Re: [Discuss-gnuradio] Signal reconstruction
Dear Aadil, 1) First upgrade to latest gnuradio release. 2) Put the USRP behind. 3) Start generating the sinewave by software using gr.sig_source 4) Do the mathematics or FFT or whatever you want on this simulated signal. 5) If everything is ok, switch back to USRP, if not, then you have a problem in using the gnuradio, and you should learn more. Regards, Firas - Original Message From: Aadil Volkwin <[EMAIL PROTECTED]> To: Eric Blossom <[EMAIL PROTECTED]> Cc: Firas abbas <[EMAIL PROTECTED]>; discuss-gnuradio@gnu.org Sent: Saturday, November 10, 2007 6:27:40 PM Subject: Re: [Discuss-gnuradio] Signal reconstruction Also, it's not clear to me what you're actually trying to do. I'd like to capture FM signals and perform ambiguity measurements on them. at the moment, i am failing to capture data correctly. If you want to plot data in real time, please use either the usrp_fft.py or usrp_oscope.py applications. You can capture data to disk using the usrp_rx_cfile.py example. I suggest you start with these, then do your own experiments. These are the files that I have been using. usrp_rx_cfile.py to write to file and usrp_fft.py and usrp_oscope.py for realtime examination of the data and Matlab for post processing, based on the utils in gnuradio-core. Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
> Also, it's not clear to me what you're actually trying to do. I'd like to capture FM signals and perform ambiguity measurements on them. at the moment, i am failing to capture data correctly. If you want to plot data in real time, please use either the > usrp_fft.py or usrp_oscope.py applications. You can capture data > to disk using the usrp_rx_cfile.py example. > > I suggest you start with these, then do your own experiments. These are the files that I have been using. usrp_rx_cfile.py to write to file and usrp_fft.py and usrp_oscope.py for realtime examination of the data and Matlab for post processing, based on the utils in gnuradio-core. Eric > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
On Sat, Nov 10, 2007 at 02:34:11PM +0200, Aadil Volkwin wrote: > The Scope was definitely usrp_oscope.py Used Directly from the from the > examples folder: > > [EMAIL > PROTECTED]:~/Desktop/GnuRadioResources/gnuradio-3.0.2/gnuradio-examples/python/usrp$ > ./usrp_oscope.py > I note that you are using gnuradio-3.0.2. That's almost a year old. I suggest that you consider using the latest stable code, the 3.1.1 release, available at ftp://ftp.gnu.org/gnu/gnuradio/gnuradio-3.1.1.tar.gz Also, it's not clear to me what you're actually trying to do. If you want to plot data in real time, please use either the usrp_fft.py or usrp_oscope.py applications. You can capture data to disk using the usrp_rx_cfile.py example. I suggest you start with these, then do your own experiments. Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Thanks for responding and for your input, I answer your questions below, >You're transmitting a 250kHz square source which is the summation of all odd harmonics of >250kHz. I believe that is why you were told to switch over to a sine wave which you would >probably just see a single tone. I have switched over to a sine wave, but I still don't get the single peak on the FFT as one would expect, that's the source of this conversation. >I am sorry if I am unfamiliar, but what exactly are you trying to >accomplish, and how do you expect to do it with a square wave? What I want to do (for now) is be able to correctly digitise a signal and write it to file (thereafter I will do various signal processing). My short term objective is to digitise "off air FM signals" and perform ambiguity measurements. I'm using the sine wave as input and plotting it's FFT to see if I was able to correctly digitise it. This should be a fairly trivial 5min process but I've been at it for a week!! Thus far non of the suggestions have helped cure my problem. Images of my matlab plots are available here: https://rrsg.ee.uct.ac.za/members/aadil/ I hope you can help, I feel hopeless right now. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
On Nov 10, 2007 9:39 AM, Aadil Volkwin <[EMAIL PROTECTED]> wrote: > Ok, > > I still have the problem with the reconstruction though. > > When I perform the FFT on the sample set, the plots are not as you would > expect for a pure 250KHz signal? You're transmitting a 250kHz square source which is the summation of all odd harmonics of 250kHz. I believe that is why you were told to switch over to a sine wave which you would probably just see a single tone. Due to bandwidth limitations, transmitting square waves over the air doesn't work quite as one may expect. > This is the major concern for me and the crux of my problem. I am sorry if I am unfamiliar, but what exactly are you trying to accomplish, and how do you expect to do it with a square wave? Brian ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Ok, I still have the problem with the reconstruction though. When I perform the FFT on the sample set, the plots are not as you would expect for a pure 250KHz signal? This is the major concern for me and the crux of my problem. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
