Yes, for this reason I am trying a signal source to cop-with the project for real analysis. By the way I have no any YouTube page for " just plain clickbait ". I am doing all this as hobby to dive into and to gain knowledge.

 

Years back I designed a digital signal generator. I used a device much like the 74LXC8T245 for the output stages. It needed to output from 1.1V to 5V at speed. Then I made a 1 to 5V power supply for it. "They wanted it to do 0.8V to 5.5V but when I showed the price difference they change the specifications. I was not running 400mhz! I think there is a single stage version in a very small package.

 

Present computer systems can run in the gigahertz frequency range, so it is not likely that a 400 megahertz pulse rate will be difficult to produce. The serious challenge will be in setting and controlling the frequency.

 

Agreed, trying my best to achieve the target

 

A quite simple and very primative scheme to produce a digital square wave is to assemble a ring with an odd number of inverters. The period of the waveform will be the sum of the propagation delays of the inverters. That is the simplest scheme I can come up with. I do not claim it is original, or that will be stable. BUT it is one scheme to produce a logic level frequency. Adding a bit of resistance between segments will reduce the frequency some, as will adding more inverters to the string.