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Electronic Engineering

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Browsing Electronic Engineering by Subject "Amplitude modulation."

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    Application of real-world modulation schemes to advanced spatial modulation systems.
    (2022) Khalid, Ahmad Bin.; Quazi, Tahmid Al-Mumit.; Xu, Hongjun.
    Abstract available in PDF.
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    A proportional timing generator for measuring intermodulation product distortion on television transposers.
    (1989) Bouwer, Paul Frederick.; Broadhurst, Anthony D.
    Broadcasting authorities presently measure intermodulation distortion by applying a three tone simulation of a composite video and sound signal to the transposer and then measuring the relative amplitude of the major in-band intermodulation product (nominally at vision carrier frequency plus 1,57 MHz in the 625 line I/PAL System) on a spectrum analyser. This method is slow and requires a skilful operator to achieve repeatable results. Furthermore it tests the common RF amplification equipment at one luminance level and one chrominance level and therefore does not subject the transposer equipment to operation over its full range. A new sampling measurement technique has been proposed which overcomes all these problems by selectively mixing, while transmitting a colour bar test pattern, the demodulated output video signal of the frequency transposer with a pulse train coinciding with a particular colour. This thesis describes the design of a very stable proportional timing generator and its application to the measurement of intermodulation distortion on frequency transposers. The timing generator, which locks automatically onto the video signal and produces narrow sampling pulses which coincide accurately with a particular section of each line over a 50°C temperature range, is applicable to all PAL and NTSC TV Systems.
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    Signal space diversity with and without Alamouti transmit diversity using generalised selection combining.
    (2015) Essop, Aadil.; Xu, Hongjun.
    The first contribution is based on M-ary quadrature amplitude modulation (M-QAM) constellations with signal space diversity (SSD) using a single transmit and receive antenna system in the presence of Rayleigh fading. Two commonly used techniques to derive an angle of rotation is investigated across different ordered M-QAM signal constellations to determine the optimum angle of rotation for this system. Thereafter a closed form expression using the nearest neighbour (NN) approach to quantify the symbol error rate (SER) in the presence of fading channels is presented. The diversity order and the signal-to- noise ratio (SNR) gap is investigated for different generalised selection combining (GSC) cases for an M-QAM with SSD system. The second contribution is based on an Alamouti coded M-QAM scheme with SSD and GSC using a two transmit and receive antenna system in the presence of Rayleigh fading. A closed form expression using the NN approach is used to accurately derive the SER performance of an Alamouti coded M-QAM with single rotated SSD and GSC system. An additional level of diversity is added by rotating a constellation once again. Simulation results of M-QAM with double rotated SSD and GSC are used to compare the actual performance differences between single and double rotated SSD for this system. All deductions presented are validated with the aid of simulations.