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Re: [Discuss-gnuradio] GMSK Modulator Discontinuity


From: Josh Blum
Subject: Re: [Discuss-gnuradio] GMSK Modulator Discontinuity
Date: Mon, 12 Feb 2007 20:35:32 -0500
User-agent: Thunderbird 1.5.0.9 (X11/20070103)

I tried it with the samples.txt and the random source doing 1's and 0's. The constellation doesnt seem to be showing a discontinuity. I attached the screenshot. Maybe this is a bug in the newer version of the GMSK code? I am running whatever I checked out of the release branch a month ago. -Josh

Brian Padalino wrote:
I have been playing around with the GRC (amazing tool - really love
it!) and I was just taking a look at the GMSK Modulator with some
random data.

I couldn't get the random data block to work properly, so I used a
file source that is just some ascii text.  I didn't think this would
matter since it's just random data anyway.  I have it set to repeat
the data once done.

I notice there is a discontinuity with the GMSK modulator.  I am not
sure where it's coming from, or if it's in the Constellation Sink, but
I thought I would just bring it up to the list.

I have attached the sample.grc.xml file along with the samples.txt
ascii file I made.  The concern is when the Constellation Sink format
is set to "line".

I have also attached a picture of the discontinuity I am seeing.

Brian
------------------------------------------------------------------------

<?xml version='1.0' encoding='UTF-8'?>
<flow_graph>
  <timestamp>1171304037.45</timestamp>
  <hostname>SC064299</hostname>
  <version>0.60</version>
  <valid>True</valid>
  <window_width>1200</window_width>
  <window_height>800</window_height>
  <vars>
    <var>
      <key>samp_rate</key>
      <value>28.8e6</value>
      <min/>
      <max/>
    </var>
  </vars>
  <signal_blocks>
    <signal_block>
      <tag>About</tag>
      <id>About0</id>
      <x_coordinate>20</x_coordinate>
      <y_coordinate>20</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>GMSK Example</param>
        <param>Brian Padalino</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Note</tag>
      <id>Note0</id>
      <x_coordinate>20</x_coordinate>
      <y_coordinate>100</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>This is an example of a GMSK modulator generating random 
data.</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Constellation Sink</tag>
      <id>Constellation Sink0</id>
      <x_coordinate>538</x_coordinate>
      <y_coordinate>30</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>Constellation</param>
        <param>512</param>
        <param>$samp_rate</param>
        <param>1</param>
        <param>0</param>
        <param>0.01</param>
        <param>0.01</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>FFT Sink</tag>
      <id>FFT Sink0</id>
      <x_coordinate>535</x_coordinate>
      <y_coordinate>457</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>0</param>
        <param>FFT</param>
        <param>20</param>
        <param>20</param>
        <param>512</param>
        <param>$samp_rate</param>
        <param>0</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Complex Components</tag>
      <id>Complex Components0</id>
      <x_coordinate>532</x_coordinate>
      <y_coordinate>225</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>0</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Scope Sink</tag>
      <id>Scope Sink0</id>
      <x_coordinate>794</x_coordinate>
      <y_coordinate>185</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>1</param>
        <param>Scope</param>
        <param>512</param>
        <param>$samp_rate</param>
        <param>1</param>
        <param>0</param>
        <param>0.001</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Complex Components</tag>
      <id>Complex Components1</id>
      <x_coordinate>524</x_coordinate>
      <y_coordinate>333</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>1</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Scope Sink</tag>
      <id>Scope Sink1</id>
      <x_coordinate>794</x_coordinate>
      <y_coordinate>322</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>1</param>
        <param>Scope</param>
        <param>512</param>
        <param>$samp_rate</param>
        <param>1</param>
        <param>0</param>
        <param>0.001</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>File Source</tag>
      <id>File Source0</id>
      <x_coordinate>21</x_coordinate>
      <y_coordinate>291</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>4</param>
        <param>/tmp/samples.txt</param>
        <param>0</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>GMSK Modulation</tag>
      <id>GMSK Modulation0</id>
      <x_coordinate>276</x_coordinate>
      <y_coordinate>291</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>24</param>
        <param>0.35</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>GMSK Demodulation</tag>
      <id>GMSK Demodulation0</id>
      <x_coordinate>528</x_coordinate>
      <y_coordinate>601</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>2</param>
        <param>0.05</param>
        <param>0.5</param>
        <param>0.005</param>
        <param>0</param>
      </params>
    </signal_block>
    <signal_block>
      <tag>Char to Float</tag>
      <id>Char to Float0</id>
      <x_coordinate>788</x_coordinate>
      <y_coordinate>631</y_coordinate>
      <rotation>0</rotation>
      <params/>
    </signal_block>
    <signal_block>
      <tag>Scope Sink</tag>
      <id>Scope Sink2</id>
      <x_coordinate>998</x_coordinate>
      <y_coordinate>592</y_coordinate>
      <rotation>0</rotation>
      <params>
        <param>1</param>
        <param>Scope</param>
        <param>512</param>
        <param>$samp_rate</param>
        <param>1</param>
        <param>0</param>
        <param>0.001</param>
      </params>
    </signal_block>
  </signal_blocks>
  <connections>
    <connection>
      <input_signal_block_id>Complex Components0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Modulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Complex Components1</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Modulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Constellation Sink0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Modulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>FFT Sink0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Modulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Scope Sink0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>Complex Components0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Scope Sink1</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>Complex Components1</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>GMSK Modulation0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>File Source0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>GMSK Demodulation0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Modulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Char to Float0</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>GMSK Demodulation0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
    <connection>
      <input_signal_block_id>Scope Sink2</input_signal_block_id>
      <input_socket_index>0</input_socket_index>
      <output_signal_block_id>Char to Float0</output_signal_block_id>
      <output_socket_index>0</output_socket_index>
    </connection>
  </connections>
</flow_graph>
------------------------------------------------------------------------

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------------------------------------------------------------------------

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