Correlator Troubleshooting

https://youtu.be/T6TwN2FvfAo

 

Here’s an update from the lab on correlator¬†troubleshooting.¬†We are trying to get correlation understood and under control over the air.

We have two flowgraphs that we believe aren’t working due to the Correlation Estimation Issue here https://github.com/gnuradio/gnuradio/issues/1207

We don’t think it’s operator error, but we’re relatively new to GNU Radio, and would welcome any comment or critique that helps to solve this!

FM_ARAP_to_downlink.grc is the flowgraph we are using for transmit side.

What does it do?

It collects up four analog FM channels, digitizes, and transmits a time division multiplexed signal out. This is, in general, a simple model of our uplink for a Groundsat or payload.

We see the expected transmitted signal on a spectrum analyzer and on a HackRF portapack and on the receiving system across the lab.

The receiving flowgraph is called TDM_downlink_rx.grc

What does it do?

It takes the time division multiplex signal and is supposed to break the channels back out.

This demo has worked in the past, but not anymore, and definitely not over the air now.

The problem seems to be the correlator, and it seems to be the same trouble reported in the issue.

We want to write a DVB-S2/X correlator. I think we can also help fix this correlation estimation block. In all cases, we want to comply with the tag scheme produced, so that downstream blocks already in GNU Radio get what they’re expecting, if they are expecting these types of tags.

Plenty more at https://github.com/phase4ground

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