I was making a circuit to generate voltage sag signal as shown in the image in the link below: http://img830.imageshack.us/img830/5792/matlab.jpg

As you can see in the oscilloscope, there are two signals instead of one signal generated when I was trying to combine one sine wave signal with one step input. It is a product of a sine wave and a step input so supposed the answer should be only one signal. The mdl file can be downloaded here. Please advised. Much appreciated.

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