| Non-geostationary satellites are increasingly being considered for use as communications platforms. They also have value for multimedia, data, telemetry and related applications. For handheld user devices, which have limited power, the link budget is an area of great interest. Today's satellite communications networks require that the earth-based user have a clear line of sight to the satellite. This study evaluates the situation where there is foliage between the receiver and transmitter. While for most communications scenarios, placing a receiver or transceiver in the open where it can establish a line of sight path to the satellite is not at issue, in some, notably military operations, the unit on the ground would prefer to remain concealed. In order to investigate the effects of foliage on the received signal, synthetic aperture radar (SAR) data obtained from satellite or airborne platforms is analyzed. Using the SAR return and a model of the foliage imaged by the SAR signal, the attenuation through the foliage can be determined. Based on the foliage attenuation, the signal strength that would be received by a receiver located under the same foliage can be estimated. The uniqueness of this study is that neither ground personnel nor communications equipment need to be placed in the area where the communication link is to be evaluated. The study calibrates the effect of the foliage on the returned SAR using data from areas adjoining the forested area of interest. |
