What is the meaning of standing waves in VSWR terms and correlated the definition in area...

What is the meaning of standing waves in VSWR terms and correlated the definition in area of antena. please explain it briefly

Expert Solution

In antenna theory, for a source to deliver power to an antenna, the impedance of the source and transmission line must be well matched to the impedance of the antenna. The parameter VSWR (Voltage Standing Wave Ratio) is a measurement of the level of standing waves on a transmission line, i.e., it numerically describes how well the antenna is impedance matched to the source or transmission line. Thus, standing waves represent the power that is not accepted by the load and reflected back along the transmission line.

Standing waves in terms of VSWR:

In any system, the source, transmission line and antenna all have a characteristic impedance and to obtain the maximum power transfer from the source to the transmission line, or the transmission line to the antenna, the impedance levels must match. However, if the impedance of the antenna doesn't match with that of the transmission line, then it is not possible for all the power to be transmitted. In such a situation, the power that is not transferred to the antenna travels back along the transmission line towards the source. In such a situation, the voltages and currents of the forward and reflected waves in the transmission line superposes to form a standing wave.

VSWR is mathematically expressed as

where is the reflection coefficient. The VSWR is always real and positive for antennas. The smaller the VSWR, the better the antenna is impedance matched to the transmission line and more power is delivered to the antenna. The minimum VSWR is 1.0, i.e., no power is reflected from the antenna, which is ideal.

Area of antenna:

The effective area or effective aperture is an important parameter that determines the receive power of an antenna. It describes how much power is captured from an incident plane wave with the same polarization as the antenna and travelling towards the antenna in the antenna's direction of maximum radiation (i.e., the direction from which the most power would be received).

The effective area is mathematically expressed as

where is the antenna gain which describes how much power is transmitted in the direction of peak radiation to that of an isotropic source.

genius_generous answered 2 years ago

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