Compact and Efficient Magnetron Source for Continuous Wave Microwave Power Generation

The objectives of the proposed Phase II program are to design, fabricate, test, and deliver a 5 kW CW, S-Band magnetron capable of fast tuning across =5 MHz with a data transmission rate of 2 Mb/sec using simple frequency shift keying, and with minimum size, power and weight. Frequency and phase control of the magnetron will be accomplished using an array of varactors controlled by feedback loop circuitry.Ā Development will be done at a frequency of 2450 MHz to utilize existing microwave hardware, but the results will be applicable to magnetrons over a wide range of frequency and power. The phase-locked magnetron will not require a circulator or high-power driver. Instead, the magnetron will be locked by a feedback circuit providing high loop bandwidth and low phase noise.Ā The system will electronically tune the magnetron cavities with a varactor array driven by a closed-loop, feedback circuit.Ā The magnetron will thusly beĀconverted into a voltage-controlled oscillator locked to an RF reference source. When fully packaged, the circuitry will add less than 10% to the system size and weight. The result will be an efficient, low-cost system with low size, weight, and power, (SWaP). Because the purpose of this program is to demonstrate the basic technology, the specific frequency was chosen to be 2450 MHz.Ā This allows use of relatively inexpensive and readily available components. The prototype RF source will be a modified, commercial magnetron. This will be faster and less expensive than developing a new tube. The technology will scale with minimal effort to other frequencies in S-Band, and for that matter, other frequencies for which magnetrons are available.Ā The control circuitry is derived from a phase-locked laser system developed by SLAC National Accelerator Laboratory (SLAC), the research partner on the program. The proposed program is in three one-year phases: Base, Option 1 and Option 2.Ā In the base program, the magnetron with the port for the varactor array will be fabricated and tested without the varactors. A varactor array will be fabricated and used, with a simple biasing scheme without feedback, to test the ability to tune the magnetron.Ā These tasks (1-3) will be performed primarily by Calabazas Creek Research, Inc. (CCR) and Communications & Power Industries, Inc. (CPI), the industrial partner on the program. The control circuit will be developed in parallel at SLAC.Ā SLAC will build a benchtop control circuit, write firmware and software, and test the system.Ā (Tasks 4 ¢ 7).Ā In Option 1, the control system will be tested with the magnetron: first with it unpowered (Task 8), then at full power (Tasks 9-11).Ā A fully packaged system will be designed in Task 12.Ā In Option 2, the packaged system will be fabricated, tested, and delivered to the Navy for evaluation.