------------------ ???????? ------------------
??????: "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!
>> >