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Sensors 2013, 13(3), 3549-3567; doi:10.3390/s130303549
Article

Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions

1,2
 and 1,2,*
Received: 20 December 2012; in revised form: 5 February 2013 / Accepted: 5 March 2013 / Published: 13 March 2013
(This article belongs to the Section Physical Sensors)
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Abstract: As a ranging sensor, a continuous transmission frequency modulation (CTFM) sonar with its ability for range finding and range profile formation works effectively under stationary conditions. When a relative velocity exists between the target and the sonar, the echo signal is Doppler-shifted. This situation causes the output of the sensor to deviate from the actual target range, thus limiting its applications to stationary conditions only. This work presents an approach for correcting such a deviation. By analyzing the Doppler effect during the propagation process, the sensor output can be corrected by a Doppler factor. To obtain this factor, a conventional CTFM system is slightly modified by adding a single tone signal with a frequency that locates out-of-sweep range of the transmitted signal. The Doppler factor can be extracted from the echo. Both verification experiments and performance tests are carried out. Results indicate the validity of the proposed approach. Moreover, ranging precision under different processing setups is discussed. For adjacent multiple targets, the discrimination ability is influenced by displacement and velocity. A discrimination boundary is provided through an analysis.
Keywords: CTFM; ultrasonic ranging sensor; Doppler shift; deviation; correction; range profile CTFM; ultrasonic ranging sensor; Doppler shift; deviation; correction; range profile
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Wang, Y.; Yang, J. Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions. Sensors 2013, 13, 3549-3567.

AMA Style

Wang Y, Yang J. Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions. Sensors. 2013; 13(3):3549-3567.

Chicago/Turabian Style

Wang, Yang; Yang, Jun. 2013. "Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions." Sensors 13, no. 3: 3549-3567.


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