# How many multiple/simultaneous PLLs can I have running on USRP2? **URL:** \ **Category:** GNU Radio\ **Created:** [May 9, 2013, 12:22am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820 "2013-05-09T00:22:27Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:22am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/1 "2013-05-09T00:22:27Z")
Dear Community, I have a question: I want to run multiple (as many as possible) PLLs that track the phase of multiple carriers in my band using the USRP N210. How many can I have running in real time simultaneously? If I use the phase from these loops, are there unknown (gotcha) phase offsets between/among them? Thanks for reading, LD ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:27am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/2 "2013-05-09T00:27:43Z")
> LD Could you clarify your question? Do you mean software PLLs in a Gnu Radio flow-graph? As many as you want until your computer runs out of steam. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:32am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/3 "2013-05-09T00:32:58Z")
Thanks for your prompt answer. I have a 1MHz band of signals from which I would like to extract say 30 carriers. Is it possible to set up say 30 PLLs in the flow graph and each will extract its own phase (and locked frequency), and there are no additional phase offsets between/among the different PLLs? What I mean by phase offsets is that the different PLLs preserve the original phase relationships in the original 1MHz band of data stream. Is it difficult or easy? Thanks much, LD From: discuss-gnuradio-bounces+ldz10565=removed\_email\_address@domain.invalid [[mailto:discuss-gnuradio-bounces+ldz10565=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ldz10565=removed_email_address@domain.invalid)] On Behalf Of Marcus D. Leech Sent: Wednesday, May 08, 2013 3:27 PM To: removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? Dear Community, I have a question: I want to run multiple (as many as possible) PLLs that track the phase of multiple carriers in my band using the USRP N210. How many can I have running in real time simultaneously? If I use the phase from these loops, are there unknown (gotcha) phase offsets between/among them? Thanks for reading, LD Could you clarify your question? Do you mean software PLLs in a Gnu Radio flow-graph? As many as you want until your computer runs out of steam. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:35am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/4 "2013-05-09T00:35:54Z")
I guess there may be an issue that since different PLLs will lock up at different time, so there are unknown amount of initial phase offsets for each PLLs. Would love to know if there are any ways around that. LD From: LD Zhang [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Sent: Wednesday, May 08, 2013 3:32 PM To: ‘Marcus D. Leech’; ‘removed\_email\_address@domain.invalid’ Subject: RE: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? Thanks for your prompt answer. I have a 1MHz band of signals from which I would like to extract say 30 carriers. Is it possible to set up say 30 PLLs in the flow graph and each will extract its own phase (and locked frequency), and there are no additional phase offsets between/among the different PLLs? What I mean by phase offsets is that the different PLLs preserve the original phase relationships in the original 1MHz band of data stream. Is it difficult or easy? Thanks much, LD From: discuss-gnuradio-bounces+ldz10565=removed\_email\_address@domain.invalid [[mailto:discuss-gnuradio-bounces+ldz10565=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ldz10565=removed_email_address@domain.invalid)] On Behalf Of Marcus D. Leech Sent: Wednesday, May 08, 2013 3:27 PM To: removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? Dear Community, I have a question: I want to run multiple (as many as possible) PLLs that track the phase of multiple carriers in my band using the USRP N210. How many can I have running in real time simultaneously? If I use the phase from these loops, are there unknown (gotcha) phase offsets between/among them? Thanks for reading, LD Could you clarify your question? Do you mean software PLLs in a Gnu Radio flow-graph? As many as you want until your computer runs out of steam. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:39am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/5 "2013-05-09T00:39:59Z")
> I guess there may be an issue that since different PLLs will lock up > at different time, so there are unknown amount of initial phase > offsets for each PLLs. Would love to know if there are any ways around > that. > > LD Well, presumably, you’d be using a PFB filterbank or something to create the multiple streams, and then use PLL demodulators to extract bits from those. The PFB filterbank should have uniform group delay across all streams, as far as I know. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 12:52am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/6 "2013-05-09T00:52:51Z")
