During which stage does the central processing unit analyze the instruction and encode it in the form of a number, and then generate an electronic signal?

Fetch stage

Explanation:

Fetch stage is level of central processing unit(CPU) that fetches the instruction and data from CPU in instruction cycle.It receives instruction from memory address to get stored in internal temporary memory.

The instructions obtained from memory is analyzed to perform the purpose activity behind the instruction and then next instruction is fetched. Instructions are encoded in this cycle with certain  numbers which later gets decoded and executed.