Spontaneous parametric down-conversion - Wikipedia
A Simple Complex Down-conversion Scheme - Rick Lyons
Digital Down Conversion (DDC) - theory
The Basics of Mixers | DigiKey
algorithms - Difference between these two digital down conversion methods - Signal Processing Stack Exchange
What's Up With Digital Downconverters—Part 1 | Analog Devices
A COMPLEX DOWN-CONVERSION EXAMPLE | Chapter Eight. Quadrature Signals
Up/down conversion luminescence properties of (Na0.5Gd0.5)MoO4:Ln3+ (Ln = Eu, Tb, Dy, Yb/Er, Yb/Tm, and Yb/Ho) microstructures: synthesis, morphology, structural and magnetic investigation - New Journal of Chemistry (RSC Publishing)
What's Up With Digital Downconverters—Part 1 | Analog Devices