So maybe the PLL is not a good solution between it will have an unknown amount of initial phase offsets by the time it locks. Since the relative phase between different carriers is the essential information sought after, maybe the better way is to construct very narrowband filters. Now very narrowband can mean a lot of taps, hence a lot of resources consumed. Here is where I don’t know the limitation of resources. If I want to set up a filter of say 4 Hz bandwidth for a signal at 1MHz, and if you have a lot of these signals at different frequencies, what would be the best way to extract these? Maybe the way to go is to have the LO at 1MHz, so the many signals being looked at are +/- many hundreds of kHz. How many taps would it require to extract a signal at say 300 kHz with the 4Hz bandwidth? Can the USRP do 200 taps for each of the 30 carriers (I am just asking without exact calculation here)? Thanks, LD From: Marcus D. Leech [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Sent: Wednesday, May 08, 2013 3:39 PM To: LD Zhang Cc: removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? I guess there may be an issue that since different PLLs will lock up at different time, so there are unknown amount of initial phase offsets for each PLLs. Would love to know if there are any ways around that. LD Well, presumably, you’d be using a PFB filterbank or something to create the multiple streams, and then use PLL demodulators to extract bits from those. The PFB filterbank should have uniform group delay across all streams, as far as I know. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 1:01am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/7 "2013-05-09T01:01:02Z")
> at are +/- many hundreds of kHz. How many taps would it require to > extract a signal at say 300 kHz with the 4Hz bandwidth? Can the USRP > do 200 taps for each of the 30 carriers (I am just asking without > exact calculation here)? > > Thanks, > > LD The USRP doesn’t care, since this all runs on the host under Gnu Radio–unless you were under the impression (wildly incorrect) that Gnu Radio blocks run on the USRP hardware–they don’t. Unless you want to implement in the FPGA. In either case, the answer is “it depends”. Narrow filters consume insane numbers of taps, which are resource-hogs whether it’s a FPGA implementation or host-side hardware implementation. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 1:03am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/8 "2013-05-09T01:03:58Z")
> Or am I wrong that the resource is in the computer and not in the USRP? > > LD It’s all in the computer, unless you do an FPGA-based implementation. Gnu Radio blocks run on the host machine, not the USRP hardware. I admit to being a little bit surprised that you don’t know that already, given how long you’ve been posting things to this list, and using USRP hardware. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 1:35am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/9 "2013-05-09T01:35:27Z")
Sorry for the confusion. I have been using USRP in a rather micky-mouse way. For the longest time, I was just capturing data on host computer disk and do brute force processing in MATLAB. It’s time for me to think about speed up. And the first thing is to consider the USRP processing capability. The PLL may still be the right solution if the PLL faithfully replicates the original signal, which I think it should. But having the gnu-radio doing the PLL, I am not sure there is much of a speed gain. Maybe there are intelligent ways of organizing this so that it can be sped up? Maybe the Gnuradio is faster than Matlab. But these days the matlab has been awful fast, not much slower than C. Still my matlab is not organized as nicely as the gnuradio. Right now I don’t have any streamlined processing. The suggestion on using the PFB filterbanks and PLLs in parallel and streaming operation may have significant speed up? Your opinion is appreciated. LD From: Marcus D. Leech [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Sent: Wednesday, May 08, 2013 4:03 PM To: LD Zhang; removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? Or am I wrong that the resource is in the computer and not in the USRP? LD It’s all in the computer, unless you do an FPGA-based implementation. Gnu Radio blocks run on the host machine, not the USRP hardware. I admit to being a little bit surprised that you don’t know that already, given how long you’ve been posting things to this list, and using USRP hardware. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 8:12pm UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/10 "2013-05-09T20:12:06Z")
