Spatially Separated Nested Vector-Sensor Array With Reduced Mutual Coupling

For a polarization sensitive array (PSA) composed of electromagnetic vector sensors (EMVSs), all component-antennas of an EMVS are spatially collocated at a same location in the PSA, and mutual coupling introduced has an adverse effect on parameter estimation. The mutual coupling is not only among antennas in adjacent elements, namely, inter-element coupling (IEC), but also among component-antennas which are collocated to give an EMVS [namely inter-polarization coupling (IPC)]. In existing array design, component-antennas of each EMVS are spatially separated into different elements for IPC reduction, and then the spacing between EMVSs is increased for IEC reduction. However, such designed arrays are usually implemented as 2-D arrays which are large compared with linear arrays, and provide only <inline-formula> <tex-math notation="LaTeX">${O}({N})$ </tex-math></inline-formula> degrees of freedom (DOFs) with <inline-formula> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> antennas. To overcome such problems, this paper proposes two kinds of spatially separated augmented nested vector-sensor arrays (SS-ANVSAs), which are linear arrays, can reduce both IEC and IPC, and provide <inline-formula> <tex-math notation="LaTeX">${O}({N}^{2})$ </tex-math></inline-formula> DOFs with <inline-formula> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> antennas. Specifically, we introduce a scalar-sensor array and propose a sparse scalar-sensor array for IEC reduction, and then propose the SS-ANVSAs by restricting physical space and EMVSs’ number for IPC reduction. Theoretical analysis and simulation results are given to illustrate the superior performance of the SS-ANVSAs.