Luke, I have not used B2xx, but its TX/RX antenna port should be similar to USRP N2xx. In GR application if u stop feeding samples to USRP-sink and last sample has "End-of-burst" EOB tag, then the TX/RX antenna port, automitically switches from transmission path to reception path. This is done using a GPIO named ATR in UHD.
http://files.ettus.com/uhd_docs/doxygen/html/classuhd_1_1usrp_1_1dboard__iface.html Probably u can identify this GPIO pin on B2xx hardware schematic and can use it to control an external TR switch as well. Moreover using this u need not to modify anything in FPGA or even on Host side. As Ralph said,using usb or u-controller u cannot synchronize the required timing. If transmitter pulse-width is in micro-seconds then timing-synchronization accuracy between USRP-transmitter and the external-switch must be in nano-seconds. -Adeel On Thu, Jan 23, 2014 at 7:43 PM, Luke Hough <dlho...@gmail.com> wrote: > Ralph, > > Are you familiar at all with the B2x0? I don't have the device with me at > the moment, but I see a debug header on the schematic (J502). Do you know > if that can be used as a GPIO with some VHDL mods? I'm wondering if I could > control the switch using that. > > -Luke > > > On Thu, Jan 23, 2014 at 8:24 AM, Ralph A. Schmid, dk5ras <ra...@schmid.xxx > > wrote: > >> With USB or serial control I guess you will never reach the necessary >> accuracy in switching time. I see the only possibility in some hard wired >> connection to the USRP. >> >> >> >> Ralph. >> >> >> >> >> >> *From:* USRP-users [mailto:usrp-users-boun...@lists.ettus.com] *On >> Behalf Of *Luke Hough >> *Sent:* Thursday, January 23, 2014 3:22 PM >> *To:* Adeel Anwar >> *Cc:* usrp-us...@lists.ettus.com; discuss-gnuradio@gnu.org >> *Subject:* Re: [USRP-users] [Discuss-gnuradio] B200 gain control and RF >> input power >> >> >> >> Adeel, >> >> >> >> Unfortunately, I planned to operate at 3.4GHz and designed my antenna to >> match that. A lot of the Minicircuits devices stop at around 3GHz. The >> limiter really doesn't achieve much relative to the required input power. >> Also, a circulator may be of little use after considering the reflected >> energy from the antenna. Even with a >90% efficiency, the reflected power >> will still be nearly 20dBm (if I understand the calculations right). >> >> >> >> I have material to construct a second antenna. My new plan is to build >> that antenna and measure the isolation provided by independent antennas. >> That probably won't be enough, so I'm thinking about an RF switch >> controlled via usb/serial and microcontroller (arduino maybe). >> >> >> >> -Luke >> >> >> >> On Wed, Jan 22, 2014 at 12:13 PM, Adeel Anwar <adeela...@gmail.com> >> wrote: >> >> Luke, >> >> I am also doing a similar project in which i plan to use TR switch >> instead of circulator because of high TX/RX isolation (60/70 dB) as >> compared to isolators (20/30 dB). >> >> Currently u are using power amplifier ZVE-8G which have output power ~=30 >> dBm so circulator will work as well but if u plan to go to higher power >> levels 60/70 dBm (kilo watts) range then T/R switch will be a better option. >> >> Otherwise if u just want a Radar test setup, then then simplest approach >> will be to use commonly available WiFi "Bi-Directional Amplifiers". Then >> have built-in limiters, power-amps, T/R-switches and LNA's etc. >> >> >> >> Limiter VLM-63-2W <http://www.minicircuits.com/pdfs/VLM-63-2W+.pdf> has >> Saturated output-power = +11.5 which is very w.r.t USRP max input power ( < >> -10 dBm ). >> >> Minicircuits ZFLM-252-1WL+ has Saturated-output power =0dBm, so in my >> opinion this will be a better option compared to VLM-63-2W (provided ur >> freq of operation is < 2.5G). >> >> Hope this helps. >> >> -Adeel >> >> >> >> On Sat, Jan 18, 2014 at 10:57 AM, Marcus D. Leech <mle...@ripnet.com> >> wrote: >> >> On 01/18/2014 12:31 AM, Luke Hough wrote: >> >> Get your tomatoes ready, I have attached a proposed block diagram and >> possible component specs. I have not actually purchased the limiter or the >> circulator, but I do have the power amp and antenna. The power amp is a >> ZVE-8G <http://www.minicircuits.com/pdfs/ZVE-8G+.pdf>. I was looking at >> the VLM-63-2W <http://www.minicircuits.com/pdfs/VLM-63-2W+.pdf> limiter >> and possibly a JCC3300T3800S10 circulator ( hoping for a sample ). >> >> >> >> The numbers on the block diagram don't exactly match the specs shown. The >> numbers are closer to the table values. I have also not taken insertion >> losses into account. >> >> >> >> Looking at the the B200 >> schematic<http://files.ettus.com/schematics/b200/b200.pdf>, >> I