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

[Yeo Jin Kuang Alvin (IA)]

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