Activity for leroy105
Type | On... | Excerpt | Status | Date |
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Comment | Post #281226 |
High Q passives -- no real improvement. Within the margin of error in our reading in a chamber. (more) |
— | about 3 years ago |
Comment | Post #281274 |
Yep... There's an economic reason or semiconductor reason first and then the standard gets drafted... (more) |
— | about 3 years ago |
Comment | Post #281246 |
Yeah for sure in LiPos. If we a had semiconductor designer guy here, I'm sure there's some insight at that level as well. OP got dismissed as this being a stupid question and in reality it's really probably preety deep. It just happens to not be a solve an analog circuit type inquiry. (more) |
— | about 3 years ago |
Comment | Post #280791 |
Actually I think this is a really good question. It's kind of more historical though I guess (and I don't know the answer either). (more) |
— | about 3 years ago |
Comment | Post #281021 |
I'm all for pulling SE information off a for-profit-company's services (and I've learned a heck of lot on EE SE), but this post kind of proves the difficulties in moderation and the needs to include folks. I found EE SE super dogmatic; "don't discuss design"/"design comments too much, you are banis... (more) |
— | about 3 years ago |
Comment | Post #281165 |
C1 - 3.6pF, L1, 10nH, C2, 3.6pF -- was what the calculator I used said [really similar to your values]. I tweaked the capacitance and inductance bit in two other test runs and in both cases +0.4dB (in the wrong direction!). You could make a week long science experiment and do a bunch of iteration t... (more) |
— | about 3 years ago |
Comment | Post #281226 |
@ Andy aka - I'm ordering some high Q components to see if we can get that 12dB drop to increase a little more. I have some folders of some rando. low grade passives for tuning work. I did a few passes tweaking some values and the filter response is still not exactly what a calculator would say, bu... (more) |
— | about 3 years ago |
Comment | Post #281165 |
@Andy, I didn't get a perfect response from the filter calculator I used. Do you think that is most likely due to a not-perfect 50 ohm match on the board, so the filter calculations are off a bit? (more) |
— | about 3 years ago |
Comment | Post #281165 |
@Lundin - I've worked on a number of LoRa systems we have seen all kinds of over-limit harmonics in the past (never been tasked to filter one). LoRa transmit is usually 20+dBm + antenna gain, so you can get some pretty honking regulatory readings on the spurious emissions side. (more) |
— | about 3 years ago |
Comment | Post #281165 |
@Andy Aka -- I got the hardware in hand and implemented a Chebyshev using the PI network in front of the reference stack of matching components and filtering. 0.2dBm drop at the fundamental of 915MHz & 12 dB drop at the most severe 7GHz harmonic. That's going to be darn close to passing FCC limits... (more) |
— | about 3 years ago |
Comment | Post #281083 |
We care about the harmonics coming out of the product because they are over the FCC limits! There's no antenna switch, it's a reference design LoRa radio (there's a lump of passive components to tune to 50 ohms out of the chip, and then I've got an empty pi network now to fix these harmonics). I'... (more) |
— | about 3 years ago |
Comment | Post #279886 |
I do lot of EMC testing, and agree with all these rules of thumbs, but specifically we are targetting the shield. The GND'ing is pretty much locked in place. I know much blood has spilt on the shield to GND plane discussion. (Also, bypass caps for ESD is a real thing...). We have a series 0402 fo... (more) |
— | over 3 years ago |