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Simulators >> RF Simulators >> THD calculation
https://designers-guide.org/forum/YaBB.pl?num=1237382945

Message started by david on Mar 18^th, 2009, 6:29am

Title: THD calculation
Post by david on Mar 18^th, 2009, 6:29am

hi
Please tell me how to get THD values using spectre (cadence simulator).......I am using calculator as shown in attachment. Please let me know what mistake i am doing..........than you!!!

Title: Re: THD calculation
Post by pancho_hideboo on Mar 18^th, 2009, 6:34am

What is different between this question and the following ?
http://www.designers-guide.org/Forum/YaBB.pl?num=1237382023/0#0

I don't use thd() function in calculator.
I wrote method of evaluation of THD in the following as Ocean Script.
http://www.designers-guide.org/Forum/YaBB.pl?num=1237208147/1#1

What is "IIM3" ?

Did you read answers to your questions surely ?
http://www.designers-guide.org/Forum/YaBB.pl?num=1237208368/1#1
http://www.designers-guide.org/Forum/YaBB.pl?num=1237293628/1#1

Read documentations.
Your usage of thd() is wrong.

david wrote on Mar 18^th, 2009, 6:29am:

Please tell me how to get THD values using spectre (cadence simulator).......I am using calculator as shown in attachment.
Please let me know what mistake i am doing..........than you!!!

Enter ocnHelp 'thd in CIW. Then read messages.

Quote:

thd( o_waveform n_from n_to x_num ) => o_waveform/n_thdValue/nil
Description
Computes the absolute value of the total harmonic distortion of the input waveform.
The accuracy of this function depends on how you set certain simulator options and analysis parameters.
The computation uses the dft command and takes the same arguments.
Assume the dft function returns the complex components f0, f1…
(where f0 is the DC component, f1 is the component at frequency 1/(to - from)) then the total harmonic distortion is computed as
Arguments
o_waveform Waveformobject representing simulation results that can be displayed as a series of points on a grid.
(A waveform object identifier looks like this: drwave:XXXXX.)
n_from Starting value for the computation.
n_to Ending value for the computation
x_num Number of timepoints. If x_num is not a power of 2, it is forced to be the next higher power of 2.
Value Returned
o_waveform Returns a waveform representing the absolute value of the total harmonic distortion if the input argument is a family of waveforms.
n_thdValue Returns the absolute value of the total harmonic distortion of the input waveform.
nil Returns nil and an error message otherwise.
Example
plot( thd( v( "/net8" ) 10u 20m 64 "rectangular" ) )
Computes the absolute value of the discrete Fourier transform, fast Fourier transform, of the waveform representing the voltage of "/net8".
The computation is done from 10u to 20m with 64 timepoints.
The resulting waveform is plotted.

Title: Re: THD calculation
Post by david on Mar 18^th, 2009, 11:58am

I dont understand ocean script.what is this and how to write command in that?? i am familiar with using only the spectre gui.
in my previous post it was IM3 which was mistakenly written as IIM3.
Please help me.

Title: Re: THD calculation
Post by david on Mar 18^th, 2009, 12:12pm

please tell what is this CIW?

Title: Re: THD calculation
Post by pancho_hideboo on Mar 18^th, 2009, 4:45pm

david wrote on Mar 17^th, 2009, 5:40am:

I am a new bee to cadence tools.

If you are new to only Cadence Tool, what vendor's tool are you familiar with ?

Did you follow oermens's advice surely ?
http://www.designers-guide.org/Forum/YaBB.pl?num=1237293628/1#1

I think you don't read documentations at all.
Read documentations surely.

david wrote on Mar 18^th, 2009, 11:58am:

I dont understand ocean script.what is this and how to write command in that??

OCEAN(Open Command Environment for ANalysis)
Read documentations surely.

david wrote on Mar 18^th, 2009, 12:12pm:

please tell what is this CIW?

CIW(Command Interpreter Window)
Read documentations surely.

Anyway read documentations surely.

Title: Re: THD calculation
Post by david on Mar 18^th, 2009, 11:36pm

hii
Actually I am new to analog design and also for vlsi cad tools. I started designing using Cadence .This is the first tool I am using. I need guidance how to proceed
I started reading documents from cdnshelp. But due to time constraint I am not able to quickly find answers to all my queries.
Please guide.

Title: Re: THD calculation
Post by pancho_hideboo on Mar 19^th, 2009, 1:40am

david wrote on Mar 18^th, 2009, 11:36pm:

Actually I am new to analog design and also for vlsi cad tools. I started designing using Cadence .This is the first tool I am using.

From first, I've thought you are new to everything which is not restricted to EDA Tools.
If we read your sentences where almost all terminologies are wrong or improper, it is very obvious that you are new to everything.

david wrote on Mar 18^th, 2009, 11:36pm:

I started reading documents from cdnshelp. But due to time constraint I am not able to quickly find answers to all my queries.
Please guide.

There is no Short-Cut.
Read, Read and Read documentations with cutting down your sleeping time.

If you are lack of ability of understanding documentatios quickly, attend trainings provided by Cadence which are charged not free.

Title: Re: THD calculation
Post by david on Mar 19^th, 2009, 9:02am

thank you for your reply . I started reading cadence help documents. now i am able to calculate THD values. I know there are no shortcuts but actualy I didnt know how to use cadence help documents that is why i was wondering about tool usage and hence asked such questions. anyways thanks again for your replies