ABSTRACT
This chapter demonstrates that the far-field beam pattern of a linear aperture is just a special case of the far-field beam pattern of a volume aperture. It shows that the far-field beam pattern of a closed-surface, volume aperture–based on the Fraunhofer approximation of a time-independent, free-space, Green's function–is given by the following three-dimensional spatial Fourier transform. A linear aperture can represent either a single electroacoustic transducer or a linear array of many individual electroacoustic transducers. If a linear aperture represents a single electroacoustic transducer that is being used in the active mode, that is, as a transmitter; then this physical situation corresponds to the classic problem of a continuous line source. The various amplitude windows are used to model the frequency response of linear apertures. The chapter shows that phase response of a linear aperture was equal to zero and concentrated efforts on deriving closed-form expressions for the far-field beam patterns of various amplitude windows.
