The next-generation consumer microwave oven: a review

Abstract

It seems possible that Solid-State Radio Frequency (RF) transistors will one day replace magnetrons in consumer microwave ovens. These new ovens have the potential to be smaller and more energy efficient. Because they are closed loop systems, they can precisely cook food in ways that consumers have not seen before. This review outlines the basics of Solid-State RF systems and the consumer ovens that are currently available. There are two potential approaches for this new technology: first, the oven could be like current appliances and serve as a reheating device. Second, the oven could take advantage of the new technology to be a high-end cooking appliance. The food industry would be best served by learning more about this technology change and preparing for their products to be cooked using this type of equipment. Due to the even heating and overall consistency of the technology, it is possible that there are benefits to both quality and food safety for this technology.

Keywords:

• Solid-State radio frequency
• consumer microwave oven

1. Introduction

The technology that will most likely replace the cavity magnetron as a microwave source in consumer ovens is called Solid-State Radio Frequency (RF), and it uses solid-state transistors to generate microwaves. Current Solid-State RF devices heat food faster and more evenly during manufacturer demonstrations (Barry 2017; Sclocchi 2018). They are also predicted to offer an improved consumer experience (Drucker 2020). Finally, consumer systems could be more reliable and longer-lasting than current magnetron systems (RF Energy Alliance 2014; Sclocchi 2018). In addition to consumer ovens, this technology could also be used to replace automotive spark plugs, improve medical ablation devices, and develop new horticultural heating systems (RF Energy Alliance 2014; Hambling 2016; DeMartino 2017b). Table 1 summarizes the differences between magnetron and Solid-State RF consumer ovens.

Table 1. Technology comparison.

Technology	Basis	Frequency range	Loop	Antenna(s)?
Magnetron	Vacuum Tube	Single	Open	No
Solid-State RF	Transistor	Variable	Closed	Yes

A magnetron produces energy at one electromagnetic frequency, which sets up standing waves in the oven (Wesson 2016; Wäppling Raaholt 2020). Because the waves do not migrate throughout the cavity, they unevenly heat stationary food, which can lead to hot and cold spots. Most current magnetron home ovens have turntables, which move the food around the cavity and provide more even heating. Even with a turntable, there can be hot and cold spots in reheated food, which is why reheating instructions often tell consumers to let the food stand for a specific amount of time (DeMartino 2017a).

A Solid-State RF system is a closed loop, while a magnetron is an open loop system. RF systems include one or more antennas that monitor the absorbance of the electromagnetic energy in the cavity and, through a feedback loop, provide real-time adjustments to the RF energy output (RF Energy Alliance 2014). These adjustments have the potential to eliminate standing waves in the cavity, allowing more precise energy application. A block diagram of a Solid-State RF system is shown in Figure 1. A 500 W RF setup could replace an 1100 W magnetron, meaning these systems have the potential to be more energy efficient. The system would not need a turntable, making possible a smaller oven footprint. In addition, an RF oven can be used to cook different food items at the same time to the proper temperature. Web articles tout the ability to cook a complete meal with protein, starch, and vegetables on one tray (RF Energy Alliance 2014; Barry 2017).

Figure 1. Solid-State RF block diagram.

The oscillating field inside a microwave oven heats the food by inducing dipole and ion movement in the target substrate. The dielectric properties of the substrate define how that material reacts to microwaves (Wäppling Raaholt 2020). The feedback antenna and the oven control adjust the output frequency in the RF oven in real time to provide the most efficient absorption for the target substrates. To take advantage of this feedback loop, the Solid-State RF system works better if the consumer can tell the oven what type of food (e.g. protein, starch, or vegetable) is placed inside the chamber, and control algorithms select the best input frequency based on the food's dielectric properties (RF Energy Alliance 2014; Drucker 2020).

2. Current Solid-State RF ovens for the consumer market

There are two Solid-State RF systems that are commercially available in the United States since the beginning of 2022. The first is a multi-function oven for the restaurant market called the Ibex. Ibex was developed by ITW Food Equipment Group and costs around $18,000 (Wolf 2017). The oven is designed with a touch panel so users can start the cooking process with two taps. The cooking times are built into the system, and users can add their own recipes, presumably with assistance from Ibex. ITW has been promoting and testing the oven prior to this year (Sclocchi 2018). They promise better results for baking bread and cooking all types of meat. They claim their baking is done four times faster than other commercial combination ovens, and they say their meat cooking is more uniform, providing 30% more yield than other commercial combination ovens.

