Use of decimated photodetector arrays in spectrum analysis
Anthony VanderLugt · Applied Optics · 1988
Temporal heterodyne spectrum analysis requires the use of discrete photodetector arrays that have a large number of elements. Each element is generally followed by an amplifier, a bandpass filter, a demodulator, and nonlinear devices to handle the large dynamic range. When the number of elements in the array is of the order of 1000-2000, the readout hardware is difficult to implement. We consider decimating the array so that a much smaller number of elements are used. The spectrum is scanned across this array so that each element reads out o set of 3patial frequencies in a time division multiplexing fashion. In some cases there is no penalty in dynamic range; in others, the penalty is more strongly related to the reduction in the number of photodetectors. Similar techniques are applied to a cross-spectrum analyzer that uses temporal heterodyning to derive angle of arrival information from wideband signals.