how to 1 pwm signal is coverted into four pwm signal with the help of arduino...

Help me in this regard........

Need more details in this regard (and perhaps a translation into English)
(why are you having so much difficulty in understanding that PWM != PPM ?)

Its called PPM sum, all the rising edges are sort of collected into a single stream of data.
As you are grinding your self with quads and you dont seem to know how to use google go read this:

And specifically this one and all the links provided in the first topic and well all the info that its in there:

And dont forget the google repository that is linked in that last link.

all the rising edges are sort of collected into a single stream of data.

Called a ... what?

In the RC world they call it PPM sum, and I forgot to complete the explanation.
You can even google for PPM sum and get good responses.