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Nonlinear operation of small signal noise in Verilog-A (Read 5630 times)
cheap_salary
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Nonlinear operation of small signal noise in Verilog-A
Oct 15th, 2015, 8:33am
 
See LISTING-8 at page-22 in the following.
http://www.designers-guide.org/Analysis/PLLnoise.pdf

Phase-domain fractional-N divider is modeled like following.
Code:
Theta(out) <+ Theta(in) / ( ratio + noise_table(...) ); 



I can easily understand this expression if it is for Transient Noise Analysis.
However this expression is for small signal noise analysis.

How is this expression treated in small signal noise analysis ?
I think this is Nonlinear operation of small signal noise.

Synopsys HSPICE and Cadence Spectre gives fairly different noise result.

Can it be valid such Nonlinear operation for small signal noise analysis ?
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Ken Kundert
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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #1 - Oct 18th, 2015, 9:00am
 
The model in my paper is wrong. The noise_table function should not be in the denominator. It should be simply added to the output.

Sorry about that.

-Ken
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cheap_salary
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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #2 - Oct 19th, 2015, 8:07am
 
Thanks for answering.

Another notice.
OVI Verilog-A 1.0 uses [] to specify arrays but OVI Verilog-AMS 2.0 uses {}.
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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #3 - Oct 21st, 2015, 11:17pm
 
order has to be 2*order because noise value in noise_table() is phase_noise**2 not phase_noise.
Quote:
Theta(out) <+ Theta(in) / ratio;
Theta(out) <+ noise_table({0,    n,
                          bw,   n,
                          fmax, n * pow((fmax/bw), 2*order)},
                         "dsn") );

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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #4 - Oct 23rd, 2015, 1:45pm
 
Thanks for your suggestions. I have updated papers to incorporate them.

-Ken
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cheap_salary
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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #5 - Oct 24th, 2015, 2:31am
 
Since the following is defined in this module.
Code:
parameter real fc = 0 from [0:inf); // flicker noise corner frequency (Hz) 



I think noise implementation should be like following.  
Quote:
Theta(out) <+ Theta(in) / ratio;
Theta(out) <+ flicker_noise(n*fc, 1, "fpn");
Theta(out) <+ noise_table({
                           0, n,
                          bw, n,
                        fmax, n*pow((fmax/bw), 2*order)
                          }, "dsn"));
or
Quote:
Theta(out) <+ Theta(in) / ratio;
Theta(out) <+ flicker_noise(n*fc, 1, "fpn");
Theta(out) <+ white_noise(n, "wpn")
Theta(out) <+ noise_table({
                          bw, 0,
                        fmax, n*pow((fmax/bw), 2*order)
                          }, "dsn"));

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Re: Nonlinear operation of small signal noise in Verilog-A
Reply #6 - Feb 6th, 2016, 1:34am
 
cheap_salary wrote on Oct 21st, 2015, 11:17pm:
order has to be 2*order because noise value in noise_table() is phase_noise**2 not phase_noise.
Quote:
Theta(out) <+ Theta(in) / ratio;
Theta(out) <+ noise_table({0,    n,
                          bw,   n,
                          fmax, n * pow((fmax/bw), 2*order)},
                         "dsn") );

It has to be 2*(order-1), since it is phase signal.

For example, frequency charcteristics of MASH-111(order=3) is +40dB/dec for phase noise not +60dB/dec.
On the other hand, +60dB/dec for frequency noise.

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