Reflectarray Design for 120-GHz Radar Application: Measurement Results

In this paper, we present design and experimental results on reflectarrays at 120 GHz. The offset-fed reflectarrays consist of conductor-backed coplanar patch antennas with phase-shifting stubs. Three 138-mm reflectarrays are lithographically fabricated and evaluated in a near-field measurement rang...

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Bibliographic Details
Published in:IEEE transactions on antennas and propagation 2013-10, Vol.61 (10), p.5036-5047
Main Authors: Tamminen, Aleksi, Makela, Sampo, Ala-Laurinaho, Juha, Hakli, Janne, Koivisto, Paivi, Rantakari, Pekka, Saily, Jussi, Luukanen, Arttu, Raisanen, Antti V.
Format: Article
Language:English
Subjects:
Antenna arrays
Antenna measurements
Antennas
Applied sciences
Exact sciences and technology
Feeds
Finite element analysis
Millimeter wave measurements
near-field imaging
Phase shifters
Radiocommunications
reflectarray
Reflection
Reflector antennas
Telecommunications
Telecommunications and information theory
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Summary:In this paper, we present design and experimental results on reflectarrays at 120 GHz. The offset-fed reflectarrays consist of conductor-backed coplanar patch antennas with phase-shifting stubs. Three 138-mm reflectarrays are lithographically fabricated and evaluated in a near-field measurement range. Their measured beam patterns are compared to the theoretical ones. The theoretical -3-dB beam width is 60-64 mm at 3-m distance from the reflectarray. Measured beam widths of the different reflectarrays deviate less than 10% from the theoretical values. The beam pointing is found to be close to theoretical, whereas the sidelobe level is up to 5 dB higher. The efficiency, alignment accuracy, and surface shape of the reflectarray are studied with near-field imaging of the reflectarray aperture field. The measured average efficiency is 0.11 whereas the predicted average efficiency is 0.54. The low efficiency is most likely due to over-etching of the structures of the reflectarray element, and could be improved in future fabrication processing rounds. Beam pattern measurement close to the main beam is well suited for evaluating the beam width and pointing accuracy, but it gives little information on the element performance. We propose near-field imaging of the reflectarray to evaluate both element efficiency and phase shift.
ISSN:0018-926X
1558-2221
DOI:10.1109/TAP.2013.2273256