Mini Generator "Marx" the Way to Directed Energy Advances

  • Published
  • By Chunte Lu
  • Directed Energy
KIRTLAND AIR FORCE BASE, New Mexico --  Working under Small Business Innovation Research contract to Air Force Research Laboratory, Physical Optics Corporation developed a novel generator technology of import to improvements sought for Air Force airborne and ground-based radar and high-power microwave systems. Applying its unique expertise as a technology-based small systems integrator, including vast experience with related electronic and high-voltage technologies, the company created the Solid-State Mini-Marx generator--a lightweight, pulsed-power, miniature device that surpasses existing Marx generator technology.

The small Marx generators currently in place, though presently the AF's lightest means for achieving high voltages, fall short of desired performance requirements: 150-250 kilovolts (kV) damped sine wave between 100 MHz and 1 GHz. While constructing an array of several Marx generators provides a workaround, the preferred length of 12" and diameter of 3" renders such an assembly less than ideal.

Conversely, at 11.5" long and 4" in diameter, POC's SSMM provides a 24-stage solution. Specifically, the device comprises a 24-stage array of avalanche bipolar junction transistors configured as an ultrafast solid-state switch. A single trigger on the first transistor of the first stage fires the sequenced switches of all subsequent stages like a traveling wave. This setup, which completely eliminates jitter problems, routinely achieves nanosecond high-voltage impulse. Rise times of 2.5 ns and 100 MHz are typical, as are intermediate voltages of 51.6 kV-peak peak (pp--limited by the high-voltage probe capability) at the 12th stage and expected voltages exceeding 100 kV-pp at the 24th stage.

This SBIR-enabled technology could conceivably impact a substantial number of systems serving government and commercial concerns alike. An application of immediate AF interest involves the SSMM's use as an electromagnetic interference source in a nonlethal weapons system, given its capacity to produce 50 kV amplitude (100 kV-pp), 100 MHz sine waves at 10 A and meanwhile accommodate an 18 V battery, a 4 kV-30 mA DC/DC power supply, and a 100 MHz dipole antenna. Included among possible AF applications of the future is the generator's use in modulating klystron microwave sources capable of emissions topping even 10 GHz. The breakthrough technology also promises exceptional utility in the area of ultrabroadband radar development and will likewise prove useful for enhancing HPM capability, once subnanosecond rise times and, in turn, pulses in the gigahertz range become a reality.