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Re: [Discuss-gnuradio] question on gmsk mod block

From: Achilleas Anastasopoulos
Subject: Re: [Discuss-gnuradio] question on gmsk mod block
Date: Wed, 09 May 2007 16:07:58 -0400
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

I guess I am answering my own question here.
Just realized that GMSK is defined with pulses that are
indeed the convolution of Gaussian and square pulses.
What a missnomer....


Matt Ettus wrote:
Anastasopoulos Achilleas wrote:


I noticed that the Gaussian pulse is convolved with a rectangular window
in the GMSK modulator. Why is that so?

The pulse is convolved with a rectangular window because the incoming data is not. For example, if you wanted to send 1011 and had 4X interpolated data, the data stream into the gaussian filter would look like:


however, the input to the block in question is:


It was easier to precombine the zero-order hold with the gaussian filter by convolving it rather than having 2 separate filters in the real-time portion of the code.


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