RF Balun Basics & Selection
A Balun is a device that is used to join a balanced line to an unbalanced line. A balanced line is one that has two terminals, neither of which are connected to the ground, whereas an unbalanced line has one terminal connected to ground. RF Baluns can also be used as transformers to provide impedance transformations. To learn more about RF Baluns, you can read white papers and notes in the Knowledge Center on everything RF - Just search for RF Baluns.
Selecting RF Baluns
When selecting a RF balun it is important to know the parameters that you need to specify. Below are a list of the key parameters to look out for when selecting a balun:
Phase Balance: One of the most important criteria of a Balun is how close the balanced outputs are to having equal amplitude and a 180 degree phase difference. This is one of the key parameters to look at when selecting a balun.
Amplitude Balance: It is the measure of how closely the two unbalanced signals are in amplitude.
Impedance Ratio: This is the ratio of the unbalanced impedance to the balanced impedance. It is usually specified as 1:n (i.e. 1:1, 1:2, 1:4). The differential impedance is between the balanced signal lines is twice the impedance between the signals and ground.
Common Mode Rejection Ratio: This is the amount of attenuation of a signal from the balanced port of the balun to the unbalanced port. It is measured in dB.
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