| 1. |
- Du, Zhou, et al.
(författare)
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Reflection phase characterization of the MEMS-based high impedance surface
- 2012
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Ingår i: European Microwave Week 2012: "Space for Microwaves", EuMW 2012, Conference Proceedings - 42nd European Microwave Conference, EuMC 2012<em></em>. - : IEEE. - 9782874870279 ; , s. 617-620
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Konferensbidrag (refereegranskat)abstract
- The reflection properties of the MEMS-based HIS illuminated from oblique angles of incidence have been characterized numerically, and a quasi-optical measurement setup has been built for experimental characterization. The resonance frequency and the relative bandwidth are slightly increasing with the increase of the angle of incidence. The comparison between the simulated and measured results is discussed.
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| 2. |
- Kahkonen, Henri, et al.
(författare)
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Comparison of additively manufactured and machined antenna array performance at Ka band
- 2022
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 1536-1225 .- 1548-5757. ; 21:1, s. 9-13
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) is a rapidly developing field which potentially decreases the manufacturing costs and enables increasingly complex antenna shapes. Metal-based AM might be particularly useful to manufacture antennas at mm-wave range, because there antennas are physically small enough making additive manufacturing cost efficient, and manufacturing accuracy could still suffice for good electrical performance. In this paper, two additively manufactured and an identical machined fully metallic Ka-band Vivaldi antenna arrays are compared. The manufactured antenna arrays are compared using RF-measurements to conclude the feasibility of AM for manufacturing antenna arrays at mm-wave frequencies. Comparison of the measured radiation patterns and realized gains of each of the antenna arrays between 26 and 40 GHz shows close to identical radiation patterns for all the arrays. A loss in efficiency of 0.51.5 dB is observed in the AM arrays when compared to the machined array due to the used materials and the surface roughness.
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| 3. |
- Nefedova, Irina, et al.
(författare)
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Design of a quasioptical test bench for VNA extenders
- 2020
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 2020-November, s. 552-553
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Konferensbidrag (refereegranskat)abstract
- The CAD design, simulated optical performance, and test measurements of a quasioptical test bench for VNA extenders are presented. The system allows straightforward integration of off axis parabolic mirrors and VNA extenders. The mirror orientation reduces aberrations and results suggest optical properties are close to what is expected with geometric ray tracing.
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| 4. |
- Nefedova, Irina, et al.
(författare)
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THz Frequency Quantification of Water Gradients in Drying Paper
- 2020
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 2020-November, s. 844-845
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Konferensbidrag (refereegranskat)abstract
- THz-reflection spectroscopy was used to extract time-varying water gradients in drying paper targets mounted on electrically thick dielectric substrates. The data showed a pronounced and prolonged drop below dry reflectivity when the water content that peaks at low weight (∼10%). A binomial distribution fitted to the acquired data confirms the existence of the time-varying water content gradient and suggests aqueous thin film hydration can be quantified even when the contrast between the film and backing material is low.
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| 5. |
- Pälli, Samu Ville, et al.
(författare)
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Imaging experiments with a 340-GHz FMCW radar and frequency-diverse holograms
- 2023
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - 0277-786X .- 1996-756X. ; 12535
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Konferensbidrag (refereegranskat)abstract
- We present recent developments of a standoff imaging system based on a frequency-diverse phase hologram and deep neural networks. The single-pixel imaging system operates in a monostatic configuration consisting of a 340-GHz FMCW radar and a frequency-diverse phase hologram to interrogate the radar down range direction with spatially varying, frequency-dependent field patterns. The measured back-reflected signal contains spatial reflectivity information from the target, and the fast chirp rate of the radar enables real-time imaging performance. Together with simultaneously acquired visible-light images, a deep neural network integrated into the submillimeter-wave data readout electronics can map the received signal onto a 2D image without mechanical or active electrical beam scanning. In experiments, we have collected submillimeter-wave and visible-light data of a moving target in the region of interest with a 60-Hz frame rate. The results suggest that the system can image the moving target with a resolution comparable to the theoretical diffraction limit. The minimal hardware complexity and good imaging performance of the demonstrated computational submillimeter-wave imaging system support its potential as a cost-effective and easily deployable solution for various imaging applications.
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| 6. |
- Rezapoor, Pouyan, et al.
(författare)
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Cross polarization in swept beam THz imaging systems using off-axis parabolic mirrors
- 2022
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Ingår i: 2022 16th European Conference on Antennas and Propagation, EuCAP 2022.
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Konferensbidrag (refereegranskat)abstract
- The optical behavior of a terahertz imaging system employing a train of four identical off-axis parabolic mirrors with oblique incidence angle illumination is investigated in this work. The aperture filling and aberrations of a single off-axis parabolic mirror when illuminated by a Gaussian terahertz beam at its focus point is measured and simulated. The amplitude of E-field in transverse electric (TE) and transverse magnetic (TM) polarizations at target plane reveals a significant cross polarization, even when there is zero cross polarization at the source beam, amplitude of which is ∼ 33% of TE polarization. The investigation of the E-field on the detector plane reveals that this ratio is ∼ 1.5% at the detector plane, and the cross polarized E-field at the target plane is rotated back to co polarization. Although its amplitude is negligible, the TM distribution at detector plane is bimodal and tilted about the optical axis.
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