Interpreting Frequency Shift in Translational-Rotational Mobility Using Source-Generic Mode Channel

This paper investigates how the translational and rotational mobility influences radio link in terms of frequency shift, using the intrinsic mode channel that does not reply on particular realizations of radiating sources. Arbitrary field in source-free region can be modeled as a weighted sum of different modes of spherical vector waves. Through translation and rotation of spherical waves, the channel mapping the transmit and receive modes can be acquired analytically. The spatial frequency spectrum (SFS) is obtained from the mode-mapping channel by Fourier transform, regarding the spatial samples taking from translational or rotational movement. Effects of 1) rotating orientation (pitch, yaw, roll), 2) rotation radius, 3) carrier frequency, and 4) translational distance between source and observer coordinates, on the SFS and frequency shift are analyzed. It is found that in roll mobility that is transverse to the direction of observer, the spatial frequencies associated to the primary SFS peaks do not change with carrier frequency, rotation radius or distance between source and observe coordinates; the spatial frequencies of SFS peaks do not vary among modes either except for that when the elevation mode indexes are zero and there are no secondary SFS peaks. In pitch or yaw mobility, the SFS peaks occur more frequently with the increase of carrier frequency, increase of rotation radius, or decrease of the distance between source and observe coordinates. This work serves as a start for modeling and recognizing translational-rotational mobility in view of source-generic mode channel which is further transferable with particular source applied.