Hi Taeyeop,
What you are seeing is correct - this is how the signal was intended to look.
To be clear the generated signals are formatted and coded to work ONLY with our HSDC Pro software which connects to our TSW14xxx family for the purpose of evaluating our DACs. They will not work with any other software.
This tool is not intended to be used as a generic signal generator. For that purpose I would recommend using something like Agilent Signal Studio - I believe they offer a 30 day Trial License.
Ken