A stepped-frequency continuous wave ranger for aiding pedestrian navigation

Pedestrian navigation is readily enabled by GPS in outdoor environments. However, there are many locations - indoors, urban canyons and underground - where the GPS signal is unreliable or unavailable. Compact, MEMS inertial navigation, augmented by a Shoe Ranging Sensor (SRS) that measures scalar range between shoes, greatly reduces navigational error over large distances in simulations. Existing sensors have insufficient measurement dynamic range or environmental resiliency. Here, the authors report on an SRS based on stepped-frequency continuous wave radar with RMS ranging accuracy of 0.59 mm and 1 m range. This is an order-of-magnitude more accuracy over recent ultra-wideband rangers.