YIG technology

Updated October 16, 2006

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New for August 2006! It's about time we at least mentioned this cool technology! YIG stands for yttrium iron garnet. Yttrium is quite often misspelled, "yittrium" would be a phonetically correct spelling.

Yttrium is atomic symbol Y atomic number 39.

Ytterbium is atomic symbol Yb, and atomic number 70. Don't confuse the two!

This quick lesson was contributed by Richard from Tasmania!

YIG is actually a synthetic form of garnet. It has interesting magnetic properties which allow it to perform as a tunable microwave filter for example.

This additional material on YIG technology just in from James, a semiconductor guy with some RF test experience:

YIG is a ferrite with very high resistivity and a sharp ferrimagnetic resonance. These properties allow YIG resonator oscillators to achieve DRO-like phase noise performance and very wide tuning ranges: 2-20 GHz tunable oscillators are available. High performance, with unloaded Q's >1000, demands a resonator that is a highly polished sphere or ellipsoid made from a single crystal of YIG. Frequency tuning of the YIG resonator is accomplished by varying the currents in electromagnets that are an integral part of the YIG oscillator (or filter) module. Filters can be built that are reciprocal or non-reciprocal depending on coupling structures.

There are some prices to be paid for this performance. The YIG sphere is not cheap, and needs to be oriented carefully. The magnetic fields required are large, so YIG oscillator modules need heavy pole pieces, are power hungry and tune slowly. Further, temperature control of the resonator is required, and the resonator coupling loops are generally 3D structures that further increase the cost of production.

If you want to reuse a YIG oscillator that you got cheap on ebay, then this article:

http://www.vhfcomm.co.uk/pdf/A%20Simple%20Approach%20tyo%20YIG%20Oscil.pdf

could be very helpful. Along with guidance on the care and feeding of YTO's, there are some very clear photos of the inner workings.