At one time, millimeter-wave (mmWave) frequencies were mainly relegated to the laboratory. They went beyond the frequency range of most test instruments and were available only in a handful of active and passive components from a small number of manufacturers. But, almost without warning, mmWave frequencies and components have become mainstream topics of conversation, largely because of highly anticipated application areas: automotive safety systems and fifth-generation (5G) wireless communications technology.
Some of the automotive systems, based on 76- to 81-GHz radar sensors for advanced driver-assistance systems (ADAS), are already on the road, with many more to follow. However, 5G is perhaps the most intriguing opportunity that lies ahead for mmWave frequencies and components.
Wireless networks have evolved from their humble first-generation (1G) analog beginnings based on the Advanced Mobile Phone Service (AMPS) standard to the current, quite sophisticated fourth-generation (4G) Long Term Evolution (LTE) digital wireless standard. Already, though, LTE is being made to appear obsolete when compared to all of the services and functions that 5G will bring. Perhaps the biggest challenge facing wireless communications of any kind is that they have simply run out of bandwidth.
When commercial wireless communications went public with the AMPS system, the number of cell phones and wireless users was relatively small but growing. As the number of users grew with each new generation of wireless system, the number of functional requirements for those users also grew, from simply voice communications to adding functions such as transferring data files, high-speed Internet access, and video streaming. In short, wireless network generations 1G through 4G have simply run out of bandwidth to provide continually improving service and functions on the now ubiquitous mobile devices.
Just when it appeared that 4G LTE would be the wireless communications network to serve all needs, it has simply become saturated with users as more people rely on their smartphones. Network designers have considered the needs and possibilities for 5G for several years now, and the basic need for more bandwidth has turned the attention to where it’s available: at mmWave frequencies, which generally range from 30 to 300 GHz.
Millimeter-wave frequencies have their share of challenges, including the small wavelengths with their short propagation distances, the significant foliage and rainfall signal attenuation, and the signal blockage cause by concrete buildings. In addition, the components for generating and receiving signals within licensed and unlicensed portions of the mmWave frequency spectrum (starting at about 24 GHz) are expensive.
But for 5G to do everything that its supporters are promising, such as futuristic smartphones, connected autonomous vehicles, and Internet of Things (IoT) devices everywhere that can be accessed instantly with a smartphone, bandwidth is needed. And mmWave frequencies offer that bandwidth.
The opportunities for mmWave components, test, even software developers in 5G networks are too obvious to ignore. 5G will use techniques like beamforming, MIMO, and thousands of closely spaced small cells to make mmWave technology an everyday reality. Semiconductor companies have already had a taste of the possibilities for large-volume sales of mmWave devices in the automotive radar markets. But when 5G networks are constructed, the demand for mmWave components and ICs will make those earlier automotive markets simply look like a wrong turn.
