The RTL-SDR is only an RF front-end that brings down the desired RF signal to a baseband frequency, followed by an quadrature AD converter, followed by a USB interface.
All the DSP operations are already done by the Raspberry Pi.
In the diagram above, it shows “DSP” but that’s just two basic multiplications and a low pass filter. It doesn’t do any heavy lifting.
If you want to get rid of the RTL-SDR, you’d need that analog RF block and the AD converter inside the Pi. That doesn’t make a lot of sense of a general purpose SOC.
The challenge is that the raspberry pi doesn't have an analog to digital converter with enough bandwidth to sample the ADS-B data, or any way to downconvert the signal from 1090MHz to see it to begin with, so you are going to need hardware.
ADSB uses pulse amplitude modulation, so if you built or bought a downconverter and amplifier, you might be able to pick up the modulation by sending the downconverted/amplified signal to a GPIO pin and reading its state at say 5-10 MHz.
It'd be pretty messy and you'd have to write the demodulator from scratch, but might be able to pickup the frame decoding from one of the other products out there to actually read the content.
Would be a really fun project but not likely to save money and definitely not time.
TomVDB|5 years ago
All the DSP operations are already done by the Raspberry Pi.
http://aaronscher.com/wireless_com_SDR/rtl_sdr_info.html
In the diagram above, it shows “DSP” but that’s just two basic multiplications and a low pass filter. It doesn’t do any heavy lifting.
If you want to get rid of the RTL-SDR, you’d need that analog RF block and the AD converter inside the Pi. That doesn’t make a lot of sense of a general purpose SOC.
jcims|5 years ago
ADSB uses pulse amplitude modulation, so if you built or bought a downconverter and amplifier, you might be able to pick up the modulation by sending the downconverted/amplified signal to a GPIO pin and reading its state at say 5-10 MHz.
It'd be pretty messy and you'd have to write the demodulator from scratch, but might be able to pickup the frame decoding from one of the other products out there to actually read the content.
Would be a really fun project but not likely to save money and definitely not time.
OrangeMango|5 years ago
vegasbrianc|5 years ago