1. Valma Prifti, Polytechnic University of Tirana, Albania
The behaviour of a transmission circuit device with two gates, in different conditions of frequency and load is determined by measuring the voltage and current. Since the measurement of voltage and current at high frequencies and very high transmission line is very difficult, instead of measuring them is performed the measurement of their main parameters. In case of waveguides the parameters are: wave resistance, remission in waveguide line, the constant of phase, the power, wavelength and spead of phase in waveguide, frequency and wavelength v.
Very high frequency electronic circuits, present some changes in their behavior towards circuits that work in low frequencies. At higher frequencies the wave length becomes comparable to the physical dimensions of circuit elements. These changes in circuit behavior are conditioned by the nature of distributed parameters. Thus the very HF circuit cannot be described through voltage and current at a given node of the transmission lines, but as waves transmitted in a given environment.
At frequencies above 1 GHz, geometrical dimensions of components become comparable with the wave length in which they work and this intensifies the changes in the behavior of circuits.
Analysis of system transmission and reception in the microwave is limited to linear networks. Because of the limitations of these networks, the network (the circuit with 2-doors) is excited with an incoming sinusoidal signal.
Of particular interest to us there are three types of wave propagation: TEM (transverse electric modes);
In this type, both electric and magnetic fields are perpendicular to the direction of diffusion. In the spread direction (passing) there is not any field component. TEM modes are not used in waveguides. TE (transverse electric modes) or H-modes; In this type, there is only the magnetic field in the spread direction, the electric field is absent. All components of the field can be derived from the axial component of the electric field Ex. TM (transverse magnetic modes) or E-ways; In this type, only the electric field exists only in the direction of the spread, the magnetic field is absent. All components of the field can be derived from the axial component of the magnetic field Hx.
The measurements are performed using the standing wave mode (stationary mode) in waveguides. In this case the waveguide was left open-ended, in which we decided reflective sheet metal in contact with the line (to cover it). It was decided the waveguide regime or staying stationary waves. In this paper, for each frequency, we defined two consecutive positions where minimums are detected.
Ključne reči :
Tematska oblast:
Measures and instruments
Datum:
03.02.2014.
REDETE 2014 - Researching Economic Development and Entrepreneurship in Transition Economies
