Communications – electrical: acoustic wave systems and devices – Distance or direction finding – By combining or comparing signals
Reexamination Certificate
2007-10-30
2007-10-30
Lobo, Ian J. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
By combining or comparing signals
C367S092000
Reexamination Certificate
active
10987629
ABSTRACT:
The present invention is directed to a sonar system that includes a transmitter configured to direct multi-frequency transmit signals into a propagation channel. Each multi-frequency transmit signal includes a first frequency and a second frequency. A receiver is tuned to receive multi-frequency return signals propagating in the propagation channel. Each multi-frequency return signal includes a first frequency return signal and a second frequency return signal. The first frequency return signal has a first phase and the second frequency return signal having a second phase. A signal processor is coupled to the receiver. The signal processor is configured to extract the first phase and the second phase from the multi-frequency return signal and calculate a phase difference. The phase difference is the difference between the first phase and the second phase. The phase difference corresponds to an acoustic impedance value of a material disposed in the propagation channel, and may be used to detect and classify a target of interest in background noise.
REFERENCES:
patent: 4905207 (1990-02-01), Fellinger et al.
patent: 5561641 (1996-10-01), Nishimori et al.
patent: 5745437 (1998-04-01), Wachter et al.
Kurpiewski Thaddeus J.
Tietjen Byron W.
Bond Schoeneck & King , PLLC
Lobo Ian J.
Lockheed Martin Corporation
McGuire George R.
Nocilly David L.
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