| Transponder position calibration system is a long baseline acoustic positioning system for accurate measurement of the position of an underwater transponder.The rangefinder studied in this paper is a key part of the transponder position calibration system.Its main functions include measuring array of underwater transponder array,transmitting interrogation and answering signals,receiving and calculating the data returned by transponder,detecting and processing of command signals,etc.In this paper,the principle of signal detection,software design and realization flow of the whole signal processing part of the rangefinder system are given,and the performance of the system is tested comprehensively.Since the signal used in this system is narrow-band single-frequency pulse signal,in order to suppress the out-of-band noise and extract the target frequency signal,the principle of narrow-band signal preprocessing based on adaptive Notch filter is firstly studied.In order to realize signal detection,time delay estimation and underwater acoustic remote command communication,a narrow-band signal detection scheme based on energy detector and width discriminator is designed.In order to reduce the influence of background noise spikes and channel string leakage,instantaneous frequency variance detection is studied to retest the detection signal and reduce false alarm probability.At the same time,in order to improve the detection capability of the system in multi-path condition,the response signal detection principle based on pulse splitting feature and the multi-path signal separation principle based on homomorphic filter technology are studied.The simulation results show that this algorithm can fulfill the expected function of the range finder of the transponder position calibration system.Because the transponder position calibration system rangefinder needs to realize real-time and efficient detection and processing,a set of signal processing software is designed on the development board TMDSEVM6678 L and the onboard multi-core DSP TMS320C6678.Firstly,the overall structure and functional module division of the signal processing software are constructed according to the platform requirements,and then the design scheme and hardware implementation flow of the signal processing software including network communication module,narrow-band signal detection and delay estimation module,underwater acoustic remote command communication module and inter-core communication module are given.Finally,the network communication function,underwater acoustic remote control command communication function and narrowband signal detection and delay estimation function of the rangefinder signal processing platform of the transponder position calibration system are tested and verified by using the laboratory environment and the test data of qiandaohu lake.The results show that the system can well achieve the expected functions and meet the requirements of system functionality and reliability. |
PDF Full Text Request