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Simulators >> Circuit Simulators >> question about .meas in hspice
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Message started by daisy on Jul 23^rd, 2008, 7:22pm

Title: question about .meas in hspice
Post by daisy on Jul 23^rd, 2008, 7:22pm

Hi!
I'm simulating a low pass filter and I want to see the frequency point when the output value decreases 3dB.I wrote the statement like this:

.meas ac gainmax max vdb(vout)
.meas ac band find f when vdb(vout)='gainmax-3'

however,there is a warning in the .lis file,saying that the band is not defined.So how should I describe the statement?
Thanks a lot!

daisy

Title: Re: question about .meas in hspice
Post by ywguo on Jul 24^th, 2008, 1:07am

Hi Daisy,

It seems that the simulator does not identify what f is. When I try your .measure card. It report the following warning message in the listing file.

**warning** could not identify variable type f

I simulate successfully with the following cards.

Code:

.meas ac gainmax max vdb(vout)
.meas ac f3db when vdb(vout)='gainmax-3'

Please note that time or frequency are independent variables in a HSPICE simulator. However, we have never quote a variable like frequency or time in SPICE.

The .measure syntax is
.measure <DC|TRAN|AC> result when out_var=val
where result is time for TRAN and frequency for AC. They are independent variables.

Best regards,
Yawei

Title: Re: question about .meas in hspice
Post by daisy on Jul 24^th, 2008, 3:11am

Hi! I have simulated successfully with your cards.
Thank you for your help!

daisy

ywguo wrote on Jul 24^th, 2008, 1:07am:

.meas ac gainmax max vdb(vout)
.meas ac f3db when vdb(vout)='gainmax-3'