Re: 回复： Problems implementing USRP b210 dual channel transceiver

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, 能书能言 wrote:
> Hi,
>     Thank you for your reply, based on your suggestion I have tried the following:
>     ①No LO offset set (no uhd.tune_request)
>        Ch0:Center Freq : freq1
>        Ch1:Center Freq : freq2
>        （freq1 = 2.4G, freq2=2.39G,samp_rate=300k）
>      ②Set 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 ①：
>     In this case, the number of packets received is incorrect and the problem becomes
> more serious.
>     for ②：
>     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！
>
> ------------------ 原始邮件 ------------------
> *发件人:* "Marcus Müller" <marcus.mueller@ettus.com>;
> *发送时间:* 2022年12月6日(星期二) 晚上8:49
> *收件人:* "discuss-gnuradio"<discuss-gnuradio@gnu.org>;
> *主题:* 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, 能书能言 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!
> >