A Multitarget Active Backscattering 2-D Positioning System With Superresolution Time Series Post-Processing Technique

An active backscattering 2-D positioning system is studied and demonstrated in this paper. The hardware is based on an investigated principle of switched injection phase locking for wireless ranging. A new post-processing technique and a system modeling for multitarget time-of-arrival (TOA) and direction-of-arrival (DOA) estimations are proposed and studied. The technique features a joint singular value decomposition-based ESPRIT algorithm and a matrix diagonalization technique using Moore-Penrose pseudoinverse for model order estimation as well as the TOA/DOA extraction. They make use of the shift invariant property of a backscattered signal in the time-domain. The accuracy and resolution are studied and are shown to be superior to those of the conventional frequency-domain technique using a fast Fourier transform (FFT). Moreover, the proposed algorithms take full advantage of the chirp bandwidth and allow all the targets to operate at the same modulation frequency and arbitrary carrier frequency. These merits avoid a commonly exercised compromise of the FFT method among the resolution, target quantity, signal-to-noise ratio, and other critical specifications. The system is simulated, and the demonstrator is constructed for experimental verifications in both indoor and outdoor environments, with a bandwidth of 600 MHz centered at 5.6 GHz.