Fig. 2From: Fractional difference co-array perspective for wideband signal DOA estimationThe positions of virtual sensors. a The conventional DCA \(\mathbb {D}(1,1)\) and the corresponding redundancy and b FrDCA \(\mathbb {D}(\alpha _{k},\alpha _{k})\) for different sub-band signals, where the selected uniformly distributed sensors \(\overline {\mathbb {U}}\) are marked with red face colorBack to article page