| 1. |
- Montofre, Daniel, 1989, et al.
(författare)
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Single-Layer Dichroic Filters for Multifrequency Receivers at THz Frequencies
- 2020
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 10:6, s. 690-697
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report the design, construction, and characterization of two free-standing single-layer frequency-selective surface structures to be used as dichroic filters in the THz range. Their spectral responses are aimed to fulfill a stringent band-pass performance in the atmospheric window between 600 and 725 GHz. Specifically, the dichroics have been required to allow a transmission of electromagnetic radiation of at least 90%, achieve a rejection in the stop-band lower than -25 dB, and have cross-polarization levels below -30 dB. All these specifications were demanded to be satisfied at normal and nonnormal beam incidence. We have studied dichroic filters with hexagonal patterns of two different apertures, a well-known single-hole geometry and, in order to enhance the spectral performance, a novel aperture geometry that we call the flower type. Their transmission characteristics were measured using a Fourier transform spectrometer. The electromagnetic simulations and experimental results not only show a good agreement but they demonstrate that the flower-type geometry can greatly outperform its single-hole counterpart achieving all the desired requirements. In this way, we demonstrate the feasibility of implementing single-layer systems at (sub)-THz frequencies suitable for low-noise astronomical applications.
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| 2. |
- Tan, B. K., et al.
(författare)
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Investigation of the performance of an SIS mixer with Nb-AlN-NBN tunnel junctions in the 780-950 GHz frequency band
- 2018
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Ingår i: 2018 29th IEEE International Symposium on Space Terahertz Technology, ISSTT 2018. ; , s. 139-142
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present preliminary measured performance of an SIS mixer employing a Nb/AIN/NbN tunnel junction in the frequency range of 780-950 GHz range. The mixer design is an upgrade of the Carbon Heterodyne Array of the Max-Planck-Institute Plus (CHAMP+) mixer, coupled with an easy to fabricate smooth-walled horn. The noise temperature of the mixer is measured using the standard Y-factor method, but all the RF optics is enclosed in the cryostat. We use a rotating mirror in the cryostat to switch between a room temperature load and a 4 K blackbody load. With this method, we have measured a noise temperature of 330 K around 850 GHz, corrected for a mismatch between a reduced height rectangular waveguide at the input of the mixer block and a full height waveguide at the output of the horn. To remove this mismatch we now plan to redesign a new mixer chip with a full-height waveguide back-piece. The expected performance of the new mixer chip is also reported.
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