CC2640R2F-Q1: RF_P and RF_N pins output impedance

Hi Torstein,

God day. My Customer reply was

He needs both to transmit and receive. He wants to do is to study the matching circuit of the antenna in ADS Keysight.

He needs to do this for two reasons:
-As a study case for my thesis
-In order to achieve a better matching by changing the default values with new ones by keeping in consideration the real layout of the PCB (considerng traces as microstrips).

So he needs to know the impedance or some other informations about the RF_P and RF_N pins in order to add them in the simulator. By using the complex conjugate of the impedance suggested in the previously linked file, I obtain an S11 value which has a minimum at 3.4GHz. I expect a minimum in 2.4GHz since this is the carrier frequency for bluetooth.

Thnks in advance.

Regards,

-Jejomar

We only provide the information found in the document you are referring to. If this is for a thesis he should do his own load-pull or source-pull measurements. Please note that the document you link to state:

"Output impedance is normally used to design complex conjugate impedance matching between amplifier and load. For linear amplifiers this is sufficient to secure optimum power transfer. This method is thus not valid for the CC13xx/CC26xx series."

The network from the RF_P/N pins towards the antenna consists of 3 parts:

- Balun: Does differential to single ended + some impedance matching

- Filter: Filter harmonics etc and impedance matching. The output of the filter is 50 ohm

- Antenna matching: from 50 ohm to the antenna impedance. 

Hence I don't really understand the question since we never go directly from RF_P/N to the antenna. 

Hi TER,

Appreciated this response. Thank you so much for the Support.

Good Afternoon,

I don't wanto to go directly from RF_P/N to the antenna. I want to study the Balun and the filter circuit with a simulator, in order to change the values of the components to keep into account the impedance of the lines of the PCB. 

To do this I used the following scheme:

Obtaining the following graph for the scattering matrix:

I expected a minimum in 2.4GHz but it is in 3.7GHZ, however I used 50Ohm as input impedance (RF_P/RF_ pins) which is not for sure the correct value. I need that value in order to insert it in this simulation and later I will do what I explained before.

Is this methodology uncorrect for the cc2640?

Thanks in advance.

" I want to study the Balun and the filter circuit with a simulator, in order to change the values of the components to keep into account the impedance of the lines of the PCB.": From the network you have shown, it looks like you use ideal components and you are not including the layout in the simulation. 

Normally a different length of the traces in your layout vs the reference design have limited impact. If you want to be sure, you should simulate the reference design layout with component models and compare with your layout. Then the impedance of the terminals have no impact since you are comparing. 

I have used ideal components as a first test in order to understand the behaviour of the matching circuit, I wanted to add the layout after this.

I will try to compare the refernce design to the mine as suggested, thank you.