High Performance, Solid-State High Voltage Radar Modulators

Switching power supplies and solid-state high voltage modulators are being used to upgrade conventional tube-type radar modulators, extending their operating lifetimes. The new technology is cost-effective, improves reliability, and delivers better protection to the RF amplifier than conventional transmitter designs. In 2003, DTI upgraded the X-band radar transmitters in the Cobra Judy system on the USNS Observation Island. DTI built the complete transmitter, including all electronics required from ship power to modulating the two 100 kW average power TWTs. Based on the success of this effort, DTI is employing similar solid-state technology to the transmitter driving the Cobra Judy S-band phased array radar. Installation of the sixteen-TWT S-band transmitter upgrade is scheduled for early 2006. DTI is also developing a new transmitter for the Haystack ultra-wideband imaging radar (HUSIR) in Westford, Massachusetts. This transmitter will drive four W-band (94 GHz) high power gyro-devices, and will be capable of future expansion to sixteen tubes. The design builds on both the upgraded Cobra Judy X-band transmitter, and DTI´s development of a modulator for the Navy Research Laboratory´s 94 GHz Warloc gyroklystron in 2002. This paper will discuss the key pulsed power technologies common to these radar transmitters, with emphasis on the system requirements for pulse stability and control.