Re: [Discuss-gnuradio] Tx Burst for Chirp signals

[CEL]

Could you be a little more specific, please, than "receive, digitize
and re-transmit"? For what purpose? Why a chirp? Can you please give us
the bigger picture, here? What's the thing you need to build?

Best regards,
Marcus
On Fri, 2018-05-11 at 02:03 +0000, Yeo Jin Kuang Alvin (IA) wrote:
> Hello,
> 
> I am currently trying to work on the USRP B210 to act as a
> transceiver. Basically, what I am tasked to do is to receive,
> digitize, modulate and re-transmit. So what I am planning to do now
> is to create a chirp signal in the USRP B210 and transmit back to
> itself to the RX port. As a result, I have to send a pulse and stop
> for a moment while it is receiving and then transmit again.
> 
> Thank you in advanced!
> 
> -----Original Message-----
> From: Müller, Marcus (CEL) [mailto:address@hidden 
> Sent: Thursday, 10 May 2018 9:09 PM
> To: Yeo Jin Kuang Alvin (IA); address@hidden
> Subject: Re: [Discuss-gnuradio] Tx Burst for Chirp signals
> 
> sure, but it's not the way I'd recommend for perfectly periodic
> transmissions and I'm almost certain this will just lead us further
> down your XY problem: https://xyproblem.info
> 
> Can you maybe explain in detail what you need chirps for, why you
> need
> them at this low repitition rate, what the purpose of all this is? We
> might be better at helping you that way.
> 
> thank you,
> Marcus
> 
> On Thu, 2018-05-10 at 09:58 +0000, Yeo Jin Kuang Alvin (IA) wrote:
> > Hi,
> > 
> > Thank you again. Are there any examples or guides I can refer to
> > regarding the tx_time tags? Will this allow me to transmit every
> > few
> > seconds?
> > 
> > Thank you in advanced!
> > 
> > -----Original Message-----
> > From: Müller, Marcus (CEL) [mailto:address@hidden 
> > Sent: Thursday, 10 May 2018 5:34 PM
> > To: Yeo Jin Kuang Alvin (IA); address@hidden
> > Subject: Re: [Discuss-gnuradio] Tx Burst for Chirp signals
> > 
> > Hi!
> > 
> > So, you're continuously generating data to send, so it continuously
> > sends data – it works as you've designed it. Maybe you want to
> > somehow
> > add "tx_time" tags every "packet length" samples?
> > Also, make sure that one packet really contains one chirp. In your
> > previous flow graph, that wasn't the case, so make sure the packet
> > length corresponds to the number of samples per chirp.
> > 
> > Best regards,
> > Marcus
> > 
> > On Thu, 2018-05-10 at 09:20 +0000, Yeo Jin Kuang Alvin (IA) wrote:
> > > Hi, 
> > > 
> > > Thanks Marcus! Corrected it and thanks for the info!
> > > 
> > > 1)      I would like to transmit burst signals of the chirp
> > > generated  from the flowgraph attached. I tried using the “stream
> > > to
> > > Tagged stream” way, but when I ran the GNU Radio Companion, it’s
> > > being  transmitted continuously. Nothing seems to be happening.
> > > Am
> > > I
> > > doing  something wrong and is there a better way for burst
> > > transmission?
> > > 
> > > Does anyone know this?
> > > 
> > > Thanks in advanced!
> > > 
> > > -----Original Message-----
> > > From: Müller, Marcus (CEL) [mailto:address@hidden 
> > > Sent: Thursday, 10 May 2018 5:06 PM
> > > To: Yeo Jin Kuang Alvin (IA); address@hidden
> > > Subject: Re: [Discuss-gnuradio] Tx Burst for Chirp signals
> > > 
> > > Hi!
> > > 
> > > your receiver low pass filter is incorrectly parameterized,
> > > probably
> > > (sampling rate isn't 32 MS/s). And so is the rest of your flow
> > > graph
> > > –
> > > your USRP is using a sampling rate of 2 MS/s, but you act as if
> > > it's
> > > running at 32 MS/s. Start with 2 MS/s and make it work with that
> > > –
> > > then
> > > later scale up (the processing load of 32 MS/s is harder than you
> > > probably think).
> > > Remember that GNU Radio is pure DSP, so all the axis labels on
> > > your
> > > visualizations are just that – labels, interpreting relative
> > > frequencies (i.e. frequencies divided by the sampling rate) by
> > > multiplying them with the value you entered in bandwidth. The
> > > "physical
> > > meaning" of your signal is defined by the sampling rate of your
> > > physical device.
> > > Thus, you want to use the same sampling rate everywhere in your
> > > flow
> > > graph. These things mean! something.
> > > 
> > > Best regards,
> > > Marcus
> > > 
> > > On Thu, 2018-05-10 at 08:31 +0000, Yeo Jin Kuang Alvin (IA)
> > > wrote:
> > > > Hi everyone,
> > > >  
> > > > There are two questions that I would like to ask.
> > > >  
> > > > 1)      I would like to transmit burst signals of the chirp
> > > > generated
> > > > from the flowgraph attached. I tried using the “stream to
> > > > Tagged
> > > > stream” way, but when I ran the GNU Radio Companion, it’s being
> > > > transmitted continuously. Nothing seems to be happening. Am I
> > > > doing
> > > > something wrong and is there a better way for burst
> > > > transmission?
> > > >  
> > > > 2)      I noticed something with the sampling rates of the
> > > > blocks.
> > > > When I use the same sampling rate for all the blocks, I get
> > > > underflow
> > > > “UUU”. However, when I changed all the block’s sampling rate to
> > > > 32MHz
> > > > and leave the USRP Sink and Source to 2MHz, no underflow is
> > > > seen
> > > > but
> > > > there is still overflow (seen in the attached screenshot).
> > > >  
> > > > What is the difference between the USRP’s sampling rate
> > > > compared
> > > > to
> > > > the other block’s sampling rate?
> > > >  
> > > > Thank you in advanced!
> > > > _______________________________________________
> > > > Discuss-gnuradio mailing list
> > > > address@hidden
> > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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