In echo-location and imaging systems, interference suppression is accomplished by shaping the transmitted signal waveform. Interference suppression permits more accurate range estimates or image formation, respectively. These specially shaped waveforms can also be used in communication...http://www.google.com.hk/patents/US5790475?utm_source=gb-gplus-share專利 US5790475 - Process and apparatus for improved interference suppression in echo-location and imaging systems 
