Problems with signal reception (BladeRF-x40 , GNUradio)

Hi everyone, I am having problems when I receive signals using two SDRs (BladeRF - x40), one to transmit and one to receive (I know I can transmit and receive using 1 SDR, but I need the complete schematic transmitter, receiver), the problem is the following, I have a complex signal , with the following values:
in-phase component (i(t)) tx = Ac * x(t)
quadrature component (q(t)) tx = 0
Vy (t) tx = i(t) + j q(t)

I send this signal to the channel and therefore it is received by the SDR receiver.
What I receive in the reception is not similar to what I transmitted, because of a tone appears both in its component in phase and in quadrature, by making q(t) rx /≈ q(t) tx /≈ 0.

For a better compression, I will transmit the following signal x(t) = 0 (equivalent to i(t) tx = 0, q(t) tx = 0), so in theory in reception it would only have noise, but this is not the case.

When I use a single SDR to transmit and receive this does not happen, I don’t know if this is due to some kind of synchronization, but with this problem I can not correctly classify the type of modulation.

BLOCK SDR Transmitter.
BLOCK SDR Receiver.

This is what i am getting (Frecuency Domain) when i am transmitting a message with amplitude = 0 and both SDRs have gain equal to 0

When I increase the gain, that peak increases, in addition another peak appears symmetrical to that one with less amplitude

This does not happen when I transmit and receive with the same sdr,
Could this be due to mismatches between both SDRs?

I need help to know how to make it not transmit and receive that unwanted signal.
Thank you very much in advance!

Have you tried either asking the people who make and sell the hardware, or people own and use the hardware ?

I’d try searching the hardware manufacturers website by plugging something like “ filetype:pdf bladerf” into any search engine.

1 Like

Hello, first of all thank you very much for your answer.
Yes, I have been commenting on the problem in the developer’s official forums, but I do not receive a response or perhaps the response is received too late.

My bladeRF 2.0 micro xa5 will not operate at any bandwidth of less than about 1 MSPS. Perhaps, yours is erroring on the 150 KSPS and actually using some default value.

I took a look at the BladeRF driver and it picks the actual bandwidth used from a table - taking the closest value to that requested.

+1. BladeRF is not a MyriadRF project and you’d be better asking in the appropriate forum.

Hi @raul8883,
Did you end up finding a solution to this problem? I am currently working on a transceiver and need to use two bladeRF SDR’s. The signal I received also shows the same sort of response yours does - my signal seems to be “riding” on a sine wave noise floor. Thanks.

I saw “signal seems to be “riding” on a sine wave noise floor”. I think that it was when the receiver port was not connected to an antenna.

Hi, thank you for your response. This effect is happening while I have the antenna connected. The moment I disconnect the transmitter side the noise returns to 0 again