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tdnoise overestimation ?

analogy

So I have a basic inverter circuit and the input signal is 1 GHz clock.

I ran PSS + PNoise analysis (shooting engine) for time domain noise.Being a clock signal I should have used full spectrum but we use a rather old version of Spectre (7.0.1.179.isr16).

So I plot my integrated noise in frequency range from 50 MHz to 7GHz.But I noticed that integrating over this bandwidth the noise voltage was in order of Volts !

And so I plotted noise spectrum (Pnoise>tdnoise) and found that I have a huge spike (spur) at 5 GHz.For reference :

Integrating noise from 50MHz to 1050MHz yielded noise of ~5.1 mV

Integrating noise from 50MHz to 7GHz yielded noise of ~170 V

What might be the problem ?

Parents

  • Okay. This sounds difficult to grasp - if signal through system is square wave (hence odd harmonics), as a quick notion , integrated noise bandwidth would be frequency of a particular harmonic slightly above noise floor. But if I integrate noise until PSS/2 , how does that correspind to "right" bandwidth for total integrated noise ?

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  • Okay. This sounds difficult to grasp - if signal through system is square wave (hence odd harmonics), as a quick notion , integrated noise bandwidth would be frequency of a particular harmonic slightly above noise floor. But if I integrate noise until PSS/2 , how does that correspind to "right" bandwidth for total integrated noise ?

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