A novel free-electron maser as a high power microwave source of sophisticated signals

A novel Free Electron Maser (FEM) developed at Tel-Aviv University and operating in C-band is described. The FEM, utilizing prebunching of its e-beam at the operating frequency, can operate as an oscillator or as an amplifier. In first experiments the FEM was operated as an oscillator without and with e-beam prebunching. Without prebunching the signal builds up out of noise in resonator modes for which the gain is highest. Mode competition and single mode evolution were observed. With prebunching the FEM oscillator could be locked to the prebunching frequency which could be at or near every eigenfrequency of the resonator for which the round trip net gain is larger than the loss. Use of the prebuncher as a signal modulator to obtain AM, FM and PM modulation is described. Frequency-agile operation can be achieved by switching of the prebuncher locking frequency. An FEM utilizing a broadband prebuncher enables smart signal modulation and frequency agility, together with a wideband interaction circuit should allow development of high power, wide band sophisticated signal FEMs.