Concepts for circular deflection modulated tubes and frequency multiplying millimeter wave sources

Most common microwave vacuum tubes like klystrons use a density modulated electron beam to excite electromagnetic fields in the output section of the device. In this paper we present a concept called trajectory or deflection modulation where a beam with an uniform longitudinal velocity is modulated by changing its transverse position. This allows a quite uniform deceleration of the electrons what enhances the efficiency and leads to new possibilities in the design of millimeter wave tubes. In this manuscript we will discuss the advantages of circular deflection modulated devices based on different types of modulators and it will be shown how they can be used for frequency multiplication.