Removal of interference inherent in the lens radar system
The NASA GSFC/Wallops Flight Facility focused radar system employed a large (43 cm diameter) dielectric focusing lens such that the water surface (target) was illuminated by a small radar spot (~1.25 cm diameter). With this small spot size, surface profiles and probability density functions could be generated. The system suffered an interference problem which made reliable data collection impossible. Study showed that the system had to be operated bistatically in order to reduce the effects of interference found to be caused by signal leaking directly from the transmitter to the receiver. Since the system was operated in a confined space (the wind-wavetank), multipath was found to generate interference signals. The multipath interference was reduced via strategic placement of radio frequency absorber. A comparison was made between experimental results with the original system and the final bistatic system to demonstrate the effect of the reduction in interference. A model was also derived for the direct leakage interference and used to explain experimental results.