Directional diversity of HF signals received over high latitude paths, and the possibility of improved data throughput by means of spatial filtering

作     者：Warrington, EM Jackson, CA Lundborg, B 

作者机构：Univ Leicester Dept Engn Leicester LE1 7RH Leics England Def Res Estab S-58111 Linkoping Sweden 

出 版 物：《IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION》 (IEE Proc Microwaves Antennas Propag)

年 卷 期：2000年第147卷第6期

页      面：487-494页

核心收录：

主　　题：array signal processing Antenna arrays spatial filtering delays Doppler shift diversity reception data communication ionospheric electromagnetic wave propagation modems Filtering methods in signal processing Modems HF radio propagation data throughput Doppler shifts multipath propagation high latitude ionosphere Radiowave propagation high latitude paths digital communication systems antenna arrays Doppler spreads ionospheric disturbances high speed modems reflection points HF radio signals multipath delay spread reduction filtering theory ionospheric movements multipath channels spatial filters directional diversity Radio links and equipment delay spread 

摘      要：The high latitude ionosphere is a dynamic propagation medium in which HF radio signals associated with each propagation mode may arrive at the receiver over a range of angles in both azimuth and in elevation. Furthermore, ionospheric movements at the reflection points impose Doppler shifts and Doppler spreads onto the signals. Large Doppler spreads and multipath propagation in which the delay spread is large are particularly prevalent at these northerly latitudes and can result in a significant degradation in the performance of digital communication systems. This investigation suggests that the application of spatial filtering from simple antenna arrays comprising pairs or triplets of antennas can significantly reduce the level of apparent Doppler spreading, frequently to levels at which modern, high speed modems are expected to operate satisfactorily. The investigation concentrated on Doppler spread since this was the most significant factor in the data employed in this study: however, it is noted that reductions in effective multipath delay spread are also possible.