Multistage Depressed Collector Klystrons

Communications & Power Industries Canada Inc. (CPI Canada)
Georgetown, Ontario, Canada

MWJ20TA Finding ways to operate satellite communications (SATCOM) high power klystrons more efficiently has a double-edged benefit. The SATCOM transmitter uses less prime power, saving uninterruptible power supply capacity, and the klystron runs cooler, significantly improving its reliability. The multistage depressed collector (MSDC) high power klystron has been specifically designed for SATCOM uplink applications and features a collector efficiency of 60 percent or greater. This improved efficiency permits a prime power savings of two to three kilowatts when operating at full power. For low operating powers under clear-sky conditions, the prime power savings could amount to five to six kilowatts.

Figure 1 shows the prime power savings vs. RF output power of the MSDC klystron compared to a standard klystron design. Since most klystrons operate at low RF operating powers for intermodulation consideration, the MSDC has the capability to provide maximum savings at the most likely set of operating conditions. Thus, the MSDC tube runs cooler with the potential of a longer lifetime than its standard klystron cousins.

MSDC klystrons have been developed for both C- and Ku-band commercial satellite service and feature a small, compact design and a four-stage depressed collector configuration specifically intended for satellite earth station use. Utilizing collector depression the collector heat dissipation is much reduced, thus lowering the required air flow for cooling. This reduced air flow permits the use of smaller AC power systems, especially in hot, humid environments. Lower collector temperatures are key to enhancing the klystron's lifetime.

Table 1 lists the various MSDC klystron models and their typical operating characteristics. Both the C- and Ku-band klystrons are mounted with the collector up and use permanent magnet focusing. The C-band klystrons' RF input connector mates with a type-N plug, YG-21 D/U or equivalent, and the RF output connector is a CPR 137 waveguide flange. The Ku-band units' RF input and output ports mate with UG-419/U waveguide flanges. All models require external air flow cooling.

& Power Industries Canada Inc. (CPI Canada),
Georgetown, Ontario, Canada
(905) 877-0161.