How to generate a pulse signal with varying pulse width in Virtuoso

[circuitking]

Dear all, I would like to generate a pulse signal with varying pulse width with in the given time limits. The center of all these pulse should be in the same place on the x-axis. I used variables for delay time and pulse width for Vpulse component in analoglib and did a parametric analysis but there should some other way because the parametric sweep includes signal outside the given range also.

 

[BradtheRad]

The method is similar to pulse width modulation. A triangle wave and a DC voltage go to the inputs of a comparator. By varying the DC voltage you can select the point where it intersects the triangle wave. This determines the duty cycle of outgoing pulses, short or long.