Short-range ultrasonic communications in air using capacitive transducers
Li, C. (Chuan) (2009) Short-range ultrasonic communications in air using capacitive transducers. PhD thesis, University of Warwick.Full text not available from this repository.
Official URL: http://webcat.warwick.ac.uk/record=b2334460~S15
This thesis describes the development and characterisation of an airborne ultrasonic
communication system using electrostatic transducers.
Initially, digital modulation schemes, namely OOK, BFSK and BPSK were used
for transmission of a digital binary stream across an air gap of 0 – 1.2 m. BPSK was
found to be the most favourable solution for the lowest BER performance. BFSK, being
the second best among the three was simpler to implement and was more robust against
synchronisation errors. Later, to further improve bandwidth efficiency, several M-nary
modulations, namely QPSK, MSK and 8PSK were used. The data rate reached 800
kbps when 8PSK was used. An ultrasonic keyboard using BFSK were developed as a
simple application. A real-time communication system was also developed using a PXI
system and LabVIEW, with which broadband data communication and real-time
performance analysis was realised.
The channel response of the ultrasonic communication link was modelled, with
the characteristic of ultrasonic absorption in air, transducer response, and spatial field
response. The latter was found to be crucial factor when the transreceivers were not
aligned in parallel. The results recorded at various distances were in good agreement
with those predicted using the system model developed.
Several equalisation techniques were looked at in this thesis, to combat the
selective attenuation response for longer-range propagation, and its effectiveness has
been compared to using multicarrier modulation. This thesis has also looked at
multipath interference, which is likely to be effect the performance in future
applications. It shows that by using spread spectrum techniques, multipath interference
can be tackled in an ultrasonic system.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||T Technology > TK Electrical engineering. Electronics Nuclear engineering|
|Library of Congress Subject Headings (LCSH):||Ultrasonics -- Research, Phase modulation -- Research, Phase shift keying, Communication -- Research|
|Official Date:||November 2009|
|Institution:||University of Warwick|
|Theses Department:||School of Engineering|
|Supervisor(s)/Advisor:||Hutchins, David A.|
|Format of File:|
|Extent:||224 leaves : ill., charts|
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