Re: [Discuss-gnuradio] multi_file usrp tuning options
Dear Ematlis, I want to draw your attention to this remake: When using std_4rx_0tx.rbf FPGA file, the 4 FPGA DDCs does not have low pass filter (the HBF) and you have to do the low pass filtering by software. Firas, ematlis wrote: Ok, great. This simplifies things; I was afraid I was going to have to create a modulating circuit to modulate those low-frequency timing signals so they could be captured along with the 2 MHz am-modulated signals using a single tuning frequency. I have some questions about the deinterleaver. Firstly, how does it know how many channels are interleaved? Does it determine this information from the Mux settings, or from the number and type of subdevices detected, or something else? Secondly, in terms of computational efficiency, is there any advantage to performing the deinterleave operation earlier in the flow-graph sequence, or later? For example, I'm doing AM demodulation. So, currently my flow graph consists of the usrp block connected to a low-pass filter, connected to a mag block, connected to a high-pass filter (to remove dc), connected to a block that corrects for gain, connected to a block that factors in a calibration constant for the data path, and finally the file-write. I also branch off to some fft sinks. Is it necessary for me to introduce a deinterleave block immediately after the usrp block or can I put it anywhere? Thirdly, if all I was doing was capturing to file, is the deinterleaver strictly necessary? I could write a program to deinterleave the data in the file in post-processing, correct? thanks! eric On Fri, 1 Jun 2007, Eric Blossom wrote: On Fri, Jun 01, 2007 at 09:27:55AM -0400, [EMAIL PROTECTED] wrote: Excellent. Just so I understand how this is done- when one tunes different subdevices to different frequencies, is there one LO on the USRP which is being switched between these frequencies, or is there more than one LO? In general, the tuning is split between an LO on the daughterboard and the DDCs in the the FPGA. In the case of the Basic Rx and LF RX, there is no LO on the daughterboard, so all the tuning is handled by the DDC. When using std_4rx_0tx.rbf, there are 4 DDCs available in the FPGA. u.tune(...) handles adjusting the LO (if any) and the DDCs transparently for the common case. Also- Can I tune all four subdevices independently, or am I restricted to using the same frequency on a given daughterboard? With the Basic and LF Rx everything is independent, since there's no LO on the daughterboard. In the case of daughterboards with LO's, life is a bit more complicated and you'll have to explicitly control the LO on the daughterboard, and then explicitly control the 2 DDCs that are being fed from the given daughterboard. You of course need to ensure that that two frequencies that you want within the IF passband of the daughterboard. To see how this is currently handled, take a look at the implementation of tune in gr-usrp/src/usrp.py Finally- I would guess that at a minimum the decimation factor set in the fpga must be the same for all subdevices. Is this correct? Yes, the decimation rate applies to all subdevices. thanks again, eric You're welcome! Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio -- View this message in context: http://www.nabble.com/multi_file-usrp-tuning-options-tf3848653.html#a10962532 Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] multi_file usrp tuning options
On Fri, Jun 01, 2007 at 09:27:55AM -0400, [EMAIL PROTECTED] wrote: Excellent. Just so I understand how this is done- when one tunes different subdevices to different frequencies, is there one LO on the USRP which is being switched between these frequencies, or is there more than one LO? In general, the tuning is split between an LO on the daughterboard and the DDCs in the the FPGA. In the case of the Basic Rx and LF RX, there is no LO on the daughterboard, so all the tuning is handled by the DDC. When using std_4rx_0tx.rbf, there are 4 DDCs available in the FPGA. u.tune(...) handles adjusting the LO (if any) and the DDCs transparently for the common case. Also- Can I tune all four subdevices independently, or am I restricted to using the same frequency on a given daughterboard? With the Basic and LF Rx everything is independent, since there's no LO on the daughterboard. In the case of daughterboards with LO's, life is a bit more complicated and you'll have to explicitly control the LO on the daughterboard, and then explicitly control the 2 DDCs that are being fed from the given daughterboard. You of course need to ensure that that two frequencies that you want within the IF passband of the daughterboard. To see how this is currently handled, take a look at the implementation of tune in gr-usrp/src/usrp.py Finally- I would guess that at a minimum the decimation factor set in the fpga must be the same for all subdevices. Is this correct? Yes, the decimation rate applies to all subdevices. thanks again, eric You're welcome! Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] multi_file usrp tuning options
Ok, great. This simplifies things; I was afraid I was going to have to create a modulating circuit to modulate those low-frequency timing signals so they could be captured along with the 2 MHz am-modulated signals using a single tuning frequency. I have some questions about the deinterleaver. Firstly, how does it know how many channels are interleaved? Does it determine this information from the Mux settings, or from the number and type of subdevices detected, or something else? Secondly, in terms of computational efficiency, is there any advantage to performing the deinterleave operation earlier in the flow-graph sequence, or later? For example, I'm doing AM demodulation. So, currently my flow graph consists of the usrp block connected to a low-pass filter, connected to a mag block, connected to a high-pass filter (to remove dc), connected to a block that corrects for gain, connected to a block that factors in a calibration constant for the data path, and finally the file-write. I also branch off to some fft sinks. Is it necessary for me to introduce a deinterleave block immediately after the usrp block or can I put it anywhere? Thirdly, if all I was doing was capturing to file, is the deinterleaver strictly necessary? I could write a program to deinterleave the data in the file in post-processing, correct? thanks! eric On Fri, 1 Jun 2007, Eric Blossom wrote: On Fri, Jun 01, 2007 at 09:27:55AM -0400, [EMAIL PROTECTED] wrote: Excellent. Just so I understand how this is done- when one tunes different subdevices to different frequencies, is there one LO on the USRP which is being switched between these frequencies, or is there more than one LO? In general, the tuning is split between an LO on the daughterboard and the DDCs in the the FPGA. In the case of the Basic Rx and LF RX, there is no LO on the daughterboard, so all the tuning is handled by the DDC. When using std_4rx_0tx.rbf, there are 4 DDCs available in the FPGA. u.tune(...) handles adjusting the LO (if any) and the DDCs transparently for the common case. Also- Can I tune all four subdevices independently, or am I restricted to using the same frequency on a given daughterboard? With the Basic and LF Rx everything is independent, since there's no LO on the daughterboard. In the case of daughterboards with LO's, life is a bit more complicated and you'll have to explicitly control the LO on the daughterboard, and then explicitly control the 2 DDCs that are being fed from the given daughterboard. You of course need to ensure that that two frequencies that you want within the IF passband of the daughterboard. To see how this is currently handled, take a look at the implementation of tune in gr-usrp/src/usrp.py Finally- I would guess that at a minimum the decimation factor set in the fpga must be the same for all subdevices. Is this correct? Yes, the decimation rate applies to all subdevices. thanks again, eric You're welcome! Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] multi_file usrp tuning options
Hi- I'm developing a 4-channel receiver using 4 rx paths and 2 LFRX daughter boards. I'm basing my code on the multi_* examples in the multi-antenna directory. Two of the channels I want to capture are AM-modulated at roughly 2 MHz carrier frequency, the other two signals are not modulated and are low frequency on the order of 1 kHz. My question is, can I tune each subdevice to a different frequency? I would need to in order to capture both sets of signals simultaneously in a phase-locked fashion (this is important). thanks, eric Eric H. Matlis, Ph.D. Aerospace Mechanical Engineering Dept. 120 Hessert Center for Aerospace Research University of Notre Dame Notre Dame, IN 46556-5684 Phone: (574) 631-6054 Fax: (574) 631-8355 ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
