@hfiennes, just a shot in the dark but I’m really wanting to design in the electrons antenna. I am wondering if you foresee any issue if the the electrons antenna is mounted as below? This will be completely be enclosed in ABS, and the PCB above the antenna would not have any copper, but the LCD scree dose lay on top of it slightly.
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It’ll definitely detune significantly, and the motor (which I assume is a big hunk of metal) is not a good thing that close either. May be worth asking taoglas about mounting on curved surfaces, I’d say putting it on the inside of the outer housing would be worthwhile as it’d keep further away from solid things.
btw, if your device will be used hand-held or body worn, you may need to do SAR testing.
@hfiennes, thanks, I’ll see what I can do to separate the antenna as much as possible.
This device will actually become a pill dispenser. In this case 99% of the time it’ll be sitting on kitchen counter top with more then 20cm of separation. The only interaction will be when the person picks it up to flip it over to dispense the pills.
In this situation, would you think SAR testing is needed?
Also do you think this would be any better config for the antenna?
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I’m afraid you likely need a professional opinion on SAR. The rules say this:
Portable device:
A portable device is defined as a transmitting device designed to be used so that the radiating structure(s) of the device is/are within 20 centimeters of the body of the user.
• Mobile device:
A mobile device is defined as a transmitting device designed to be used in other than fixed locations and to generally be used in such a way that a separation distance of at least 20 centimeters is normally maintained between the transmitter’s radiating structure(s) and the body of the user or nearby persons. In this context, the term ‘‘fixed location’’ means that the device is physically secured at one location and is not able to be easily moved to another location.
…SAR testing only applies to portable devices.
It certainly looks like sticking the antenna to the left hand surface here is furthest from everything and hence will be best performing, but there’s no substitute for actual testing.
Love having a bunch of people jumping in and contributing to this conversation. Happy to try to add clarity to any additional questions if you have them!
When you guys have time, I think it would be helpful to have the certification guide updated for the electron: https://docs.particle.io/guide/how-to-build-a-product/certification/
Right now its pretty confusing trying to reference between this page and that page, as that page, which seems more authoritative, is out of date.
Definitely and fully agreed. I will make sure it is updated as soon as the PTCRB provides us with final documentation of the certification.
Hey folks! The PTCRB certification is finally official. Head over to this page and search for “Particle”, and you should see the U260 listed on the site:
Thanks for the update. I looked at this and it lists a hardware/firmware version, does this mean any versions outside of the these the PTCRB is not applicable?
Hey there,
That is the hardware version and SW version running on the device when it was certified.
Particle has created a set of firmware rules that guide device connection behavior to ensure that it complies with PTCRB standards. Changes to the system connection rules that affect PTCRB compliance would have to be recertified, but those rules are not exposed through the user application and are generally managed by Particle’s team. General product development is unlikely to affect these connection rules.
As far as hardware goes, yes–any changes to the Electron PCB would have to be recertified for continued compliance or reregistered under a new product.
Will
I’ve got a couple of questions…
Thanks in advance for any help you can offer.
Hey @AnthonyD -- I'll do my best to answer:
We have completed all the required tests for the G350 for PTCRB, but have not yet submitted them to the PTCRB certification body. The reason for this is that the submission of these reports is an expensive process, and we've not yet had any customers who are looking to scale with the Electron 2G. The primary reason for this is longevity of coverage--if you are interested in scaling with the 2G platform, please reach out to us to arrange a time to discuss the tradeoffs between our 2G and 3G platform.
If you use an antenna with a greater gain that the included antenna, you would be required to re-complete FCC and PTCRB certification as our existing grants would no longer apply.
@hfiennes said it very well -
You would need to ensure your antenna's peak gain, in every band, is less than or equal to the Taoglas antenna's peak gain, in every band. This ensures that the combination of module + your antenna will never emit more than the tested antenna did during tests.
Hope that helps. Please let me know if you have additional questions!
Thanks for responding, @will.
Apologies, made an error in my original question. I keep mixing up the Electron versions - U260 is 3G, not 2G.
We will be using the U260.
Which part of FCC will we have to re-do if we use a higher gain antenna? We have to do FCC part 15 B anyway. I believe that FCC Part 15 C covers intentional WIFI radiators. Is there another part of FCC that covers cellular radiators or does part 15 C cover ALL intentional radiators?
