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Sensor and data fusion can occur using several types of passively acquired information. For example, the raw signals themselves or various types of information extracted from the signals may be selected as inputs to data fusion processors. The signals, sensor data, and communications media available in a particular command-and-control system often dictate the optimum data fusion technique. This chapter addresses data fusion architectures applicable to multiple sensor and multiple target scenarios in which range information to the target is missing, but where the target location is required.
10.1 Data fusion options
Unambiguous target track files may be generated by using data association techniques to combine various types of passively acquired data from multiple sensors. In the examples described in this chapter, multiple ground-based radars are used to locate energy emitters, i.e., targets, by fusing either of three different types of received data: (1) received signal waveforms, (2) angle information expressing the direction to the emitters, or (3) emitter angle track data that are output from the sensors. The alternate fusion methods illustrate the difficulties and system design issues that arise in selecting the data fusion process and the type of passively acquired data to be fused.
These fusion techniques allow range information to be obtained from arrays of passive sensors that measure direction angles, or from active sensors where range information is denied (as for example when the sensor is jammed), or from combinations of passive and active sensors. For example, electronic support measure (ESM) radars can use the fused data to find the range to the emitters of interest. These fusion methods can also be used with surveillance radars that are jammed to locate the jammer positions. In a third application, angle data from a netted array of IRST sensors, or for that matter from acoustic or any passively operated sensors, can be fused to find the range to the emitters.
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