CC1200 Spectrum?

MikeH

Other Parts Discussed in Thread: CC1200

Gents,

Below is a snapshot of the output of the CC1200 when configured for CW. Is this correct? Why are there sidebands at +/-500kHz?

over 11 years ago

0 TER over 11 years ago

TI__Guru**** 317180 points

Do you get the same spectrum if you use SmartRF Studio? I don't have access to a spectrum this week but the spectrum does not look like correct. It should be a small spur (~-60 dBm) at 920 MHz (multiple of the xosc frequency) but no other spurs should be visible.

0 CHS over 11 years ago in reply to TER

TI__Mastermind 18780 points

What hardware are you using? If it is your own HW, have you tried a CC1200 EM? Do you see the same? If it is your HW, could you post the schematic and layout for us to look at? How do you power the board? As TER said, we do not have instruments this week so we appreciate that you can help us debugging.

0 MikeH over 11 years ago in reply to CHS

Guru 15580 points

Sorry guys. I must have had something set incorrectly (i.e. modulation). Here's the correct CW spectrum shot. Spurs are at ~-65dbc @+/- 18.5MHz from fo. (TER did you mean ~-60dbm or dbc?).

To answer your questions, it is my own HW and layout. But I did carefully follow the ref design. It appears to be working fairly well now that it is configured properly.

0 TER over 11 years ago in reply to MikeH

TI__Guru**** 317180 points

That looks correct. To be honest I don't remember the exact level the spur is on.

0 Iurii Voitenko over 10 years ago in reply to MikeH

Prodigy 120 points

Hello Mike,

can you, please, describe what exactly you did to get rid of those sidebands. Seems I have the same problem...

Thanks in advance,

Iurii

0 TER over 10 years ago in reply to Iurii Voitenko

TI__Guru**** 317180 points

Lurii: Please post a plot of your spectrum and the settings you are using.

0 Iurii Voitenko over 10 years ago in reply to TER

Prodigy 120 points

Hello TER,

Well, seems like I solved one problem creating another... Now, the signal from CC1200 is very weak.

Check out, the spectrum.

Note, it's official TI eval kit in 100kbps , continuous TX mode. Settings come from SmartRFstudio. No changes.

Any suggestions, how to get back to +14 dBm ?

BR,

Iurii

0 TER over 10 years ago in reply to Iurii Voitenko

TI__Guru**** 317180 points

Either a software or hardware problem.
- Check that the PA_CFG2 = 0x7F
- From the plot it could look like you have lost a component on the board. I have only seen plots like this when a connection has been broken somewhere.

0 Iurii Voitenko over 10 years ago in reply to TER

Prodigy 120 points

Well, take a look at the testbed.

It's the official TI kit, no components missed. PA_CFG1 = 0x7F.

Output power -43 dBm....

How could that be? I 'd be happy, if someone could help to resolve this mistery...

Cable losses are around 0.1 dB, very well known on other devices.

0 TER over 10 years ago in reply to Iurii Voitenko

TI__Guru**** 317180 points

Have you checked that the SMA is selected and not the PCB antenna? It should be default but make sure the PCB antenna is not used.

0 MikeH over 10 years ago in reply to TER

Guru 15580 points

Also, don't let the "RP"-SMA bug bite you. An air gap at 2.4GHz makes a pretty good attenuator....:) (Although, I've never done that....:)

0 Iurii Voitenko over 10 years ago in reply to MikeH

Prodigy 120 points

Hello Mike,

I checked RP-SMA, as you mentioned. The adapter is correct and plugged properly.

I am wondering, could that be a register setup?

Can you, please, share your settings while having +14 dBm output power as shown on your plot?

This might help a lot.

Thanks in advance,

Iurii

0 TER over 10 years ago in reply to TER

TI__Guru**** 317180 points

If you use cont. Tx unmodulated from SmartRF Studio it's not a register issue. Is it this mode you are using today?

0 Iurii Voitenko over 10 years ago in reply to TER

Prodigy 120 points

Hello TER,

I have figured out what was going on. Apparently, I plugged wrong RP-SMA adapter. -30 dB attenuator actually...

But they all look the same)))

Now the spectrum is just perfect +13,3 dBm.

Thanks to all of you guys for help!

Br,

Iurii

0 MikeH over 10 years ago in reply to Iurii Voitenko

Guru 15580 points

Luril,

I haven't used this in many months. Attached is the last settings I used. Not sure if this will help.

cc1200_reg_settings.zip

Sub-1 GHz

Sub-1 GHz forum

CC1200 Spectrum?