On dual-polarization signalling techniques in satellite communications

Doctoral thesis (2015)

In satellite broadcasting and broadband communications, two orthogonal polarizations can be employed for signalling. Typically, two independent carrier signals are transmitted on the horizontal and ... [more ▼]

In satellite broadcasting and broadband communications, two orthogonal polarizations can be employed for signalling. Typically, two independent carrier signals are transmitted on the horizontal and vertical linear polarizations. In this way the available frequency spectrum is used twice. Contrary to this independent use, the present work investigates the combined use of both polarizations for signalling and the possibly associated benefits. Two different modulation techniques are investigated. The first, polarization shift keying, modulates the state of polarization of the electromagnetic wave to convey information. It is based on the phase and amplitude relationship between both carriers and is advantageous for channels strongly impaired by phase noise. The second technique defines a four-dimensional signal space for the combined modulation of amplitude and phase on both carriers. It was initially introduced as 4-quadrature signalling and permits transmission with improved power efficiency. Both techniques come from optical fibre communications, where similar propagation conditions exist. The conducted investigation is based on an analysis, simulations and the experimental verification using a specially developed demonstration transmitter and receiver. The simulations compare the power efficiency of the proposed modulation techniques with that of alternatives currently in use and analyse their behaviour upon disturbance by phase noise or non-linear distortion. The demonstrator is used to validate the findings in experimental measurements and to confirm the feasibility of both proposed techniques through a live satellite transmission. [less ▲]