What is a Marchand balun?

The Marchand balun may be one of the most popular forms of microwave balun used to generate a balanced signal. In particular, the planar coupled-line Marchand balun shows good compatibility with microwave integrated circuits (MIC) and monolithic MICs (MMIC).

What is microstrip balun?

Abstract: Tapered microstrip Balun is used as an impedance transformer network in feeding sections of spiral antennas as it provides impedance transformation over a large range of frequency and also serves the purpose of conversion of single ended port to a symmetric port.

Why is it called a balun?

The term balun is a portmanteau of balanced and unbalanced, indicating that a balun will transition between a balanced (also called ‘differential’) transmission line (where opposite currents both travel in transmission lines) and an unbalanced (also called ‘single ended’) transmission line (where the return current …

What are the types of balun?

There are two types of balun, Voltage baluns and current baluns. Voltage baluns produce a balanced voltage at their output and current baluns produce a balanced current. Current baluns are the most commonly used balun type and consist of a transmission line wound as a choke (inductance).

How does a balun work?

Voltage baluns work by continually trying to force the output terminals to equal voltages. They sometimes start a phase shift between the ground and each output terminal that’s connected. The high impedance at each terminal must be precisely equal, or else the current loads will not be equal or opposite.

Why is balun used?

Baluns are used both to sort out the flow of AC signals and make the necessary impedance transformation between coaxial cable, which has a low impedance, and balanced loads, which have higher impedances.

Does a balun reduce noise?

Whilst a balun is usually associated with reduced unwanted transmission line radiation (eg. from the feedline and power cord), a balun can also help minimise unwanted noise picked up by your feedline.

The Marchand balun was first reported in December 1944 issue of Electronics, titled “Transmission line CONVERSION TRANSFORMERs” (their caps, not ours), by author Nathan Marchand of Federal Radio and Telephone Laboratories. Marchand provided an excellent means of converting from coax to a two-conductor transmission line.

What is a balun?

A balun is any three port device with a matched input and differential outputs. It is most succinctly described by the required (ideal) S-parameters: Note what is implied by this: •A balun is a three port power splitter, similar to a Wilkinson or resistive power divider. The two outputs will be equal and opposite.

Are the two outputs of the balun necessarily matched?

• The two outputs are not necessarily matched. • The outputs of the balun may or may not be the same impedance as the input. • There is no constraint on S23, so the outputs may or may not have isolation. • Therefore there may be a different return loss on the outputs for differential and common mode signals.

Is there a coaxial Marchand balun available in Microwave Office?

Then, one of these days we will develop a coaxial Marchand balun design in Microwave Office (they have a microstrip balun in their example library you might want to look at).