Enabling the acquisition of multivariate data at any time, in any weather, and contributing to sustainable social infrastructure
Figure 1: Comparison of conventional plane waves (on the left) and structured radio waves newly developed by Hitachi (on the right) (Green: wavefront; arrows: electric field vector; color map on the right side: positive/negative amplitudes for the electric field).
Summary
In the field of Earth observation using artificial satellites, Hitachi has succeeded in verifying the principles of structured radio waves.*1 This technology will help address various issues facing society, such as disaster monitoring, social infrastructure maintenance and management, and environmental monitoring. Structured radio waves represent an original technology for controlling and analyzing radio waves that makes it possible to acquire multiple features such as the shape, motion, and material of objects (multivariate data) simultaneously, which was difficult with conventional radio observation. Utilizing the properties shared by acoustic waves and radio waves, Hitachi confirmed the effectiveness of techniques for generating, controlling, detecting, and analyzing structured radio waves that have a vortex wavefront (i.e., orbital angular momentum, OAM*2) through experiments using acoustic waves . As a result, Hitachi anticipates that many types of information, such as three-dimensional images and speed in addition to the usual distance information, can be acquired without being affected by weather or time of day. This technology is expected to be useful for swift on-site decision-making or early detection of signs of anomalies. Going forward, Hitachi will work with partner companies, universities, and research institutes to promote the use of structured radio waves in diverse fields, including Earth observation, environmental monitoring, and disaster monitoring, and contribute to achieving sustainability, safety, and security for society.
Figure 2: An illustration of Earth observation using structured radio waves
*1 Structured radio waves are radio waves created by controlling the degrees of freedom in properties such as polarization state, phase, and frequency. The experiments used superposed vortex wavefronts.
*2 OAM stands for orbital angular momentum. A radio wave with OAM is characterized by having a vortex wavefront in which the phase of the azimuthal direction rotates to the right and left within a plane orthogonal to the direction of progression.
Background of the technology and related challenges
In recent years, maintaining and managing social infrastructure and reducing the risks of disasters have become challenges worldwide due to such factors as aging urban infrastructure and intensifying natural disasters as a result of climate change. Wide-area observation using artificial satellites is drawing attention as a method for efficient, large-scale checks. However, conventional optical observation*3 tends to be affected by weather or time of day. Radio observation*4 can be used in all types of weather and at any time of day, but it is difficult to intuitively interpret the results. This is because information that looks natural to the human eye cannot be acquired through radio observation, and the observed shape of objects may be distorted. In light of these realities, there has been demand for new observation technology that enables multivariate and high-precision information to be visualized in an easy-to-understand manner, without being impacted by weather or time of day, in order to improve the ability to monitor disasters, monitor the environment, and assess the integrity of social infrastructure.
*3 Optical observation: A method of observing the state of a ground surface or an object using light, including visible light and infrared rays.
*4 Radio observation: A method of observing the state of a ground surface or an object using radio waves.
Technologies and solutions developed to address these challenges
In response, Hitachi developed structured radio wave technology that makes it possible to acquire a wide range of information with high precision, irrespective of weather conditions or time of day. The main advantage of structured radio waves is that radio waves optimized for observation can be generated and analyzed through the combination of various properties such as wave shape (wavefront structure), polarization state, phase, and frequency. As a result, multivariate data such as the shape and motion of objects are acquired simultaneously, contributing to swift decisions and early detection of anomalies. The advantages of the technology are as follows.
1. Structured radio wave control technology for multivariate and high-precision observation
Hitachi has developed technology for freely designing and controlling the state of structured radio waves, which are made by superposing vortex wavefronts (OAM), with a user interface that allows visual confirmation of the wave state. By enabling the selection of radio waves with the highest sensitivity for the observation target, the technology will contribute to improving the precision of Earth observation.
2. Technology for the spectral detection of structured radio waves that enables object identification and speed estimation
Hitachi has developed techniques that enable the OAM spectrum*5 and Doppler component*6 to be detected with high sensitivity using frequency analysis of the structured radio waves. This makes it possible to simultaneously detect the shape, material, and motion of the observation target, contributing to the early detection of disaster risks or signs of anomalies in infrastructure.
3. Technology for analyzing the scattering characteristics of structured radio waves to facilitate intuitive data interpretation
Hitachi has developed methods for visualization and analysis that enable people to intuitively understand changes in the shape or properties of structured radio waves that occur when the waves hit an object and are reflected or scattered. These methods make interpreting observation data easier, contributing to swift decision-making on-site, improved infrastructure integrity assessment, and streamlined environmental monitoring.
*5 OAM spectrum: A distribution indicating the type and strength of the vortex component included in a radio wave having orbital angular momentum (OAM).
*6 Doppler component: A frequency component acquired through the phenomenon in which the frequency of a radio wave changes when the observation target is moving (the Doppler effect).
Confirmed results
Utilizing properties shared by acoustic waves and radio waves, Hitachi carried out experiments for generating and receiving structured acoustic waves using an eight-channel circular speaker array. As a result, Hitachi demonstrated the effectiveness of its wavefront structure control and OAM spectrum detection and confirmed that multivariate data can be acquired. Hitachi was able to overcome the lack of available information and the difficulty of intuitive data interpretation, which have traditionally been problems with radio observation. The technology will contribute to achieving high-precision and high-functionality monitoring of social infrastructure, leveraging its all-weather, all-day capability. Swifter and more accurate decision-making will also be possible on the front lines of disaster monitoring and infrastructure management.
Future outlook
To establish sustainable social infrastructure and strengthen society’s ability to adapt to climate change, Hitachi will cooperate with partner companies and research institutes in areas such as demonstrations using actual radio waves and promote the practical use of structured radio waves in society. Through the spread of this technology, Hitachi aims to help create a sustainable, safe, and secure society by, for example, streamlining infrastructure management, reducing the risks of disasters, and minimizing environmental footprints. Some of these outcomes are slated for presentation at the 39th Annual Small Satellite Conference to be held at Salt Lake City, Utah (USA), on August 10–13, 2025.
For more information, use the inquiry form below to contact the Research & Development Group, Hitachi, Ltd. Please make sure to include the title of the article.
https://www8.hitachi.co.jp/inquiry/hitachi-ltd/hqrd/news/en/form.jsp
