers and variations in the electron-beam current in TWT in the absence of such circuits are considered. The suppression of the nonlinear intermodulation distortions (IMDs) of the test two_frequency signal is studied for the above variants and the suppression of the third_order IMD by 6–19 dB corresponds to the known experimental data on the microwave transistor amplifier. The generalization of the quasistationary method for the analysis of the nonlinear transformation of signals allows the analysis of the amplification and suppression of IMD for more complicated multifrequency signals that are used in radio systems.
The possibilities of use as the output stage television transmitter traveling wave tube to amplify simultaneously several television channels. TWT has a wide bandwidth and a high gain. The simulation of the transformation of multi-frequency signals, including a lest of the television signal. The method of analysis — a quasistationary. Lamp determined by its amplitude and fazo-amplitude external characteristics. The case of sufficiently smooth characteristics that can be approximated by a polynomial of low degree. For a given bandwidth requirements for high-frequency signal and intermodulafion interference investigated for optimal arrangement of three to six TV channels in a given band TWT. We also consider the effect of the phase of each channel at the level of the Raman background. It is shown that the use of the phase shifter on the even (or odd) channels to reduce intermodulation background caused by combination up to 5 dB at the same total power. The calculations of the nonlinear interaction of the six channels, received frequency and levels of combinational components with different capacities and placement of frequency channels. We give conditions for selection of the total input power TWT in which intermodulation interference is less than the level specified by the standard.
The suppression of the nonlinear distortions in amplifier using the effect of the envelope signal of the amplified HF oscillations on the amplifier parameters is analyzed. A slow (on the time scale of the HF oscillations) variation in the parameters gives rise to additional frequency components of oscillations that compensate for the nonlinear distortions of the original signal. Describes the various options to include compensating signal. Describes the criteria for the use of amplifiers with a traveling wave tube and solid state amplifiers. Several variants to employ the compensating signal using the feedback circuits in the transistor amplifiers and variations in the electron beam current in TWT (modulation beam current) in the absence of such circuits are considered. The suppression of the nonlinear intermodulation distortions (IMDs) of the test two frequency signal is studied for the above variants and the suppression of the third order IMD to 19 dB corresponds to the known experimental data on the microwave transistor amplifier feedback on the frequency of the envelope. Separately, it was the influence on the level of performance fazoamplitudnoy distortion at the output of the microwave amplifier with a traveling wave tube.
Generalized error-locating codes are discussed. An algorithm for calculation of the upper bound of the probability of erroneous decoding for known code parameters and the input error probability is given. Based on this algorithm, an algorithm for selection of the code parameters for a specified design and input and output error probabilities is constructed. The lower bound of the probability of erroneous decoding is given. Examples of the dependence of the probability of erroneous decoding on the input error probability are given and the behavior of the obtained curves is explained.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
Let k be a field of characteristic zero, let G be a connected reductive algebraic group over k and let g be its Lie algebra. Let k(G), respectively, k(g), be the field of k- rational functions on G, respectively, g. The conjugation action of G on itself induces the adjoint action of G on g. We investigate the question whether or not the field extensions k(G)/k(G)^G and k(g)/k(g)^G are purely transcendental. We show that the answer is the same for k(G)/k(G)^G and k(g)/k(g)^G, and reduce the problem to the case where G is simple. For simple groups we show that the answer is positive if G is split of type A_n or C_n, and negative for groups of other types, except possibly G_2. A key ingredient in the proof of the negative result is a recent formula for the unramified Brauer group of a homogeneous space with connected stabilizers. As a byproduct of our investigation we give an affirmative answer to a question of Grothendieck about the existence of a rational section of the categorical quotient morphism for the conjugating action of G on itself.
Let G be a connected semisimple algebraic group over an algebraically closed field k. In 1965 Steinberg proved that if G is simply connected, then in G there exists a closed irreducible cross-section of the set of closures of regular conjugacy classes. We prove that in arbitrary G such a cross-section exists if and only if the universal covering isogeny Ĝ → G is bijective; this answers Grothendieck's question cited in the epigraph. In particular, for char k = 0, the converse to Steinberg's theorem holds. The existence of a cross-section in G implies, at least for char k = 0, that the algebra k[G]G of class functions on G is generated by rk G elements. We describe, for arbitrary G, a minimal generating set of k[G]G and that of the representation ring of G and answer two Grothendieck's questions on constructing generating sets of k[G]G. We prove the existence of a rational (i.e., local) section of the quotient morphism for arbitrary G and the existence of a rational cross-section in G (for char k = 0, this has been proved earlier); this answers the other question cited in the epigraph. We also prove that the existence of a rational section is equivalent to the existence of a rational W-equivariant map T- - - >G/T where T is a maximal torus of G and W the Weyl group.