John C. Tucek

220 GHz power amplifier development at Northrop Grumman

A 220 GHz vacuum electronic (VE) power amplifier has been designed and is being tested as part of the DARPA HiFIVE program. Minimum power goal is 50 watts at 220 GHz. This amplifier uses advanced, high current density cathodes, a folded waveguide slow-wave circuit, and a depressed collector for improved overall device efficiency. Operation at duty cycles of 50-100% is anticipated.

220 GHz folded waveguide circuits for high power amplifiers

Folded waveguide interaction circuits for a vacuum electronic amplifier have been designed. Microfabrication efforts to produce the FWGs are underway and preliminary analysis of the properties of these slow wave circuits has been completed.

Testing of a 0.850 THz vacuum electronic power amplifier

A 0.850 THz vacuum electronic power amplifier capable of >50 mIV output power is being tested at Northrop Grumman Electronic Systems. The compact power amplifier is based on a DRIE-fabricated folded waveguide slow-wave circuit, together with a high current density thermionic cathode, a high field permanent magnet solenoid, and a single-stage depressed collector for overall device efficiency. The new 0.850 THz power amplifier design is based on a 0.670 THz source that achieved over 100 mIV of output power with 21.5 dB of saturated gain, 15 GHz of operational bandwidth, a collector efficiency of 93% and an overall device efficiency of 0.44%.

9.3: Fabrication of solid copper 220 GHz folded waveguide circuits by UV lithography

We report the fabrication results for an all-copper 220 GHz folded waveguide circuit. The fabrication method is based on UV lithography using SU-8 negative photoresist followed by copper electroforming. The method achieved the necessary dimensional accuracy, smooth vertical side walls, low cost of fabrication, and all-copper structure suitable for high power applications.

A 0.85 THz vacuum-based power amplifier

A 0.850 THz vacuum electronic power amplifier capable of >;100mW output power is being developed at Northrop Grumman Electronic Systems. The compact power amplifier is based on a DRIE-fabricated folded waveguide slow-wave circuit, together with a high current density thermionic cathode, a high field permanent magnet solenoid, and a single-stage depressed collector for overall device efficiency. The new 0.85 THz power amplifier design is based on a 0.67 THz amplifier that achieved over 100mW of output power with 21.5 dB of gain, 15 GHz of operational bandwidth, a collector efficiency of 93% and an overall device efficiency of 0.44%.

Development and Operation of a 650 GHz Folded Waveguide Source

Northrop Grumman Corp. has fabricated and demonstrated a vacuum electronic (VE) device based on a folded waveguide (FWG) circuit which operates between 600 and 675 GHz. Output powers up to 16 mW at duty cycles up to 1% and a source efficiency of 0.08% have been demonstrated. Development continues toward increasing the source efficiency by improving beam transmission and incorporating a depressed collector to recover a significant fraction of the spent beam energy.

233 GHz high Power amplifier development at Northrop Grumman

Northrop Grumman has developed a folded-waveguide vacuum electronic high power amplifier at 233 GHz. The amplifier demonstrates output power over 79 W (49 dBm) from 232.6-234.6 GHz, and greater than 50 W (47 dBm) over a 2.4 GHz instantaneous bandwidth. Saturated gain is approximately 23-24 dBm over this bandwidth, with an input drive of 26-27 dBm required for saturated output power. The device operating point is 20.95kV, 114mA for a frequency range centered at 233.6 GHz, but is capable of producing 50W at frequencies up to 237.8 GHz by varying the operating voltage. Typical instantaneous (3 dB) operating bandwidth ranges from 2.4-3.0 GHz for a beam voltage range of 20.5-21 kV. The amplifier uses a compact permanent magnet solenoid for beam focusing and confinement, and typically achieves 95-98% beam transmission through the folded-waveguide circuit and into the single-section depressed collector. This device has demonstrated operational duty cycles up to 50% with liquid cooling and using Northrop Grummans Microwave Power Module compact integrated power conditioner technology. A more compact version of this power amplifier is being developed with emphasis on reducing the size of the permanent magnet solenoid.

A multiple electron beam array for a 220 GHz amplifier

An electron beamlet array is being developed for use with power-combined, micro-machined folded waveguide circuits for a 50W, 220 GHz submillimeter RF device.

Operation of a compact, 0.65 THz source

A compact, 0.65 THz vacuum electronic source based on micro-fabricated folded waveguide circuit technology has been demonstrated. The resonant circuits in the prototype devices were made using deep reactive ion etching. Several sources were built and operated between 0.605 and 0.675 THz. RF powers up to 98 mW were generated by the circuits, with a maximum of 50 mW measured outside the output window. Circuit interaction efficiencies of 0.45% were also achieved. These measurements were made at duty cycles up to 3%.

Vacuum electronics development at Northrop Grumman [TWTs]

Summary form only given. The past decade has seen revolutionary advancements in traveling wave tube (TWT) performance, with single tube broadband TWTs having a 2-18 GHz bandwidth, and narrowband TWTs having efficiencies near 65%. The development of RF devices using cold cathode field emitter arrays as a replacement for the thermionic cathode is also underway. Millimeter wave TWTs show good performance between 18 and 40 GHz. Several cusp guns have been designed, built and tested, for operation in gyro devices at 35 and 94 GHz. Folded waveguide design and fabrication techniques for 100 GHz operation are also being conducted. Recent results of the above vacuum electronics development programs are presented.