CC2652R7: CC2652R7

Hi Ryan

Thank you. But we are not giving any bias. It is just RF_ P & RF_N connected to a Balun transformer from Murata and connected to antenna.What is the use of this bias in CC2652R7?

In datasheet of Murata Balun it is just mentioned that the balance port impedance as Conjugate match to TI CC26xx.

Regards

Sreejith

Hi Sreejith,

Because you're using an integrated passive component, you're very likely using internal bias. If you're using the Murata transformer balun that we recommend (LFB182G45BG5D920), it does not have an external bias option and it should run in differential mode. So, the 42 + j21 target load impedance is the correct one for this configuration. 

Best,

Nate

Hi Nate

Thanks for the reply.

1. I understand that with internal bias, in differential mode, the IC RF o/p impedance is 42-j21 ohm and if we are using Single ended configuration each RF o/p pin will have 38-j5 ohm. Conjugate impedance I have considered. Please confirm.

2. Also, please confirm if this same impedance we can consider in Tx (For PA) and Rx (For LNA) mode.

Regards

Sreejith

Hi Sreejith,

1. I understand that with internal bias, in differential mode, the IC RF o/p impedance is 42-j21 ohm and if we are using Single ended configuration each RF o/p pin will have 38-j5 ohm. Conjugate impedance I have considered. Please confirm.

This is accurate at 5 dBm. As is stated in section 9 of SWRA640, since our device is inherently non-linear, the output impedance will be a function of input power as well as frequency. We optimize our components for just a couple of the output powers (5 and 0 dBm I believe).

2. Also, please confirm if this same impedance we can consider in Tx (For PA) and Rx (For LNA) mode.

This is accurate. You just need to match the Tx impedance. The Rx impedance is designed to adjust for the expected TX impedance match.

Best,

Nate

Hi Nate

Thanks. I got a better output RL when I used Differential port impedance as 42+j21 connected to Balun S3P file in CST simulation connected to antenna. No matching network used. It is degrading when I assign differential port impedance as 42-j21. Now I am a little bit confused. Which is the correct value to assign Port for S3P file simulation. Can you help?

Regards

Sreejith

Hi Sreejith,

I've asked internally and confirmed that the IC output impedance would be the 42 - j21. Your simulation may give better results under different conditions. I can't really speak to whether the balun is simply also a good match for an IC whose output impedance is 42 + j21. It may simply be coincidental, or there may be an issue with the simulation. I don't know.

For an accurate simulation, you'll need to confirm that your .s3p file was taken under similar conditions (5 dBm output power, short and straight trace lengths, carrier wave inputs...etc). You may find that with a different PCB, or different output power, you can achieve better results with a different matching impedance. We simply provide the matching impedance that works for our PCB under our conditions. If you follow our reference design (use similar trace widths, board stack-up, component values...etc), you should see similar results to those that we publish in the datasheet. If you chose to differ from our reference design greatly, you may find that you need to alter the matching accordingly.

Best,

Nate