You need to be far more explicit about exactly what you want..

You say 'signal' what sort of signal?..RF? audio?...mains power?

If you have a signal which is in phase can't you just invert it? maybe clip it first...? Or stick a fixed time delay onto it.. simple CMOS logic and an RC time constant could do this ...

Del

I am talking about Mains Power 230VAC 50HZ.

For experiment purpose, I like to show that a small Electric Fan (Brushless Type) working with 230VAC 50Hz can reverse it rotation by adjusting the reverse phase signal.

Hope to find a shematic diagram to build the experimental box. Thanks.

I think you are seriously mistaken as to how AC electricity works...

If it is a single phase AC motor, some can be reversed, some cannot. It all depends upon the design of the motor. Actually they can almost all be technically reversed, but in many cases the manufacturers do not intend for that to happen so they do not provide the necessary wiring access to do so.

If it is a 3 phase AC motor, it can be reversed by simply swapping any 2 of the phase power leads.

If it is a Brushless DC motor, you will have a controller that converts the AC to DC, and that controller will likely have the ability to reverse the polarity.

How about fitting a fan with the opposite-handed pitch on its blades instead?

Either that or disconnect the fan assembly and install it the other way round?