RF power transistors to reach consumers' dishes

June 23, 2015 // By Julien Happich
While RF power transistors have been typically reserved for telecom infrastructures and other demanding industrial applications, Freescale Semiconductor hopes to expand its solid state offering to the comparatively much larger consumer market through the development of low-cost RF power transistors specifically aimed at a new generation of smart microwave ovens.

Over the last few years, the company has been stealthily working with Israeli startup Goji Solutions to help it develop a new oven concept based on so-called Volumetric Cooking, whereby an array of RF amplifiers and antennas are controlled in phase, frequency and amplitude for a spatially-controlled energy delivery within the oven's cavity (through sequenced beam forming).

"Depending on which parameters you choose, you can play on the different resonance modes and direct the energy precisely", told us Jean-Claude Loirat, Director of RF operations at Freescale and lead researcher at the company's RF labs in Toulouse who provided the silicon.

Although beam forming is nothing new, the novelty here are Goji's unique Adaptive Volumetric Energy Delivery (AVED) algorithms developed to precisely drive the energy delivery to the different types of food placed within the oven, while using signal processing to sense the different RF absorption and resonance levels within the cavity and adjust the cooking parameters in real time.

This could revolutionize cooking and meal preparation in general, since all the raw ingredients of a complete meal (say fresh or frozen fish, vegetables, potatoes, and bread dough) can all be placed on the same dish, yet be individually cooked in one single pass, each receiving just what it needs of RF energy to reach the right temperature profiles for the optimum result.

Because the RF feedback loop analyses the microwave interactions with the proteins, carbohydrates, and lipids within the food, the oven is able to constantly and spatially adjust RF energy delivery to prevent overcooking. This even works across complex food structures such as multi-layered cakes, avoiding the melting of any of the layers.