Real-time measurement of wave components and intensity in a beam in the presence of a near field

The wave components are measured by digitally filtering and combining the outputs of an array of sensors, with an array of three, equally spaced sensors being considered in detail. The filters are designed in the frequency domain using a wave decomposition approach, and implemented in the time domain as FIR filters. Design, implementation and performance issues are discussed and an experimental implementation described. It is seen that accurate estimates of the amplitudes of the wave components can be obtained using FIR filters of moderate order, and that the method is relatively insensitive to sensor miscalibration and measurement noise.