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Re: [Discuss-gnuradio] Using Correlate Estimation with hardware

From: Robert McGwier
Subject: Re: [Discuss-gnuradio] Using Correlate Estimation with hardware
Date: Mon, 28 Aug 2017 11:11:17 -0400


What center frequency did you use?
What RF cards are you using?
Are you using coaxial cable,to connect transmit to receive or are you transmitting and receiving through an antenna?

If you are using antennas please describe them. 



On Aug 26, 2017 12:12 PM, "Sebastian" <address@hidden> wrote:



Hi all,


i run into trouble using the correlate estimation block.


As far as i understand this blocks is used to search for a praeamble which is modulated and filtered with match filter.

To achieve this i used modulate vector. I used this block like it`s done in the corr_est exapmles provided in  /gnuradio/gr-digital/examples/.


Using no UHD but a channel modell everything works fine having clear correlation peak.

Using it with hardware device it doesn`t work anymore, having more peaks avaiable.


My flowgraph is very simple:


Vector_source (using prae+data as vector tagged with tx_sob and tx_eob) -> constellation Modulator(default-QPSK-object) -> stream mux with null_source for break -> uhd sink(sync = PC_clock)


Uhd source (sync = PC_clock) -> low_pass -> corr_est(modulated_vector, 0.9) -> Pll-clock-sync -> Costas Loop -> constellation-demodulator -> float_to_char -> qt time sink



Modulate vector is called with default-qpsk-object as constellation object and [1] as filter taps which i think is right.

The praeamble i am using is the one provided in the examples, so it should be ok too.


I dont have that much experience in this topic so I hope somebody is able to help me.

I am looking forward to hearing from you and thank you in advance.





PS : I am not sure where and how to provide the flowgraph itself but i´ll try to do it asap.





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