External Quarzoscillator with SMA Output

You can buy packaged oscillators with SMA output connectors, and then you can use an SMA patch cable to connect the two. See, for example,

Be aware that fully packaged oscillators are generally quite a bit more expensive than simple oscillator "cans". But first, I think you need to establish better just what output you want. An oscillator may have sinewave output, or logic level output in various formats (ECL, PECL, LVPECL, CMOS and LVCMOS all come immediately to my mind). If the output is something like PECL, it may well need a particular external termination (generally 50 ohms to Vcc-2V). Then there are the questions of stability and spectral purity. Is it a simple clock, and you don't much care about the frequency, or do you want it stable to one part in 10^9? Does phase noise matter to you? If your application is non-critical, I would suggest getting a common crystal oscillator "can" with appropriate output level and patching it onto the board you have, and forget about using the SMA on the board, though of course it's up to you to decide what's appropriate.

Cheers, Tom

Hi Tom,

Thanks for your comment!

Looks pretty good I have to admit on first sight!

An oscillator may have

If the

The thing is it should be quite stable to get proper measurement results. I have intended to use it as a clock frequency for a circuit that is implemented on an FPGA. As I am unfortunately no electronics guru I havent heard the expressions ECL, PECL etc except CMOS. The most important thing is that the frequency is stable, that i have proper edges and that it can be connected via SMA ;)

Thanks, Rob

OK, so if it is driving an FPGA input, I suppose that LVCMOS should work. The clock requirements should be stated in the board and FPGA documentation, though I know from personal experience that it is not always trivial to extract them.

When it comes to crystal oscillators, "quite stable" has very little meaning. Can you quantify that? Does it need short-term stability, over a period of a second or a minute? Does it need long-term stability, over a period of a year or a decade? Just HOW stable? The very cheapest of crystal oscillators should manage 100 parts per million initial accuracy (with respect to the marked frequency) and stability over their operating temperature range at least that good (and commonly quite a bit better). It is not terribly difficult to get down to a few parts per million stability at a little higher cost. With compensation techniques, you can get down in the one part per million range or a bit better. With oven temperature control and (expensive) attention to detail, you can get down to a few parts per billion, where long-term drift will dominate in a relatively short period. So, what do you need? The difference in cost from one end of the range to the other is a few orders of magnitude, easily 1000:1.

A Google search on "SMA crystal oscillator" gives several useful hits. But again, be aware that two things are in play here: the package with SMA connector is inherently considerably more expensive than a simpler leaded package (and you will have to supply power to each anyway), and the sort of oscillator that you will find packaged with an SMA connector will practically always be at the more expensive end of the price range (have tighter specs on stability, initial frequency accuracy, phase noise, etc.).

Cheers, Tom