On the antenna, you’re going to have to re-do at least part of PTCRB yourself - as I noted, you can re-use the cert if you have an equal or lower performance antenna than the one the certification was performed with. That doesn’t help much in the case where you need to improve performance over the tested antenna.
FCC 15C does not cover cellular devices. There are other parts (eg 22, 24, 27) which cover cellular service, depending on which frequency bands you operate on. You should consult a lab as to what re-testing is required, you may be able to adjust transmit parameters (ie reduce maximum output power) and re-use existing testing if you increase antenna gain.
hi @hfiennes, I’m wondering if you can look at this antenna to verify that it is lesser gain then the FCC approved electron antenna and can be used as a drop in replacement. I believe it is, but would like a second view.
Thanks
Looking only at GSM850 and PCS (1900) bands, and based on your posting for the Electron’s gains above, this would seem to be the case:
850: original peak gain 0.77dBi. This antenna -3.83dBi.
1900: original peak gain 2.13dBi. This antenna 1.03dBi.
So yes, it’s at least 3dB worse in the tested bands. Obviously this means performance will be worse too…
@hfiennes I’ve also come across this for SAR exclusion based on output and seperation calculation
Do you know what the maxium output power would be for the SARA-R410M-02B LTE M1?
Then we can calculate the distance needed.
Assuming the max freqency is: 2.1GHz Band 1 (2100 MHz) (based on the data sheet)
Example Below
SAR Exclusion Justification
This device FCC ID: is excluded from SAR testing by the following justification
The maximum power that the transmitter is capable of is 1.39 mW
Using the following formula from section 4.3.1 of KDB 447498 at test separation distances ≤ 50 mm
[(max. power of channel, including tune-up tolerance, mW) / (min. test separation distance, mm)] * [√f(GHz)]
Duty Cycle
11.00%
Value 1-g (mW) 10-g (mW)
0.16 152 535
"Value" is 3 , the SAR test exclusion threshold
I don’t think you are going to be able to get SAR exclusion here; I’m guessing the Cat-M/NB max output power is 23dBm in common with other modules (uBlox don’t mention it) so that’s 200mW. SAR exclusion tends to be something you can get with Bluetooth, or WiFi if you dial the power back a lot. It’s very hard to get it with cellular devices.
The other problem is with SAR is that the duty cycle is generally driven by what the radio can sustain, not how you will be using it - eg on WiFi they insist on back to back transmit, which is essentially impossible if you’re running a TCP connection to a remote server.
@hfiennes thanks, from my understanding this calcuation is for speration distance and exclusion based on the power.
IE basically all devices are excluded if the seperation distance is more the 20cm. Using the power and the calculation the separation distance can be less and still not need SAR.
So for the LTE M1 basaed on 200 mW, 1900MHz and Appendix B of 447498 General RF Exposure Guidance
if the seperation distance is more than 60mm then SAR is exluded. Is this your understanding?
I believe you also may need to take into account peak directional gain of the antenna (not TRP) - SAR testing is done in 3D space close to the device with a robot arm and a sense coil.
For real advice, you should check with a SAR lab.
Further edit: that table doesn’t really make sense. Lower frequencies need more separation at the same power level - see the original formula you posted. eg, the limit at 700MHz for 50mm separation is:
At 0.7GHz:
3.0 = (power mW) / (50 * sqrt(0.7))
power mW = 3.0 * (50 * sqrt(0.7)) = 125mW
At 2.1GHz:
3.0 = (power mW) / (50 * sqrt(2.1))
power mW = 3.0 * (50 * sqrt(2.1)) = 217mW
Conversely, minimum separation distance for +25dBm (seems like power output tolerance needs to be taken into account, most devices are +/- 2dB)… still not counting antenna gain:
3.0 = 316mW / (dist * sqrt(0.7))
dist = 316 / (3.0 * sqrt(0.7)) = 125.89mm minimum separation
More good info here: https://apps.fcc.gov/kdb/GetAttachment.html?id=f8IQgJxTTL5y0oRi0cpAuA%3D%3D&desc=447498%20D01%20General%20RF%20Exposure%20Guidance%20v06&tracking_number=20676
Some notes about duty cycles here: https://apps.fcc.gov/kdb/GetAttachment.html?id=7MrO52l3lVpGzJz3Hbb0PQ%3D%3D&desc=865664%20D02%20RF%20Exposure%20Reporting%20v01r02&tracking_number=28242
(not clear what “source-based” duty cycles are - unless this is “what the hardware is capable of”)
