Sökning: "optical antennas"

Visar resultat 11 - 15 av 24 avhandlingar innehållade orden optical antennas.

  1. 11. Low Cost Remote Antenna Units in CMOS for Fiber-fed Distributed MIMO Systems

    Författare :Waqas Ahmad; Institutionen för elektro- och informationsteknik; []
    Nyckelord :Remote Antenna Unit; distributed MIMO systems; CMOS technology; power amplifier; linearization; CMOS photodiodes; transimpedance amplifier; radio over fiber; optical communication;

    Sammanfattning : Massive multiple input multiple output (MIMO) is a revolutionary communication technique, where large numbers of antennas are employed at the base stations to increase the spectral efficiency, reliability and data rate of the system. Moreover, in multi-user MIMO (MU-MIMO) multiple users can be served by the base stations on the same time-frequency resource. LÄS MER

  3. 12. Design, Characterization, and Calibration of Low-Noise Terahertz Receivers

    Författare :Olle Nyström; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; receiver characterization; instrumentation; antenna design; Radio astronomy; calibration; optics;

    Sammanfattning : This thesis is focused on the field of instrumentation for radio-astronomy and atmospheric science, and specifically deals with problems such as optical design and its verification, horn antennas and receiver optics’ components, different aspects of measurement systems in order to characterize low-noise THz receivers, and its calibration techniques.Ultra low-noise Terahertz receivers, used in radio-astronomy, are typically coupled to the telescope system through relay optics that provides guiding of the signal to the receiver frontend with minimal loss. LÄS MER

  4. 13. Antenna Integrated Superconducting Mixers

    Författare :Hans Ekström; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; tapered slotline antenna; mixer; double dipole antenna; superconducting; hot electron; receiver; Niobium; bolometer; trilayer junction; edge junction; Niobium Nitride; SIS;

    Sammanfattning : This thesis investigates the prospects of some different superconducting mixers integrated with planar antennas for the millimeter and submillimeter regime. Two kinds of Superconductor/Insulator/Superconductor (SIS) tunnel junctions for use in mixers have been fabricated; Nb/PbBi edge junctions and Nb trilayer junctions. LÄS MER

  5. 14. Time-Domain Antenna and Scattering Analysis for Micro- and Millimeter-Wave Applications

    Författare :Iman Vakili; Institutionen för elektro- och informationsteknik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

    Sammanfattning : Telecommunications industries are investing tremendously to meet the ever-increasing demands for higher data rates and capacity. In particular to develop standardization for 5G, which is expected around 2020. The existing spectrum for traditional mobile networks is limited to highly occupied bands at microwave frequencies below 6 GHz. LÄS MER

  7. 15. NbN and NbTiN Hot Electron Bolometer THz Mixers

    Författare :Pourya Khosropanah; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; receiver noise; hot electron bolometer; superconducting detector; spiral antenna; NbTiN; submillimeter mixer; THz mixer; HEB; FTS; NbN; quasioptical receiver; heterodyne receiver; double slot antenna; twin slot antenna; Fourier Transform Spectrometer;

    Sammanfattning : The thesis reports the development of Hot Electron Bolometer (HEB) mixers for radio astronomy heterodyne receivers in THz frequency range. Part of this work is the fabrication of HEB devices, which are based on NbN or NbTiN superconducting thin films (≤5 nm). They are integrated with wideband spiral or double-slot planar antennas. LÄS MER