Hi Simon, I’d just like to clarify that these are the schematics for the boards that people will be receiving and are not a special version done for GSM development. Not sure where you got this idea from?
@andrewback You wrote it yourself about month ago: “There won’t be filters on the final boards and these should be pretty much as the one you have is.”
I have already asked in that linked topic. But for the record, please can you answer also here (there are more people watching this topic)? Thanks, I am really confused by it now…
On LimeSDR RF ports, we use broadband Baluns, however every port has additional matching network (placed in between LMS7 and Balun) for fine tuning. This means, that you can get very optimized RF performance for the frequency or band of your choice or use it for broadband matching as well (depends on component values).
@RicardasVadoklis
So what you are saying is that by default there are filters in place to optimise performance on bands which have extremely limited legal SDR uses. Although probably less convenient it sounds like this should be pushed to external filters. Otherwise bait and switch or false advertising come to mind.
LNAL - is tuned for 800 - 900 MHz (3GPP Band V). LNAH - is tuned for 1900 MHz (3GPP Band I).
LNAW - has broadband matching up to 2000 MHz. TXout1 - is tuned for 2600 MHz (3GPP Band VII) .
TXout2 - has broadband matching up to 2000 MHz.
Understood Ricardas . But what will be provided on each Rx input and Tx output on the limeSDR boards to be provided for those of us who ordered these through the crowd sourcing promotion? This is what we need specific clarification on . Please take the time to read the full thread above . We have received conflicting information from the Lime Micro team . Which is concerning.
@SimonG4ELI On which RX input is it 15 - 20 dB down compared to Airspy (in FM band)? I would have thought that on RXLNA-W it shouldn’t be that much filtered. And 5 - 7 dB noise figure isn’t that bad (Airspy has 3.5 dB noise figure if I remember right).
You will see that the so called " wideband" LNAW input is stated as only having a frequency passband of 700MHz - 2.6 GHz .
The LNAH input is defined as 2- 2.6 GHz and the LNAL input as 700- 900MHz
This supports our concerns about wideband performance options . The filter component values are also supplied and we can use these to estimate the filter characteristics using a suitable RF network modelling software .
Yes, looking again at LimeSDR schematics, I see different ranges than what @RicardasVadoklis mentioned earlier:
RX L: 700 MHz - 900 MHz
RX H: 2 GHz - 2.6 GHz
RX W: 700 MHz - 2.6 GHz
TX A: 30 MHz - 1.8 GHz
TX B: 1.9 GHz - 2.6 GHz
So what is right? Can you please give us plots for all RX inputs and TX outputs @RicardasVadoklis or @andrewback? So we don’t have to speculate (or waste time with modeling / simulation) and can know exact characteristics of filters.
This is a serious issue for a lot of funders. Most of us cannot modify SMD Designs and bought the board to use out of the box. So please lime find a solution for good. There’s still time enogh to do it.
And please: don’t say it was written in the schematics. You did not adress engineers but a broad audience. You might as well have published the specs in kisuaheli (no offense to people speaking that language intended).
Currently we are using components on LNA inputs to fine tune for some cellular bands. On the final version of the LimeSDR we shall match the receivers for the optimum broadband performance as shown in the pictures below:
Many thanks for this confirmation . I truely believe you have made the right design change here to widen the market potential for this board and honour the way the product has been marketed . The performance plots look good . I look forward to receiving my boards and testing them in a number of applications I have in mind both professionally and for hobby experimental use.
All, apologies! Hadn’t appreciated that the matching networks would be tweaked for the campaign boards!
Also are we now all in agreement that these are matching networks and not filters? As such and like matching networks on other platforms, they will obviously have areas where they perform best, but filtering is left to off-board devices — which as far as I know is something that matching cannot be offloaded to. That is, matching TX and RX to a 50 ohm line and not to the antenna (which ATUs are used for, of course).
Just a reminder what Lime Micro promised to offer as the specification in terms of broadband gain and NF for the 1.4 units . It seems that this has not been honoured with their design choice of matching network components at the antenna port inputs
@PA4MSA@freebil I understand that, following overall feedback from experiences with v1.2 hardware, the decision was made to not change the matching networks. I appreciate that this will not be welcome news for some, but we are looking at a number of solutions and a detailed update with options will be posted later today.
As such and like matching networks on other platforms, they will obviously have areas where they perform best, but filtering is left to off-board devices — which as far as I know is something that matching cannot be offloaded to. That is, matching TX and RX to a 50 ohm line and not to the antenna (which ATUs are used for, of course).