Re: [USRP-users] Fwd: Re: USRP's B210 sluggish start of transmission
W dniu 13.11.2017 o 11:36, Piotr Krysik via USRP-users pisze: > Dear list, > > Little update on transmitting bursts and simultaneous receiving with > USRP B210. When I connect anything that has some path between TX/RX SMA > port's body and inner female sleeve contact (like 3dB attenuator or even > my finger) the output signal starts to look ok. I don't know what is > causing this and if it can be corrected with a firmware change (I'm not > actively looking for the cause currently). Another update: With a log periodic antenna connected to Tx port (the 850-6500MHz one from Ettus) everything works fine. With vertical antennas (like VERT900 or VERT2450 from Ettus) the mentioned problem appears. I suppose that for all antennas that have connection between the active pin and the ground it might work fine. Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Fwd: Re: USRP's B210 sluggish start of transmission
Dear list, Little update on transmitting bursts and simultaneous receiving with USRP B210. When I connect anything that has some path between TX/RX SMA port's body and inner female sleeve contact (like 3dB attenuator or even my finger) the output signal starts to look ok. I don't know what is causing this and if it can be corrected with a firmware change (I'm not actively looking for the cause currently). Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Fwd: Re: USRP's B210 sluggish start of transmission
W dniu 06.10.2017 o 17:48, Nick Foster pisze: > This is especially baffling to me, because I recall that the > SKY13335-187LF switches used in B210 must be isolated from DC on all > RF ports. But they are! The only components connected to the SMA > connectors are a series 470pF capacitor. > > Perhaps the problem is exacerbated by poor impedance matching rather > than by lack of a DC path. If reflected power was causing the problem > I'd expect lowering the transmit gain to affect your results. Could > you try that for me? > > Nick, There is no difference. Even for transmit gain 0 the problem persists. I have a feeling that the answer to the question might be easier to find if we know what is state of TX/RX switches before start of burst and after it. Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Fwd: Re: USRP's B210 sluggish start of transmission
Piotr, This is especially baffling to me, because I recall that the SKY13335-187LF switches used in B210 must be isolated from DC on all RF ports. But they are! The only components connected to the SMA connectors are a series 470pF capacitor. Perhaps the problem is exacerbated by poor impedance matching rather than by lack of a DC path. If reflected power was causing the problem I'd expect lowering the transmit gain to affect your results. Could you try that for me? Nick On Fri, Oct 6, 2017, 1:41 AM Piotr Krysik via USRP-users < usrp-users@lists.ettus.com> wrote: > W dniu 27.09.2017 o 07:06, Piotr Krysik via USRP-users pisze: > > Hi all, > > > > I narrowed down when the issue occurs. > > > > When using separate sides of B210 for transmitting (i.e. TX/RX port on > > RF A side) and receiving (i.e. RX2 port on RF B side) everything is fine > and B210 starts transmitting like i.e. X310. > > > > > > The problem appears when transmitting and receiving on the same side of > > B210 and it is dependent on what you connect to the TX port. The 300us > > transition appears if I don't connect anything and measure the TX-RX > > leakage or when VERT900 antenna from Ettus is connected. > > > > I tried also to connect a power splitter to the TX port and an antenna > > to one of the splitter's ports - with the same result. But as soon as I > > connected the 30dB attenuator to another port of the splitter, the > > problem immediately goes away. > > > >> The attenuator also has a path (resistive 50 ohms) to groundan > >> antenna with a small pad on it (say 1 db) will probably work fine as > well. > >> Kent Torell > > So you might be right here Kent that it was the path to the ground in > the attenuator that > > changed how the output behaves. It is funny thought that the problem > > only appears when RX2 port on the same side of B210 is also used :). > > > Hi all, > > As for my current application transmitting bursts and receiving > continuous signal with use of all B210 RF ports is not required, I can > avoid the problem. So I don't have currently motivation to pursue the > investigation further. > > The problem isn't solved though. There are of course applications in > which it is required to use all RX and TX ports and it is convenient to > transmit burst. If someone needs it I can provide the codes that I used > for tests (they are not secret, I just don't want to lose time on > preparing them in case there is no such person). What I have is a GNU > Radio block that adds tx_time and length tags to a signal, with user > defined burst length and gap length. From the tagged stream UHD sink is > able to produce bursts instead of continuous signal. I have also a GRC > application that presents the problem. > > Best Regards, > Piotr Krysik > > ___ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] Fwd: Re: USRP's B210 sluggish start of transmission
Hi all, I narrowed down when the issue occurs. When using separate sides of B210 for transmitting (i.e. TX/RX port on RF A side) and receiving (i.e. RX2 port on RF B side) everything is fine and B210 starts transmitting like i.e. X310. The problem appears when transmitting and receiving on the same side of B210 and it is dependent on what you connect to the TX port. The 300us transition appears if I don't connect anything and measure the TX-RX leakage or when VERT900 antenna from Ettus is connected. I tried also to connect a power splitter to the TX port and an antenna to one of the splitter's ports - with the same result. But as soon as I connected the 30dB attenuator to another port of the splitter, the problem immediately goes away. > The attenuator also has a path (resistive 50 ohms) to groundan >antenna with a small pad on it (say 1 db) will probably work fine as well. > Kent Torell So you might be right here Kent that it was the path to the ground in the attenuator that changed how the output behaves. It is funny thought that the problem only appears when RX2 port on the same side of B210 is also used :). -- Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
