Multiple Frequencies for Accuracy Improvement in Near Field Electromagnetic Ranging (NFER)

Near field electromagnetic ranging (NFER) can offer high localization accuracy from moderate precision measurements with inherent immunity against non-line-of-sight and multipath problems. This paper explores the factors affecting accuracy in ranging and 2-D localization using NFER by deriving the Cramer Rao bounds (CRBs). From the CRBs, it can be seen that besides the signal-noise ratio, the accuracy is dependent on the true location and the frequency used. Exploiting this property, ranging and maximum likelihood estimation (MEE) localization algorithms are developed for application of multiple frequencies to NFER to improve accuracy. Simulation results show that substantial improvement in accuracy is achieved for the algorithms over using a single frequency for NFER