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30 Inverse Problems in Array Processing

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Signal reception has numerous applications in communications, radar, sonar, and geoscience among others. However, the adverse effects of noise in these applications limit their utility. | Kevin R. Farrell. Inverse Problems in Array Processing. 2000 CRC Press LLC. http www.engnetbase.com . Inverse Problems in Array Processing Kevin R. Farrell T-Netix SpeakEZ 30.1 Introduction 30.2 Background Theory Wave Propagation Spatial Sampling Spatial Frequency 30.3 Narrowband Arrays Look-Direction Constraint Pilot Signal Constraint 30.4 Broadband Arrays 30.5 Inverse Formulations for Array Processing Narrowband Arrays Broadband Arrays Row-Action Projection Method 30.6 Simulation Results Narrowband Results Broadband Results 30.7 Summary References 30.1 Introduction Signal reception has numerous applications in communications radar sonar and geoscience among others. However the adverse effects of noise in these applications limit their utility. Hence the quest for new and improved noise removal techniques is an ongoing research topic of great importance in a vast number of applications of signal reception. When certain characteristics of noise are known their effects can be compensated. For example if the noise is known to have certain spectral characteristics then a finite impulse response FIR or infinite impulse response IIR filter can be designed to suppress the noise frequencies. Similarly if the statistics of the noise are known then a Weiner filter can be used to alleviate its effects. Finally if the noise is spatially separated from the desired signal then multisensor arrays can be used for noise suppression. This last case is discussed in this article. A multisensor array consists of a set of transducers i.e. antennas microphones hydrophones seismometers geophones etc. that are arranged in a pattern which can take advantage of the spatial location of signals. A two-element television antenna provides a good example. To improve signal reception and or mitigate the effects of a noise source the antenna pattern is manually adjusted to steer a low gain component of the antenna pattern towards the noise source. Multisensor arrays typically achieve this .