CC1200: Noise floor at 138MHz

Did you check with a spectrum analyzer as a suggested in your previous thread? 

The noise is most likely not from CC1200. YOu can verify by doing the background noise measurement in a shielded chamber as a reference measurement. 

I did check with the spectrum analyser by setting the RBW equal to the RX filter BW as advised. However, this significantly increases the noise floor of the spectrum analyser thus masking the signal of interest.

I found the same rise in background RSSI at the office, at home and in the country side (I was doing range test). I will try and see if I can get access to a shielded chamber.

In the meantime, if you have any other suggestions, please do advise.

Thank you.

Regards.

Which antenna (link to datasheet) do you use?

I am using a custom made 138MHz whip antenna, which is reasonably well matched (see plots below).

I also have the same observations on custom board with well-matched PCB antenna.

I have placed the CC1200 custom board inside a fully enclosed TEM cell, which we believes provide adequate shielding.

The board is set up to to measure the background RSSI, and then to wirelessly transmit the result out; this is read from the RF cable to the TEM cell.

With the above, I am observes the same rise in background RSSI.

In the meantime, I am still trying to get access to a shielded chamber.

If you have any comments, please do advise.

Regards.

And this is the case with the EM you have modified with the antenna in question? I assume that a DC block has ben used? 

The results does not make too much sense at first glance. 

The test in the fully enclosed TEM cell was done with our CC1200 custom boards only.

The EM needs to be tethered to teh PC hence too large for the TEM cell.

As the EM shows similar behaviour to our CC1200 custom boards outside the TEM cell, we concludes the result will be similar.

Thank you for your continuing help with this issue.

Regards.

To be help you here I think I would need to reproduce it here but that would require that this request comes from a interesting business case. 

Please message me directly and advise on how I can intiate this request.

On a related note, I have requested technical support through our supplier Arrow Electronics, but do advise if I can do anything to help escalate this.

Thank you.

Regards.

You can send me a friend request and when I have accepted this you can send me a message with mode details. 

Done. Thanks.

Hi ,

I have a similar problem with 2FSK modulation and 900 MHz frequency band. I was wondering if you have found anything that can be helpful.  

The reason for the raised noise floor was, as expected, found to be background noise. 

Thanks, it seems that my problem is different.I have significantly bad Sensitivity and RSSI value cant get less than -75 dBm even if I measure in the isolated chamber. I think I have hardware issues but cant specifically point the noise source.