Reflection coefficient

The term reflection factor (also reflection coefficient ) is in physics, the amplitude ratio between reflected and incident wave in the transition to a different propagation medium.

The amplitude refers to the scalar or vectorial field size, for example, the electric voltage on a line, the pressure in the sound or the electric field strength in electromagnetic waves. The reflection coefficient is in general a complex quantity. Its value indicates by what proportion of the reflected wave is weaker than the incident and his argument which phase has the reflected wave with respect to the incident wave. The reflection coefficient depends on the angle of incidence. If a wave on an optically or acoustically denser medium, as occurs for shallow incidence angle of total reflection, and the reflection coefficient is 1 side of the angular dependence depends on the reflection factor of the wave type from: Thus it is different for longitudinal waves and transverse waves in acoustics and optics depending on the polarization of the wave. The latter is described by the Fresnel equations.

The amplitude ratio of the incident and of transmitted wave is called transmission factor. The energy transmission of the individual shafts ( the incident, reflected, transmitted ) to calculate the degree of reflection must be considered, related to the power or intensity of the wave. This is often indicated for component a whole rather than a single transition, and may be highly dependent on the wavelength by interference.

Reflection in lines

The propagation of electromagnetic waves on wires at the cable end result is a reflection if the there connected circuit has a different value from the wave impedance Z input impedance Za. The ratio of reflected to hinlaufender voltage wave is called the reflection coefficient and is given by the equation

In this case, mean

• Zl: the wave impedance of the line,
• Za: the input resistance of the connected at the line end circuit.
• Uh: the voltage of the departing wave
• Ur: the voltage of the reflected wave

Za = Zl, the reflection factor is zero. During the transmission of a narrow frequency band, an impedance matching with the resonance transformer is possible.

Return Loss

In particular in the description of the concept of line characteristics of the return loss R is frequently used. The return loss factor refers to the ratio of transmitted power to reflected power. Since the power is proportional to the square of the voltage, the return loss factor can be expressed by the reflection factor:

If the return loss logarithmic factor, obtaining the Rückflussdämpfungsmaß commonly in the pseudo unit decibels ( dB):

Line theory

In the transmission line theory, the reflection coefficient is defined as:

It occurs everywhere where a wave on an interface between two media (1 and 2) collides with different material properties. In this case, the phasor of the reflected wave and the incident wave of the medium 1 is just the wave impedance of the medium i The reflection coefficient is dimensionless.

On the other hand, the transmission coefficient is defined as:

Can also be obtained as follows:

Water waves

When monochromatic water waves, the reflection coefficient is defined as the ratio of the height of the reflected wave and the height of the oncoming wave.

It can be determined experimentally technically from the resulting water surface elevations of the building at a partially standing wave.

In this formula:

• .

For the analysis of the frequency- dependent reflection of wave spectra seaward of a building can be the extreme values ​​of the integrated energy density and are used for defined frequency bands i instead of an imposed vertical surface elevations.

With

• = Amount of energy maximum of contributing to the partial wave frequency components at the antinode and
• = Amount of energy minimum of contributing to the partial wave frequency components at vibration nodes.