A system for the relative navigation of aircraft and spacecraft is
disclosed which uses a series of short duration, unmodulated radio pulses
transmitted from a phased array antenna. The aircraft or spacecraft whose
position is to be determined from another is called as the local station,
whereas the other craft with the phased array antenna system is called as
the transmitting station. The local station transmits a radio query pulse
to the transmitting station. In response to the radio query pulse, the
transmitting station transmits a series of unmodulated radio pulses,
where each radio pulse is transmitted with a three dimensional radiation
pattern that is different than the three dimensional radiation patterns
of the other radio pulses transmitted by the transmitting station. A
receiver attached to the local station aircraft or spacecraft receives
each radio pulse, generates a signal that describes the radio signal
strength of the received signal and sends that signal strength number to
a stored program processor which stores that signal strength number into
memory. After a series of radio signals are received at the local station
and at least two radio signal strength measurements are stored in memory,
the stored program processor calculates the power ratio or ratios of each
received radio signal strength from each radio pulse transmitted by the
transmitting location. Bearing is then determined by comparing the
calculated radio signal power ratios with a library of angles that
correspond to specific power ratios for all radio radiation patterns
transmitted. The local station also records the time elapsed from when
the first radio pulse is received from the transmitting station after the
radio query pulse is sent. Range is determined by dividing that elapsed
time by two and multiplying that time with the speed of light.