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PSS, PNOISE and Transient Noise

pcardoso73

Hi all,

 I have several questions which i will describe by topics. All the circuit design is made in Candence using Spectre.

 1 - As transient noise introduces noise in the transient simulation, I export the data to Matlab to perform the Jitter (RMS and Peak-to-Peak) calculations. How can I do this in Cadence ?

2 - How can be compared the results obtained from MatLab (from Cadence exported data), and those obtained by cadence ?

3 - What kind of noise is introduced by transient noise ? Can this noise be upconverted into phase noise ?

4 - Calculating phase-noise using PSS+PNOISE, if done with transient noise on, will affect the phase noise analysis result ? Should I disable the transient noise, when performing PSS and PNOISE ?

 5 - I am designing a VCXO for a PLL. The requirements are: frequency - 80 MHz, tunning range - +- 8 kHz, cload 15 pF. To simulate this circuit with transient noise I have used the following parameters:

Noise Fmax 1e9
Noise Fmin 10k
Noise Seed 1
Noise scale 1
Noise Tmin 4u

Is this correct ?

 

Thanks To all.

 

Best regards,

Pedro 

Parents

  • Pedro,

    To try to answer your questions:

    1. You can either import the results into Matlab using the "spectre toolbox" for Matlab (covered in the documentation), or in ViVA you can use File->Save from the results browser to save into Matlab form.
    2. Presumably you could compare them in Matlab?
    3. Transient noise is including the same as a small signal noise source. If using noisefmax only, you get white noise at noisefmax across the whole spectrum. If you specify noisefmin you get coloured noise (i.e. flicker noise) from noisefmin upwards. Yes, the noise is up and down converted. Bear in mind that you get the signal containing both the signal and the noise.
    4. PSS+PNOISE are completely independent from transient noise. PSS+PNOISE will be a much more efficient way of simulating the noise in a periodic circuit - and probably more accurate - unless the circuit has a large signal response to the noise.
    5. It depends! Very hard to know without looking at the circuit. Why do you want to use transient noise rather than PSS+PNOISE anyway?

    Regards,

    Andrew.

Reply

  • Pedro,

    To try to answer your questions:

    1. You can either import the results into Matlab using the "spectre toolbox" for Matlab (covered in the documentation), or in ViVA you can use File->Save from the results browser to save into Matlab form.
    2. Presumably you could compare them in Matlab?
    3. Transient noise is including the same as a small signal noise source. If using noisefmax only, you get white noise at noisefmax across the whole spectrum. If you specify noisefmin you get coloured noise (i.e. flicker noise) from noisefmin upwards. Yes, the noise is up and down converted. Bear in mind that you get the signal containing both the signal and the noise.
    4. PSS+PNOISE are completely independent from transient noise. PSS+PNOISE will be a much more efficient way of simulating the noise in a periodic circuit - and probably more accurate - unless the circuit has a large signal response to the noise.
    5. It depends! Very hard to know without looking at the circuit. Why do you want to use transient noise rather than PSS+PNOISE anyway?

    Regards,

    Andrew.

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