CC2652R: LAUNCHXL-CC2652R1 Rf Line impedance confusion

Dear Ti,

I purchased the LaunchXL-CC2652R1 development board.

• I routinely measure the impedance of some RF Lines without matching components,it may be 30Ω-j*14.

• I double check the cross-section from designfile(WCS037B), RF line Width is 0.5mm, the gap to the ground is 0.15mm ，reference layer is second and the Height is 0.175mm.

I want to confirm why the impedance control of our RF Line is such a value.

I look forward to your reply.

Thanks~

BR/Zhemin

Cherry Zhou：

Hi we have received you question and feedback to the engineer, if there is any new info I will update to you asap. Thanks!

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Albin Zhang：

CC13xx/CC26xx Hardware Configuration and PCB Design Considerations (Rev. E)

RF PCB Simulation Cookbook

Hi, 

You can check upper two doc to find related information. 

9 Optimum Load Impedance 

BR. Albin

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xue zhemin：

Hi Albin,

Thanks for your reply.

PCB Design guide shows a good impedance design advice. I understand that the chip's load impedance is for better performance based on the result of load-pull.

I mean why is the impedance of the RF transmission line after the matching network not designed at 50 ohms . Because the line Width is 0.5mm, the gap to the ground is 0.15mm ，reference layer is second and the height is 0.175mm from cross-sectioin. Simulations and tests show this is not a 50Ω transmission line.

Maybe I am not clear about TI's design point about this，could you tell me for the reason?

Thanks~

 

BR//Zhemin

,

Albin Zhang：

It should be around 50ohm. 

show me the simulation line model and parameters you selected. 

BR. Albin

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xue zhemin：

Please refer to the results of the following pictures.

I'm using the CPWG transmission line model, the results show that the impedance exceeds the range of 50 ohms ±10% with or without solder. 

Please let me know if I have any problems with my understanding.

Thanks~

BR/Zhemin

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Albin Zhang：

Good finding. Let me check with designer and get back you soon. 

if you check the LaunchPad of CC1352P, it uses W=0.32 and D=0.65. it is close to 50ohm 

BR. Albin

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Albin Zhang：

Hi Zhemin, 

Agree that this is incorrect.

For LP's stackup, you can use below options for 50ohm. 

First Option: 300 um (W) & 500 um (G) (similar with CC1352P's launchPad)

Second Option: 250 um (W) & 150 um (G)

BR. Albin

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xue zhemin：

Our pre-plan was to use cc2652R and BOOSTXL for AOA  design. Could u please tell me how much AOA will be affected by using this development board?

 Maybe I can continue to design with my current development board?

Or will TI improve the Launch board? I can re-order it.

,

Albin Zhang：

This will not impact the time/Phase domain coefficient. More likely Amplitude a little bit only as the line is short. I don't think it will impact the your AoA implementation. you can evaluate it with current BP+LP

BR. Albin

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xue zhemin：

Thanks for your reply.

Have a nice day!