Software
Defined Radio is a radio system that uses software to perform the functions of
signal demodulation as well as perform audio bandpass filtering and notch
filtering. The software also contains the automatic gain control as well
as noise blanker functions.
The modes of operation that are demodulated
in the SDR Radio System are: AM, SSB, CW, FM, AM Synchronous, C QAM Stereo, and
DRM. Which is an astonishing accomplishment in such a simple radio.
The receiver
hardware itself works by splitting the incoming signal from the antenna into two
channels that are then phase shifted 90 degrees from each other to create two
low frequency i.f. channels that are within the audio passband of the sound
card. The stereo like channels are referred to as the I and Q
outputs. This is known as Quadrature
Phase Detection.
The phase shifting of the two helps the software
processes to define the upper and lower sidebands and other information in the
passband. The passband is so wide, 24, and to 48 and 96 kHz that the
software can detect and display signals above and below the tuned to frequency
on a spectrum analyzer display in the software.
