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EETE JULAUG 2015

Microwaves RF power transistors to reach consumers’ dishes 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. Of course, Goji’s secret recipes lay in the algorithms and the empirical data it gathered while experimenting with different heating profiles, working with nutritionists and chefs to ensure they struck the right energy balance for a tasty meal. The startup will also leverage its know-how by developing consumer-level smart recipe applications. Later the oven could access a virtually unlimited library of recipes, learn new cooking methods within online social communities or adapt to consumer cooking preferences, and add and store recipes in real-time. Other benefits over the traditional magnetron based microwaves include a much better energy efficiency (it is only delivered where needed), and a much higher reliability and stability by design (using solid state transistors). “The business model that we hope will develop around this disruptive oven concept is that consumers would order raw food (pre-plated or not through a logistic chain) and the internet-connected oven would collect the data during the order to pre-configure itself”, said Loirat, “A small interface could also let the user define his/her cooking preferences (rare or medium-rare etc...)”. “In the case of large professional ovens, say for collectivities, you could envisage to have several rows of dishes where the meat would be cooked for different tastes, all in one pass”, he added. For Freescale, shipping RF power transistors to such a potentially large market would be an incredible boon, and already in discussion with several OEMs, the company has put together a reference design to help them take the new concept rapidly to market. It comes with either two of four antennas, tied to either 500W or 250W RF power transistors. These could operate at 900MHz or 2.4GHz. “This is a consumer market due to take-off soon, and with our SAGE oven reference design, we want to initiate a fast adoption to displace today’s inefficient magnetron-based microwaves”, Loirat explained. “But in order to do so, we need to develop RF power transistors on a similar price range as today’s 2.4GHz magnetrons, or at least within the same order of magnitude”, he added, saying that in Freescale’s RF labs, his team had already started the necessary R&D to address this high volume market in a costeffective manner. “Parts developed for the consumer market would not have the same packaging and reliability requirements as for industrial or telecom applications” he clarified. Loirat is confident Freescale will play a leading role, should this market develop. “First, because we started early on this development and we already have some products specifically tailored for this application, and secondly because we already hold 60% of the telecoms market and are very capable to deliver in high-volumes. 14 Electronic Engineering Times Europe July-August 2015 www.electronics-eetimes.com


EETE JULAUG 2015
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