Doppler Spectrum of Microwaves at Forward Scattering from the Sea Surface

The work is aimed at developing a new approach to bistatic remote sensing of the sea surface. The basis of the new approach is the analysis of the shape of the Doppler spectrum of the signal reflected in the forward direction from the sea surface. The Doppler spectrum contains more information about the reflecting surface than the scattering cross section, since the cross section is an integral characteristic of the Doppler spectrum. The advantage of the Doppler spectrum is also its greater versatility when comparing the measurements of various instruments comparing to the scattering cross section. The paper presents the final expressions for the width and shift of the Doppler spectrum of microwaves reflected by the sea surface during bistatic sensing in the case of a moving receiver and a transmitter. An important feature of the proposed approach is the consideration of the antennas patterns of the receiving and transmitting antennas. And it is taken into account that the antennas patterns of the receiver and transmitter can be different and asymmetrical. The correct choice and use of antennas with different patterns allows directly expressing the sea surface parameters of interest from the measured characteristics of the Doppler spectrum.