An up-converter with gain and stabilized frequency can be realized through the sideband locking of an IMPATT oscillator. An up-converter with a gain of 13.3 dB (microwave to microwave) and an output power of 13.3 dBm over the bandwidth 30 MHz is realized and operated at 10.18 GHz. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.