Climate Changes Pose Future Hazards to RF Sensors, Says Scientist

Climate changes caused by increased greenhouse gas emissions have raised concerns among many scientists and engineers that are trying to analyze potential effects on our ecosystem and develop long-term solutions. One area that hasn’t received much attention is radiofrequency communications, which with the advent of 5G and beyond dictates more sensors and other electronics monitoring and transmitting signals at very high frequencies.

While higher operating frequencies offer the potential for higher accuracy and performance, they also leave RF sensors and other electronics more vulnerable to the effects of climatic change as issues such as higher water vapor become more critical, according to Jonathan Gehman, an applied physicist for Johns Hopkins Applied Physics Laboratory. In this fascinating e-mail interview with Design News, Gehman discusses the risks changing climatic conditions pose for current-generation RF sensors, and how RF systems may have to compensate for performance comprises.

What are limitations of current sensing technology with regards to climate and environmental conditions? Are these issues related to range, sensitivity, or other factors?

Jonathan Gehman: Sensing and communications via radio, infrared, and optics are range-limited by weather. For infrared and optical RF sensors, rain and clouds are the limiting factors when present. Without rain or clouds, aerosols and humidity are the limiting factors. For radio frequency (RF) sensors, the higher-frequency RF bands are also limited by rain and water vapor (humidity), and nearly all RF signals can experience mirages over the ocean. These mirages can be beneficial or detrimental depending on the application.

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What aspects for RF systems require modifications due to short- and long-term environmental changes? Are these systems going to need to be made more robust or incorporate other features?

Jonathan Gehman: Many RF systems currently operate between 2 and 6 GHz. New systems often look to higher frequencies for a less-crowded spectrum (less interference). Higher frequencies also give better accuracy for remote sensing, and higher data rates for communications. However, higher frequencies are also more prone to degradation due to climate change. This is because frequencies above ~6 GHz are increasingly sensitive to water vapor. As earth’s climate warms, there will be a tendency for higher water-vapor content in the air, which means these systems will experience increased losses over long-range paths. To counter these additional losses, higher-frequency systems will need to transmit more power, or suffer a performance hit.

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What aspects of RF system performance are adversely by climatic and environmental changes?

Jonathan Gehman: Without extra power, RF systems operating above 4 GHz could be prone to “outages” in the future climate. More specifically, communication systems may not reach their advertised data rates, and sensing systems may not reach their desired surveillance range. Statistically speaking, the severity and frequency of outages will be more likely as the climate warms, with higher frequencies more severely impacted.

How much cost will these RF system modifications add to the product/system cost?

Jonathan Gehman: It is too early to say with any amount of confidence how much these costs will be. This picture will become clearer with further research. Generally speaking, however, design requirements and consequently costs will likely increase for longer-range systems, and for higher-radio-frequency systems.

Jonathan Gehman is an applied physicist specializing in radio-frequency propagation modeling in the Air and Missile Defense Sector of the Johns Hopkins Applied Physics Laboratory. With more than 20 years of experience in his field, he is a nationally recognized thought leader in the use of numerical weather prediction for RF analysis. Gehman presents regularly at national symposia and conferences on radio science. He leads the APL Climate Network’s Tech Talks committee. He holds bachelor’s and master’s degrees in engineering physics from Cornell University and the Johns Hopkins University, respectively.

Spencer Chin is a Senior Editor for Design News covering the electronics beat. He has many years of experience covering developments in components, semiconductors, subsystems, power, and other facets of electronics from both a business/supply-chain and technology perspective. He can be reached at [email protected].