Over the uhd example tx_waveforms.cpp (without any modificaiton), the exact
invocation I'm using is the following:
./tx_waveforms --rate 61440000 --bw 50000000 --freq 2440000000 --channels
"0" --wave-type SINE --wave-freq 100000 --gain 60
and its output:
--
[INFO] [UHDlinux; GNU C++ version 5.4.0 20160609; Boost_105800;
UHD_3.11.0.git-208-g1da86f9c]
[INFO] [B200] Detected Device: B210
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] pass
[INFO] [B200] Performing register loopback test...
[INFO] [B200] pass
[INFO] [AD936X] Performing CODEC loopback test...
[INFO] [AD936X] CODEC loopback test passed
[INFO] [AD936X] Performing CODEC loopback test...
[INFO] [AD936X] CODEC loopback test passed
[INFO] [B200] Setting master clock rate selection to 'automatic'.
[INFO] [B200] Asking for clock rate 16.000000 MHz...
[INFO] [B200] Actually got clock rate 16.000000 MHz.
[INFO] [CORES] Performing timer loopback test...
[INFO] [CORES] Timer loopback test passed
[INFO] [CORES] Performing timer loopback test...
[INFO] [CORES] Timer loopback test passed
Using Device: Single USRP:
Device: B-Series Device
Mboard 0: B210
RX Channel: 0
RX DSP: 0
RX Dboard: A
RX Subdev: FE-RX2
RX Channel: 1
RX DSP: 1
RX Dboard: A
RX Subdev: FE-RX1
TX Channel: 0
TX DSP: 0
TX Dboard: A
TX Subdev: FE-TX2
TX Channel: 1
TX DSP: 1
TX Dboard: A
TX Subdev: FE-TX1
Setting TX Rate: 61.440000 Msps...
[INFO] [B200] Asking for clock rate 61.440000 MHz...
[INFO] [B200] Actually got clock rate 61.440000 MHz.
[INFO] [CORES] Performing timer loopback test...
[INFO] [CORES] Timer loopback test passed
[INFO] [CORES] Performing timer loopback test...
[INFO] [CORES] Timer loopback test passed
Actual TX Rate: 61.440000 Msps...
Setting TX Freq: 2440.000000 MHz...
Actual TX Freq: 2440.000000 MHz...
Setting TX Gain: 60.000000 dB...
Actual TX Gain: 60.000000 dB...
*Setting TX Bandwidth: 50000000.000000 MHz...Actual TX Bandwidth:
40000000.000000 MHz...*
*[WARNING] [AD936X] Selected Tx bandwidth (61.44 MHz) exceedsanalog
frontend filter bandwidth (56 MHz).*
Setting device timestamp to 0...
Checking TX: LO: locked ...
Press Ctrl + C to stop streaming...
--
The invocation does not produce any error, but there is a warning that
makes believe that somewhere inside the code something is trying to set th
BW to the same value as the sample rate. Furthermore, you can also see that
although the BW inserted is 50MHz, the value is finally set to 40MHz...
If you don't mind, let me take the opportunity to ask you about a doubt
related to the sample rate and dual channel transmission. Looking in the
documentation I found here (https://files.ettus.com/manua
l/page_usrp_b200.html#b200_mcr), that there is a limitation of 30.72 MHz in
the clock rate for dual-channel mode. What is this limitation related to?
Host, UHD, FPGA, AD9361 chip? Is there any way to increase this value?
[image: logo_170x100px.png] <http://www.gradiant.org/>
Lucas Val Terrón
Investigador - Desarrollador | Área de Comunicaciones Avanzadas
Researcher - Developer | Advanced Communications Department
Ph. (+34) 986 120 430 Ext. 3016
l...@gradiant.org | www.gradiant.org
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2018-03-14 10:36 GMT+01:00 Lucas Val Terrón <l...@gradiant.org>:
> Hi all,
>
> Working with the example "tx_waveforms.cpp" provided in the uhd, i found
> myself with two problems trying to set the sample rate and the tx bandwith
> of the USRP B210 (UHD_3.11.0).
>
> ./tx_waveforms --rate 61440000 --freq 2350000000 --wave-type SINE
> --wave-freq 1000000 --gain 40 --bw 50000000 (with sc16 format)
>
>
> 1. The first thing I realized is that despite the sample rate was the
> maximum available, the bandwidth is limited to 40 MHz. Furthermore, the
> following warning appears:
>
> [WARNING] [AD936X] Selected Tx bandwidth (61.44 MHz) exceeds
>
> So, it seems that somewhere inside the code tries to set the Tx bandwith
> to the same value as the sample rate...
>
>
> ./tx_waveforms --rate 500000000 --freq 2350000000 --wave-type SINE
> --wave-freq 1000000 --gain 40 --bw 50000000 (with sc16 format)
>
> 2. With sample rates greater tham 40 MHz, I get continuous underflows in
> transmission. Does anybody knows what's happening? Is there any limit in
> the maximum sample rate transmitting only in one channel?
>
>
> Thanks in advance!!
> Lucas
>
>
> --
> Laptop specifications
> - Processor: 8x Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
> - Operating System: Ubuntu 16.04.2 LTS
> - Memory: 8192 MB DDR4-2400MH
>
>
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