FIELD EMISSION CATHODE, AND ELECTROMAGNETIC WAVE GENERATING DEVICE USING THE SAME

PROBLEM TO BE SOLVED: To provide a small-sized field emission cathode, capable of efficiently emitting the electron beam of high output modulated at an arbitrary frequency within a millimeter wave or microwave band with the simple structure, and provide an electromagnetic wave generating apparatus. SOLUTION: A surface of a collector 11, made of the N-type semiconductor material, is formed with a needle-like cathode chip 11a, and a gate electrode 13 formed with an opening 13a so as to surround the cathode chip 11a is provided, and the other surface of the collector 11 is formed with a base 14 made of the P-type semiconductor material, and the surface of this base is formed with an emitter 15 made of the N+-type semiconductor material. A high-frequency power source 18 is connected between a base electrode 16 and an emitter electrode 17, and a direct current power source 19 is connected between the collector 11 and the gate electrode 13, so that the electron beam of high output modulated by the high frequency is emitted efficiently from the cathode chip 11a. This electron beam and the high frequency circuit are made to work each other, so as to efficiently generate electromagnetic waves having high output in the millimeter wave band or microwave band.