It seems that the signal is ok. If you use a pure sinusoidal signal you will see a much clearer picture. Firas Aadil Volkwin <[EMAIL PROTECTED]> wrote: It seems I need to hit return after i've entered the values, my error. the new plot is on the website: https://rrsg.ee.uct.ac.za/members/aadil/ ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
It seems I need to hit return after i've entered the values, my error. the new plot is on the website: https://rrsg.ee.uct.ac.za/members/aadil/ ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi, Sorry about the scope file, I using a modified version and it seems that I being confused with the standrad one. However, there is something strange in the data shown in your picture. Since you are using decimation =8, the data coming across the USB should be complex 8 Msps. But your scope is showing ([EMAIL PROTECTED]: 4M) which is wrong. another thing, the DDC be should equal 0 , while in your picture it is being (DDC : -8M) . Firas Aadil Volkwin <[EMAIL PROTECTED]> wrote: The Scope was definitely usrp_oscope.py Used Directly from the from the examples folder: [EMAIL PROTECTED]:~/Desktop/GnuRadioResources/gnuradio-3.0.2/gnuradio-examples/python/usrp$ ./usrp_oscope.py Aadil On 10/11/2007, Firas abbas <[EMAIL PROTECTED]> wrote: Hi, Input signal level is ok.The scope pictures was not generated by usrp_oscope.py. What is the program used to generate it ? Test The signal with usrp_oscope.py Firas Aadil Volkwin <[EMAIL PROTECTED]> wrote: Hi, I've updated the scope screenshot on the website. Two shots are available, notice there seems to be some kind of modulation??? I've tested the input signal with an external scope and the input signal is fine. I don't know why the usrp scope is "misbehaving" The input signal level is set at -16.02dBm Aadil On 10/11/2007, Firas abbas < [EMAIL PROTECTED] > wrote:Hi, Use center frequency =0 in the usrp scope. If you use center frequency = 250K, you will shift the signal to 0 Hz. What is your signal input level in dBm ? Firas Aadil Volkwin < [EMAIL PROTECTED]> wrote: Hi, Firstly my apologies for posting known quantities, I guessed that members would like to see in what way I tinkered with usrp_rx_cfile.py. point taken though. Screen shots of the MATLAB plots as well as the usrp_oscop.py output can be found at: https://rrsg.ee.uct.ac.za/members/aadil/ I'm pretty sure the MATLAB is correct. I have upped the input freq to 250KHz, now attempting a square wave (in desperation) and set the options.freq to 0 in ---> self.u.tune(0, self.subdev, options.freq) I'm Still not getting sensible plots. Thanks again, Aadil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
The Scope was definitely usrp_oscope.py Used Directly from the from the examples folder: [EMAIL PROTECTED]:~/Desktop/GnuRadioResources/gnuradio-3.0.2/gnuradio-examples/python/usrp$ ./usrp_oscope.py Aadil On 10/11/2007, Firas abbas <[EMAIL PROTECTED]> wrote: > > Hi, > > Input signal level is ok.The scope pictures was not generated by > usrp_oscope.py. What is the program used to generate it ? Test The signal > with usrp_oscope.py > > Firas > > *Aadil Volkwin <[EMAIL PROTECTED]>* wrote: > > Hi, > > I've updated the scope screenshot on the website. Two shots are available, > notice there seems to be some kind of modulation??? I've tested the input > signal with an external scope and the input signal is fine. I don't know why > the usrp scope is "misbehaving" > > The input signal level is set at -16.02dBm > > Aadil > > On 10/11/2007, Firas abbas <[EMAIL PROTECTED] > wrote: > > > > Hi, > > > > Use center frequency =0 in the usrp scope. If you use center frequency = > > 250K, you will shift the signal to 0 Hz. > > > > What is your signal input level in dBm ? > > > > Firas > > > > *Aadil Volkwin < [EMAIL PROTECTED]>* wrote: > > > > Hi, > > > > Firstly my apologies for posting known quantities, I guessed that > > members would like to see in what way I tinkered with usrp_rx_cfile.py. > > point taken though. > > > > Screen shots of the MATLAB plots as well as the usrp_oscop.py output can > > be found at: > > > > https://rrsg.ee.uct.ac.za/members/aadil/ > > > > I'm pretty sure the MATLAB is correct. > > > > I have upped the input freq to 250KHz, now attempting a square wave (in > > desperation) and > > set the options.freq to 0 in ---> self.u.tune(0, self.subdev, > > options.freq) > > > > I'm Still not getting sensible plots. > > > > Thanks again, > > > > Aadil > > > > > > > > > > > > > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi, Input signal level is ok.The scope pictures was not generated by usrp_oscope.py. What is the program used to generate it ? Test The signal with usrp_oscope.py Firas Aadil Volkwin <[EMAIL PROTECTED]> wrote: Hi, I've updated the scope screenshot on the website. Two shots are available, notice there seems to be some kind of modulation??? I've tested the input signal with an external scope and the input signal is fine. I don't know why the usrp scope is "misbehaving" The input signal level is set at -16.02dBm Aadil On 10/11/2007, Firas abbas <[EMAIL PROTECTED] > wrote:Hi, Use center frequency =0 in the usrp scope. If you use center frequency = 250K, you will shift the signal to 0 Hz. What is your signal input level in dBm ? Firas Aadil Volkwin < [EMAIL PROTECTED]> wrote: Hi, Firstly my apologies for posting known quantities, I guessed that members would like to see in what way I tinkered with usrp_rx_cfile.py. point taken though. Screen shots of the MATLAB plots as well as the usrp_oscop.py output can be found at: https://rrsg.ee.uct.ac.za/members/aadil/ I'm pretty sure the MATLAB is correct. I have upped the input freq to 250KHz, now attempting a square wave (in desperation) and set the options.freq to 0 in ---> self.u.tune(0, self.subdev, options.freq) I'm Still not getting sensible plots. Thanks again, Aadil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi, I've updated the scope screenshot on the website. Two shots are available, notice there seems to be some kind of modulation??? I've tested the input signal with an external scope and the input signal is fine. I don't know why the usrp scope is "misbehaving" The input signal level is set at -16.02dBm Aadil On 10/11/2007, Firas abbas <[EMAIL PROTECTED]> wrote: > > Hi, > > Use center frequency =0 in the usrp scope. If you use center frequency = > 250K, you will shift the signal to 0 Hz. > > What is your signal input level in dBm ? > > Firas > > *Aadil Volkwin <[EMAIL PROTECTED]>* wrote: > > Hi, > > Firstly my apologies for posting known quantities, I guessed that members > would like to see in what way I tinkered with usrp_rx_cfile.py. point taken > though. > > Screen shots of the MATLAB plots as well as the usrp_oscop.py output can > be found at: > > https://rrsg.ee.uct.ac.za/members/aadil/ > > I'm pretty sure the MATLAB is correct. > > I have upped the input freq to 250KHz, now attempting a square wave (in > desperation) and > set the options.freq to 0 in --->self.u.tune(0, self.subdev, options.freq) > > I'm Still not getting sensible plots. > > Thanks again, > > Aadil > > > > > ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi, Use center frequency =0 in the usrp scope. If you use center frequency = 250K, you will shift the signal to 0 Hz. What is your signal input level in dBm ? Firas Aadil Volkwin <[EMAIL PROTECTED]> wrote: Hi, Firstly my apologies for posting known quantities, I guessed that members would like to see in what way I tinkered with usrp_rx_cfile.py. point taken though. Screen shots of the MATLAB plots as well as the usrp_oscop.py output can be found at: https://rrsg.ee.uct.ac.za/members/aadil/ I'm pretty sure the MATLAB is correct. I have upped the input freq to 250KHz, now attempting a square wave (in desperation) and set the options.freq to 0 in --->self.u.tune(0, self.subdev, options.freq) I'm Still not getting sensible plots. Thanks again, Aadil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi, Firstly my apologies for posting known quantities, I guessed that members would like to see in what way I tinkered with usrp_rx_cfile.py. point taken though. Screen shots of the MATLAB plots as well as the usrp_oscop.py output can be found at: https://rrsg.ee.uct.ac.za/members/aadil/ I'm pretty sure the MATLAB is correct. I have upped the input freq to 250KHz, now attempting a square wave (in desperation) and set the options.freq to 0 in --->self.u.tune(0, self.subdev, options.freq) I'm Still not getting sensible plots. Thanks again, Aadil ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Signal reconstruction
Hi,
I think your problem is simple, you are wrong in two thinks,
1) You chooses to input 50 KHz signal to your USRP, and I think you are using
the Basic RX daughter board, which have an RF transformer that needs at least
200KHz input signal to pass it without distortion.
2) You used a DDC default center frequency of 50KHz, which means that your
input 50 KHz signal will be centered around the 0 Hz!.how you will plot it ?
To have thinks work, input 200 KHz signal, and use 0 Hz as the default frequency
[ parser.add_option("-f", "--freq", type="eng_float", default=0, help="set
frequency to FREQ", metavar="FREQ")]
Firas,
Aadil Volkwin <[EMAIL PROTECTED]> wrote: Hi,
I've been bashing my head for a couple of days on what should be a trivial
process.
