Chapter 1 featured the computation of signal power measured from a laser pulse reflected from a target. The assumed waveform of the pulse was a rectangular function in time. This chapter describes more complicated waveform models that will allow for a better temporal understanding of a LADAR system's performance. This chapter will explain the tools necessary to compute the shape of the returned pulse that has been reflected from a laser-illuminated target under a variety of conditions. Target interaction models will be introduced that predict how the shape of the laser pulse in time is modified by the target surface geometry. Both waveform signal and noise models will be used to simulate realistic LADAR returns and facilitate the derivation of algorithms that are capable of extracting range information from the LADAR signal. Chapter 4 will show that the shape of the waveform has an effect on the accuracy of range measurements extracted from the LADAR return signal.
This chapter also features the use of the discrete Fourier transform (DFT) for processing laser RADAR data. The DFT is an important tool for both simulating LADAR waveforms and estimating range from measured LADAR data. To utilize the DFT, it is necessary to gain some familiarity with its form and properties. This chapter features some examples of the DFT of typical waveform shapes and signals.