Sökning: "Frequency Modulation"

Visar resultat 16 - 20 av 268 avhandlingar innehållade orden Frequency Modulation.

1. 16. Frequency Reconfigurable and Linear Power Amplifiers Based on Doherty and Varactor Load Modulation Techniques

   Författare :William Hallberg; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; gallium nitride GaN ; wideband; Class-J; linear; microwave; radio frequency RF ; Doherty; broadband; AM AM; silicon carbide SiC ; bandwidth; power amplifier PA ; AM PM; varactor; dynamic load modulation DLM ; fifth generation mobile networks 5G ; energy efficiency;

   Sammanfattning : In future mobile communication networks, there will be a shift towards higher carrier frequencies and highly integrated multiple antenna systems. The system performance will largely depend on the available RF hardware. As such, RF power amplifiers (PAs) with improved efficiency, linearity, and bandwidth are needed. LÄS MER

3. 17. Further development of NICE-OHMS : – an ultra-sensitive frequency-modulated cavity-enhanced laser-based spectroscopic
 technique for detection of molecules in gas phase

   Författare :Patrick Ehlers; Ove Axner; Joakim Bood; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NICE-OHMS; Frequency Modulation; Cavity Enhancement; Molecular Spectroscopy; fysik; Physics;

   Sammanfattning : Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy, NICE-OHMS, is a laser-based spectroscopic detection technique that comprises the concepts of frequency modulation (FM, for reduction of 1/f-noise by detecting the signal at a high frequency) and cavity enhancement (CE, for a prolongation of the optical path length) in a unique way. Properly designed, this gives the technique an intrinsic immunity against the frequency-to-noise conversion that limits many other types of CE techniques. LÄS MER

4. 18. Frequency Noise in Coherent Optical Systems: Impact and Mitigation Methods

   Författare :Aditya Kakkar; Richard Schatz; Sergei Popov; Gunnar Jacobsen; Xiaodan Pang; Oskars Ozolins; Magnus Karlsson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Equalization enhanced phase noise; frequency noise; coherent optical communications; carrier phase recovery; carrier phase estimation; circular quadrature amplitude modulation; EEPN; CmQAM; blind phase search; phase noise;

   Sammanfattning : The increase in capacity demand along with the advancement in digital signal processing (DSP) have recently revived the interest in coherent optical communications and led to its commercialization. However, design and development of robust DSP algorithms for example for carrier phase recovery (CPR) becomes complex as we opt for high order modulation formats such as 16QAM and beyond. LÄS MER

5. 19. Radio Frequency Power Amplifiers : Behavioral Modeling, Parameter Reduction, and Digital Predistortion

   Författare :Magnus Isaksson; Peter Händel; José C. Pedro; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Telecommunication; Telekommunikation; Electronics;

   Sammanfattning : This work considers behavioral modeling, parameter-reduction, and digital predistortion of radio frequency power amplifiers. Due to the use of modern digital modulation methods, contemporary power amplifiers are frequently subjected to signals characterized by considerable bandwidths and fast changing envelopes. LÄS MER

7. 20. System Aspects and Modulation Strategies of an HVDC-based Converter System for Wind Farms

   Författare :Stephan Meier; Hans-Peter Nee; Boon-Teck Ooi; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Isolated AC DC Converter; Mutual Commutation; Soft Switching; Voltage Source Converter; Cycloconverter; Modulation Strategies; Medium-Frequency Transformer; HVDC Transmission; Wind Power; Wind Farms; Electric power engineering; Elkraftteknik; Electrical engineering; Elektroteknik;

   Sammanfattning :   In this thesis, a new HVDC-based converter system for wind farms is investigated. It is based on a mutually commutated soft-switching converter system and provides a unique integrated solution for the wind turbine generator drive systems, the wind turbine interconnection, and the power conversion for HVDC transmission. LÄS MER