Other Parts Discussed in Thread: CC1190, , LMR23610
This post is in support of one of my customers.
Here is the background information from the customer:
I have been trying to get our wireless network Hub through FCC and we have run into some stumbling blocks. I will be receiving a preliminary report Tuesday detailing the issues found. I would like to know if TI would be willing to help me resolve these issues so we can get this product into production? If so, I will forward the report to you. I’m looking for suggestions that I can implement and test. Also, please let me know what additional information you will need, i.e., schematics, BOM, GERBERs, functional PCB assembly etc.
Some Background:
- This design is based on the CC1120 + CC1190
- The TI reference design was followed as closely as possible
- The schematic, BOM and GERBERs were reviewed by TI
- TX power is about 25 dBm (15.247)
- TX BW is < 14 kHz at -20 dBm
I have the following information from the customer:
I cannot attach them here for obvious NDA considerations.
- Hub schematic
- Hub BoM
- Hub PCB GERBR files
- Hub firmware header file (CC1120.h) with CC1120 register config values
- Pre scan report from FCC lab
- Photo of assembled PCB (RF shield for CC1190 not installed in photo but was installed for FCC test)
My comments: to the customer:
Question – The Single Board computer (SBC)… I don’t know what this is or what processor it is running with, etc. – But I noticed that in the FCC report (Fig 3, pg. 5) that there is a set of GHz spikes of RF transmission. Was the SBC in the test chamber? Was it connected to the Hub? And, if so, were any of the cables filtered (either in-line or with a ferrite blocking bead)?
The reason I ask is that the GHz spectrum would not be something I would expect from the MSP430, LMR23610, CC120 or the CC1190.
Also – it looks like the only emissions that look to violate the FCC test are in the GHz range. Correct?
The scans centered at 915MHz do indeed appear to have unwanted ~5MHz periodic spikes. Not sure where these are originating from.
Customer answer:
The SBC is an ARM based single board computer with a 4” color display, 3G cellular modem, WiFi and Bluetooth. It is a legacy device that we have been asked to repurpose for our project. We are trying to figure out how to turn off the WiFi and Bluetooth modules as we don’t need them. The SBC connects to the Hub via RS-485 (19.2kbps) and there are no filters. That being said, we were still seeing the 5MHz spikes and the 3rd and 4th harmonic when the Hub was not connected to the SBC. I will confirm with the test lab to verify.
Please contact me for the test reports and design files!
Thank you!
