MEASUREMENT SYSTEM WIRELESS DISTANCE

1
WIRELESS DISTANCE MEASUREMENT SYSTEM
The problem was to evaluate a distance measuring
system based on acoustical signals. A prototype
system was going to be developed and its
measurement accuracy and operating range were
decided. By measuring the time for an acoustic
signal to propagate from a loudspeaker, reflect
on an object, and propagate back to a microphone,
the distance to the reflecting object was
estimated.
Chirp signal A linear chirp signal is a cosine
where the frequency increases linearly with time.
The transmitted signal and the received signal
are correlated. The correlation gives a cosine
that has a frequency that is proportional to the
propagation time of the signal, and thereby the
distance.
PN sequence An original cosine signal is
multiplied with a PN sequence and transmitted.
The received signal is then correlated with the
transmitted signal. When the received signal
matches with the transmitted, the code is decoded
and only the cosine remains and gives a peak in
the fourier transform.