[quote=“david.baker”]FlightAware is a plane tracking company and FlightAware’s ADS-B network will work with other receivers so definitely post about receivers that do ADSB and how they work.
The LimeSDR is made by lime microsystems using their next generation SDR chip. The 7002 specs are much better than the 6002.
Looks like lime is doing a fire sale on their older generation chips. The new chip 7002 chips are what the older 6002 chip were priced at.
digikey.com/product-search/e … 6,fff80545
The hardest part of using the LimeSDR for ADS-B is the FPGA decoding. You will also probably not find an open sourced version of the FPGA ADS-B decoder and I haven’t seen anyone announce an open sourced FPGA RTL. The new SBS trilby receiver also has an FPGA and they will definitely have an FPGA ADS-B decoder. They haven’t said anything about how open their ADS-B decoder is or how well it performs.
We are mostly finding that arm Cpu are getting cheaper much faster than FPGA. If FPGA are cheaper this might change but I don’t see this happening in this decade. So boards like the limeSDR are going to be in a niche where performance and low power are the main driving factors instead of cost.
Actually, funny you should mention no one open sourcing the VHDL to an ADS-B decoder… github.com/Nuand/bladeRF-adsb . We announced this just last week. It is a piece of bladeRF specific IP, and cannot run on other devices for a variety of reasons.
The algorithm we implemented runs in realtime on the bladeRF’s FPGA but cannot run in realtime on a modern Intel i7 or even most GPGPUs. Essentially every new sample triggers about 7000 new arithmetic operations, at 40MSPS that is about 280 GMACs (Multiply and Accumulates) which would translate to 280GFlops. However the GFlops require some logic, meaning a GPGPU would suffer from pipeline stalls, causing the effective GMAC/GFLOP requirement to jump 10x.
And you are right, the hardest part is definitely the VHDL, and the validation of the whole system. We began this project at your and Karl’s behest last summer and finished it by November, it’s a pity we never heard back from you.