UNIVERSAL INVARIANT ECHOCOMPENSATION METHOD IN DUPLEX COMMUNICATION SYSTEMS

Предлагается универсальный метод эхокомпенсации в дуплексных системах связи, инвариантный относительно амплитудной характеристики паразитного эхотракта устройств разделения направлений передачи. Теоретическое обоснование метода базируется на отображении линейных и нелинейных измерений сигналов передатчика в эхотракте проективной группой преобразований и использовании инварианта этой группы для расчета копий сигналов передатчика на выходе эхотракта. It is proposed the universal method of echocompensation in duplex communication systems, which is invariant with respect to the amplitude characteristic of the parasitic echo path of transmission direction separation devices. The theoretical justification of the method is based on the mapping of linear and nonlinear measurements of the transmitter signals in the echo path by a projective group of transformations and using the invariant of this group to calculate copies of the transmitter signals at the output of the echo path.

Modeling of Amplitude Characteristic in Radio Channels of Code Division Multiple Access Systems

In CDMA radio access systems, amplitude distortions in a nonlinear amplifier (NA) of a group signal lead to bit errors at the outputs of subscriber channels. To assess the permissible distortion limits and their influence on the transmission quality of subscriber signals, an electronic model of the amplitude characteristic (AC) and analytical relations are needed that relate the probability of an error when registering the output signal of the communication channel with the nonlinearity of the AC NA and other destabilizing factors. The article compares alternative mathematical models of AC NA. In contrast to traditional methods of analysis, usually limited to the choice of models with fixed parameters, a method for variably determining the parameters of AC is considered. The results are: a comparison of known methods for approximating the AC of broadband nonlinear power amplifiers of radio signals is given, an algorithm for selecting model parameters for CDMA systems with QAM using the Rapp model is proposed.

Phase relations in resonant circuits with a wide falling section on the amplitude characteristic

This article examines the features of circuits in order to determine the possibility of their use for controlling thyristors when building new, simple and reliable circuits for controlling boost voltage stabilizers. In ferroresonant circuits connected to a voltage source with a low internal resistance, with a certain combination of parameters, oscillations are excited at the fundamental frequency, the initial phase of which has a shift with respect to the phase of the applied voltage. Moreover, the phase of the excited oscillations depends on the magnitude of the applied emf.

Amplitude-Based Filtering for Video Magnification in Presence of Large Motion

Video magnification reveals important and informative subtle variations in the world. These signals are often combined with large motions which result in significant blurring artifacts and haloes when conventional video magnification approaches are used. To counter these issues, this paper presents an amplitude-based filtering algorithm that can magnify small changes in video in presence of large motions. We seek to understand the amplitude characteristic of small changes and large motions with the goal of extracting accurate signals for visualization. Based on spectrum amplitude filtering, the large motions can be removed while small changes can still be magnified by Eulerian approach. An advantage of this algorithm is that it can handle large motions, whether they are linear or nonlinear. Our experimental results show that the proposed method can amplify subtle variations in the presence of large motion, as well as significantly reduce artifacts. We demonstrate the presented algorithm by comparing to the state-of-the-art and provide subjective and objective evidence for the proposed method.

The Cause and Eliminate Method of Self-excited Oscillation in Long Cable Amplifier Circuits

SMA long cable distributed capacitance is easy to trigger broadband amplifier circuit’s self-oscillation. In this study we design an amplifier circuit based on OPA691 chip, discuss the influence of long cable’s distributed capacitance, then prompt a solution to add 50Ω compensation resistor between the output terminal and the load capacitance. According to the Tina simulation analysis, when 50Ω compensation resistor is added, bode diagrams show amplitude characteristic is smaller than 0 dB at -180 ° phase. The selfoscillation also disappeared in actual circuit measurement, which verify the rationality of this solution.

NEW TYPE OF NEARLY MONOTONIC PASSBAND FILTERS WITH SHARP CUTOFF

New type of nearly monotonic rational function with one pair of zeros on imaginary axis has been proposed. By using these new functions with zeros as a parameter, it is possible to make tradeoff between minimum stopband attenuation and selectivity of the amplitude characteristic. In order to present efficiency of the proposed filter, comparison with allpole filter monotonic in the passband and inverse Chebyshev filter is presented. Also, design example for the seventh order new type lowpass filter is given.