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how to generate a frequency variable pulse signal in hspice

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playdc2002

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hspice pulse

I want to generate a frequency variable pulse signal in hspice. For example, the nominal frequency is 50Mhz, at 2us, it jump to 51Mhz, at 4us. it drop to 49Mhz and so on. How to do it? Thanks!
 

Re: how to generate a frequency variable pulse signal in hsp

Try "pwl" statement.

hanm
 

you can use macro of Hspice to implement the function.
 

If phase shift is not important, you can use voltage controled resistor and capacitor to consist a vco and the control voltage implemented in vpwl, then you can get a sin wave with frequency changed as the controled voltage, and the pulse signal can be available.
Maybe this method can work

ablue
 

Re: how to generate a frequency variable pulse signal in hsp

First design an ideal VCO running at a free-running frequency of 50 MHz.

and then calculate what voltage will cause this to go to 49 MHz and 51 MHz. This depends on the Kvco.

Then change the input control voltage of the VCO at the desired time using a PWL source.

Also 50 MHz corresponds to a period of 20ns; so you cannot change frequencies faster than this if you have to see it do some work in your circuit.

Hope it helps.
 

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