ABSTRACT
This chapter explores array gain (AG) for a linear array composed of an odd number of identical, equally-spaced, complex-weighted, omnidirectional point-elements lying along the axis. The array is being used in the passive mode as a receiver. The received signal at the output of each element in the array is a random process and is equal to the sum of the output signals due to the acoustic field radiated by a target, the ambient noise in the ocean, and receiver noise. The chapter shows how to implement complex weights in a linear array using the method of fast-Fourier-transform (FFT) beamforming and how to compute the beam pattern of the linear array by using frequency-domain data already obtained from the method of FFT beamforming. In addition to an output electrical signal from each element in the array due to the sound-field radiated by the target, there is also present an output electrical signal due to ambient noise in the ocean.
