T. Cesky [full-text] [Download Citations]
WARC: The First and the Last

WARC-92 was the last of its kind. The "Last Big WARC". The process was very difficult and some refer to the conference as consensus by exhaustion, clearly demonstrating one of the reasons for restructuring the ITU.
CEPT (Conference europeenne des Administrations des postes et des telecommunications) countries entered this Conference with their ECPs - European Common Proposals - extending thus the potential for frequency harmonization within Europe. The CEPT preparation for, and participation in, WARC-92 was the most effective yet and built on lessons learned at a number of previous WARC's. This WARC was the first Conference where CEPT was present with its new expanded membership.
European countries therefore had to be constantly on the guard to avoid giving the impression that CEPT was an inflexible political block with 32 potential votes. Lastly, the Soviet Union together with its satellites was, for the first time, no longer in evidence, although the Russian Federation was generally supported by other countries from within the new Commonwealth of Independent States.
The objective of this article is to point out principal WARC decisions from European point of view.

M. Gimersky, J. Bornemann [full-text] [Download Citations]
Utilisation of Symmetry Properites for the Pattern Analysis of Mutually Coupled Patch Radiators

The influence of mutual coupling effects on the radiation pattern of microstrip antennas is investigated by introducing symmetry properties in the surface current distributions. The standard method of moments is used, which requires only the upper half of three x— and y— direction offset patch radiators to be solved, while the symmetric lower half is incorporated after the determination of the current distribution. Furthermore, the Toeplitz symmetry of the impedance matrix is taken into account, and the singular value decomposition is used to invert the resulting non-square matrix in a numerically stable way. Both the symmetry property and the Toeplitz symmetry procedures reduce storage and CPU-time requirements in the analysis of broadside microstrip arrays. The pattern characteristics calculated with and without mutual coupling interactions are found to differ up to 10 dB in sideloge levels which clearly demonstrates that the pattern can be as severely affected by mutual coupling as the commonly investigated input impedance. The predicted results are in good agreement with measured data on single patches.

J. Brzobohaty, J. Pospisil [full-text] [Download Citations]
Decomposed Implicit Models of Piecewise - Linear Networks

The general matrix form of the implicit description of a piecewise-linear (PWL) network and the symbolic block diagram of the corresponding circuit model are proposed. Their decomposed forms enable us to determine quite separately the existence of the individual breakpoints of the resultant PWL characteristic and their coordinates using independent network parameters. For the two-diode and three-diode cases all the attainable types of the PWL characteristic are introduced.

V. Sebesta, P. Kilian [full-text] [Download Citations]
The Testing of Pseudorandom Generators Using Correlation Properties

The statistical properties of a pseudorandom sequence being characterized by the distribution of the values near to the uniform distribution may differ from the expected ones. On doing a quantitative evaluation of the differences, it is advantageous to start with the properties of an ideally random sequence. The results of the study of the absolute value of autocovariance sequence point show that the estimate is characterized by the unilateral normal distribution with the parameters dependent on the sequence length. Thanks to this it is possible to determine the criteria that enable the relatively simple testing of the behaviour of pseudorandom sequence generators. These criteria have been verified on the four generators.

V. Ricny, J. Mikulec [full-text] [Download Citations]
Optoelectrical Method of Measuring the Aircraft Track Velocity Vector

This article deals with new principal and basic algorithm of the optoelectronics measuring method of aircraft track velocity vector using digital processing of video signals of CCD line sensors.

D. Levicky, P. Chromek [full-text] [Download Citations]
Progressive Image Reconstruction Using Morphological Skeleton

This paper presents the results of a study on use of morphological skeleton to represent, progressive transmission and reconstruction of binary images. For images containing blobs and large areas, the skeleton subsets are much thinner than the original image therefore encoding of skeleton results in lower information rates than other standard coding methods.