Sökning: "aperture"

Visar resultat 41 - 45 av 198 avhandlingar innehållade ordet aperture.

1. 41. Analysis and Design of Base Station Antennas for Mobile Communications

   Författare :Björn Lindmark; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; polarization diversity; dual polarization; adaptive antennas; moment method; genetic algorithm; antenna arrays; radio propagation; channel sounding; aperture coupled patch;

   Sammanfattning : The thesis deals with base station antennas and the environment they work in. Polarization diversity, dual band operation, and adaptive antenna systems are discussed with emphasis on how antennas for these applications should be designed. We compare the polarization diversity performance of different types of dual polarized antenna elements. LÄS MER

3. 42. Temporal Characteristics of Boreal Forest Radar Measurements

   Författare :Albert Monteith; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; antenna array; Synthetic aperture radar; temporal coherence; tomography; backscatter; remote sensing;

   Sammanfattning : Radar observations of forests are sensitive to seasonal changes, meteorological variables and variations in soil and tree water content. These phenomena cause temporal variations in radar measurements, limiting the accuracy of tree height and biomass estimates using radar data. LÄS MER

4. 43. Sea Ice Concentration Estimation and Ice Type Classification from Dual-Frequency Satellite Synthetic Aperture Radar

   Författare :Wiebke Aldenhoff; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; sea ice concentration; sea ice; SAR imaging; sea ice classification; Fram Strait;

   Sammanfattning : The sea ice cover in the Arctic has undergone dramatic changes in recent years. The perennial sea ice extent is decreasing by 12.2 % per decade while annual mean sea ice thickness has decreased by more than 2 m for the central Arctic Basin from 1975 to 2012. LÄS MER

5. 44. Spaceborne SAR in Sea Ice Monitoring: Algorithm Development and Validation for the Baltic Sea

   Författare :Anders Berg; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; synthetic aperture radar; ice drift; sea ice; ice type; ice concentration;

   Sammanfattning : The usefulness of new spaceborne synthetic-aperture radar (SAR) sensors at L-, C-, and X-band for operational sea ice monitoring in the Baltic Sea has been evaluated. It is concluded that the information content in C-band and X-band data is largely equivalent, although larger spatial coverage is an advantage of the current C-band satellites. LÄS MER

7. 45. Beamforming and timing design issues for a large aperture array radar applied to atmospheric research

   Författare :Gustav Johansson; Jan Bergman; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Industrial Electronics; Industriell elektronik;

   Sammanfattning : This thesis describes the work done by the author during the development of a Large Aperture Array Radar (LAAR) receiver for the EISCAT 3D project. The main focus was on digital beamforming of a bandpass-sampled wide band signal in base-band and the development of a picosecond-level distributed timing system applicable over hundreds of meters. LÄS MER