Rotating Reflector RF Load for High Power Handling
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Solution Overview
Problem
Existing high power microwave loads reflect a significant portion of input energy back to the input port, leading to electric field enhancement, plasma arcing, and non-sustainable erosion, while being limited by power density and temperature constraints of RF absorbing coatings.
Innovation Solution
A microwave load with a cylindrical body and rotating reflector that redistributes power density, minimizes standing waves, and reduces reflected energy by using a baffle and variable thickness absorptive coatings to direct reflected energy away from the input waveguide, incorporating a rotating reflector and water cooling for thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a prior art device uses a cylindrical cavity with a far wall reflector to handle high input power density, then the device can dissipate large input power, but a significant fraction (6% or more) of the applied power is reflected back to the input port
Solution Approach 1:
The load device is divided into multiple functional sections: an input section with a first reflector, a dissipation section with absorptive material, and an output section with a second reflector. This segmentation allows each section to perform its specific function optimally while minimizing overall reflections back to the input port.
Solution Approach 2:
Absorptive material is introduced as an intermediary between the input waveguide and the far wall reflector. This material absorbs a portion of the incident power, preventing it from reflecting back to the input port, thereby reducing the reflected power fraction while still handling high input power density.
2Ease of operation
If the input port is exposed to reflected power in the cylindrical dissipation cavity, then the device can operate, but it is not possible to reduce the reflected input power below a certain level
Solution Approach 1:
The harmful reflected power is extracted from the system by using absorptive material to absorb it before it can reflect back to the input port. The absorptive material effectively removes the reflected energy from the cavity, preventing it from reaching the input port and causing damage.
Solution Approach 2:
The reflected power, which would normally be harmful, is converted into a beneficial effect by using absorptive material to absorb it. This absorbed energy is then dissipated as heat, which can be managed through cooling systems, thereby converting the harmful reflection into a controllable thermal load.
3Power
If a rotating reflector is used to distribute power density, then the device can handle higher power, but the RF absorbing coating is limited in operating temperature to less than 300°C before damage occurs
Solution Approach 1:
Different sections of the load device have different absorptive coating thicknesses optimized for their specific power density levels. The input section has a first thickness, the dissipation section has a second thickness, and the output section has a third thickness. This local optimization allows each section to handle its local power load while keeping temperatures within safe limits.
Solution Approach 2:
A rotating reflector is used to dynamically distribute the incident power density over time and space. By rotating the reflector, the power is distributed across different areas of the absorptive coating, preventing any single location from exceeding the maximum operating temperature of 300°C, thereby enabling higher overall power handling capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes reflected power back to the input port, enhances power handling capacity, and prevents plasma arcing by uniformly dissipating energy and managing thermal loads, thereby improving the operational sustainability of the load device.
Implementation Method 1
a rotating reflector coupling microwave energy from the input waveguide to an inner surface of the cylindrical body
Implementation Method 2
the inner surfaces of the enclosed volume having a coating which reflects a fraction of impinging RF (radio frequency) and absorbs the remainder of the RF
Implementation Method 3
water cooling for thermal management
Data Source
AI summary
A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.