By difference treatment of the rate of change of the radial distance,
the interchange relationship between the Doppler shift and the path
difference is obtained, so that the Doppler shift can be used to obtain
the path difference in an equivalent way. On this basis, by using the
linear solution of the double-base linear array and constructing a
virtual double-base array, a Doppler direction finding method using only
the single-base array is obtained. Because the transformation method
based on frequency shift and path difference avoids the direct
comparison of phase, and the equivalence of transformation is mainly
related to the accuracy of frequency shift measurement, the new method
is likely to lay a theoretical foundation for the application of Doppler
direction finding method in higher frequency bands.