amplitude of FFT for chirp function with changing amplitude

Hi all. I have a output as uploaded image1( http://testybab.blogspot.com/2013/06/fft-peoblem.html ). actually, i should take a Fast Fourier Transform of this output but i got exactly twice of desired amplitude and for phase, i got image2 (<http://testybab.blogspot.com/2013/06/fft-peoblem.html>) that obviously wrong.

Please help me

[Honglei Chen]

It's hard to comment if you don't tell us what you did to get these figures.