November 1993, Volume 2, Number 3
A Conical Dielectric-Loaded Horn with Symmetrical Radiation Pattern
A relatively broadband dual-mode conical horn, which has a symmetrical radiation pattern and extremely low sidelobes, can be obtained by loading a dielectric layer inside the feedhorn. An investigation of the radiation behaviour of conical horn antenna with small flare angle is described. Measured radiation characteristics in the X-frequency band are shown.
P. Kulla, P. Sevcik, M. Chrenek, J. Misun
System for Digital 1D-Image Processing with 1024 Pixel CCD Sensor
The conception of system for digital 1D-images processing with digital CCD camera is presented. The system is created from these three basic parts: the digital CCD camera with linear image sensor CCD L133C, 8-bit interface and a personal computer. The scanning digital CCD camera generated a video signals, which are processed in the analog signal processor. The output signal is continually converted to 8-bit data words in A/D converter. This data words maybe transfer over a bus driver to the operation memory of personal computer, by setting one of the three work regimes of digital CCD camera. Some application possibilities and basic technical parameters of this system are given.
Technical Aspects of Electrical Neurostimulation
This paper deals with technical aspects of electrical neurostimulation. Attention is given to problems of transmission of signals and power through inductive link created by coupled resonant circuits. Both geometric and electronic approaches are shown and compared. In geometric approach factors influencing mutual coupling are presented. In electronic approach two types of tuning of coupled resonant circuits are presented. The main stress is laid upon the principle of stagger tuning. At the end an example of stimulator using coupled resonant circuits stagger tuned is given.
P. Sevcik, P. Kulla, J. Misun, M. Chrenek
A New Modification of Photometric Method
For the digital 1D-image processing we go out from the so-called photometric method. For the concrete applications of the introduced method its accuracy lowers, owing to that the form of an output video signal of linear CCD sensor is not smooth and not symmetrical. In some cases the output video signal of linear CCD sensor is devalued by the certain disperse of pixel sensitivity, respectively also that a measured object and its background are not uniform. Therefore we introduce a new modification of photometric method. The obtained results show, that introduced method gives a possibility to raise the measurement accuracy of the object dimension considerably.
Some Problems in Elaboration of Equivalent Electrical Schematics of Linear Mechanical Systems
The solution of different acoustical signal processing problems in electroacustic transducers are usually based on the method of electromechanical analogies.
Finding of equivalent electrical schematics of mechanical systems as a planar graphs has some limitations in first analogy, (force - voltage, velocity -current). Systematic analysis and general conclusions about solvability of this problem are made on the basis of Kuratowski's Theorem. Some examples of solution are included.
M. Karasek, H. Tobben
Theoretical Comparison of PR3+-Doped La-Ga-S and Fluoride Glass Fibre Amplifier
The performance and efficiency of a praseodymium-doped La-Ga-S chalcogenide glass fibre amplifier have been analyzed using a comprehensive large-signal numerical model. The four level laser model incorporates the LP01 mode radial field distribution in step-index single-mode fibre and experimentally obtained emission and absorption cross sections. The model has been used to optimize the fibre parameters for small-signal operation. The optimum cut-off wavelength of the LP11 mode has been found to be 700 nm. It follows from the analysis that at 1310 nm a small-signal gain of 36. 7 dB can be expected from the Pr3+-doped chalcogenide fibre amplifier for a pump power of 200 mW in contrast to 18. 8dB for the same pump power in the Pr3+-doped fluoride fibre amplifier.