Range measurement using modulated retro-reflectors in FM radar system

In a variant of the FM radar technique, an essentially clutter-free range measurement may be made to a cooperative target. To enhance the link budget in such a measurement system, modulated retro-reflectors are demonstrated as passive transponders which maintain a high radar cross section over a wide range of RF incidence angles. Range measurement accuracies the order of 1 cm are demonstrated in a high-clutter indoor environment.