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noise_table function (Read 7870 times)
ORNITORINCO
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Posts: 5
noise_table function
Feb 07
th
, 2008, 4:50pm
Hello everyone,
I am trying to simulate PLL phase-noise in phase-domain using verilog-AMS description of each block under SpectreRF (I perform AC and NOISE analysis with analog_environment). To include the output phase noise spectrum I am following Kundert's guide "Predicting the Phase Noise of PLL-Based Frequency Synthesizers" and I am using the noise_table function to give the values of phase-noise for discrete points in frequency.
My problem is that I would like to have a piecewise-linear interpolation of the points in the log-log plot as it is usual in phase-noise spectrum description (dBc/Hz vs log(freq)). Is there anyone knowing how to do that?
Thanks!
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Geoffrey_Coram
Senior Fellow
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Posts: 1999
Massachusetts, USA
Re: noise_table function
Reply #1 -
Feb 12
th
, 2008, 6:40am
Your request has already been brought up for the next version of the V-AMS standard.
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Christoph
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Posts: 3
Germany
Re: noise_table function
Reply #2 -
Feb 29
th
, 2008, 6:50am
Hi!
I was trying to do a similar thing in a Verilog-AMS model for spectre. Unfortunately spectre did not seem to support arrays. Did someone managed to create an array of (constant) real values?
Kind regards,
Christoph
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Geoffrey_Coram
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Posts: 1999
Massachusetts, USA
Re: noise_table function
Reply #3 -
Feb 29
th
, 2008, 12:57pm
Are you using a current version of Spectre? I'm pretty sure it does support arrays.
I have this in one of my modules ...
I(a,b) <+ noise_table({10.0,5.0,100.0,6.0,1000.0,10.0,1.0G,6.0},"tabnoi");
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Marq Kole
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Hmmm. That's
weird...
Posts: 122
Eindhoven, The Netherlands
Re: noise_table function
Reply #4 -
Mar 19
th
, 2008, 2:29pm
Currently Spectre still does not support array parameters and it will give an error when trying to initialize such a parameter with an array literal.
You will have to create a real array variable and assign it a value in an initial_step event if you want to use it that way.
Cheers,
Marq
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Geoffrey_Coram
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Posts: 1999
Massachusetts, USA
Re: noise_table function
Reply #5 -
Mar 20
th
, 2008, 6:14am
Marq -
I recall some problem with using array variables for noise_table; are you sure spectre supports this?
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neoflash
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Mixed-Signal
Designer
Posts: 397
Re: noise_table function
Reply #6 -
Oct 29
th
, 2009, 10:10am
Geoffrey_Coram wrote
on Feb 29
th
, 2008, 12:57pm:
Are you using a current version of Spectre? I'm pretty sure it does support arrays.
I have this in one of my modules ...
I(a,b) <+ noise_table({10.0,5.0,100.0,6.0,1000.0,10.0,1.0G,6.0},"tabnoi");
Hi, Geoffery:
Is there any way that we put the table data in a file, then call it in the noise_table(function)?
I'm using verilogA in hspice.
Regards,
Neo
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Geoffrey_Coram
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Posts: 1999
Massachusetts, USA
Re: noise_table function
Reply #7 -
Nov 2
nd
, 2009, 5:33am
Verilog-AMS LRM 2.3 added support for using a filename input for noise_table. I don't know how many simulators have implemented this as yet.
Quote:
When the input is a file name, the indicated file will contain the frequency / power pairs. The file name argument shall be constant and will be either a string literal or a string parameter. Each frequency / power pair shall be separated by a newline and the numbers in the pair shall be separated by one or more spaces or tabs. To increase the readability of the data file, comments may be inserted before or after any frequency / power pair. Comments begin with ‘#’ and end with a newline. The input file shall be in text format only and the numbers shall be real or integer.
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neoflash
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Posts: 397
Re: noise_table function
Reply #8 -
Nov 2
nd
, 2009, 6:02am
Geoffrey_Coram wrote
on Nov 2
nd
, 2009, 5:33am:
Verilog-AMS LRM 2.3 added support for using a filename input for noise_table. I don't know how many simulators have implemented this as yet.
Quote:
When the input is a file name, the indicated file will contain the frequency / power pairs. The file name argument shall be constant and will be either a string literal or a string parameter. Each frequency / power pair shall be separated by a newline and the numbers in the pair shall be separated by one or more spaces or tabs. To increase the readability of the data file, comments may be inserted before or after any frequency / power pair. Comments begin with ‘#’ and end with a newline. The input file shall be in text format only and the numbers shall be real or integer.
I think that's why I failed to do so in hspice. HSPICE doesn't support AMS extension yet.
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