?????? ?????? Problems implementing USRP b210 dual channel transceiver

[????????]

    The number of data packets in ?? is not correct, but the number of data packets in ?? is correct. Therefore, to avoid more problems, I choose ??.
    By viewing the pictures in the attachment and your explanation, f_ RF is LO frequency? Then the two channels share one LO, so setting f_ Offset adjusts the frequency to f_ target?

     I tried the following:

        freq1=   2.4G
        freq2=   2.39G
        lo_off1=   5M
        lo_off2=  -5M
        samp_rate=300K

    But the problem still exists, and the bit error rate is very high : (

    Another thing I forgot to say is that I did a dual channel transmission experiment before (I call it experiment A. ), and the parameter settings are the same as when I first set them??freq1 = 2.4G, freq2=2.39G, lo_off1=2M, lo_off2=-2M,samp_rate=300k??,which performs very well. The only difference between experiment A and this experiment now is that the modulation of the signals on the RFA and RFB of experiment A are different. I copied the USRP sink and USRP source components directly from the GRC of experiment A, and the parameter settings are the same, experiment A performed very well, but in this experiment a high BER occurred, so now I am confused where the problem lies

Best regards??

------------------ ???????? ------------------

??????: "Marcus M??ller" <mmueller@gnuradio.org>;

????????: 2022??12??7??(??????) ????5:37

??????: "discuss-gnuradio"<discuss-gnuradio@gnu.org>;

????: Re: ?????? Problems implementing USRP b210 dual channel transceiver

Sorry, typo, hit ctrl-enter to send accidentally when trying to fix it. Let me say it
correctly:

Re: ?? But you receive packets! So that's a good thing, I guess?

Re: ?? So, maybe the attached figure helps. The offset is the difference between the
physical LO frequency f_{RF}, and the center frequency of what becomes your baseband.

So, I incorrectly said "the offsets need to add up to 10 MHz"; correct would be to say that
freq1-offset1 = freq2-offset2.
Now, since freq2 = freq1 - 10 MHz follows
freq1-offset1 = freq1 - 10 MHz - offset2
10 MHz = offset1 - offset2

Note that offsets can be negative.

Best regards,
Marcus

On 07.12.22 10:30, Marcus M??ller wrote:
> Your LO offset still don't add up to the difference between freq1 and freq2. What
> frequency is the physical LO supposed to have? It cannot have frequency 2.4 GHz - 5 MHz
> and 2.39 + 2 MHz at the same time. These are different numbers!
>
> Best regards,
> Marcus
>
> On 07.12.22 09:09, ???????? wrote:
>> Hi,
>>      Thank you for your reply, based on your suggestion I have tried the following:
>>      ??No LO offset set (no uhd.tune_request)
>>         Ch0:Center Freq : freq1
>>         Ch1:Center Freq : freq2
>>         ??freq1 = 2.4G, freq2=2.39G,samp_rate=300k??
>>       ??Set LO Offset
>>         Ch0:Center Freq : uhd.tune_request(freq1,lo_off1)
>>         Ch1:Center Freq : uhd.tune_request(freq2,lo_off2)
>>         ??freq1 = 2.4G, freq2=2.39G, lo_off1=5M, lo_off2=5M,samp_rate=300k??
>>       or ??freq1 = 2.4G, freq2=2.396G, lo_off1=2M, lo_off2=2M,samp_rate=300k??
>>       or ??freq1 = 2.4G, freq2=2.396G, lo_off1=2M, lo_off2=-2M,samp_rate=300k??
>>
>>      for ????
>>      In this case, the number of packets received is incorrect and the problem becomes
>> more serious.
>>      for ????
>>      In this case the BER is still very high (I don't think it's my system because the
>> transmit power is set to 1 (Normalized) and the BER is quite low when using one RF
>> channel, but I still think I'm using the USRPB210's dual channel transmission mode
>> incorrectly)
>> Best Regards??
>>
>> ------------------ ???????? ------------------
>> *??????:* "Marcus M??ller" <marcus.mueller@ettus.com>;
>> *????????:* 2022??12??6??(??????) ????8:49
>> *??????:* "discuss-gnuradio"<discuss-gnuradio@gnu.org>;
>> *????:* Re: Problems implementing USRP b210 dual channel transceiver
>>
>> There's only one physical TX LO; so either you just don't specify offsets, OR they must
>> add up to the difference between the two target frequencies.
>>
>> In your case, the difference is 10 MHz, but your offsets don't add up to 10 MHz, and
>> you're requesting something impossible.
>>
>> Best regards,
>> Marcus
>> On 06.12.22 12:45, ???????? wrote:
>>  > Hi,
>>  >      I am using OFDM + USRPB210 for data transmission. I am using two USRPB210s, one
>> being
>>  > used as a transmitter and the other as a receiver. When I use only one of the channels
>>  > (RFA or RFB) the data can be transmitted properly. I needed to transmit two different
>> data
>>  > at the same time, so I used both the USRP RFA and RFB. the baseband processing part
>> of the
>>  > link was the same for both channels (including channel coding, modulation, FFT,
>> etc.), but
>>  > at this point I found that I was transmitting data with a very high BER (for both
>> links).
>>  > again, mentioning that there was no problem when sending on one channel alone, I The
>> USRP
>>  > Sink and Source settings are shown in the attached picture.
>>  >      where
>>  >      freq1=2.4G
>>  >      freq2=2.39G
>>  >      lo_off1=2M
>>  >      lo_off2=-2M
>>  >      samp_rate=300K
>>  >     The two signals are separated using different frequencies, I don't think there
>> should
>>  > be any interference between them, and I have troubleshot errors other than USRP
>> source and
>>  > sink, so I think there is something wrong with my parameter settings, or I am using the
>>  > two RF channels in an incorrect way. How should I modify this?Looking forward to your
>>  > response??
>>  >
>>  > Best Regards!
>>  >