Figure 4-48. Power Divider 4. 3.6 CONVERTER FILTER REQUIREMENTS The section on radio frequency allocation and interference covers the importance of reducing noise in the MPTS to preserve a maximum of the spectrum for other users. The klystron has a built-in bandpass filter effect due to its basic construction and needs no further addition except possibly for a harmonic filter as noted later. Its characteristics are shown in Figure 4-52. The five cavity tube case is selected for the recommended design. The amplitron on the other hand according to current estimates will need an output filter to reduce both random noise and harmonics. In the amplitron circuit designed for MPTS the phase shift versus frequency characteristics are such as to locate the 180° mode (eight re-entrant spokes) at 2450 MHz. The network consists of 17 equally spaced vanes with a drift space of 1. 0 pitch. Because of the MPTS narrow band requirements, the 180° mode operation is preferred which is close to the lower frequency cutoff of the amplitron network. The lower frequency cutoff of the network will occur at 2437. 5 MHz.
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