Sökning: "aperture efficiency"

Visar resultat 21 - 25 av 34 avhandlingar innehållade orden aperture efficiency.

  1. 21. On millimeter and submillimeter wave focal plane arrays implemented with MEMS waveguide switches

    Författare :Henrik Frid; Joachim Oberhammer; Vessen Vassilev; Mikro- och nanosystemteknik KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Extended Hemispherical Lens; Beam Steering; Focal Plane Array FPA ; Ray-Tracing; RF MEMS; waveguide switch; micromachined waveguide; submillimeter-wave; rectangular waveguide; terahertz; lenses; antenna theory; silicon; Electrical Engineering; Elektro- och systemteknik;

    Sammanfattning : This thesis presents research towards enabling micromachined millimeter and submillimeter wave focal plane arrays (FPAs). The FPAs operate under the following principle: a switch network consisting of microelectromechanical (MEMS) switches, integrated with micromachined waveguides, is used to feed an array of antenna elements, located in the focal plane of a high-gain quasi-optical system. LÄS MER

  3. 22. Active and Passive Unequally Spaced Reflect-Arrays and Elements of RF Integration Techniques

    Författare :Dhanesh G. Kurup; Anders Rydberg; Mohamed Himdi; Peter S Hall; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electrical engineering; Active Antenna; Reflect-arrays; NRD guide; RF integration; Elektroteknik; elektronik och fotonik; Electrical engineering; electronics and photonics; Elektroteknik; elektronik och fotonik;

    Sammanfattning : Using an array synthesis tool based on a modified differential evolution algorithm, it is shown that the position-phase synthesis exhibits improved pattern characteristics compared to both the phase only and position only synthesis of uniform amplitude antenna arrays. The design of an unequally spaced planar reflect-array and an active power combining reflect-array are presented. LÄS MER

  4. 23. Single and dual band horns for multi-beam satellite antennas - application of artificially hard surfaces

    Författare :Omid Sotoudeh; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Multi-beam reflector antennas; Multi-mode hard horns;

    Sammanfattning : The latest trend for the multimedia satellite systems is operation at the Ka-band, 17.7-20.2 GHz downlink and 27.5-30. LÄS MER

  5. 24. SPECT Imaging using Pinhole Collimation : System Design and Simulation Studies for Pre-Clinical and Clinical Imaging

    Författare :Mikael Peterson; Lund Medicinsk strålningsfysik; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Pinhole SPECT tomography; Nuclear medicine imaging; Monte Carlo-based image reconstruction;

    Sammanfattning : The focus of this dissertation is the use of pinhole collimation in Nuclear Medicine. A pinhole is a single aperture in an opaque material that is placed between the detector and source of interest, and photons must pass through the hole to reach the detector. The choices of pinhole parameters, e.g. LÄS MER

  7. 25. Energy scaling of infrared nanosecond optical parametric oscillators and amplifiers based on Rb:KTiOPO4

    Författare :Riaan Stuart Coetzee; Valdas Pasiskevicius; Gunnar Rustad; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik;

    Sammanfattning : High-energy, narrowband, nanosecond pulsed mid-infrared sources centred on 2 μm are requiredin applications in remote sensing, standoff detection and pollution monitoring using LIDARs.Currently, space-borne LIDAR missions are under development by major space agencies aroundthe world for active measurements of the atmospheric gas constituents and their dynamics. LÄS MER