Digital single-sideband mixer

A single-sideband (SSB) frequency converter using only exclusive-or logic gates and no reactive or frequency-selective analog circuit elements takes square-wave inputs at two arbitrary frequencies f
1
and f
2
and generates an output waveform whose principal spectral component is at either f
1
+f
2
or f
1
-f
2
, selectably. A pair of outputs is generated in phase quadrature.