On the design of time-domain implementation structure for steerable spherical modal beamformers with arbitrary beampatterns

It is noted that the existing time-domain implementation structure for steerable spherical modal beamformers is only applicable to the specific beamformers with rotationally symmetric beampatterns about the look direction, which may limit its applications. To overcome the restriction, this paper presents an alternative time-domain implementation structure for spherical modal beamformers using the Wigner-D function, which enables three-dimensional beam steering with arbitrary patterns. In particular, a necessary condition for guaranteeing only real-valued operations to make the time-domain implementation viable is derived. Design examples are presented to demonstrate the effectiveness of the presented time-domain modal beamformer structure.