[Discuss-gnuradio] LMS-DD Equalizer with OOK Modulation

[Vijay Galbaransingh]

Hello,

 

I am trying to demodulate an on-off-keyed signal, and in doing so am trying to use the LMS-DD equalizer as follows:

 

Source --> BPF --> AGC --> PLL --> RRC --> M&M Clk Recovery --> LMS-DD EQ --> GUI Sink.

 

The LMS-DD has gain set to 0.01, taps set to 20, and sps set to 1 to match the M&M output. The constellation object I’m passing to the LMS-DD has: Symbol Map [0,1], Constellation Points [0,1], Rot. Symmetry 1, Dimensionality 1.

 

The issue I’m having is that the equalizer’s output converges towards being zero-centred—instead of getting values between 0 and 1, it’s spitting them out in the range -0.5–0.5. Also the waveform itself doesn’t look at all like a pattern of high and low.

 

Am I using this module incorrectly? Did I mess up in the constellation settings? I’ve tried tinkering with all of the parameters of the LMS-DD and constellation blocks but with no success. It is entirely possible that the noise and multipath issues in my testing environment are too much, but I’d like to make sure I’m at least using the modules correctly before I go back to the drawing board!

 

Thanks,

Vijay