SparkFun Forums

[jimmy409]

Hello everyone,

My name is Jimmy. I'm new here. Nice to meet you all.

Here is a question for you:

I need to produce a Square wave 12 MHz - 15 MHz, with adjustable duty cycle.

Can the AD9850 be forced to produce a square wave in this range?

[Valen]

The AD9850 chip generates a DDS-sinewave. Which is a approximated analog sinewave but contains high frequency noise due to the digital creation proces. Most of those cheap AD9850 boards (No suggestion to buy. Just an example) contain a filter to clean that up and result in a reasonable pure sinewave. Those can also output a square wave but that is actually generated by a comparator with the sinewave as input. And it doesn't support the full bandwith range as the analog output bandwith. The specs I've seen suggest it is limited to 1 MHz.

So no, not a square wave 12-15 Mhz. And certainly not adjustable duty-cycle, which is the same as PWM.

If you need 12 to 15 MHz square-waves (fixed duty-cycle) then there are crystal oscillator or resonator cans made for that. See an older thread for similarity and suggestions:

https://forum.sparkfun.com/viewtopic.php?f=14&t=27767

[jimmy409]

Thank you Valen for your informative reply.

Do you know of, or can you suggest a ready made device that can be controlled with an Arduino (or a small stand alone device that is not Arduino controlled), that will produce 12 MHz - 15 MHz square wave? -- regardless of duty cycle capabilities.

Jimmy

[Valen]

No, I do not. You'll have to search for examples yourself.