The Measurement of Crosswind by Non-Coherent Dual-Arm Bistatic Radio Tropo-Scatter Techniques

Abstract

The use of a dual-arm non-coherent bistatic tropo-scatter link is proposed as a means of measuring the cross-path motion of the wind. The arms are skewed symmetrically to either side of the great circle path so that one is pointing upwind and the other downwind. The signals received on each arm are then associated with Doppler frequency shifts of opposite sign. When summed at the receiver, their beating produces a signal fluctuation spectrum having a secondary peak equal to the difference in the mean Doppler frequencies on the two arms. This is directly proportional to the crosswind. Another approach involves the measurement of the mean-square signal fluctuation rate or spectrum variance on each arm of the link separately and then with both arms combined. The latter is the power-weighted sum of the variances on the individual arms plus a term which is proportional to the difference of the mean Doppler frequencies between the two arms of the link, and thus to the speed of the crosswind.