The proposed program will concentrate on the design of pulse-amplitude modulators using innovative architectures to overcome the limitations of conventional designs in driving predominantly capacitive loads, such as the modulating anodes of high-power microwave vacuum tubes. The design will necessarily be capable of operation at high pulse voltage levels and at high pulse repetition rates. Typical of such an architecture is the "quasi-resonant" arrangement described in 11.1.8 of "High-Power Microwave-Tube Transmitters" (Reference 1 of N98-003), wherein the capacitance associated with the modulating anode is charged and discharged through a resonating inductor, or inductors, in a sinusoidal fashion, transferring stored energy rather than dissipating it. There are numerous variants of this concept which must be investigated in order to determine an optimum design depending on the type of electronic switches and how they are used. The program will include the evaluation of the various available electronic switches, including Field-Effect Transistors (FETs), Insulated-Gate Bipolar Transistors (IGBTs), Silicon-Controlled Rectifiers (SCRs), conventional triode and tetrode vacuum tubes, and the "Crossatron" gas-filled switch. This evaluation will concentrate on selecting the best electronic switch for this application. The effort will also include breadboarding of appropriately scaled portions of complete switches.
Keywords: Solid-State Capacitive-Load Modulating-Anode Magic Modulator Modulator Quasi-Resonant High-Repetitio
