Tunable single sidebands in the infrared were generated by electro‐optically mixing a 14–18‐GHz tunable microwave and a fixed‐frequency CO2laser signal, both circularly polarized, in a resonant modulator. With 10 W microwave drive power, a peak single‐sideband conversion efficiency of 280 &mgr;W/W laser power was achieved. Sideband discrimination was 30 dB throughout the tuning range.