Doppler beam sharpening in passive bistatic radar with spaceborne illuminators of opportunity

The applicability of Doppler beam sharpening (DBS) is assessed for the use in a passive bistatic system using a spaceborne transmitter in the Inmarsat constellation (Alphasat) as the illuminator of opportunity, for potential application in low cost maritime early warning systems in vessels. The effect of sharpening for both stationary and moving targets is discussed in theory, with models to show the effects for stationary targets that predicted a large improvement in angular resolution through the use of DBS. Experimental results show the effect in action, with three distinguishable targets found within 10 degrees using an antenna with a full beamwidth of 30 degrees, for a receiver moving at a mean of 11.6m/s over a coherent integration time of 1s, a carrier wave wavelength of 0.193m, a target range of 2.5-3km, and target look angle of 20-30 degrees. The results from the experiment are shown to agree with a simulation of a similar system, and a visual demonstration of the results overlaid on a satellite map is also displayed.