Disclosed are embodiments of methods, systems, and apparatus for ranging
or determining a distance between a reader and a wireless tag. In one
embodiment, a query signal is transmitted from the reader to the wireless
tag. The carrier signal from the reader may then be modulated and the
modulated signal transmitted from the reader during at least a portion of
a response period for the wireless tag. A modulated backscatter response
from the wireless tag is received at the reader and is used to calculate
a distance between the reader and the wireless tag.