June 1996, Volume 5, Number 2
This paper presents an analysis of the electromagnetic field radiated by micro-strip patch antennas printed on inclined surfaces. The theoretical approach allows to apply spatial rotations to each source. The computer simulation developed permits us to experiment different antenna structures and two original realisations are proposed: a 2-element array printed on two inclined planes and a 4-element array laid out on a pyramidal surface. In addition, it enables the choice of the phase applied to each radiator to produce a beam deflection function. A good accuracy is obtained between theoretical and experimental results. The aim of this study is to optimise the parameters of such antennas to achieve the desired radiation patterns, from printed phased arrays on conformal surfaces. We also present the theoretical behaviour of a octagonal pyramid.
The paper deals with the design of floating one- and/or two-port high-order networks. The current conveyor CCII+ seems to be a suitable active building block for this purpose. Some examples of the above mentioned networks are shown .
Both the current distribution and characteristic impedance variations along a hexaedric antenna are analysed in this paper. The presented arrangement by auxiliary wires may ensure equal currents in all antenna wires. The results are required for calculations of the field in the operating volume and may be used for antenna design.
When designing transmission line matching circuits, there exist often overlooked, additional, not much used, degree of choice in the selection of the transmission line impedance. In this work are presented results of CAD analysis for the two element transmission line matching networks, demonstrating that selecting matching circuits transmission lines with higher impedance, than usually used 50 or 75 ohms, can in most cases substantially decrease the physical dimension of the final matching circuit. Computer program, analyzing the influence of the matching line impedance on the length of the matching elements was developed and results are presented. It appears, that it is advantageous to choose matching circuits with high characteristic impedance. This results in a reduced dimension of the matching circuits.
The contribution describes a program system to design digital IIR filters by optimisation of impulse response. Besides briefly presenting the already published method, it emphasizes the necessity to regularize the problem by changing the requested impulse response into a causal one by reshuffling its values. The program enables to design the filters starting from either frequency or time domain response and also from a manually prescribed pole configuration which is particularly useful for teaching purposes.
The human electroencephalogram (EEG), is record of the electrical activity of the brain and contains useful diagnostic information on a variety of neurological disorders. Normal EEG signal are usually registered from electrodes placed on the scalp, and are often very small in amplitude, of 20 µV. The EEG, like all biomedical signals, is very susceptible to a variety of large signal contamination or artefacts (signals of other than brain activity) which reduce its clinical usefulness. For example, blinking or moving eyes produces large electrical potentials around the eyes called the electrooculogram (EOG). The EOG spreads across the scalp to contaminate the EEG, when it is referred to as an ocular artefact (OA). This paper includes method of identification portion of the EEG record where ocular artefact appears and classification its type by neural network.
A large number of signal processing problems are concerned with estimating unknown parameters from sensor array measurement. This paper presents simple algorithm for estimating spatio-temporal spectrum of signals received by passive array derivated from MUSIC algorithm, based on eigenstructure of covariance matrices of received signals. Some simulation results are presented.