Chapter 14: Hybrid Processors, Meteorological Radar, and System Performance Analysis

14.1 The Moving Target Detector (MTD)

In the early 1970s the ground-based surveillance radars were bothered by ground clutter, birds, various forms of anomalous propagation, and weather. Air traffic control radars were capable with large commercial aircraft, but marginal in detecting and tracking the increasing general aviation fleet. MTI processors improved and numerous fixes were applied to the radar output. There were still too many false alarms to implement automatic detection and tracking. It was a time of rapid advances in digital processors and memory, but poor communication between the digital community and the radar designers who had a primarily analog background. It was recognized that better clutter rejection could be obtained with a coherent pulse Doppler processor than with an MTI, and that high-clutter locations could be stored in a map with a digital memory.

M.I.T. Lincoln Laboratory brought together several of these concepts into the moving target detector (MTD) [493, 385, 284].

The first MTD was basically an MTI canceler in cascade with an eight-point FFT or DFT plus some clever digital circuitry called a "clutter map," which collected the output of a zero Doppler filter. An early MTD block diagram is illustrated in Fig. 14.1 (from R. M. O'Donnell). The MTI gave a certain degree of clutter rejection and at the same time reduced the dynamic range of the residual clutter signals into the discrete Fourier transform. This allowed the DFT to be built with fewer bits in the multipliers and accumulators than with a pure...