Title:
水中通信システム
Document Type and Number:
Japanese Patent JP2004528773
Kind Code:
A
Abstract:
In a digital acoustic transmission device in which a digital sequence ( 31 ) is electrically modulated ( 22 ) on a carrier cos omegat, the modulated carrier ( 23 ) is prefaced with at least two pulse signals ( 24 ) of known timing relative to each other and to the modulated digital sequence to provide an output signal ( 13 ) for acoustic transmission. The pulse signals indicate to receiver the start of a transmission, and contain Doppler information for resampling the modulated signal prior to demodulation. Where the information sequence is in encoded blocks of equal length, the relationship between successive blocks can be used to update the Doppler information for use with the following block. Channel information can also be derived from the pulse signals and/or blocks for raking the next part of the incoming signal. Preferably the pulse signals have good correlation characteristics. In the embodiments the pulse signals are an immediately successive identical pair of linearly rising chirps.
Inventors:
Davis Jonathan James
Dan Sean Michael
Pointer steven arthur
Downer samuel william
Dan Sean Michael
Pointer steven arthur
Downer samuel william
Application Number:
JP2002580530A
Publication Date:
September 16, 2004
Filing Date:
March 28, 2002
Export Citation:
Assignee:
QINETIQ LIMITED
International Classes:
H04B11/00; H04B1/707; H04B13/02; H04L1/00; H04L27/10; (IPC1-7): H04B11/00
Attorney, Agent or Firm:
Sadao Kumakura
Fumiaki Otsuka
Toshio Imajo
Takaki Nishijima
Fumiaki Otsuka
Toshio Imajo
Takaki Nishijima