How to measure scattering parameters of power amplifier and Low Noise Amplifier of CC1190 integrated in our circuits with only one connector: the antenna conector

Dear Customer,

To measure a power amps s-parameters is much more involved than your simple questions.   Probably the best way to help you is have you contact the vendor of the Vector Network Anaylzer to demostrate using the equipment.   For Power Amps we do what is called load pull measurements.  If you try to do s-parameters by them self that is a small signal measurements which will not get you the correct impedance.     So instead you must load the amplifier at full output power which involves a device whiich optimizes the impedance load for the maixmum output power at each frequency step.    This is also dependent upon the bias the CC1190 so basically you must control the input dc bias,  step the frequency,  and optizimize the load at the desired maximum output voltage. 

Texas Instruements gives yuou the output load impedance the CC1190 would like to see.    We also have reference kits connect the CC1101 and CC190 at 868MHz and 915MHz.    We pick the values based upon maximum power,  best bias and for the most stable condition for the two devices.

For you to do this besides s-parameters you must become famiiiar with load pull and a few other detials.  Our apps team will work on this for several months with the layout and selection of components.  So it doesn't make sense why you want to spend this time and money when we provide the information for the operatiing frequenc of 868 and 915MHz.  

Rgds

Hello,

Perhaps you did not understand  me at all. We have your cc1190 evaluation kits, and they work well, and I could mesure the s-params with a vector network analyzer.

The think is that when we integrate the CC1190 in our circuits, or PCBs, the RF spectrum mask, the carrier power at the output of the CC1190 is dependent on the layout and we would make sure to check as well the s-params. We can see the gain of the power amplifier using a spectrum analyzer and veryfing the spectrum mask and the carrier power, since we know the input power to the power amplifier. However we cannot check or we do not know how to measure the LNA gain when the front end is built in our PCBs. Did you understand me now?

Thank you very much

Best regards

Albert

Alert,

Thanks for clairfication.     LNA gain is measured with S21. But you should maintain the correct input impedance.   Since the chip is matched the CC1101 it has a particular load impedance that it likes to see which is specified for the varioius frequencies.   This of course is not 50 ohms.  So you could take a balun and match the two frequencies so the input is 50 ohms to match the vector analyzer and the output would look the same impedance as the CC1101. 

We of course just monitor the TX mode and adjust the components so its maximum output power is correct.  Then assume the LNA is matched.   The values given int he data sheet are selected as the best match for both LNA and Transmit.  So by using output power  and S11 measurements for checking how close the impedance match should be sufficient.

Calibration of the Vector analyzer and the use of de-embing is how we are able to get close matches.   We also compare this to simuated values and both agree to the tolerance of the components used.

If you are changing the board thickness this will change the impedances of the traces.  We suggest using a line calculator to derive the reference designa and scale trace widths so the match stays the same.    The components and the traces (inductance) add to create a better match.  This tends to be closer than just using the standard values where the increments are spaced to far appart to achieve a VSWR match of > 1.2. 

The reference design are tuned in by using a electronic load pulls,  Vector networks,  spectrum analyzer and looking at several different parts lots.  So I suggest keeping the values close to those given by TI.

Rgds,