Observations of Doppler and delay spreads on HF signals received over polar cap and trough paths at various stages of the solar cycle

摘要

Information on delay and Doppler spreading is of importance to designers and operators\udof digital communication systems within the HF band since modem performance rapidly\uddeteriorates when delay and Doppler spreads exceed system dependent thresholds. The\udnortherly ionosphere is a particularly challenging region in this regard as delay and Doppler\udspreads often significantly exceed those for similar length paths at midlatitudes. This paper\udpresents results from an extensive set of measurements undertaken over three northerly paths:\udtwo subauroral paths aligned along the midlatitude trough (Uppsala to Bruntingthorpe and\udNurmijärvi to Bruntingthorpe) and one path (Qaanaaq to Ny-Ålesund) contained entirely\udwithin the polar cap. Measurements span the period from the 2009 solar minimum to July\ud2012, close to solar maximum and 2001, close to the previous solar maximum.