We’re all familiar with the microwave. It has changed the way we cook meals by allowing families to rapidly heat food that, before, took some time to prepare.

By using electromagnetic radiation in the microwave spectrum, the microwave allows families to reheat leftovers, defrost frozen foods, and make popcorn in a matter of minutes. However, the quality of the food can suffer due to the microwave’s current design.

Tube Source vs. Solid State Source

Conventional microwaves use a filament tube-type device called a magnetron, which requires the use of a 4,000-volt power supply and has as little as 500-hours lifetime. Energy is flooded into the cavity and heating is controlled by a crude on/off apparatus that continuously adjusts the power delivered to heat the food. In addition, a stirrer is used to help distribute the microwave field and a turntable is used to rotate the food being heated.

Both are used in an attempt to increase the probability of even heating. However, this approach has not solved the problems of inconsistent cooking within the food, leaving parts of it over- or undercooked.

Even though magnetron technology has been successful, its performance has been inept and inconsistent, so Freescale Semiconductor (Austin, TX) has come up with a way to modernize RF power with solid state transistors. 

The RF power transistors and architectures will provide a full range of power control, phase shifting, and frequency adjustment allowing microwaves to cook complex combinations. For example, commercial chefs will be able to perfectly cook a steak in a shorter amount of time, maintaining the same quality as cooking it on a grill.

Future microwaves will also have high-resolution control that will improve cooking consistency, increase the oven’s lifetime, and help reduce cooking time. Solid state microwaves will allow consumers to perform the same functions as conventional microwaves, as well as giving them more possibilities with more efficient heating at a lower operating voltage and with greater control.

More Control

Solid state microwaves’ biggest advantage is control. Consumers will not only have more control over how much energy the appliance is delivering, but they will also have control over where that energy is being dispersed in the cavity. 

In conventional microwaves, the magnetron creates the energy and pushes it through a waveguide. The energy then passes through a stirrer, or fan-like device, that forces the energy into the cavity. The stirrer works in conjunction with a turntable, trying to facilitate random distribution of the energy in the cavity. The cavity’s walls reflect the energy causing it to bounce around, while the turntable rotates the food trying to effectively absorb the energy. With this design, the amount of energy is entering the cavity is uncertain.  Where it is going? What it is being used for? Is it being absorbed by the cavity walls or by the food?

Solid state microwaves use multiple antenna feeds to create a steady input of microwave energy into the cavity – not just cycling power on and off. Multiple antennas help create various cooking profiles by allowing consumers to control the phase shifting (steering) of the energy, directing it more in one biometric area versus another.

Solid state circuitry also provides detection functions, potentially adding intelligence to the microwave that tells consumers how much energy is being used at a certain time.  

Potential Innovations

Freescale’s solid state transistors for RF microwave heating and cooking opens the door to a variety of opportunities. Manufacturers have the potential for different design approaches, with the possibility for smaller, portable devices.

The technology also enables users to cook more diverse foods simultaneously. For example, chefs can create a whole meal in one microwave that includes meat, vegetables, and bread by directing the heat to certain zones within the cavity without overcooking one item and undercooking another.

By changing conventional microwaves’ cooking paradigm, it’s easier to tailor healthier meals without having to purchase pre-cooked and pre-packaged options.

For more information visit www.freescale.com/RFheating