Analysis of polarization diversity at terahertz frequencies

Terahertz frequencies offer the possibility of high resolution surveillance capabilities in areas requiring high levels of security. Terahertz imaging offers wavelengths providing high resolution with modest apertures while remaining able to penetrate clothing. In addition, they are not significantly affected by scatterers such as dust, fog and rain particles. Signal-to-noise ratio, dependent on antenna alignment, plays a critical role in providing high fidelity images. In this paper, performance of this ratio is analysed for the case of mutual orthogonality in three dimensions. Multiple-input multiple-output polarization diversity offers a way of improving system performance without the limitations associated with spatial diversity. In the general case of a Rician fading channel the inclusion of a third orthogonal dipole may provide a useful additional degree of freedom and allow high capacity irrespective of antenna alignment. We develop a novel Rician fading channel model for a tri-orthogonal half-wave dipole transmitter and receiver imaging system employing polarization diversity. Capacity is observed to be more robust than that of a dual-polarized system over the majority of a field of view. Simulation results have been compared to reference papers and show excellent agreement. The model design is applicable to other areas of high capacity systems research.