Biomedical Engineering Reference
In-Depth Information
Fig. 13 a
Ultra-wideband (UWB) pulse searching algorithm flow chart.
b
UWB pulse tracking
algorithm flow chart
counter will be used to track UWB pulse. As tracking algorithm only corrects drift
upon detection of 1s, slow clock drift coupled with short consecutive transmission
of 0s are needed to ensure the proper operation of the algorithm. This is a reasonable
assumption given that typical crystal oscillator exhibits frequency stability of
50
ppm. When tracking counter value is zero, it indicates the position of duration window
where UWB pulse should occur. Under normal condition with no pulse detected,
tracking counter would repetitively count to ten cycles and reset, which matches
symbol period exactly. The algorithm will reset tracking counter to zero once UWB
pulse is detected. If the position of UWB pulse does not change over time, it will
be detected when tracking counter value is zero. Therefore, it would not incur any
change on tracking counter as well as duration window. However, if clock drift causes
the UWB pulse position to change to the adjacent duration window, received UWB
pulse will reset the tracking counter to zero instantaneously and the position of the
center duration window will now be updated.
The operation status switching of this radio SoC is controlled either by using
command strobes or by internal events [
18
]. There are three main states: IDLE,
TRANSMIT, and RECEIVE, and the state machine diagram is presented in Fig.
14
.
Once the system is powered on or reset, it goes to IDLE state, in which most of the
radio modules are inactive. The system calibration and the configuration registers
initialization are performed in this state. When the command strobe register of
turning on transmitter is set (STXON
±
=
1), and there are valid transmission data in
transmitter FIFO (TFIFO
1), the system goes to TRANSMIT state. On the other
hand, when the command strobe register of turning on receiver is set (SRXON
=
1),
the system goes to RECEIVE state. In TRANSMIT state, if the internal state
indicator of transmission completion is on (Trans_complete
=
=
1), and the previous
Search WWH ::
Custom Search