At this frequency the phase shift across the circuit is 0°. In the cutoff region the network will provide an attenuation of -18 dB/octave. Insertion loss is only 0.2 dB. The low frequency attenuation together with characteristics for two possible designs for an output filter are shown in Figure 4-53. The filter center frequencies are offset from the MPTS operating frequency of 2.45 MHz in such a way as to minimize attenuation or insertion loss at that frequency while still providing a significant attenuation at higher frequencies. The parameters in Figure 4-2 include provision for the output filter. 4.4 CONCLUSIONS AND RECOMMENDATIONS For the amplitron: a. Cold pure metal cathode (platinum) for long life. b. Pyrolytic graphite radiator for cathode and anode for light, efficient waste heat radiation. c. Samarium cobalt permanent magnet for light weight and low cost. d. Operating frequency 1.5 GHz to 3.0 GHz; 2.45 GHz preferred. e. Power added 5 kW to 10 kW per tube; 5 kW preferred. f. Efficiency with rf noise and harmonic filters is conservative 85 percent; improvement to 90 percent is a realistic goal. g. Cascade configuration because of low gain characteristic. h. Regulation of constant current or constant phase by movable pole piece or impulse magnet technique for high efficiency. i. Open tube construction, possibly with contaminant baffle, for higher reliability, simple thermal control, and lower weight. For the klystron: a. Hot cathode design used in study, but a cold cathode development desirable for a longer life. b. Pyrolytic graphite radiators for efficient heat radiation.
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