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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.
The insertion loss is not such a problem for an unequal split of power: for instance -40 dB at port 3 has an insertion loss less than 0.2 dB at port 2. Isolation can be improved at the expense of insertion loss at both output ports by replacing the output resistors with T pads. The isolation improvement is greater than the insertion loss added ...
In real systems, relatively little loss is due to mismatch loss and is often on the order of 1dB [dubious – discuss]. According to Walter Maxwell [2] mismatch does not result in any loss ("wasted" signal), except through the transmission line. This is because the signal reflected from the load is transmitted back to the source, where it is re ...
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.
As the albedo of the Moon is very low (maximally 12% but usually closer to 7%), and the path loss over the 770,000 kilometre return distance is extreme (around 250 to 310 dB depending on VHF-UHF band used, modulation format and Doppler shift effects), high power (more than 100 watts) and high-gain antennas (more than 20 dB) must be used.
The Smith chart (sometimes also called Smith diagram, Mizuhashi chart (水橋チャート), Mizuhashi–Smith chart (水橋スミスチャート), [1] [2] [3] Volpert–Smith chart (Диаграмма Вольперта—Смита) [4] [5] or Mizuhashi–Volpert–Smith chart) is a graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio ...