GPS signals and abnormal ADC outputs

[teb]

Dear all,

Here's my first attempt of GPS signal acquisition with bladeRF:
http://translate.google.com/translate?h ... eb74c20a8f

I could somehow acquire GPS signals from the bladeRF-cli sampling data,
but the distribution of ADC outputs seem a bit odd. GPS signals are buried
under thermal noise, and the signal distribution has to be Gaussian.

Does anyone have any kind of idea of what causes the abnormal ADC outputs
and how to fix them?

teb

[bpadalino]

We recently added an asynchronous library for reading samples inside the API, but it hasn't been integrated into the CLI just yet. Setting the sample rate to 16368000 is probably causing discontinuities on the received sample stream, contributing to the low SNR. We read 1024 samples at a time currently. Some tricks to getting the samplestream saved to disk quicker are using a file in /dev/shm instead of normal disk.

Getting the async interface in place is one of our main development tasks. If you are feeling adventurous, there is a test for the async interface which can possibly do what you want to do. With a few changes, it might be possible to make it a specific GPS receiver executable. As for the DC offset, we are working on calibration to eliminate the DC offset so you won't have to do it in the MATLAB script.

Let us know if you have any success with the async interface. This is definitely very cool!