Hi Vaibhav, how do you make sure the PSD measures the power in *exactly* the 6ms you're sending in? Or do you continously measure? If the latter: do you multiply with the duty cycle of each subchannel (ie. when you hop to 10 channels sequentially, each channel would only be used 10% of the time, and thus, a long observation will only see 10% of power)? Are you looking at an offline analysis, or at a live updated PSD plot, which might actually miss a lot of bursts by only looking every 1/updates_per_second ?
I don't know the T-Mote sky nor the Received Signal Strength Indication algorithm it uses, so I can't really say anything about that. Best regards, Marcus On 03/02/2015 01:41 PM, vaibhav kulkarni wrote: > Hi Marcus, > > Thanks for the quick reply. yes, that may be the issue. As I am using > the frequency_hopping.py module for specifying the hopping sequence > and controlling the time and connecting it to other modulation blocks. > > Signal width : 3Mhz > I record the the received signal on another USRP and plot the PSD to > check power. Further I also measure the RSSI values on a T-Mote sky > node and plot them to check the RSSI of the Transmitted signal. > > I start from 2.41Ghz and hop until 2.45 Ghz , separation of 5Mhz. > Thanks a lot for your inputs. I will try them right away. > > Best, > Vaibhav > > > On Mon, Mar 2, 2015 at 12:39 PM, Marcus Müller > <[email protected] <mailto:[email protected]>> wrote: > > Hi Vaibhav, > > tuning is an issue, here. The problem is not that you're only > retuning the LO, the whole signal chain has to be correctly locked > in again after each tune. > If the total bandwidth you're spanning is less than 40MHz, which > is the baseband bandwidth of the daughterboard's you're using, try > setting your LO frequency to the center of that band, and hop via > frequency shifting in the FPGA only[0]. To do that, you'll need to > use tune_request_t[1] objects rather than simple using the target > frequency when tuning using set_tx_freq in your USRP sink. > > Further things of interest: How do you measure the power of a 6ms > burst? How wide is your signal? > > Greetings, > Marcus > > [0]http://files.ettus.com/manual/page_general.html#general_tuning_process > [1]http://files.ettus.com/manual/structuhd_1_1tune__request__t.html > > On 03/02/2015 12:24 PM, vaibhav kulkarni wrote: >> Dear All, >> >> I am trying to implement some frequency hopping schemes in the >> ISM band with USRP N210 with RFX 2400 board ( I also tried the >> same with the SBX 40MHz board). I hop to the next channel >> (channel seperation : 5MHz) after every 6ms (tuning time for RFX >> board is 250usec) so tuning is not an issue. I set max gain (20dB >> in case of RFX board) and 30 dB in case of (SBX Board) and send >> random modulated (BPSK) bits. >> >> However, I get very low power at the receiver (another USRP, RX >> gain 20dB) around -70 to -80 dB 1 meter away from the tx USRP. >> When I dont perfrom frequency hopping I get a rx power of -10 dB. >> I am not able to understand why the tx power reduces by such an >> extent while perfroming fx hopping, although I give enough >> settling time. >> >> Also is there any firmware which allows to further increase the >> tx power ? >> >> Any help to resolve this issue is appreciated. >> >> Best, >> Vaibhav >> ETH Zurich >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] <mailto:[email protected]> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] <mailto:[email protected]> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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