Raw samples > amplitude

[JBKingdon]

Raw samples will reflect the intermediate frequency output by the R820. Initial implementation working, further work for optimisation.

Processing steps:

• remove DC offset

• rectify

• filter

• [x] DC offset currently calculates an average of the entire buffer for every buffer. What's the minimum that can be done?

  • A fixed offset works well for the prototype (change part of 8c1a585eae6a49642c31a51a5f51951c82c89354)

• [ ] Optimise filtering

[JBKingdon]

Currently taking the average of every buffer to determine the DC offset. Hopefully this can either be a fixed/configurable value or just initialised from the first few seconds of data.

A fixed offset works well for the prototype. How much part to part variation will there be?

[JBKingdon]

Decimation reduces the 8 Msps input rate to 2Msps, offering four positions for phase correction. Need an efficient way to choose the ideal phase. If a buffer contains packets from more than one aircraft they will likely be out of phase, so we probably need to do packet detection and phase correction per packet.

Resolved by not using decimation and performing preamble detection on the filtered samples, so we get phase information per packet.