Power Amplifier Design: A Collection from Applied Microwave & Wireless
With contributions from more than 20 experts, these articles present valuable resources for power amplifier linarization, measuring, modeling and distortion.
TABLE OF CONTENTS Power Amplifier Design: A Collection from Applied Microwave & Wireless
The Magnetron A Low-Noise, Long-Life Amplifier
This article describes how the common microwave oven magnetron can be externally locked to provide 30 dB of gain, resulting in a 500-watt, 70 percent efficient coherent microwave source
By William C.Brown
Overview
From APPLIED MICROWAVE & WIRELESS, VOL. 2, NO. 2, SUMMER 1990
The 2450 MHz magnetron, which supplies 700 watts of average power to the ubiquitous microwave oven, is made in a quantity of 15,000,000 units annually at a very low price, less than $15. It has a high conversion efficiency of 70 percent and small size and mass. What is not generally recognized is that it has very low-noise and long-life properties and can be combined with external circuitry to convert it into a phase-locked amplifier with 30 dB gain, without compromising its noise of life properties.
Such amplifiers are ideal for combining with slotted wave-guide radiators to form radiating modules in a low-cost, electronically steerable phased array for beamed power, which motivated this study. However, there are conceivably numerous other practical purposes for which these properties can be utilized.
The low noise and long life properties are associated with a feedback mechanism internal to the magnetron that holds the emission capabilities of the cathode to those levels consistent with both low noise and long life. This internal feedback mechanism is effective when the magnetron is operated from a relatively well filtered DC power supply with the cathode heated by back bombardment power alone.
The external power supply that heats the filament is removed after starting...
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