December 1992, Volume 1, Number 2
A convenient and exact method of using a sliding load to the calibration of the single six-port reflectometer is described. Neither reflection coefficient nor positions of the sliding load settings need be known. Reflection coefficient of the load is not limited to small values. No numerical iterations are involved in the calibration.
Peculiar waveguide properties of quantum waveguides are revealed using a new transfer matrix based approach in the numerical analysis of the quantum well structures. The approach is built on the solution of the 2D Schrodinger equation for the oblique incidence of an electron at the semiconductor hetero-interfaces. Both the interface parallel and interface perpendicular complex electron wave numbers are formulated in each layer of the structure. They help us to find bound states of the electron in the quantum structure via an analysis of the global transfer matrix coefficients. Successively, the rigorous curves of the real mode diagram of the quantum waveguide can be evaluated. As a particular result of it a new type of the quantum structures acting as a selectively coupled quantum waveguide pair is shown. A new effect, the longitudinal mezoscopic periodical charge distribution occuring along the waveguide structure, has been predicted.
An adaptive antenna array with the digital signal processing requires an independent receiver for each antenna element. This fact significantly influences the cost of the system. The presented paper answers the question what will happen if high-frequency signals from outputs of two antenna elements are time multiplexed and processed by only one receiver.
It is shown that such a system is a bit slower in comparison with the classical devices but) on the other hand, it requires only the half number of receiving chains what reduces the price of the adaptive antenna.
The paper deals with a method of signal filtering in the feed network of a phased array. Two alternative ways of phase control are described here. Both of them enable to set several directions of zero reception independently each other.
The Institute of Radio Engineering and Electronics of the Czechoslovak Academy of Sciences (IREE), Prague, provides the national primary time a frequency reference for the Czechoslovak metrology. The paper describes main activities of IREE in standard time and frequency generation, dissemination, and measurements.