This was a fun and short little project that I’ve recently updated. If you’re thinking about building a cheap signal generator that’ll work to 20 MHz or so, and would be DDS (direct digital synthesis) based, take a look at this:
It works pretty well.
I had a need for a cheap, quick & not-so-dirty signal generator that was frequency-accurate. All I needed was sine and square waves – nothing fancy. But I really wanted a pretty accurate frequency control, so that if I entered 1.5 MHz that’s what I got. Using a DDS is a very simple way to achieve this. It’s not the only way, but it is an easy way.
I used the Analog Devices AD9851 DDS chip. There are a number of DDS chips out there, but this one has both the ease-of-use and the features required for this job. Plus, it’s readily available from digikey.
A completely different way of generating signals would to be use the Maxim MAX038. This part is a signal generator chip. It’s an interesting chip. Digikey doesn’t appear to hold it in stock, but there are other projects out there which use this chip. Personally, I think the DDS is more fun though.
It was fun putting the signal generator on the oscilloscope as well as on the spectrum analyzer to look at its output. You can see those photos on the website. It’s a very interesting part. If you need to build a simple signal generator yourself, it’s worth taking a look.