Sökning: "Frequency Modulation"

Visar resultat 11 - 15 av 268 avhandlingar innehållade orden Frequency Modulation.

  1. 11. Multidimensional Modulation Formats for Coherent Optical Communication Systems

    Författare :Tobias Eriksson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; binary pulse position modulation QPSK; Fiber-optical communication; spectral efficiency; power efficiency; multidimensional position modulation.; 16-ary quadrature amplitude modulation 16QAM ; quadrature phase shift keying QPSK ; coherent detection; polarization-switched quadrature phase shift keying PS-QPSK ; 128-level set-partitioning QAM 128-SP-QAM ;

    Sammanfattning : Coherent optical receivers have enabled the use of multilevel modulation formats with high spectral efficiencies and long transmission reaches. Traditionally, modulation formats utilizing the two dimensions spanned by the amplitude and the phase of the signal have been dominating. LÄS MER

  3. 12. On soft-switching isolated AC/DC converters without auxiliary circuit

    Författare :Staffan Norrga; Stefan Östlund; Rik De Doncker; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electrical power technology; voltage source converter; cycloconverter; isolated converter; medium frequency transformer; soft switching; modulation; commutation; wind power; electric traction; Elkraftteknik; Electric power engineering; Elkraftteknik;

    Sammanfattning : The thesis is concerned with a class of power electronic converter systems that permit bidirectional AC/DC conversion with galvanic separation of the AC and DC sides by a transformer operating at elevated frequency. The systems consist of a capacitively snubbered voltage source converter and a cycloconverter, separated by the mentioned transformer. LÄS MER

  4. 13. Generation, Modulation, and Detection of Signals in Microwave Photonic Systems

    Författare :Andreas Wiberg; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Microwave photonics; radio over fiber; mm-wave generation; PSK; QAM; subcarrier modulation; photonic frequency multiplication; spurious free dynamic range third-order intercept point; millimeter-wave photonics; uni-travelling-carrier photodiode; millimeter-wave communication system;

    Sammanfattning : This thesis deals with the use of photonic technology in microwave and millimeter-wave applications. The two major parts of this work have been techniques for transmission and signal generation. LÄS MER

  5. 14. Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry

    Författare :Aleksandra Foltynowicz; Ove Axner; Weidong Chen; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; absorption spectrometry; frequency modulation; cavity enhancement; NICE-OHMS; Laser frequency stabilization; fiber laser; Fabry-Perot cavities; sub-Doppler spectroscopy; trace gas detection; Physics; Fysik; Molecular physics; Molekylfysik; fysik; Physics;

    Sammanfattning : Noise-immune cavity-enhanced optical heterodyne molecular spectro-metry (NICE-OHMS) is one of the most sensitive laser-based absorption techniques. The high sensitivity of NICE-OHMS is obtained by a unique combination of cavity enhancement (for increased interaction length with a sample) with frequency modulation spectrometry (for reduction of noise). LÄS MER

  7. 15. Laser-based absorption spectrometry : development of NICE-OHMS towards ultra-sensitive trace species detection

    Författare :Florian Schmidt; Ove Axner; Livio Gianfrani; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; absorption spectrometry; trace species detection; fiber laser; modulation; cavity-enhanced spectroscopy; optical saturation; laser frequency stabilization; free-spectral-range; Physics; Fysik;

    Sammanfattning : Laser-based absorption spectroscopy (AS) is a powerful technique for qualitative and quantitative studies of atoms and molecules. An important field of use of AS is the detection of species in trace concentrations, which has applications not only in physics and chemistry but also in biology and medicine, encompassing environmental monitoring, regulation of industrial processes and breath analysis. LÄS MER