On 05/08/2013 04:33 PM, LD Zhang wrote: > Matlab. But these days the matlab has been awful fast, not much slower > than C. Still my matlab is not organized as nicely as the gnuradio. > Right now I don’t have any streamlined processing. The suggestion on > using the PFB filterbanks and PLLs in parallel and streaming operation > may have significant speed up? Your opinion is appreciated. I can’t tell you if your application will run in real-time, but the polyphase filterbank is the most CPU-efficient way to extract multiple (usually, more than four) signals from a sample stream in Gnuradio. You will probably find Gnuradio much faster than offline processing in Matlab. If the relative phase offset of multiple carriers is important, then you really only want to run a single PLL on one of the carriers, and use the frequency estimate to apply to all the carriers – i.e., the entire bank of signals – so that phase is preserved relative to the “reference” carrier. –n ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [April 11, 2014, 3:22pm UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/11 "2014-04-11T15:22:46Z")
Sorry to dig up an old thread, but does anyone know of anyone who’s implemented a polyphase filter bank on a USRP FPGA? John ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [May 9, 2013, 1:02am UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/12 "2013-05-09T01:02:12Z")
Or am I wrong that the resource is in the computer and not in the USRP? LD From: LD Zhang [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Sent: Wednesday, May 08, 2013 3:51 PM To: ‘Marcus D. Leech’ Cc: ‘removed\_email\_address@domain.invalid’ Subject: RE: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? So maybe the PLL is not a good solution between it will have an unknown amount of initial phase offsets by the time it locks. Since the relative phase between different carriers is the essential information sought after, maybe the better way is to construct very narrowband filters. Now very narrowband can mean a lot of taps, hence a lot of resources consumed. Here is where I don’t know the limitation of resources. If I want to set up a filter of say 4 Hz bandwidth for a signal at 1MHz, and if you have a lot of these signals at different frequencies, what would be the best way to extract these? Maybe the way to go is to have the LO at 1MHz, so the many signals being looked at are +/- many hundreds of kHz. How many taps would it require to extract a signal at say 300 kHz with the 4Hz bandwidth? Can the USRP do 200 taps for each of the 30 carriers (I am just asking without exact calculation here)? Thanks, LD From: Marcus D. Leech [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] Sent: Wednesday, May 08, 2013 3:39 PM To: LD Zhang Cc: removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? I guess there may be an issue that since different PLLs will lock up at different time, so there are unknown amount of initial phase offsets for each PLLs. Would love to know if there are any ways around that. LD Well, presumably, you’d be using a PFB filterbank or something to create the multiple streams, and then use PLL demodulators to extract bits from those. The PFB filterbank should have uniform group delay across all streams, as far as I know. ---
**Author:** ![LD\_Zhang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/90ced4/32.png) [@LD\_Zhang](https://www.ruby-forum.com/u/LD_Zhang)\ **Post date:** [April 14, 2014, 2:26pm UTC](https://www.ruby-forum.com/t/how-many-multiple-simultaneous-plls-can-i-have-running-on-usrp2/228820/13 "2014-04-14T14:26:41Z")
Hi John, You can do a single FPGA Polyphase filter quite easily on a PicoSDR, using Xilinx System Generator FIR Compiler and control your FPGA design from GNU Radio: [http://nutaq.com/en/blog/using-nutaqs-mbdk-gnu-radio-–-part-2-implementing-polyphase-channelizer](http://nutaq.com/en/blog/using-nutaqs-mbdk-gnu-radio-%E2%80%93-part-2-implementing-polyphase-channelizer) Regards, ~Tristan De : discuss-gnuradio-bounces+tristan.martin=removed\_email\_address@domain.invalid [[mailto:discuss-gnuradio-bounces+tristan.martin=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+tristan.martin=removed_email_address@domain.invalid)] De la part de John W. Envoy : 11 avril 2014 09:22 : Marcus D. Leech Cc : removed\_email\_address@domain.invalid Objet : Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2? Sorry to dig up an old thread, but does anyone know of anyone who’s implemented a polyphase filter bank on a USRP FPGA? John On Thu, May 9, 2013 at 12:02 AM, Marcus D. Leech [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: Or am I wrong that the resource is in the computer and not in the USRP? LD It’s all in the computer, unless you do an FPGA-based implementation. Gnu Radio blocks run on the host machine, not the USRP hardware. I admit to being a little bit surprised that you don’t know that already, given how long you’ve been posting things to this list, and using USRP hardware. – Marcus L. Principal Investigator Shirleys Bay Radio Astronomy Consortium > **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org)** > > Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.