Precipitation induced co and cross-polar effects from a 9 km link operating at 38 GHz

The last few years have seen a rapid growth in the use of the 38 GHz frequency band for fixed service. It was made available for commercial PCN (personal communications network) operators to be used for linking base stations. The links are fairly short, with separations ranging from 5 and 15 km. At the moment, all links use only vertical polarisation; however, the increase in demand for this spectrum could be provided by polarisation diversity so as to maximise spectrum utilisation. In order to examine the feasibility of using two linear, orthogonal polarisations at 38 GHz, the Rutherford Appleton Laboratory has installed a 9 km link operating at 38 GHz in southern UK. The primary intention of the campaign is to make a comprehensive set of co- and cross-polar measurements, under various conditions, using a typical system used by the PCN operators, and to make recommendations on cross-polar isolation that may be required for the use of orthogonal polarisations. The link has been operating continuously for a year and we report examples of measurements taken during a variety of precipitation conditions, including drizzle, moderate to intense rain, sleet and snow. We also present the statistics of 1-year data and compare it with predictions from the relevant ITU-R recommendations.