More than 60 years ago, vacuum tubes in radios, computers, and other radio frequency and electronic gadgets began to be overtaken by solid-state electronics. We live now in the 'Silicon Age'. However, vacuum electronic devices are still present in our everyday life. Our microwave appliances make use of a magnetron, which is actually a vacuum tube. It is the same technology that made possible the development of the laser in the first half of the 20th century. The traveling wave tubes generate the electromagnetic signals in communications satellites. They provide power efficiency and exceptional reliability on the orbit.
Vacuum tubes have their origin in the 19th. For their unique ability to generate high-frequency signals they make possible today's modern aviation radar systems. Today, it is estimated that there are more than 200,000 vacuum electronic devices (VEDs) still in service in the Department of Defense. They are used to power critical radar and communications systems.
The vacuum tube technology might be the future of electronics. DARPA's Microsystems Technology Office (MTO) has in place a new innovative program called Vacuum Electronic Science and Technology (INVEST). The program aims to develop the science and technology base for a new generation of vacuum electronic devices, more capable, more reliable and lasting more. According to Dev Palmer, program manager for INVEST, a vacuum tube is the technology of choice "anytime you need to operate at the outer reaches of the power-frequency parameter space".
Palmer added that the design and construction of VEDs is labor intensive and intricate, due to "the high millimeter-wave frequencies of interest to this program". The design of requires making use of exotic materials, exquisite modeling tools and high-precision, expensive machining. So far, physical scaling laws have not allowed the design and manufacturing of millimeter-wave VEDs, according to Palmer. As the operating frequency of electronic devices is pushed upward, the devices deliver less output power. Palmer aims with INVEST, to create over the next four years a community of researchers and engineers that will be able to find a breakthrough and overcome this technical bottleneck.
The incentive to overcome cost and technical barriers in order to obtain the next-generation VEDs is very strong. As Palmer explains, the availability and proliferation of high-power and inexpensive power commercial amplifiers and sources worldwide has made the electromagnetic spectrum very crowded. However, VEDs are capable of operating at shorter wavelengths and higher frequencies, so they can outperform the current generation of devices. This could provide significant defense advantages, being harder to jam or interfere with. They could also open the way to many applications in civilian settings, such as data transmission and versatile communication.
