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The estimation of the performance of terahertz wireless communication under the effect of various weather conditions is vital. In this work, the combined effects of cold weather conditions such as snow, as well as random effects of turbulence and pointing errors (PEs) between the transmitter and receiver, on the performance of terahertz wireless line-of-sight links have been evaluated. The exponentiated Weibull distribution has been employed to derive exact analytical closed-form expressions in the presence of combined channels. Our predictions indicate that snow can have various influences on the average bit error rate (BER) and the average channel capacity of terahertz wireless links. Dry and wet snow, based on their liquid-water content, show different effects in terms of link parameters such as distance and frequency compared to that of rain. Random turbulence and PEs further deteriorate the link performance. It is concluded that the channel capacity is less affected than the BER under the effects of turbulence and PEs, while snow can have a remarkable effect. All of the predictions through the derived expressions are validated using Monte Carlo simulations.

A quadrifilar helix antenna (QHA), with an improved isoflux radiation pattern for S‐band satellite ground stations, is designed and fabricated. The performance of the antenna with respect to its beam pattern, axial ratio and efficiency is investigated. To have optimum coverage of a low earth orbit satellite rotating the Earth's surface with one fixed pattern ground station antenna, an ultra‐wide beamwidth isoflux pattern covering the complete upper hemisphere is required. The presented QHA antenna not only satisfies the required beam shape but also its pattern stays unchanged within a wide bandwidth. Besides that, an efficient Wilkinson power divider as the antenna's feed is designed to match the input impedance of helices appropriately, resulting in efficiency enhancement to >85%. The measured results, which indicate the performances of the proposed antenna in terms of the reflection coefficient, radiation pattern and axial ratio, are in good agreement with the simulation results within 2 to 2.2 GHz frequency band.

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