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ac voltage in SAW device

Posted Dec 15, 2011, 10:28 p.m. EST Version 3.5a 9 Replies

Amalina Ramli
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Hi
i'm creating saw resonator in 3.5. I want to apply ac voltage on my electrodes as a harmonic perturbation to the DC bias. Can u assists me how to do that?
9 Replies Last Post Mar 2, 2012, 5:36 a.m. EST
Edgar Kaiser
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Posted: 1 decade ago Dec 16, 2011, 3:48 a.m. EST
Hi Amalina,

I think you have two options:

1. If your model is all linear you can run a static analysis using the DC voltage and a harmonic analysis using the RF excitation and add the results. This must probably be done externally in matlab.

2. You can run a transient analysis with an explicit excitation function like V = Vdc + Vac*sin(wt), w being the angular frequency. You must make sure that it runs long enough to account for the potentially high quality factors of an SAW device. This also works in a non-linear model but consumes much more time. The time steps must resolve the waveform.

Cheers
Edgar
Hi Amalina, I think you have two options: 1. If your model is all linear you can run a static analysis using the DC voltage and a harmonic analysis using the RF excitation and add the results. This must probably be done externally in matlab. 2. You can run a transient analysis with an explicit excitation function like V = Vdc + Vac*sin(wt), w being the angular frequency. You must make sure that it runs long enough to account for the potentially high quality factors of an SAW device. This also works in a non-linear model but consumes much more time. The time steps must resolve the waveform. Cheers Edgar
Sahar Simyari
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Posted: 1 decade ago Jan 30, 2012, 9:01 a.m. EST
hi all,
I want to create a RF filter with comsol 4.1 but I have some problems about applying ac voltage,i don't know how do that,my device have some electrodes and reflectors on piezoelectric layer i created that and i just applied dc voltage to diffrent electrode and get eigenfrequencies so i have some questions:-if i select piezoelectric interface or acoustic interface?-how can i apply sin voltage with high frequency to my electrode sothat i can see deformed this voltage at the end of device?(because my device is a rf filter)
please help me because i'm realy new at comsol
hi all, I want to create a RF filter with comsol 4.1 but I have some problems about applying ac voltage,i don't know how do that,my device have some electrodes and reflectors on piezoelectric layer i created that and i just applied dc voltage to diffrent electrode and get eigenfrequencies so i have some questions:-if i select piezoelectric interface or acoustic interface?-how can i apply sin voltage with high frequency to my electrode sothat i can see deformed this voltage at the end of device?(because my device is a rf filter) please help me because i'm realy new at comsol
Amalina Ramli
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Posted: 1 decade ago Feb 12, 2012, 9:22 p.m. EST
Thank you for your reply Edgar...

I've try the second option. However i dont know where to put the explicit excitation function during transient analysis..Can you assist me ?
Thankyou
Thank you for your reply Edgar... I've try the second option. However i dont know where to put the explicit excitation function during transient analysis..Can you assist me ? Thankyou
Edgar Kaiser
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Posted: 1 decade ago Feb 13, 2012, 4:19 a.m. EST
Amalina,

that depends on which way you want to excite the model. You can apply the function to a boundary or to a port.

Make sure the time dependent solver resolves the sine wave.

Cheers
Edgar
Amalina, that depends on which way you want to excite the model. You can apply the function to a boundary or to a port. Make sure the time dependent solver resolves the sine wave. Cheers Edgar
Amalina Ramli
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Posted: 1 decade ago Feb 16, 2012, 10:09 p.m. EST
Thankyou so much Edgar..


I just got it...=)
Thankyou so much Edgar.. I just got it...=)
Amalina Ramli
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Posted: 1 decade ago Mar 1, 2012, 9:00 p.m. EST
Hi edgar..

How to do fourier transform in 3.5 using transient analysis result?For your information i need to get the graph Voltge vs Frequency for s21 plot.The transient analysis produce Voltage vs Time..Is this should be used in Matlab?Can u assist me?

Thank you for your kindness
Hi edgar.. How to do fourier transform in 3.5 using transient analysis result?For your information i need to get the graph Voltge vs Frequency for s21 plot.The transient analysis produce Voltage vs Time..Is this should be used in Matlab?Can u assist me? Thank you for your kindness
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 2, 2012, 1:42 a.m. EST
Hi

I believe the FFT appeared only in v4 for table values (I might be wrong). You have anycase matlab to further process your data

--
Good luck
Ivar
Hi I believe the FFT appeared only in v4 for table values (I might be wrong). You have anycase matlab to further process your data -- Good luck Ivar
Amalina Ramli
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Posted: 1 decade ago Mar 2, 2012, 5:17 a.m. EST
Thanks Ivar..

One more things sir ..what is the different between using Domain plot and Cross section plot in transient analysis..I am a bit confusing since thy are producing different result(voltage vs time) . Which plot should i take for my result?For your information, my design has been drawn in 2D plot.
Thanks Ivar.. One more things sir ..what is the different between using Domain plot and Cross section plot in transient analysis..I am a bit confusing since thy are producing different result(voltage vs time) . Which plot should i take for my result?For your information, my design has been drawn in 2D plot.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 2, 2012, 5:36 a.m. EST
Hi

could it be the 2D depth d ? that is different from 1[m] and that is counted in one and not in the other. Are you sure the results have the same units ?
Normally the same variable in different plots give the same results (appart sometimes in 2D-axi when one forget to integrate over the loop length with the 2*pi*r, but this shows up in the units)

--
Good luck
Ivar
Hi could it be the 2D depth d ? that is different from 1[m] and that is counted in one and not in the other. Are you sure the results have the same units ? Normally the same variable in different plots give the same results (appart sometimes in 2D-axi when one forget to integrate over the loop length with the 2*pi*r, but this shows up in the units) -- Good luck Ivar

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