Eigen Analysis Of Biodiversity In Bat Biosonar Beampattern

In this paper, numerical analysis method is used to quantify the similarity and diversity of beam patterns simulated from bat pinna in order to characterize the beam pattern of bat sonar.Smart antenna technology is becoming a hot research purpose in the field of mobile communications in recent years in order to improve the signal-noise ratio. Beam-forming is one of the key technologies in the smart antenna. Smart antenna use array antenna to form beam generally while the bat pinna only use one single antenna, through the reflection of sound in beam-forming. This provides a very good basis for the design of new type of smart antenna. But the bat has different kinds of pinna, how to select the shape with a specific beam-pattern is a very im-portant subject. This need the analysis of beam-pattern of bats, Rebuild man-made beam-pattern through eigenbeam. After the analysis of the relationship between eigenbeams and eigenears, New kinds of smart antenna can be designed.The complex structure of bat pinna results in specific beam pattern. Through numerical simulation with finite element method (FEM), Beam-pattern can be simulated. According to the analysis of beam-pattern with Principal Component Analysis (PCA), some common property can be realized. This study selected50kinds of bats. As the frequency FM bat used is variable, In each ear, beam pat-tern of10frequencies with the same steps are simulated. Then rotate the beam patterns of different ears to same direction and compress the beam patterns with wavelet, Analysis the wavelet coefficients with PCA method, we can distribute the beam pattern of different bat in the intrinsic space. According to this distribution, differences and commonalities of the bat can be characterized. Eigenbeams can also be used on man-made beam patterns. It’s a method of beam-forming.The mean beam-pattern of those bats is a single direction beam-pattern. The beam angle get narrow while the frequency goes high. That’s common in all an-tenna. From the change with the coefficients of eigenbeams, it can be realized that the physical meaning of eigenbeams. The first eigenbeam stands for the beam angle of beam-pattern. Adding the coefficient of the first eigenbeam results in a narrower beam angle. The second eigenbeam stands for the size of side-lobe. Adding the coefficient of the second eigenbeam stands for a bigger side-lobe, following with a large change referring to frequency. While the coefficient is negative, there is no side-lobe. The coefficients of beam-pattern in eigen space shows that CF bats and FM bats gather in different place. It can be realized that CF bats has a positive coefficients of the first eigenbeam which means a narrow beam angle and gather in a small place while the FM bats has a negative coefficients of the first eigenbeam and gather in a larger place. Special beam-pattern can be made with different coef-ficients. According to the relationship between eigenbeams and eigenears, antenna with specific beam pattern can be designed.