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Voltage standing wave ratio (VSWR) (pronounced "vizwar" [1] [2]) is the ratio of maximum to minimum voltage on a transmission line . For example, a VSWR of 1.2 means a peak voltage 1.2 times the minimum voltage along that line, if the line is at least one half wavelength long.
Increasing return loss corresponds to lower SWR. Return loss is a measure of how well devices or lines are matched. A match is good if the return loss is high. A high return loss is desirable and results in a lower insertion loss. From a certain perspective 'Return Loss' is a misnomer. The usual function of a transmission line is to convey ...
The voltage standing wave ratio (VSWR) at a port, represented by the lower case 's', is a similar measure of port match to return loss but is a scalar linear quantity, the ratio of the standing wave maximum voltage to the standing wave minimum voltage.
In a real directional coupler, however, the insertion loss consists of a combination of coupling loss, dielectric loss, conductor loss, and VSWR loss. Depending on the frequency range, coupling loss becomes less significant above 15 dB coupling where the other losses constitute the majority of the total loss.
For example, the SWR bandwidth is typically determined by measuring the frequency range where the SWR is less than 2:1 . Another frequently used value for determining bandwidth for resonant antennas is the −3 dB return loss value, since loss due to SWR is −10·log 10 (2÷1) = −3.01000 dB.
Examples of estimated bandwidth of different antennas according to the schedule VSWR and return loss by the help of the ANSYS HFSS [1]. Ansys HFSS (high-frequency structure simulator) is a commercial finite element method solver for electromagnetic (EM) structures from Ansys.
A standing wave ratio meter, SWR meter, ISWR meter (current "I" SWR), or VSWR meter (voltage SWR) measures the standing wave ratio (SWR) in a transmission line. [ a ] The meter indirectly measures the degree of mismatch between a transmission line and its load (usually an antenna ).
Standing wave ratio (SWR or VSWR) is a basic parameter and the one most commonly measured on a slotted line. This quantity is of particular importance for transmitter antennae. A high SWR indicates a poor match between the feed line and the antenna, which increases wasted power, can cause damage to components in the transmission path, possibly ...