at 15mhz its closer to sine than square.
No, it isn't. It's not a perfect square but it's far from being a sine wave (and even less os a pure sine, which doesn't occur in reality anyways).
BTW, my DG1062z shows the same, which is not surprising considering the similarities:
1MHz:
15MHz:![](https://www.eevblog.com/forum/testgear/best-arbitrary-waveform-generator-for-around-$500/?action=dlattach;attach=171799;image)
A quick view on the signal's frequency spectrum not only shows that this clearly isn't a sine wave but also explains why the 15MHz square wave looks like it does:
![](https://www.eevblog.com/forum/testgear/best-arbitrary-waveform-generator-for-around-$500/?action=dlattach;attach=171795;image)
It's clearly visible that the 15MHz signal contains non-harmonic components, plus some of the expected harmonics are missing.
A check with a proper spectrum analyzer confirms the malformations increasing with the frequency increasing:
1MHz:
3MHz:
5MHz:
10MHz:
15MHz:![](https://www.eevblog.com/forum/testgear/best-arbitrary-waveform-generator-for-around-$500/?action=dlattach;attach=171819;image)
However, that's an imperfection that the DG1000z shares with many other AWGs in that price class, and if you believe that a GW Instek device performs any better then I'd say you're deluding yourself.
There simply are limits what one can expect when buying low end gear, and that's true for AWGs as well. Maybe the new Siglent SDG2000X does better in this regard, but I'm not holding my breath.
Edit: I forgot to mention, the scope used is a LeCroy WavePro 7300A (3Ghz 20GSa/s 48Mpts) connected via a 50ohms BNC cable (tested to 2.7GHz) directly into the scope. The spectrum Analyzer is a Rohde & Schwarz FSP7 (7Ghz), again using the same cable setup plus a Pasternack BNC-to-N adapter.