What is meant by “direct sampling” in software defined radios?
Software is converted from source code to object code during operation of the receiver
I and Q signals are generated by digital processing without the use of RF amplification
Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal✓Bonne réponse
A switching mixer is used to generate I and Q signals directly from the RF input
Explication
In a direct-sampling receiver the antenna signal, after filtering and perhaps some amplification, goes straight into a fast analog-to-digital converter. All frequency conversion, filtering, and demodulation then happen numerically, so there is no analog local oscillator or mixer in the signal path.