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Visar resultat 1 - 5 av 7 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Dielectrically Loaded Quad-ridge Flared Horns for Ultra Wideband Reflector Feed Applications in Radio Astronomy

   Författare :Jonas Flygare; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; dielectric loaded antennas; dielectric materials; reflector antenna feeds; radio astronomy; ultra wideband antennas; quad-ridge flared horn qrfh ; radio receivers; horn antennas; broadband antennas; aperture antennas.;

   Sammanfattning : Reflector-based radio telescopes are used as tools for observations in both radio astronomy and space geodesy. To observe the weak sources in space, highly sensitive receivers, fronted by optimized reflector feeds, are therefore needed. LÄS MER

3. 2. Photonic terahertz-wave generation, radiation and quasioptical integration

   Författare :Biddut Kumar Banik; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; semiconductor device modelling; semiconductor diodes; III-V semiconductors; Catadioptric lens; imaging; dipole antennas; slot antennas; lens antennas; semiconductor heterojunctions; dielectric loaded antennas; optical mixers; photomixers; near-field imaging; computer aided engineering; indium compounds; millimetre wave imaging; near-field optics; submillimeter wave generation; photodiodes; terahertz sources; millimetre wave generation; submillimetre wave integrated circuits; microwave imaging; uni-travelling-carrier photodiodes;

   Sammanfattning : This thesis deals with the uni-travelling-carrier photodiode (UTC-PD) based photonic generation of terahertz waves, antenna designs for the terahertz radiation and a novelcatadioptric lens for quasioptical integration.The ongoing and accomplished research work on the UTC-PD, its limitations and optimisation scopes for attaining higher bandwidth and higher output power have been discussed. LÄS MER

4. 3. Miniaturized Hard Waveguides in Multifunction Array Antennas

   Författare :Malcolm Ng Mou Kehn; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; interlaced arrays; Floquet theorem; reflector antennas; focal plane array; multifunction antennas; miniaturized waveguides; multilayer structures; spectral domain technique; periodic structures; aperture reuse; method of moments; soft and hard surfaces; array antennas;

   Sammanfattning : Recent advances in technologies of wireless communications systems have led to an increasing desire for several antennas performing diverse functions at different frequencies to be integrated into a common radiating aperture. This gives rise to the so-called multifunction antenna, which affords the saving of scarce premium real estate and can alleviate problems arising from excessive antenna protrusions in aspects such as aerodynamics, aesthetics, and stealth capability in military applications. LÄS MER

5. 4. Characterization of artificially soft surfaces and their applications in antenna design

   Författare :Zhinong Ying; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; dipole antenna; UTD; GPS; broadband antennas; circular polarization; feed; moment method; soft and hard surfaces; surface impeddance; corrugated horn; antennas; multipath effect; microstrip antenna; magnetic coating; spiral antenna; corrugated surface; dielectric loaded surface; ground plane; slot antenna; monopole antenna; helical antenna; choke-ring;

   Sammanfattning : .... LÄS MER

7. 5. Analysis of Planar and Circular Cylindrical Multilayer Structures with Application to Soft and Hard Surfaces

   Författare :Zvonimir Sipus; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; antennas; periodic surfaces; integral equations; approximate boundary conditions; soft and hard surfaces; Green s functions; corrugated surfaces; moment method; periodic metal strips; multilayer structures; EFIE; microstrip antennas; spectral domain analysis; group representation theory; strip scatterers;

   Sammanfattning : This thesis deals with the analysis of planar and circular cylindrical multilayer structures, such as strip-loaded dielectric layers, corrugated surfaces and microstrip antennas. In particular, we study corrugations and strip-loaded grounded dielectric slabs when they are used to realize soft and hard surfaces. LÄS MER