CC1020 RF Output Matching problem

Trivesh Kumar

Other Parts Discussed in Thread: CC1020

Dear Sir/Madam

Technical details given about the CC 1020 (Low-Power RF Transceiver for Narrowband Systems)
given on the TI website,
http://www.ti.com/product/CC1020/technicaldocuments#doctype5

with the file name Single-Chip Low Power RF Transceiver for Narrowband Systems (Rev. F)

On page no 47 of this document, a recommended RF out put matching circuit is given (Figure. 25).

This circuit does not match to 50 Ohm impedance (Impedance of antenna) for 868 MHz, by following the components values given in Table. 21 and PA load impedance given in Table. 23.

Please, let me know if there is updated/ corrected version of this document available.

or confirm the PA load impedance at 868 MHz.

or i am not following the correct pocedure.

The procedure i followed is given below: A circuit simulator (ADS) is used here.

1. Drawn a circuit shown in Figure-25, and assigned the values as given in Table. 21 for 868 MHz.

2. replacing the RF_OUT to the impedance 15+j24 (given in Table. 23).

3. Placing a 50 Ohm terminal at the antenna end.

resultant s11 is very poor of -2.5 dB.

Help me to rectify this.

Thanks

regerds
--

Trivesh

over 9 years ago

0 TER over 9 years ago

TI__Guru**** 317180 points

Note that 15+j24 is the optimal load impedance. Looking into the network from the RF_OUT pin with a 50 ohm port for the antenna you should see 15+j24. S11 has no significance here.

0 Trivesh Kumar over 9 years ago in reply to TER

Prodigy 50 points

Looking into the network from the RF_OUT pin with a 50 ohm port for the antenna, I am seeing 19+j13 for 868 MHz. instead of 15+j24. Which one is correct, If i want to design my own matching network what RF_OUT impedance should i consider.

0 TER over 9 years ago in reply to Trivesh Kumar

TI__Guru**** 317180 points

Did you use the PCB with correct stack-up and the model for the correct Murata components when you did this sim? Note that both the PCB and real vs ideal components have an impact on the result.

0 Trivesh Kumar over 9 years ago in reply to TER

Prodigy 50 points

By using correct murata components in the simulation, I am getting 14+j13.5 instead of 14+j24. This is close but not sufficient to be considered matched.

I have incorporated the receiver circuit as well, and input impedance of receiver circuit from RF_in pin is 50+j1. Here too, RF_in impedance given data is different (54+j23).

please verify this to me.

Thanks

0 TER over 9 years ago in reply to Trivesh Kumar

TI__Guru**** 317180 points

- Have you taken the layout into account when getting these numbers?

0 Trivesh Kumar over 9 years ago in reply to TER

Prodigy 50 points

I used ADS for simulation and murata component library. I have not taken layout into account. Please suggest the way to account the layout in the simulation.

0 TER over 9 years ago in reply to Trivesh Kumar

TI__Guru**** 317180 points

In ADS, import the gerber file for the component layer. Adjust the stack-up to reflect the CC1020 EM.

For exactly how to do this you have to check the ADS documentation.

0 Trivesh Kumar over 9 years ago in reply to Trivesh Kumar

Prodigy 50 points

May i get the gerber file of matching circuit.

0 TER over 9 years ago in reply to Trivesh Kumar

TI__Guru**** 317180 points

http://www.ti.com/lit/zip/swrr025

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CC1020 RF Output Matching problem