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cybq

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SAW filter insert loss
Jul 03^rd, 2006, 1:10am

Hi friends,
A problem was found that the insert loss of SAW filter synthesized by ADS is not agreed with the specified value if the input and load impedance are different. Isn't a bug in ADS? There is several dB difference.

That is to the insert loss ( measured by the output of SAW filter load divided by the voltage when source and load are direct conected) is agreed with the specified value when in/out impedance are the same.

But, when I simulated the S parameters, setting up the Term1 and Term2 are the source and load impedances respectively, I get the result that the S21 is the same as the specified value. Why?

Thanks in advance.

cybq

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pancho_hideboo

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Re: SAW filter insert loss
Reply #1 - Jul 3^rd, 2006, 8:23am

Hi.

What do you mean by "SAW filter synthesized by ADS" ?
You synthesized the equivalent LCR circuits from measured S-parameter of SAW filter ?

S-parameters are defined by port impedances.
So it is natural that S21 is changed when you use different port impedances from vaules in S-parameter measurement.

ADS have following function.

stos()
Changes the normalizing impedance of a scattering matrix
Syntax
y = stos(S, zRef, zNew, zy)

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cybq

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Re: SAW filter insert loss
Reply #2 - Jul 3^rd, 2006, 6:29pm

I have tried to synthesized the SAW filter with LCR, but failed. Because it is not possible to synthesie the SAW high selection characteristics with electronical components, instead of using a SAW (which uses the piezoelectric effect to turn the input signal into vibrations that are turned back into electrical signals in the desired frequency range).

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