I would really appreciate it if somebody could please come to my rescue.
I'd like to digitise a signal, intented to be off air FM signal, but for the
moment, i'm capturing a 50KHz sinusiod and doing the reconstruction in
MATLAB to test that im capturing the samples correctly.
on plotting the FFT in MATLAB, it's clear that something's a miss...I don't
know where :/ i've been at this for ages!!!
here's my code: I really hope somebody can help, I know this should be a simple
matter. The Matlab code follows below the Python stuff.
=
#!/usr/bin/env python
"""
Read samples from the USRP and write to file formatted as binary
outputs single precision complex float values or complex short values
(interleaved 16 bit signed short integers).
"""
from gnuradio import gr, eng_notation
from gnuradio import audio
from gnuradio import usrp
from gnuradio.eng_option import eng_option
from optparse import OptionParser
class my_graph(gr.flow_graph):
def __init__(self):
gr.flow_graph.__init__(self)
usage="%prog: [options] output_filename"
parser = OptionParser(option_class=eng_option, usage=usage)
parser.add_option("-R", "--rx-subdev-spec", type="subdev", default=(0,
0),
help="select USRP Rx side A or B (default=A)")
parser.add_option ("-d", "--decim", type="int", default=8,
help="set fgpa decimation rate to DECIM
[default=%default]")
parser.add_option("-f", "--freq", type="eng_float", default=50e3,
help="set frequency to FREQ", metavar="FREQ")
parser.add_option("-g", "--gain", type="eng_float", default=None,
help="set gain in dB (default is midpoint)")
parser.add_option("-N", "--nsamples", type="eng_float", default=2000,
help="number of samples to collect [default=+inf]")
(options, args) = parser.parse_args ()
if len(args) != 1:
parser.print_help()
raise SystemExit, 1
filename = args[0]
if options.freq is None:
parser.print_help()
sys.stderr.write('You must specify the frequency with -f FREQ\n');
raise SystemExit, 1
# build the graph
self.u = usrp.source_c(decim_rate=options.decim)
self.dst = gr.file_sink(gr.sizeof_gr_complex, filename)
self.head = gr.head(gr.sizeof_gr_complex, int(options.nsamples))
self.connect(self.u, self.head, self.dst)
rx_subdev_spec = usrp.pick_rx_subdevice(self.u)
self.u.set_mux(usrp.determine_rx_mux_value(self.u,
options.rx_subdev_spec))
# determine the daughterboard subdevice we're using
self.subdev = usrp.selected_subdev(self.u, options.rx_subdev_spec)
print "Using RX d'board %s" % (self.subdev.side_and_name (),)
input_rate = self.u.adc_freq() / self.u.decim_rate()
print "USB sample rate %s" % (eng_notation.num_to_str(input_rate))
print "Freq is set to: %s" % (options.freq)
if options.gain is None:
# if no gain was specified, use the mid-point in dB
g = self.subdev.gain_range()
options.gain = float(g[0]+g[1])/2
self.subdev.set_gain (options.gain)
r = self.u.set_rx_freq (0, options.freq) #self.u.tune(0, self.subdev,
options.freq)
if not r:
sys.stderr.write('Failed to set frequency\n')
raise SystemExit, 1
if __name__ == '__main__':
try:
my_graph().run()
except KeyboardInterrupt:
pass
==
MATLAB
ms = 1e-3;
kHz = 1e3;
count = 2000;
decim_rate = 8;
Fsamp = 64e6;
Fsamp_real = Fsamp./decim_rate;
%set the time axis
dt = 1./Fsamp_real;
T_end = count./Fsamp_real;
t = 0:dt:T_end-dt;
%t = dt:dt:T_end;
df = fopen('signal_samples.dat');
y = fread (df,[2, count], 'float');
fclose(df);
%plot I and Q
figure (1)
subplot(211)
plot(t/ms,y(1,:));
grid on;
xlabel('ms')
title ('I data')
subplot(212)
plot(t/ms,y(2,:));
grid on;
Re: [Discuss-gnuradio] Signal reconstruction
Aadil Volkwin wrote:
> Hi,
>
> I've been bashing my head for a couple of days on what should be a trivial
> process.
> I would really appreciate it if somebody could please come to my rescue.
>
> I'd like to digitise a signal, intented to be off air FM signal, but for the
> moment, i'm capturing a 50KHz sinusiod and doing the reconstruction in
> MATLAB to test that im capturing the samples correctly.
