Methods of Radio Devices Analysis on the Basis of Functional Approximation
Known methods of approximation of nonlinear device performance have a number of essential disadvantages: a limited application field, complex implementation, and difficulty of obtaining analytical solutions at essential nonlinearity or the high level of components inertia. The suggested methods of approximation of nonlinear characteristics possess adequate accuracy, a simple analytic recording form, and the possibility of obtaining specific solutions on the basis of generalized ones. Methods of nonlinear characteristic approximation of radio units are considered on the basis of polyexponential approximation. Fundamental relations for coefficients calculation of polyexponential functions were obtained with the usage of the matrix approach of simultaneous equations solution. As for the output signal analysis of non-linear inertialess devices the spectrum breadth of base signal is determined only by the odd difference orders of intermodulation. The usage of a complex envelope of a signal is suggested for intermodulation oscillations are obtained in a narrow band of frequencies. The expressions for amplitudes of intermodulation components in the frequency band of a base signal. Examples of spectrum analysis of intermodulation oscillations in the output of nonlinear power amplifiers and quadrature power amplifier are given. Variants of both linear(generalized with compact written form, switching, including, ternary) and nonlinear (quadratic) functions are suggested for approximation of performances by continuous piecewise functions (CPF). Continuous piecewise linear functions (CPLF) approximates the performances of non-linear functions including hysteresis, devices, and carry out spectral analysis of pulse signals with the capability of obtaining analytical expressions for any spectral component of an output oscillation when the input signal is aggregate and a nonlinear characteristic is of arbitrary type. Application of CPF allows analysis the radio devices stability, and dynamic performances in linear and non-linear modes. The digital calculators synthesized on the basis of CPLF, shortencalculation time at the expense of reducing the number of operations and required memory capacity.