The Evolution of the Microwave: From Magnetrons to Solid-State Energy

Aug. 22, 2017

EvolutionBlogMicrowave.jpg (104438118)2017 marks the 50th anniversary of the invention of the microwave oven. Today an indispensable appliance in homes all around the world, the microwave has transformed the way we cook and prepare our food. Nevertheless technology is improving and advancing every day, and a new and improved microwave could be closer than you think.

The Beginning

The microwave was first invented in 1945, when a self-taught engineer by the name of Percy Spencer working for Raytheon discovered that the micro-waves emitting from an active radar set had melted a candy bar in his pocket. Spencer began experimenting and used the radar to pop popcorn and cook an egg, ultimately attaching a high density electromagnetic field generator to an enclosed metal box and testing different foods inside. Raytheon patented Spencer’s invention in 1945, and by 1947 had released the first microwave oven (then known as a Radarange) to the public. The device stood more than 5 feet off the ground, weighed 750 pounds, cost >$5,000 and used 3 kilowatts of power, almost three times as much as the typical household microwave uses today. It was twenty years before an affordable and economical microwave oven became available for sale.

Inside the Microwave Oven

This first microwave oven cooked food by transmitting the microwave radiation into the food to heat it. These microwaves were powered by magnetrons, high-powered vacuum tubes that create energy through interacting electrons in a magnetic field. As magnetrons penetrate an object, the electric dipole molecules rotate and bump into other molecules in an attempt to align themselves with the alternating electric field, thereby producing heat. The electric dipole molecules in salted liquids react the most, and are therefore heated the most, which is one of the main reasons why the typical magnetron-powered microwave may produce food with uneven hot and cold spots.

The Future of Cooking

Despite the significant evolution of the microwave over the last 50 years, the use of magnetrons in the microwave has remained fairly unchallenged. Recent technology advancements, made possible by efforts like the RF Energy Alliance (RFEA) and MACOM’s GaN-on-Silicon (GaN-on-Si), are today challenging the traditional microwave and enabling a modernized microwave powered by a solid-state RF energy source, capable of more precise and exact heating and cooking. RF energy uses precision controlled electromagnetic energy to heat items, boasting “an unprecedented control range, even energy distribution, and fast adaption to changing load conditions” (RF Energy Alliance) and can easily provide power for many different processes, perhaps most notably cooking and heating applications.

A solid-state RF transistor is capable of generating hyper-accurate, controllable and responsive energy fields, enabling a precise and ideal distribution of RF energy to ideally heat food to precise specifications. MACOM’s GaN-on-Si 300W transistor, for example, provides improved energy efficiency up to >80% in a typical cooking recipe in a small form factor at 2.45 GHz. While magnetron-powered microwaves have an average lifespan of 500 to 1,000 hours, with new solid-state RF energy transistors, we begin to see the potential for lifespans that surpass 10 years. Overcooking, and cold spots may soon be a thing of the past.

After 50 years of steady developments but essentially the same core microwave oven, the advancements of the RF Energy Alliance, together with MACOM’s GaN-on-Si technology performance, can revolutionize the microwave oven as we know it. MACOM is excited to be at the forefront of these technology breakthroughs, and make our mark on history by enabling an innovative and smarter kitchen for the world. 

The Microwave Oven and Solid-State RF Energy (Click to Enlarge - Infographic Courtesy of the RF Energy Alliance

RFEA_Microwave_Infograph (1).jpg     


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Timeline of the Microwave Oven:
The Magnetron is History. Solid-State RF Energy is Coming Soon.

(Click to Enlarge - Image Courtesy of the RF Energy Alliance)