November 22, 2022
Antennas, which can couple guided waves emitted from various sources in free space and manipulate those waves, are critical to the development of numerous technologies, including wireless communications, optical communications, and distance measurement systems. Metasurfaces, thin films composed of multiple elements, have shown promise for the development of this type of antenna.
Researchers from the City University of Hong Kong and Southeast University recently developed a new metasurface antenna that can extract and manipulate guided waves to generate desired free-space waves in both the spatial and frequency domains. This antenna featured in an article published in nature electronicscombines two distinct research advances, namely amplitude modulated (AM) leaky wave antennas and space-time coding techniques.
“Our work is based on the invention of the amplitude modulated leaky wave antenna, which was discussed in the doctoral thesis of Dr. Gengbo WU at City University of Hong Kong (CityU), and the pioneering research on space-time encoding metasurface led by Academician Tie Jun Cui at Southeast University,” said Prof. Chi Hou Chan, one of the researchers who conducted the study told TechXplore, “The AM leaky antennas are inspired by amplitude modulation in classical communications theory.”
A key benefit of AM leaky wave antennas is that their radiation pattern can be easily synthesized or tailored for specific applications by changing the shape and structure of the antenna. However, once an antenna is fabricated, its radiation characteristics typically remain fixed.
“Around the same time that the AM leaky antennas were introduced in 2020, Dr. Jun Yan Dai joined Southeast University’s CityU research group for a postdoctoral position,” said Prof. Chan. “Coming from the research group led by academics Tie Jun Cui and Professor Qiang Cheng, he brought us the use of space-time coding or software control to dynamically reconfigure antenna performance.”
Space-time coding, or space-time block coding, is a technique that allows engineers to transmit multiple copies of a data stream across multiple antennas, using the different versions of the original data to transmit data more reliably. Prof. Chan and his colleagues combined space-time coding techniques with the design of leaky AM antennas to enable modulation of emitted radiation patterns.
“By combining the two approaches, we achieve a specific radiation pattern by controlling the on-off sequences and durations of the switches on the leaky-wave antenna through a space-time matrix that can be generated by analytical means,” Prof Chan explained . “Due to the guided wave nature of the leaky wave antenna, unwanted harmonics generated by the switches can be filtered out by the waveguide, resulting in sideband rejection. The reported research results are generated through synergistic efforts and complementary expertise of the two research teams at City University of Hong Kong and Southeast University.”
The new sideband-free and space-time encoded metasurface antennas presented by the researchers ultimately allow users to achieve different radiation patterns through software control without requiring physical changes to the antenna structure. This means that the unwanted sidebands or harmonics that impede the performance of traditional antennas based on reconfigurable metasurfaces can be eliminated.
“For example, the same frequency beam steering is achievable with our antenna,” said Prof. Chan. “Since the space-time matrix is linear, different beams with different frequencies can be produced simultaneously by superimposing different space-time matrices. Since the space-time matrix is linear, different beams with different frequencies can be created simultaneously in the superposition different space-time matrices.”
Prof. Chan and his colleagues evaluated the effectiveness of their antenna design in a series of tests and found that it enabled highly efficient frequency conversion, continuous fundamental-frequency beam scanning, and independent control of multiple harmonics. In the future, their antenna could be combined with different baseband modulation schemes to achieve highly efficient and secure communication.
“In our next studies, we plan to modify the structure of the antenna to achieve better control over the radiation properties, including the polarization of the emitted beams,” added Prof. Chan. “A unique feature of the antennas is that we can control the amplitude and phase distributions on the antenna aperture. Therefore we can generate all kinds of radiation patterns, including linear sweep of a focused point along the length or perpendicular to the antenna surface. ”
Geng-Bo Wu et al, Sideband-free space-time coding metasurface antennas, nature electronics (2022). DOI: 10.1038/s41928-022-00857-0
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Citation: A Space-Time Coding Metasurface Antenna for Efficient and Secure Communications (2022 November 22) Retrieved November 23, 2022 from https://techxplore.com/news/2022-11-space-time-coding -metasurface-antenna-efficient. html
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