was wondering if during transmit I might set switch U807 to OUT2 while >> U805 is OUT1. Then on receive switch U807 back to OUT1. Basically, during >> transmit both RX1 and TX1 are set to use the TXRX1 antenna, but during >> receive, RX1 is switched back to antenna RX1. Can the switch be made in >> less than 1µs ? >> >> >> >> I don't think the switch can be made in under 1us from the host. With >> suitable mucking-about on the FPGA you might be able to come up with a >> suitable >> scheme that amounts to half-duplex switching. >> >> In the ordinary scheme of things the ATR state machine will switch the RX >> chain to the RX2 port during transmit. If this could be done fast enough, >> that >> would work fine, and you'd just put a terminator on the RX2 port in >> half-duplex mode. >> >> You could consider a scheme where some external machinery is helping with >> switching and "scheduling" things. Such machinery would perhaps arrange >> for a high-isolation path for RX during your TX cycle. >> >> This kind of problem is pretty standard in radar designs, so there are >> probably good solutions out there that could be hybridized to interface to >> an SDR approach. But radar isn't my particular expertise. >> >> >> >> >> >> On Fri, Jan 17, 2014 at 8:45 AM, Marcus D. Leech <mle...@ripnet.com> >> wrote: >> >> On 01/17/2014 09:37 AM, Luke Hough wrote: >> >> As a hobby project, I am developing an active radar. I am primarily >> familiar with simulation and signal processing, but not so much with RF >> hardware. So this is a learning opportunity. >> >> >> >> I do need to Tx/Rx on the same frequency either through a shared antenna >> or independent. I have constructed an antenna and measured the S11 >> parameter to be -11dB over a 300MHz band around the resonnant frequency. >> >> >> >> I was hoping to avoid a GPIO controlled switch. I don't think the B200 >> has any GPIO capability, so another controller device would be required. >> Would it be possible to control one of the skyworks switches on the >> frontend of the B200 in combination with a circulator and a limiter? >> Basically open the RX1 channel and keep the TXRX1 channel switched to the >> TX chain. >> >> -Luke >> >> Well, if this is a half-duplex application, the USRP already does >> switching. Whenever the unit is transmitting, the RX is connected to the >> the RX port on >> the box. >> >> Why don't you draw a diagram of what your intended setup is, and we can >> through metaphoric tomatoes at it, as it were. >> >> >> >> >> >> On Fri, Jan 17, 2014 at 1:34 AM, Ralph A. Schmid, dk5ras < >> ra...@schmid.xxx> wrote: >> >> Hi, >> >> > +7dBm is *very* risky. >> >> Hmmm...3µs are not very long...but it is a risk, agreed. >> >> > If you're feeding a common antenna, the usual approach is to use a >> > diplexer/duplexer arrangement to isolate the TX frequency from the RX >> > frequency (assuming different-frequency full-duplex). >> >> I guess he uses the same frequency for TX and RX - usage of an >> isolator/circulator makes me think so :) But this only works for a certain >> degree and requires no reflected power at all (that means, perfect >> impedance >> match) at the antenna port. >> >> Depending on the needed timing it may be an option constructing a PIN >> diode >> RX/TX switch, operated from some GPIO. >> >> > In fixed-purpose applications, like WiFi, where a common antenna is >> used, >> > there's a duplexor, usually implemented in some kind of ceramic >> > resonator technology that has bandpass and band-stop components to >> it, >> > to keep the RX isolated very deeply. >> >> This will not work for WiFi, as this transmits and receives on the same >> frequency, they usually apply the above mentioned diode method to rapidly >> switch between RX and TX path. >> >> Those ceramic diplexers are common for cellphones and some digital LMR >> systems, as they have the need for full duplex on different frequencies. >> >> > -- >> > Marcus Leech >> > Principal Investigator >> > Shirleys Bay Radio Astronomy Consortium >> > http://www.sbrac.org >> >> Ralph. >> >> -- >> >> Ralph A. Schmid >> Mondstr. 10 >> 90762 Fürth >> +49-171-3631223 >> ra...@schmid.xxx >> http://www.bclog.de/ >> >> >> >> >> _______________________________________________ >> USRP-users mailing list >> usrp-us...@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> >> >> >> >> >> >> >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> >> >> _______________________________________________ >> USRP-users mailing list >> usrp-us...@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> >> > >
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
