Im trying to figure out how to create a frequency doubler to be used on a FPGA. Im using the quick logic FPGA that's kind of a one shot burn in FPGA. So unfortunately it doesn't have a frequency double block like the xzylinx does. Forgive me if butchered the spelling of their name.

So i know if I can somehow take an original signal delay it slightly or maybe by %50 and then XOR the two signals together I have essentially what im looking for. But my problem is how do I delay one signal short from chaining a bunch of gates together to use the delay they have internally (thats kind of mickey mouse and im not even sure if it will work)

So any ideas on where to start with either delaying or creating a doubler with just logic? Im trying to do this without using external capacitors etc. So 555's are out as well as other external circuits.

Thanks in advance for any ideas!

-Ethan