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Hi,

I am trying to use Polyphase Clock Synchronization (PCS) block to

conduct

timing synchronization for QPSK signal with half-sine pulse shaping. In the

doxygen document of PCS, it says that the “taps” parameter could be the

matched filter. Thus, I put the matched filter of half-sine pulse here,

[0,sin(pi/4),1,sin(3*pi/4)]. However, the output is all 0.Is there anyone knows how to generate the “taps” parameter here? Any

suggestion would be appreciated. Thanks in advance.

I’m not an expert in all the details, but what I know is that the taps

there need to be generated at “Filter Size” * “Sample Rate”.

So I’d try something like [math.sin(math.pi*i/(32*4)) for i in

range(32*4)]

Cheers,

Sylvain

On Mon, Apr 27, 2015 at 9:34 AM, Sylvain M. [email protected]

wrote:

I’m not an expert in all the details, but what I know is that the taps

there need to be generated at “Filter Size” * “Sample Rate”.So I’d try something like [math.sin(math.pi

i/(324)) for i in range(32*4)]Cheers,

Sylvain

What Sylvain said should work, I believe. But you should study the

manual

page on this block:

http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1pfb__clock__sync__ccf.html

Hopefully understanding the way it works will help you understand why

the

taps need to be this way.

Tom

Hi Sylvain and Tom,

Thanks a lot. It works.

So the “Taps” should contain all the matched filter coefficients for

Filter_Size (32) filters instead of just one filter. Then each filter

takes

SPS (4) out of them to generate a phase-shifted shaping filter. Hence,

we

have a filterbank with different phases. The optimal sample timing could

be

estimated as described in Tutorial 7.

Best regards,

Su Li

2015-04-27 15:58 GMT+02:00 Tom R. [email protected]: