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The term power standing wave ratio (PSWR) is sometimes referred to, and defined as, the square of the voltage standing wave ratio. The term is widely cited as "misleading". [11] The expression "power standing-wave ratio", which may sometimes be encountered, is even more misleading, for the power distribution along a loss-free line is constant. ...
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 ).
Figure 1. Waveguide slotted line. Slotted lines are used for microwave measurements and consist of a movable probe inserted into a slot in a transmission line.They are used in conjunction with a microwave power source and usually, in keeping with their low-cost application, a low cost Schottky diode detector and VSWR meter rather than an expensive microwave power meter.
Generally base values of power and voltage are chosen. The base power may be the rating of a single piece of apparatus such as a motor or generator. If a system is being studied, the base power is usually chosen as a convenient round number such as 10 MVA or 100 MVA. The base voltage is chosen as the nominal rated voltage of the system.
The line is modeled by a series of differential segments with differential series elements ( , ) and shunt elements ( , ) (as shown in the figure at the beginning of the article). The characteristic impedance is defined as the ratio of the input voltage to the input current of a semi-infinite length of line.
The length of a sinusoidal wave is commonly expressed as an angle, in units of degrees (with 360° in a wavelength) or radians (with 2π radians in a wavelength). So alternately the electrical length can be expressed as an angle which is the phase shift of the wave between the ends of the conductor [ 1 ] [ 3 ] [ 5 ]
In this way the incident power wave for each of the unused ports becomes zero yielding similar expressions to those obtained for the 2-port case. S-parameters relating to single ports only ( S m m {\displaystyle S_{mm}\,} ) require all of the remaining ports to be loaded with an impedance identical to the system impedance therefore making all ...
The unit "var" is allowed by the International System of Units (SI) even though the unit var is representative of a form of power. [8] Per EU directive 80/181/EEC (the "metric directive"), the correct symbol is lower-case "var", [ 1 ] although the spellings "Var" and "VAr" are commonly seen, and "VAR" is widely used throughout the power industry.