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

[Achilleas Anastasopoulos]

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....

Achilleas

Matt Ettus wrote:
> Anastasopoulos Achilleas wrote:
>
> > Hi,
> >
> > 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:
>
> 1,1,1,1,-1,-1,-1,-1,1,1,1,1,1,1,1,1
>
> however, the input to the block in question is:
>
> 1,0,0,0,-1,0,0,0,1,0,0,0,1,0,0,0
>
> 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.
>
> Matt