MMG3006

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MMG3006

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brokencircle80
Contributor I

I'm trying to design a matching network for the MMG3006NT1 and am a bit confused by a possible disagreement between the datasheet's reference design and the S-parameters data file available on NXP's website.

Look at the input matching solution given on the data sheet for 900MHz.  If you assume the source is 50Ohm and compute the impedance at the output of the given matching network, it appears the reference design transforms 50Ohm to about 4.0 - j14Ohm.

On the other hand, the S-parameter file I downloaded for the MMG3006 gives a magnitude and phase of S11 at 900MHz of |S11| = 0.95, arg(S11) = 177deg.  This is a complex form this reflection coefficient is -0.94 + j0.05, which works out to an impedance of 1.38 + j1.35.

What am I missing here?  Are the S-parameters in that file de-embedded? I just cannot see how one gets from the given S-parameters to the given matching solution and until I can see the linkage its very difficult to use the S-parameters to optimize for different frequencies.

Thanks!

Mike

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LPP
NXP TechSupport
NXP TechSupport

The datasheet provides design performance measured on the reference board. S-parameters are also real data and we can confirm validity.

In your case, the matching network does not fit parameters of the real board and thus you get a different result.

It is a microwave design and it's behavior highly depends on the parasitic parameters of the components. The simulation must provide:

- substrate properties and the traces layout(length and width)
- component properties (parasitic parameters)
- simultaneous conjugate matching at both input and output since the device is not an unilateral amplifier

Please, I replicated two versions 900MHz design layout in ADS. The first version used S-parameter models of the capacitors from AVX. The second version used ideal capacitors. Please see the picture. The S11 represents the return loss of first version and S33 of the second. You can see that the results are very different and the more accurate version provides good matching at 900MHz.


Have a great day,
Pavel

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