Matching Networks for the LimeSDR Mini

#1

Can we get some input about the range of the matching networks present in the LimeSDR Mini? I think this should be put out in the blue before we start to get complains about the rf performance in certain bands.

#2

In accordance to presentation target is 10 MHz to 3,5 GHz,
but final prototype must show real RF performance, when ready.
I am waiting to see that too…

#3

Yes, but I don’t think the matching network will cover that whole spectrum. Just like the normal LimeSDR, the target frequency range included HF but it wasn’t usable due the matching networks.

#4

I am expecting they are going to switch at last two matching networks on one RF connector…

#5

The new prototypes only have 2 SMA connectors. The only way it could have 2 different matching networks would be using an rf switch like the HackRF does, I believe. Probably they only have one matching network (for each, rx and tx) tunned to cellular frequencies (GSM, LTE, etc).

#6

I’d guess that LimeSDR mini will use RX1_L for the RX channel, and TX1_2 for TX channel.

My vague reasoning for this, is that MN17 and MN20 are shown on the RX side of:

And looking at the schematic for the original LimeSDR those two components would be associated with RX1_L
And also on the initial prototype had RX1_L and RX2_L written on the silkscreen:

MN16 and MN10 would correspond to TX1_2 looking at the schematic for the original LimeSDR. And also TX1_2 and TX2_2 were shown on the silkscreen for the initial prototype.

So my guess would be the original “default” behaviour for RX1_L (see the red line on 2nd plot) which stops at 10MHz (well technically 6MHz but it is close enough to 10MHz):

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#7

@andrewback

#8

Looks like there is a RF switch to toggle between RF inputs with different matching networks.
" … the design was also updated with additional RF switching, enabling us to switch a single port between low and high bands."
I’m going to make a random guess that TX1_2; TX2_2 and RX1_L; RX2_L are the ports with the RF switches on them.

#9

Yes, I read the update. The switch should switch TX_ H/TX_L and RX_H/RX_L. I don’t understand I you mentioned TX1/TX2 and RX1/RX2. The switch being included, as I previewed, is an good indicator but what I am actually interested is the frequency bands and the performance in the full spectrum.

#10

I don’t disagree, but why then would the initial prototype not use those ports ? It makes sense.

#11

Measurements will be taken and plots published once the final version boards are back from assembly, which I believe is a few weeks out from now. A number of changes have been made since the prototypes pictured, including to the matching networks, in addition to changing the RF connectors and of course layout etc.

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LimeSDR Mini
#12

Hi @andrewback, any update on the matching networks / do you have plots available ? Thank you,

philip

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#13

Will enquire again and see if characterisation of the networks on the production boards has been completed now.

#14

News?

#15

Any update? Or will they never be provided?

#16

Bumping this again to bring up the fact that will still have not received an answer.

#17

Still waiting for answers from Lime.

My guess is that we will never get these answers,