The second oven is a multi-function wall oven for home users from Miele called the Dialog (Barry 2017; Wolf 2017). Their RF technology comes from an Israeli firm called Goji Food Solutions. The oven is designed for the high-end gourmet cooking market, and it costs around $10,000. This is a combination electric and RF oven, and it promises faster cooking times than standard conventional ovens. The example recipes available online are intriguing: the oven cooks frozen fish in a block of ice, a veal tenderloin in beeswax, and can heat a salmon piece half-covered in aluminum foil so part of the fillet is cooked, and the other half is raw.

As noted above, Solid-State RF ovens work better when the consumer can tell the oven what type of food is inside the cavity. Both devices promise substantial support from the manufacturer for customers to get the most out of their oven.

3. Undelivered Solid-State RF systems

One RF system that was promoted but never delivered is the Wayv® Adventurer, which is a "portable Solid-State RF food heater" (Hambling 2016; Wayv Technologies Ltd 2017). About the size of a large thermos, this device was designed to heat food and beverages and was announced to investors in 2014. The cost was promised to be $200. Product launch was supposed to be in 2017, but there has been no communication since 2016. The website and Twitter account are still online.

Another RF oven promised in 2016 but never delivered is the Midea Cooking Appliance (Ampleon 2016; everythingRF 2016). Approximately 1 cubic foot (0.0283 m³) in size, it was designed for small spaces or portable applications. Power output was between 200 and 300 W. There is no price available in the announcement articles, and no follow-up material online since 2016.

4. When are low-cost Solid-State RF systems coming to consumer kitchens?

The Dialog, Wayv® Adventurer, and Midea ovens were announced in 2016 for release in 2017, but no commercially available systems for the home market have appeared in the United States prior to 2022 (everythingRF 2016; Hambling 2016; Barry 2017; DeMartino 2017b; Wayv Technologies Ltd 2017). The Dialog oven is the only Solid-State RF system currently available for the home consumer market. RF experts state that complex oven design and systems cost are the main obstacles to high-volume market production (DeMartino 2017a). Drucker estimates a low-end Solid-State RF oven would cost approximately $5,000 if it were manufactured today (Drucker 2020).

Drucker has identified two potential milestones for Solid-State RF home ovens. First, when prices fall below $1,000, the ovens will become more attractive to consumers (Drucker 2020). This price, in 2021 dollars, is nearly equivalent to $200 in mid-1970 dollars. Once microwaves were priced under $200 in the mid-70s, they began to sell rapidly (Felton 2008).

The second milestone is that the ovens work better if they know what they are cooking. In order to take advantage of the full capability of RF systems, there needs to be post-sale support for the oven (Drucker 2020). For microwavable food, this means the oven needs to know the type and amount of food items inside the package. The Miele Dialog and Ibex ovens have built-in recipes and manufacturer support.

Drucker is developing an open-source tagging language that will be administered through the International Microwave Power Institute (IMPI) (Drucker 2020). This tagging language has the potential to notify the oven about the type of food inside the package (protein, vegetable, and starch), the current state of the food (frozen or refrigerated), and the reheating instructions for magnetron-based ovens (heating time, stir step, power adjustment, etc.).

5. Conclusions

• The solid-state technology that has the potential to replace magnetrons in consumer microwave ovens is called Solid-State Radio Frequency, and it uses solid-state electronics to generate electromagnetic energy.

• Current Solid-State RF systems on the market cost $10,000 or more; they are multi-function systems with extensive manufacturer support post-sale.

• Two simple Solid-State RF-only consumer systems were promoted in 2016, but they have not been released by their respective manufacturers yet.

Acknowledgments

The author would like to thank Dr. Sohan Birla, Dr. Lee F. Brown, Dr. Steven Hermansky, Matthew McClure, Kerstin Olson, Indarpal Singh, Bob Schiffmann, Steve Vlock, and Birgitta Wäppling Raaholt for helpful discussions and review.

Disclosure statement

The author serves on the Board of Governors of IMPI, which plans to administer the solid-state open-source tagging initiative (Drucker 2020).

Additional information

Notes on contributors

Eric F. Brown

Eric F. Brown, Ph.D. is a Principal Research Scientist at Conagra Brands, where he has worked for 16 years in the R&D Materials Lab. Formerly, he worked at Anton Paar USA (Ashland, VA) providing customer and sales support for the rheology division.