>
> on plotting the FFT in MATLAB, it's clear that something's a miss...I don't
> know where :/ i've been at this for ages!!!
Can you describe what is miss with what you see.
It would help if you could make some screenshots of yout matlab plots available
on some website.
(Please don't send them as attachments to the list)
If you run usrp_oscope.py or usrp_fft.py does your signal look OK?
If it does then probably matlab does not read in your samples the right way.
I can imagine that matlab gets the order of I and Q wrong (I=Q and Q=I)
Or do you have the axis right
I don't know if it should be
> y = fread (df,[2, count], 'float');
or maybe
> y = fread (df,[count, 2], 'float');
Greetings,
Martin
> here's my code: I really hope somebody can help, I know this should be a
> simple matter. The Matlab code follows below the Python stuff.
>
> =
>
> #!/usr/bin/env python
>
> """
> Read samples from the USRP and write to file formatted as binary
> outputs single precision complex float values or complex short values
> (interleaved 16 bit signed short integers).
>
> """
>
> from gnuradio import gr, eng_notation
> from gnuradio import audio
> from gnuradio import usrp
> from gnuradio.eng_option import eng_option
> from optparse import OptionParser
>
> class my_graph(gr.flow_graph):
>
> def __init__(self):
> gr.flow_graph.__init__(self)
>
> usage="%prog: [options] output_filename"
> parser = OptionParser(option_class=eng_option, usage=usage)
> parser.add_option("-R", "--rx-subdev-spec", type="subdev",
> default=(0, 0),
> help="select USRP Rx side A or B (default=A)")
> parser.add_option("-d", "--decim", type="int", default=8,
> help="set fgpa decimation rate to DECIM
> [default=%default]")
> parser.add_option("-f", "--freq", type="eng_float", default=50e3,
> help="set frequency to FREQ", metavar="FREQ")
> parser.add_option("-g", "--gain", type="eng_float", default=None,
> help="set gain in dB (default is midpoint)")
> parser.add_option("-N", "--nsamples", type="eng_float",
> default=2000,
> help="number of samples to collect
> [default=+inf]")
>
> (options, args) = parser.parse_args ()
> if len(args) != 1:
> parser.print_help()
> raise SystemExit, 1
>
> filename = args[0]
>
> if options.freq is None:
> parser.print_help()
> sys.stderr.write('You must specify the frequency with -f
> FREQ\n');
> raise SystemExit, 1
>
> # build the graph
>
> self.u = usrp.source_c(decim_rate=options.decim)
>
> self.dst = gr.file_sink(gr.sizeof_gr_complex, filename)
>
> self.head = gr.head(gr.sizeof_gr_complex, int(options.nsamples))
>
> self.connect(self.u, self.head, self.dst)
>
>
> rx_subdev_spec = usrp.pick_rx_subdevice(self.u)
> self.u.set_mux(usrp.determine_rx_mux_value(self.u,
> options.rx_subdev_spec))
>
> # determine the daughterboard subdevice we're using
> self.subdev = usrp.selected_subdev(self.u, options.rx_subdev_spec)
> print "Using RX d'board %s" % (self.subdev.side_and_name(),)
> input_rate = self.u.adc_freq() / self.u.decim_rate()
> print "USB sample rate %s" % (eng_notation.num_to_str(input_rate))
> print "Freq is set to: %s" % (options.freq)
>
> if options.gain is None:
> # if no gain was specified, use the mid-point in dB
> g = self.subdev.gain_range()
> options.gain = float(g[0]+g[1])/2
>
> self.subdev.set_gain(options.gain)
>
> r = self.u.set_rx_freq (0, options.freq) #self.u.tune(0, self.subdev,
> options.freq)
> if not r:
> sys.stderr.write('Failed to set frequency\n')
> raise SystemExit, 1
>
>
> if __name__ == '__main__':
> try:
> my_graph().run()
> except KeyboardInterrupt:
> pass
> ==
>
> MATLAB
>
> ms = 1e-3;
> kHz = 1e3;
>
>
> count = 2000;
> decim_rate = 8;
> Fsamp = 64e6;
> Fsamp_real = Fsamp./decim_rate;
>
> %set the time axis
> dt = 1./Fsamp_real;
> T_end = count./Fsamp_real;
> t = 0:dt:T_end-dt;
> %t = dt:dt:T_end;
>
>
> df = fopen('signal_samples.dat');
> y = fread (df,[2, count], 'float');
> fclose(df);
>
>
> %plot I and Q
> figure (1)
> subplot(211)
> plot(t/ms,y(1,:));
> grid on;
> xlabel('ms')
