Microwave Technology and Applications

- Overview

Microwaves are very short waves in the upper range of the radio spectrum used mostly for point-to-point communications systems. Much of the technology was derived from radar developed during World War II. Initially, these systems carried multiplexed speech signals over common carrier and military communications networks; but today they can handle all types of information, e.g. voice, data, facsimiles, and video, in either an analog or digital format.

Over the years, these systems have matured to the point that they have become major components of the nation's public switched telephone network. Private organizations use them to satisfy internal communications requirements and to monitor their primary infrastructure. As the nation’s cellular and personal communications systems grow, point-to-point microwave facilities, serving as backhaul and backbone links, enable these wireless systems to serve the country’s less populated areas on an economical basis. 

Today's technology enables private users to employ microwave frequencies to operate and control equipment at remote sites, such as switches and valves associated with the operation of oil and gas pipelines, to gather data related to services, control traffic signals and to obtain toll data from moving vehicles, as well as other monitoring functions.

[The electromagnetic spectrum from lowest energy/longest wavelength (at the top) to highest energy/shortest wavelength (at the bottom). (Credit: NASA's Imagine the Universe)]

- The Applications of Microwave Radio Transmission

The foundations of the modern electronics and communication environment using radio frequency (RF) and microwaves were laid in the nineteenth century with Michael Faraday's observation in 1845 of the effect of magnetic fields on the propagation of light, and James C. Maxwell's four contributions to the electromagnetic theory of light. named after a fundamental equation.

Microwave radio transmission is commonly used in point-to-point communication systems on the surface of the Earth, in satellite communications, and in deep space radio communications. Other parts of the microwave radio band are used for radars, radio navigation systems, sensor systems, and radio astronomy.

Wireless transmission of information

• One-way and two-way telecommunication using communications satellite
• Terrestrial microwave relay links in telecommunications networks including backbone or backhaul carriers in cellular networks

More recently, microwaves have been used for wireless power transmission.

- The Role of Microwave Radio in 5G Transmission

Microwave is a key enabler for 5G ubiquitous backhaul networks. The shift to commercial 5G deployments, coupled with increasingly robust Gigabit LTE networks, will require significant investment in network densification. 

As mobile service providers enhance the macro layer by overlaying street-level small cells, capex (capital expenditures) related to radio access and core networks must be supported by a 5G transport network capable of providing the fronthaul and backhaul needed to enhance the user experience. 

When considering 5G transport, it's important to remember that fiber isn't the only option; microwaves play an important role in supplementing operators' fiber footprints. Microwave product innovation across traditional licensed bands, mmWave and beyond means microwave is ready for 5G.

Definitely deploying as much fiber as possible, but fiber cannot be everywhere. It's not cost-effective to deploy in every location. Microwave is an effective tool for extending an operator's fiber footprint. To understand how microwave fits into 5G transport, let's consider some real-world deployment scenarios operators will face when they light up 5G. For example, in a dense urban environment, mmWave small cells will need to be closely clustered on streetlights and rooftops to provide users with a seamless and high-quality network experience as they move through the central business district.

- Millimeter Waves

The next higher frequency band of the radio spectrum, between 30 GHz and 300 GHz, are called "millimeter waves" because their wavelengths range from 10 mm to 1 mm. Radio waves in this band are strongly attenuated by the gases of the atmosphere.  

When mmWave signals are used for radio communication, radar or any other purpose, the attenuation of the signal with propagation distance is an important aspect. Not only is attenuation generally rising with frequency, but there are also peaks where atmospheric components react to the signal and the level of absorption increases. While this also exists in the microwave portion of the spectrum, it is more pronounced for mmWave signals.

This limits their practical transmission distance to a few kilometers, so these frequencies cannot be used for long-distance communication. The electronic technologies needed in the millimeter wave band are also in an earlier state of development than those of the microwave band.