April 1997, Volume 6, Number 1
J. Halamek, M. Kasal, M. Villa, P. Cofrancesco
Bandpass Signal Processing
We present the bandpass signal analysis based on digital receiver and call attention to the aliasing of the complex signal, the digital quadrature detector when sampling is equal to quadruple of the carrier frequency, and frequency response of narrow lowpass filters. The design of the digital receiver is described and some results of measurements are presented.
T. Dostal, R. Prokop, R. Sarman
Functional Blocks and Biquadratic ARC Filters using Transimpedance Amplifiers
The aims of the article are design and analysis of modern circuits including high performance functional blocks and biquadratic filters using transimpedance amplifiers. Here are given various types of these circuits, that works in classical voltage, current or hybrid mode. In this paper are also compared various possibilities of connection of single amplifier filters as for reduction of influence of transimpedance amplifier parasitic elements.
M. A. Shcherbakov
Statistical Identification of Kernels of Discrete Nonlinear Systems
A method for identification of discrete nonlinear systems in terms of the Volterra-Wiener series is presented. It is shown that use of a special, composite-frequency input signal as approximation to Gaussian noise provides a computational efficiency of this method, especially for high order kernels. Orthogonal functionals and consistent estimations for Wiener kernels in the frequency domains are derived for this class of noise input. A basis of the proposed computational procedure for practical identification is the fast Fourier transform (FFT) algorithm which is used both for a generating of system stimuluses and for an analysis of system reactions.
Propagation over Irregular Terrain
The computer model and computation accuracy for propagation over irregular terrain are presented. Special attention is paid to computation for low altitude propagation and the finite distance between the antenna and the observation point (diffraction field zone). The solution for the transient zone is modified to obtain continuous connection of different methods of calculations.
J. Nerad, R. C. Tozer
Preventing Inductive Output Impedance of High-Frequency Emitter Follower Stages
Large output inductance is one of major issues of high-frequency emitter follower design. The most often suggested technique to reduce its value is the decreasing of AC transconductance which offers small output inductance at the expense of loosing low output resistance. The paper presents a different approach; it is shown that output inductance can be completely cancelled while keeping very low output resistance by introducing a pole at the input node which may be more suitable in many types of design. Complete analytical evaluation based on the full hybrid-n model of the bipolar transistor device is given.