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Balun Transformer General Information

Insertion Loss (dB)

Loss due to transmission from primary dot port to secondary dot port and secondary port. Most balun

transformers are symmetrical through their central horizontal axis, therefore, an input can be applied at

the primary dot port or the primary port with differential outputs at the secondary dot and secondary ports.

Basics of Broadband Transformers

There are two kinds of broadband transformers. One is known as a conventional type, which has separate

primary and secondary windings, as do power and audio transformers. The other type is called a

transmission-line transformer. It is believed that the latter variety is the most efficient of the two.

Transmission-line transformers are wound with twisted or parallel windings and produce specific

integers of impedance transformation, such as 4:1, 9:1, and 16:1. Conventional transformers permit

you to obtain any transformation ratio you need.

Version 2010

Applications of Balun Transformers

In a balun transformer, one pair of terminals is balanced, that is, the currents are equal in magnitude and

opposite in phase. The other pair of terminals is unbalanced; one side is connected to electrical ground

and the other carries the signal. Balun transformers can be used between various parts of a wireless or

cable communications system. Some common applications denotes as following:

● Television receiver (Balanced) - coaxial cable network or Coaxial antenna system (Unbalanced)

● FM broadcast receiver (Balanced) - Coaxial antenna system (Unbalanced)

● Dipole antenna (Balanced) - Coaxial transmission line (Unbalanced)

● Parallel-wire transmission line (Balanced) - Coaxial transmitter output, or Coaxial receiver input

(Unbalanced)

Token’s baluns provide impedance transformation in addition to conversion between balanced and

unbalanced signal modes. Most television and FM broadcast receivers are designed for 300-ohm

balanced systems, while coaxial cables have characteristic impedances of 50 or 75 ohms.

Impedance-transformer baluns with larger ratios are available and used to match high-impedance

balanced antennas to low-impedance unbalanced wireless receivers, transmitters, or transceivers.

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