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[Discuss-gnuradio] Simple Correlator Input Requirements


From: Douglas Ellena
Subject: [Discuss-gnuradio] Simple Correlator Input Requirements
Date: Wed, 27 Feb 2013 20:56:58 +0000

I believe the GRC "Simple Correlator" is the inverse of the "Simple Framer," yet it takes float inputs.  What is the proper format of the input data?  I see that the code does some slicing on the input, so I expect the floats to be positive and negative float values representing ones or zeros respectively.

Asked another way, what is wrong with the simple flowgraph below?

File Source (byte) ->
    Simple Framer (Payload Size = 6) ->
        Throttle ->
            Packed to Unpacked (Byte,1 bit per Chunk, MSB) - This block causes the bits to be represented as serial bytes. ->
                Char to Float (scale 1) ->
                    Add Const (float, -0.5)  This removes the DC bias to facilitate slicing. ->
                        Simple Correlator (Payload Byte Size = 6) ->
                            File Sink (byte).

No data comes out of the Simple Correlator, but using GUI sinks, I see that all the other blocks work.

There is mention on the Internet that the Simple Correlator requires 8x oversampling.  Is that true?  I only need correlation at the bit level, not at the symbol timing.  Is the Simple Correlator the wrong block to undo the Simple Framer?

-Thanks


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