The electrical bandwidth of the infrared system is a determinant of its performance. The larger the bandwidth, the more the noise and the poorer the performance, by the square root of the bandwidth. The information bandwidth is determined by the rate at which information must be transferred, and this determines the noise.
This chapter provides the methods by which the calculation of the information bandwidth can be made and its relation to the effective noise bandwidth.
There is a very encompassing theorem of Claude Shannon that says simply that the minimum frequency needed for complete transfer of information is the reciprocal of twice the dwell time or the shortest time interval involved with measuring the data. Every infrared system has a number of resolution elements or pixels in its field of view. This is true whether it is an imaging device of television bandwidth, with about 500 pixels in a line and 500 lines in a frame with 30 frames per second, or whether it is a tracker or surveillance set that covers 360 x 10 degrees or an entire hemisphere. In a few degenerate cases there is only one pixel in the entire field, but the following discussion still applies.
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