Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 43 for “"Coherent Detection"”.
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COHERENT DETECTION OF SCATTERED LIGHT BY SUBMICROMETER AEROSOLS.
A particle counting instrument, the Coherent Optical Particle Spectrometer (COPS) has been developed for measuring particles in aerosol systems. It optically counts and sizes single particles one at a time as they pass through an optically defined inspection region so particle size distributions …
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Differential modulation and non-coherent detection in wireless relay networks
… acquiring fading channels information for coherent detection is more challenging than in the traditional point-to-point communications. To bypass the requirement of channel information, differential modulation together with non-coherent detection can be deployed. This thesis is concerned …
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Distributed optical fibre sensors based on the coherent detection of spontaneous Brillouin scattering
… and strain optical fibre sensor based on the coherent detection of spontaneous Brillouin scattering. To further improve the sensing range and the sensor's performance, the use of Raman amplification was investigated utilising different Raman pump configurations. Using frequency measurements …
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Optical communication through the turbulent atmosphere with transmitter and receiver diversity, wavefront control, and coherent detection
… that uses multiple transmitters and multiple coherent receivers to overcome these turbulence-induced outages. By controlling the amplitude and phase of the optical field at each transmitter, based on turbulence state information fed back from the receiver, we show that the system performance …
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Channel estimation for Gigabit Multi-user MIMO-OFDM Systems
The fundamental detection problem in fading channels involves the correct estimation of transmitted symbols at the receiver in the presence of Additive White Gaussian Noise (AWGN). Detection can be considered when the receiver is assumed not to know the channel (non-coherent detection), or …
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ADAPTIVE COHERENT RECEIVERS FOR DIGITAL SIGNALS OVER THE GAUSSIAN CHANNEL WITH UNKNOWN CARRIER PHASE/FADING
Conventionally, it has been assumed that coherent detection over the Gaussian channel has to be achieved with the use of some carrier tracking phase-locked-loop. However, in practice, the phase-locked-loop has limited applications, especially when fading channels are involved. In this thesis, two …
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Synchronization in Impulse Based Ultra Wideband Systems
… short pulse duration and very low duty cycle. Coherent detection of ultra wide-band signals requires complex channel estimation algorithms. In impulse based UWB systems, suboptimal receivers that require no channel estimation are proposed for low data rate applications using non coherent …
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SPECTRALLY EFFICIENT MULTICARRIER SYSTEMS FOR FIBER-OPTIC TRANSMISSION
… improved. Although different modulation and detection techniques are used, all the multicarrier systems investigated in this dissertation achieve a high spectral efficiency of 1 Baud/s/Hz. Orthogonal frequency-division multiplexing (OFDM) and Nyquist wavelength-division multiplexing …
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Ultrafast Broadband Terahertz Spectroscopy
… next two sections discuss broadband terahertz detection techniques: optically biased coherent detection and electro-absorption in a semiconductor. The subject of the fourth section is terahertz imaging with electroabsorption. Optically biased coherent detection is distinguished from …
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Performance evaluation of communication systems with transmit diversity
… for a slow, flat Rayleigh fading channel with coherent detection and with non-coherent differential encoding/decoding. The BER expression for coherent detection is exact. But for differential detection it is an approximation appropriate for a high signal-to-noise ratio. Numerical results are …
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Limitations and Improvement of Subcarrier Multiplexed Systems over Optical Fiber
Optical coherent techniques are used to eliminate the power fading found in optical subcarrier multiplexed systems. In a double-side band optical subcarrier system the signal experiences a periodic power fading that is dependent on the fiber dispersion and subcarrier frequency. This power fading is …
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RF phase modulation of optical signals and optical/electrical signal processing
… mainly focusing on Intensity Modulation Direct Detection (IMDD). The virtues of coherent detection combined with the advantages of Frequency Modulation, however, have not been explored thoroughly. By employing Frequency Modulation Coherent Detection (FMCD), the wide optical transmission …
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Performance analysis of the Link-16/JTIDS waveform with concatenated coding, soft decision Reed Solomon decoding and noise-normalization
… combining with noise-normalization. Both coherent and noncoherent detection are considered. Based on the analyses, the alternative JTIDS waveform outperforms the original in all cases considered. When only additive white Gaussian noise is present, the best performances, which result in a …
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The Effectiveness Of Data Codes And Hardware Selection To Mitigate Scintillation Effects On Free Space Optical Data Transmission
… 8 meters above ground over a 13 Km range to coherent detection devices approximately 162 meters above ground. The effects of a fading and surging beam wave were considered in regards to code techniques for error correction, amplitude modulation and hardware architecture schemes. This study …
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High Data Rate Coherent Optical OFDM System for Long-Haul Transmission
… the long-haul transmission in both direct and coherent detection. However, Coherent Optical OFDM (CO-OFDM) is the next generation technology for the optical communications, since it integrates the advantages of both coherent systems and OFDM systems. It has the ability to overcome many optical …
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Optical fibre communication over a noisy partially coherent channel
… away. The most celebrated technologies of coherent detection and wavelength-division multiplexing (WDM), widely deployed in long-haul links, are gaining ground in access networks, which is particularly challenging due to the shared-cost requirements, leading to denser channel spacings and …
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Tracking system for photon-counting laser radar
… radar that has the ability to perform direct and coherent detection measurement at low signal levels with common laser, optics and detector hardware. The heart of the tracking algorithm is a Kalman filter, and optimal Kalman filter parameters are determined using software simulations. The tracking …
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Capacity of and coding for multiple-aperture, wireless, optical communications
… coding techniques for both direct- and coherent-detection receivers. We also experimentally verify the performance of some simple techniques for optically-preamplified, direct-detection receivers.
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Multilevel Nyquist-WDM Ultra-Long-Haul Coherent Optical Transmission Systems
… optical communication networks has proven to be coherent detection. Rather than intensity modulation direct detection systems, such solution enables to implement new multilevel transmission systems, allowing a more efficient use of the optical transmission bandwidth. These novel coherent optical …
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Coherent versus non-coherent space-time shift keying for co-located and distributed MIMO systems
… Multiple-Output (MIMO) systems using both coherent and non-coherent detection. Furthermore, we conceive new serially-concatenated turbo-coding assisted STSK arrangements for the sake of approaching the channel capacity limit, which are designed with the aid of EXtrinsic Information Transfer …
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