Microwave tuners

Updated August 27, 2005

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New for September 2005! The kidneys of a load pull or source pull system are the tuners (we couldn't say "the heart" because you typically need two tuners...) These are what allow you to move from a fifty-ohm piece of test equipment such as a frequency source, power meter or noise figure analyzer, to (hopefully) anywhere on the Smith Chart.

There are several types of tuners, including mechanical "slug" tuners, and solid-state tuners that generally employ PIN diodes as variable loads. There are three things you look for in a tuner system:

1. VSWR limitations - how far from fifty ohms can you tune?
2. Bandwidth - how much can you cover with one set of tuners? For narrow-band applications, this might not seem like a big deal, but if you are characterizing a FET from 1 to 40 GHz, your investment will depend on the tuner bandwidths.
3. Accuracy considerations: are the tuner settings repeatable? Do they drift with time or temperature?

Here's a picture of a pair of mechanical tuners, made by Maury. The model number is MT983A, and they can tune from 4.0 to 26.5 GHz.

What's a tuner without autmated control? A huge headache! The MT 986 automated tuner controller provides computer and local control of the MT97X and MT98X series of automated tuners. The controllers are GPIB compatible and also provide for manual control by means of front panel motor selection switches and a rotary position control. Geez, sounds like an ad for Maury...

Active tuners

What's an "active" tuner? Here, an amplifier is used to amplify the reflection coefficient. Active tuners often have problems with stability.

Attention tuner vendors: contact us to learn how you can sponsor this page and drive web traffic to your site! Hey Focus, we'll take your Canadian Dollars but you don't get the usual 10% discount for signing up for a year! And we'll get rid of those Maury pictures, s'il vous plait!