Based on Chen-Haus ' theory~[1] , an experimental research on the reflection of SAW from a short-circuited Au -grating on YZ LiNbO3 and a short-circuited Al- recessed groove grating on ST-X quartz is first present...Based on Chen-Haus ' theory~[1] , an experimental research on the reflection of SAW from a short-circuited Au -grating on YZ LiNbO3 and a short-circuited Al- recessed groove grating on ST-X quartz is first presented in this paper where an anomalous reflection phenomena existing in two gratings are confirmed. In addition, a residual reflection which couldn 't be completely cancelled by means of changing strip-thickness is pointed out for a short-circuited Au-grating on YZ LiNbO3 both experimentally and theoretically through extending Chen-Haus 'theory to anisotropic crystals.Finally, two kinds of IDT composed of single electrodes: Au-electrode on YZ LiNbO3 and Al-recessed - groove - electrode on ST-X quartz, are proposed for high internal reflection suppression. The experimental results of bandpass filters constructed with the IDTs mentioned above show a great improvement in passband distortion and a potential usefulness of new structure in high frequency range.展开更多
Resolution enhancement of active sonar can suppress the reverberation.While it also makes the envelope data distribution diverge from Rayleigh distribution to K-distribution.The stronger scattering speckles,the heavie...Resolution enhancement of active sonar can suppress the reverberation.While it also makes the envelope data distribution diverge from Rayleigh distribution to K-distribution.The stronger scattering speckles,the heavier of the K-distribution tails.The envelope amplitudes of these strong scattering speckles are usually very big.As the interfering target,the strong reverberation decreases the performances of the background power level estimation and the target detection.The fuzzy statistical normalization processing(FSNP) is introduced to suppress the strong reverberation firstly in this paper.Then how the strong reverberation and the FSNP affect the distribution of K-distributed sonar data is studied.The influence on the constant false alarm rate(CFAR) detection performance caused by the strong reverberation and the FSNP is also simulated and analyzed.Performance comparisons between the CFAR detector based on FSNP and the conventional CFAR detectors are carried out.The simulation results show that the strong reverberation can make the shape parameter of the interfering K-distributed data become smaller than that of the original K-distributed data.While the FSNP can suppress the strong reverberation,increase the shape parameter value,and improve the performance of the shape parameter estimator and the CFAR detector.展开更多
文摘Based on Chen-Haus ' theory~[1] , an experimental research on the reflection of SAW from a short-circuited Au -grating on YZ LiNbO3 and a short-circuited Al- recessed groove grating on ST-X quartz is first presented in this paper where an anomalous reflection phenomena existing in two gratings are confirmed. In addition, a residual reflection which couldn 't be completely cancelled by means of changing strip-thickness is pointed out for a short-circuited Au-grating on YZ LiNbO3 both experimentally and theoretically through extending Chen-Haus 'theory to anisotropic crystals.Finally, two kinds of IDT composed of single electrodes: Au-electrode on YZ LiNbO3 and Al-recessed - groove - electrode on ST-X quartz, are proposed for high internal reflection suppression. The experimental results of bandpass filters constructed with the IDTs mentioned above show a great improvement in passband distortion and a potential usefulness of new structure in high frequency range.
基金supported by the National Natural Science Foundation of China(61431020,61471352,61671443)
文摘Resolution enhancement of active sonar can suppress the reverberation.While it also makes the envelope data distribution diverge from Rayleigh distribution to K-distribution.The stronger scattering speckles,the heavier of the K-distribution tails.The envelope amplitudes of these strong scattering speckles are usually very big.As the interfering target,the strong reverberation decreases the performances of the background power level estimation and the target detection.The fuzzy statistical normalization processing(FSNP) is introduced to suppress the strong reverberation firstly in this paper.Then how the strong reverberation and the FSNP affect the distribution of K-distributed sonar data is studied.The influence on the constant false alarm rate(CFAR) detection performance caused by the strong reverberation and the FSNP is also simulated and analyzed.Performance comparisons between the CFAR detector based on FSNP and the conventional CFAR detectors are carried out.The simulation results show that the strong reverberation can make the shape parameter of the interfering K-distributed data become smaller than that of the original K-distributed data.While the FSNP can suppress the strong reverberation,increase the shape parameter value,and improve the performance of the shape parameter estimator and the CFAR detector.
