RF connection: 10 U.FL connectors (6 RX, 4 TX)?

Projects LimeSDR
1

Transmitter Channels: 2
Receivers Channels: 2

So there are 3 U.FL connections for each RX channel and 2 U.FL connections for each TX channel.

Is the reason for this frequency/wavelength based ?
e.g.
One RX antenna for lets say 100kHz to 80MHz,
One RX antenna for lets say 80MHz to 1.5GHz and
One RX antenna for lets say 1.5GHz to 3.8GHz

Or is it something else ?

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2

That’s right, they are for different bands and the driver is able to select which to use.

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3

Found lots of u.fl > RP-SMA cables of various lengths from 2in to 20in on ebay and elsewhere, also u.fl > BNC

4

Could you give the frequencies on the bands?
Same applies to TX I guess?

5

@ricsi this information and much more can be found in the LMS7002 documentation.

6

Thanx.

Here for reference:
RXLNAL Frequency Range 0.1 2000 MHz Narrow band tunable, set by external matching circuit
RXLNAH Frequency Range 0.1 3800 MHz Narrow band tuneable, set by external matching circuit
RXLNAW Frequency Range 0.1 3800 MHz Broad band tuneable, set by external matching circuit

Also notice that the minimum frequency is actually 30 MHz. Lower frequencies are reached by downconverting? (Extended by TSP NCOs)

7

What about the 2 TX channels?
I could not find the info while quickly skimming through the datasheet. (I am no SDR genius …)

8

@andrewback Please can you give us more detailed informations?

E.g. RXLNAH and RXLNAW are both 0.1 - 3800 MHz according to datasheet. Is there real difference on chip or not? And if not, will there be some difference between RXINH and RXINW on LimeSDR board?

Also I couldn’t find any difference between TXOUT1 and TXOUT2. Are those outputs same on chip? Will there be some difference on LimeSDR board?

Thanks

9

@mikos ,@ricsi,

LMS7002M has 3x Rceiver RF inputs and 2x Tx output per channel. By design receiver inputs are tuned as follows:

  • LNAL - from 0.1 MHz to 2000 MHz. Gives a noise figure <2dB.
  • LNAH - from 1500 MHz to 3800 MHz. Gives a noise figure <3dB.
  • LNAW - from 0.1 MHz to 3800 MHz. Gives a noise figure 5-7dB. Usually used for sniffing.

Transmitter output bu design are similar and supported frequency range is form 0.1-3800 MHz.

However, every RF input/output is combined with RF matching network which might be band specific. On the LimeSDR the RF inputs/outputs are tuned for:

  • 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.

The matching network includes broadband Balun + network for fine tune for specific band, hence can be easily modified.

@ricsi

The LMS7002M synthesizer frequency range is from 30 MHz - 3800 MHz. We are using internal NCO to get us to 100 kHz region.

Best,
Ricardas

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10

thank you!

11

I recently wanted to have a few spare U.FL to SMA Female cables on hand when I build up my LimeSDR for multiple receive and transmit. In doing so, I found an EBay seller that had similar cables to what’s provided when you buy the Antenna Package for the LimeSDR. They’re a little longer (6" as opposed to 3") but I think they’re excellent quality and work perfectly with the LimeSDR U.FL connectors. I’m providing the sellers info and cost as a reference as well as a side-by-side comparison to what you get from CrowdSuppy and what you can buy from EBay much cheaper ($1.75 a cable). Again, quality is great and I’m using it now with my LimeSDR - pics are attached. Have fun…!

Lime Cable.jpg4249×2390 2.33 MB

EBay Seller.jpg1491×536 126 KB

12

Based on this information it looks like the broadband receive input does not offer the best front end noise figure . For general use for amateur radio use ( HF/ VHF/ UHF) this it is not at all ideal . The specific use ( 3GPP Band V and Band I) hardware Bandpass filters provided on the two other receive inputs offering the much improved noise figure make these unusable for general use without hardware modification to remove or bypass these filters. A broadband receive input with low noise figure performance for example LNAL will be of much more use and interest of the user community if it were available. I would like the design team to comment on this

Thanks
Dave Price

13

I will second that. I was one of the first Supporters and was not aware of this limitation.

14

I’m no RF expert, but uFl connectors seem very fragile to me. I suspect their performance degrades with the number of times you connect / disconnect them and at the end you probably still get what you pay for. A measurement using a network analyzer over the full frequency range of the LimeSDR will probably confirm my suspicion.

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15

I thought that the units we’ve ordered will not have these filters in place?

16

I hope so . However the board schematics and photos of the board clearly show the filters in place after the rf transformer / balun

https://github.com/myriadrf/LimeSDR-USB/blob/master/hardware/plug/1v2/Project%20Outputs%20for%20LimeSDR_1v2/LimeSDR_1v2_schematic.PDF

Dave

17

if you look back in time here: Antenna / RF Filtering you see the answer that there will not be filters on the boards we’re buying.

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18

Thanks Simon

Yes I read this thread however in Andrew’s response he referenced the schematics which show the hardware filters in place. The current schematics posted are still the same . This is what concerns me . Over to Myriad design team for a formal response
Thanks
Dave

19

These aren’t the schematics for the boards we’re buying, they are the schematics for the LimeSDR boards used for GSM type development. As far as I know they are 100% software compatible, if not any differences will be minor.

Don’t worry - start making a nice case.

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20

@csete The connectors are not supposed to be put on and off frequently. They are designed to connect the board with an external connector, and they do that perfectly as you can experience yourself with your laptop. Connectors like this are used there to connect the internal wifi antennas with the wifi-, bluetooth or lte board for example.