1962 10 394/1 The reverse procedure of down-converting is not practical because the power gain is always less than unity.
1980 H. 112 (abstract) There are many techniques for synthesising microwave frequencies, including up-converting by multiplication, sampling, down-converting and comparing to a low-frequency reference.
2010 D. Draven xvi. 252 Downconverting is a postproduction process of taking higher resolution source material..and converting to lower resolution source material.