[USRP-users] interpretation of received signal
Hi Marcus, I have no idea why you said that but I certainly did not mean to directly take the values that Marcus L mentioned and straight away add it in my report!. Since I am just learning about SDR, I just wanted an idea of what could be the minimum power levels that an SDR receiver can fairly comprehend and process. Of course I definitely have to co-relate with the results that I get in the simulation. All said and done it certainly helps when experts and professionals give their advise and feedback (due to their vast experience) and I feel there is nothing wrong in checking with experts just to see where we are heading or "are we in the right direction" ! Please excuse me if I am wrong! Ettus has always recommended that all users including beginners post their doubts in this forum and indeed this is the best place to learn more about their product! So we are all learning ! kind regards Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] interpretation of received signal
Hi Konstantin and Mike, In fact I started with 0 gains for both transmitter and receiver with different amplitudes of input signal. The received power is always in the range of -80 dbm to -100 dbm. I am not sure how to say that a certain received power (in dbm) 'is acceptable' when given an input signal (that evaluates approx to 0 dbm in fft) indoors when the transmitting and receiving antenna are very close say just 0.5 meters apart for a carrier frequency of around 800 MHz. regards Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] interpretation of received signal
Yeah got it! But don't you think the tool has those capabilities to consider the entire chain and then display the output? Since I don't have actual spectrum analyzer in the lab I am forced to use the software spectrum analyzer. The initial phase is to first confirm that the transmit and receive are proper enough to comprehend the results. I can send a table of input voltages and gains that I set and the results that I observed. I would atleast expect that given the same numbers as input , the results do not vary beyond a certain margin. That way I can declare / set that my channel of interest has passed the loop back test of transmission and reception! I am only confused that the results do not match the expected values as per path loss, power transmitted and gain equation or it could be that I am not looking the right way! regards Nirmala > > > > > On 2017-10-18 12:29, Nirmala Soundararajan via USRP-users wrote: > > Hi Marcus, > > I made a simple model using Matlab Simulink and used spectrum analyser > block to observe the transmitted and received waveform. Since 0 dbm was > the maximum input power, I just calculated (input volatge)^2 / 2. It comes > to 0.045V. I specified block parameters and gave different values. > Actually with 0 gain of transmitter and receiver I was getting -97 to > -105 dbm for the same input voltage 45mV. > > regards > > Nirmala > > On Wed, Oct 18, 2017 at 3:03 AM, Neel Pandeya via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Also note that at 0 dBm, you're at the maximum safe input power, so your >> received signal might be saturated. >> >> --Neel Pandeya >> >> >> On Oct 17, 2017 22:30, "Marcus D. Leech via USRP-users" < >> usrp-users@lists.ettus.com> wrote: >> >> On 10/18/2017 12:08 AM, Nirmala Soundararajan via USRP-users wrote: >> >>> Hi all, >>> >>> I am trying to transmit and receive a simple 10 kHz tone using a single >>> USRP B205mini-i. The input power is 0 dbm ( The amplitude of 10kHz tone >>> being 45mV). The transmitting and receiver antenna are same omnidirectional >>> type each having 3 dbi gain. I set the transmitter gain as 8 and receiver >>> gain as 70. The carrier frequency is around 800 MHz. The path loss comes to >>> around 20 db considering the fact that transmitting and receiving antenna >>> are just a foot apart. ( I took far field and did not consider near field) >>> >>> The received spectrum shows -26 dbm. How should I interpret these >>> results? >>> >>> regards >>> >>> Nirmala >>> >>> How did you get -26dBm? >> >> Unless you have painstakingly *calibrated* your USRP B205mini, and wrote >> code that converts the received data into dBm, given your carefully-derived >> calibration tables, an FFT will simply show received power relative to >> the mathematical maximum in the system. >> >> Further, given that modulating signals in the SDR world are purely >> digital number, how did you derive a figure of 45mV of modulation? >> >> >> >> ___ >> 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 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
Re: [USRP-users] interpretation of received signal
Hi Marcus, I made a simple model using Matlab Simulink and used spectrum analyser block to observe the transmitted and received waveform. Since 0 dbm was the maximum input power, I just calculated (input volatge)^2 / 2. It comes to 0.045V. I specified block parameters and gave different values. Actually with 0 gain of transmitter and receiver I was getting -97 to -105 dbm for the same input voltage 45mV. regards Nirmala On Wed, Oct 18, 2017 at 3:03 AM, Neel Pandeya via USRP-users < usrp-users@lists.ettus.com> wrote: > Also note that at 0 dBm, you're at the maximum safe input power, so your > received signal might be saturated. > > --Neel Pandeya > > > On Oct 17, 2017 22:30, "Marcus D. Leech via USRP-users" < > usrp-users@lists.ettus.com> wrote: > > On 10/18/2017 12:08 AM, Nirmala Soundararajan via USRP-users wrote: > >> Hi all, >> >> I am trying to transmit and receive a simple 10 kHz tone using a single >> USRP B205mini-i. The input power is 0 dbm ( The amplitude of 10kHz tone >> being 45mV). The transmitting and receiver antenna are same omnidirectional >> type each having 3 dbi gain. I set the transmitter gain as 8 and receiver >> gain as 70. The carrier frequency is around 800 MHz. The path loss comes to >> around 20 db considering the fact that transmitting and receiving antenna >> are just a foot apart. ( I took far field and did not consider near field) >> >> The received spectrum shows -26 dbm. How should I interpret these results? >> >> regards >> >> Nirmala >> >> How did you get -26dBm? > > Unless you have painstakingly *calibrated* your USRP B205mini, and wrote > code that converts the received data into dBm, given your carefully-derived > calibration tables, an FFT will simply show received power relative to > the mathematical maximum in the system. > > Further, given that modulating signals in the SDR world are purely digital > number, how did you derive a figure of 45mV of modulation? > > > > ___ > 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 mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] max input power
Hi Marcus, I think I did'nt frame the question properly!. I know the calculations but I just wanted to know in what voltage range must the input be given to B200? (in mV-micro volts range?) regards Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] max input power B200
Hi, B200 mini data sheet mentions maximum input power as 0 dBm. A 1V, 1 kHz signal will give 0.5W power which is above 20 dBm and way above 0 dBm! Can this please be clarified? regards Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] transmit and receive - B205mini-i
Hi, I have just started programming simple scripts in matlab for B205mini-i. Can I transmit and receive simultaneously using SDRUtransmitter and receiver objects in Matlab? I also tried to use simulink, and gave a simple cos signal as input, the value is 1 X 151 vector, just cos values between [-1 1]. however I am getting error. Error reported by S-function 'usrp_uhd_sfuntx' in 'prj1/SDRu Transmitter/usrp_uhd_sfuntx': Input signal 1 must be a column vector. Component:Simulink | Category:Modelerror Error in port widths or dimensions. Output port 1 of 'prj1/SDRu Transmitter/Data' is a one dimensional vector with 150 elements. Also how should I connect the Data and Length ports of SDRUreceiver.? request help. thanks Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] USB connector on B205mini-i
Hi, Has anyone tried to use Matlab with B205mini-i on windows? Apparently Matlab does'nt recognise the board when plugged to USB 3.0 port. It however works when used with USB 2.0 ports. Ettus recommends to use USB 3.0 specially on B205mini i. Request for help regards Nirmala ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
