RF Heating Engineering Consulting Services at 6.78, 13.56, 27.12 and 40.68 MHz

SiberSci, LLC provides RF heating engineering consulting for two kinds of work: troubleshooting and optimizing existing RF heating systems, and the research, design, development, fabrication, testing, validation and optimization of new RF heating hardware for laboratory and industrial applications. Services cover the full RF chain, including:

• RF heating and drying hardware at 6.78, 13.56, 27.12 and 40.68 MHz
• Solid-state and vacuum tube RF power amplifiers and oscillators
• RLC, parallel plate and Strayfield resonators (applicators)
• RF impedance matching circuits, filters, power combiners and splitters
• Transmission line networks — coaxial, rectangular and ridged waveguide, microstrip and stripline
• Frequency- and temperature-dependent RF material properties

Industrial RF heating equipment normally operates in the ISM (Industrial, Scientific and Medical) bands, which are set aside for non-communication uses such as heating. SiberSci designs RF heating hardware at 6.78 MHz, 13.56 MHz, 27.12 MHz, and 40.68 MHz. In the United States, ISM equipment is regulated under FCC Part 18. The best frequency for a project depends on the material's dielectric properties, the size of the load, the required heating uniformity and the available power hardware.

RF heating converts radio-frequency electromagnetic energy directly into heat inside the material, rather than conducting heat in from the surface. Two mechanisms are most common:

• Ionic conduction (dielectric) heating — when a material containing mobile ions is placed in a uniform RF electric field, the moving ions generate heat through friction throughout the volume of the material. This is used for drying, curing, defrosting, and food processing.
• Induction (eddy current) heating — an RF magnetic field induces eddy currents in electrically conductive materials such as metals and plasmas, which heat by resistive losses.

RF heating works well on materials that exhibit ionic conduction, in the form of solids, films, powders and liquids, in either continuous-flow or batch processing. Established applications include:

• Curing the emulsion on x-ray film
• Drying large volumes of grain
• Rapidly defrosting meat for commercial kitchens
• A wide range of food processing operations
• Induction heating of metals and plasmas

Because RF heating equipment is built around the specific volume of material being processed, each system is a custom design.

Yes. Optimizing the performance of existing RF heating circuits is one of SiberSci's core services. Typical problems include poor impedance matching, uneven heating, low efficiency, arcing, component overheating and unwanted emissions. SiberSci analyzes the existing applicator, matching network, filters and power source and recommends specific hardware changes to restore or improve performance.

These are different applicator (electrode) configurations for delivering RF energy to the load:

• Parallel-Plate (through-field) applicators place the material between two electrodes so the field passes through its thickness — common for thicker or bulk loads.
• Strayfield (fringe-field) applicators use closely spaced electrode bars so the fringing field heats material passing over them — common for thin webs, films and coatings.
• RLC resonators treat the applicator and load as part of a tuned resonant circuit for efficient power transfer.

SiberSci designs all three and selects the configuration that best fits the material geometry, throughput and uniformity requirements.

Both remain in use, and SiberSci designs solid-state and vacuum tube RF power amplifiers and oscillators. The right choice depends on the required power level, frequency stability, controllability, maintenance expectations, efficiency targets and budget. SiberSci evaluates these trade-offs against the client's process requirements and recommends one or more hardware configurations.

SiberSci is experienced with Ansys HFSS (Ansys Electronics Workbench), CST Microwave Studio, FEKO, COMSOL, Sonnet Software, and Keysight ADS and Genesys. Clients may specify one or more of these tools if they provide a valid license or pay for contract access to the code. If a client is unsure which tool fits the project, SiberSci helps select the appropriate computational electromagnetics (CEM) code.

SiberSci, LLC training covers: the biology of RF and microwave exposure, including ionizing versus non-ionizing radiation, exposure parameters, biological effects, and tissue heating; waveguide leakage and antenna radiation theory; FCC and OSHA RF exposure regulations and standards; safe work practices, including using distance and time averaging and avoiding eye damage from waveguide leaks; sources of RF and microwave energy, from vacuum electron devices to solid-state; and RF, microwave, and millimeter-wave personal exposure monitors. Each session ends with open discussion of the group’s own questions and concerns.

The accuracy of any RF heating simulation depends directly on the material properties used, and those properties change with both frequency and temperature. Key properties include complex permittivity, loss tangent, electrical conductivity, thermal conductivity, density and specific heat. Because these values shift as the material heats, using room-temperature or catalog values can produce designs that fail in production. SiberSci uses laboratory and contract resources to measure these properties so that only valid data goes into the simulations. For a quick first estimate, try the Dielectric Heating Calculator.

During the design review, SiberSci documents the performance and physical limitations of each RF heating concept and how each concept would need to be adapted for your material. If any part of the specification is physically impossible to achieve, those problem areas are identified early — before hardware is built — along with recommendations for working around the barriers.

Yes. SiberSci can review proprietary material specifications under an NDA to protect business-sensitive information, intellectual property (IP) and proprietary data (PD). SiberSci provides an NDA for the client to review, negotiate and amend. Please state in your first inquiry whether an NDA is required.

To recommend RF hardware configurations, SiberSci needs:

• The material to be heated and any known material properties
• The volume and mass of material to be heated
• Starting and target temperature specifications
• Time constraints (heating time or throughput)
• Whether the process is continuous-flow or batch, and lab or industrial scale

After reviewing the performance and size requirements, SiberSci provides a budgetary quotation and schedule. Work begins once a contract has been negotiated and executed by both parties.

SiberSci, LLC is an electromagnetic engineering consulting firm based in Owensboro, Kentucky, built on the industry and government experience of Dr. Scott Best. SiberSci is a BBB Accredited Business and is listed in the IEEE-USA Consultants Database. In addition to RF heating, the firm offers RF Engineering, Antenna Engineering, Microwave Engineering, Millimeter-Wave Engineering, and RF and Microwave Safety consulting.

Email Dr. Scott Best at scott_best@sibersci.com, call 270-228-4901, or use the contact form. Include a short description of your material, temperature and throughput requirements, and whether an NDA is needed.