2,758 research outputs found
Programmable rate modem utilizing digital signal processing techniques
The engineering development study to follow was written to address the need for a Programmable Rate Digital Satellite Modem capable of supporting both burst and continuous transmission modes with either binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulation. The preferred implementation technique is an all digital one which utilizes as much digital signal processing (DSP) as possible. Here design tradeoffs in each portion of the modulator and demodulator subsystem are outlined, and viable circuit approaches which are easily repeatable, have low implementation losses and have low production costs are identified. The research involved for this study was divided into nine technical papers, each addressing a significant region of concern in a variable rate modem design. Trivial portions and basic support logic designs surrounding the nine major modem blocks were omitted. In brief, the nine topic areas were: (1) Transmit Data Filtering; (2) Transmit Clock Generation; (3) Carrier Synthesizer; (4) Receive AGC; (5) Receive Data Filtering; (6) RF Oscillator Phase Noise; (7) Receive Carrier Selectivity; (8) Carrier Recovery; and (9) Timing Recovery
Optical Phase Locking techniques: an overview and a novel method based on Single Side Sub-Carrier modulation
A short overview on Optical Phase locking techniques and a detailed description of the Phase Locking technique based on Sub-Carriers modulation is presented. Furthermore, a novel Single Side Sub-Carrierbased Optical Phase Locked Loop (SS-SC-OPLL), with off the shelf optical components, is also presented and experimentally demonstrated. Our new method, based on continuous wave semiconductor lasers and optical single side sub-carrier modulation using QPSK LiNbO3 modulator, allows a practical implementation with better performance with respect to the previously proposed OPLL circuits, and permits an easy use in real time WDM signal coherent demodulation
Generalized PSK in Space Time Coding
A wireless communication system using multiple antennas promises reliable
transmission under Rayleigh flat fading assumptions. Design criteria and
practical schemes have been presented for both coherent and non-coherent
communication channels. In this paper we generalize one dimensional phase shift
keying (PSK) signals and introduce space time constellations from generalized
phase shift keying (GPSK) signals based on the complex and real orthogonal
designs. The resulting space time constellations reallocate the energy for each
transmitting antenna and feature good diversity products, consequently their
performances are better than some of the existing comparable codes. Moreover
since the maximum likelihood (ML) decoding of our proposed codes can be
decomposed to one dimensional PSK signal demodulation, the ML decoding of our
codes can be implemented in a very efficient way.Comment: 22 pages, 3 figures, submitted to IEEE transactions on communicaton
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