PN-Chirp signal for anti-multipath, multiple-access factory communication
Abstract
A hybrid of pseudorandom (PN) code modulation and the linear frequency modulation (FM) or also known as the Chirp modulation is proposed as a system to combat the problem of signal fading in a multipath environment. A PN-Chirp system, as the system is called, is capable of providing multiple-access communication. The effect of signal fading can be reduced when the multipath signal components are resolved. In order to resolve these components, a wide bandwidth signal is needed. Linear FM or Chirp modulation provides the spectral spreading needed. Further improvement in the bit-error performance is obtained by combining the resolved multipath components. To combine the energy in the multipath signal components, the dispersive nature of Chirp filter is exploited. A system that dispersively combines multipath signal energy employing extended matched filtering (EMF) of the chirp signal is shown to enhance the overall system performance. By assigning different PN-codes to different users, multiple access is possible. One station can transmit its signal during the transmission of other stations with minimal interference. Multipath interference due to the echoes of other users' signals can degrade the performance further. A method of compensating for this performance degradation is provided by the dispersive Chirp combining scheme in which the resolved multipath components are combined to give an improved SNR. The results obtained from computer analysis indicate that there is a close trade-off between the time-bandwidth product, the number of users that the system can support, and the overall system performance.
Degree
Ph.D.
Advisors
McGillem, Purdue University.
Subject Area
Electrical engineering
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