2.1
6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 2
MTI Radar
William W. Shrader
Shrader Associates, Inc.
Vilhelm Gregers-Hansen
Naval Research Laboratory
2.1 PREFACE
This chapter addresses surface-based radars; e.g., radars sited on land or installed
onboard ships. For airborne radar, rapid platform motion has a significant effect on
design and performance as discussed in Chapters 3, 4, and 5 of this Handbook.
The fundamental theory of moving target indication (MTI) radar, as presented in the
previous editions of the Radar Handbook, has not materially changed. The performance
of MTI radar, however, has been greatly improved, due primarily to four advances:
(1) increased stability of radar subsystems such as transmitters, oscillators, and receivers;
(2) increased dynamic range of receivers and analog-to-digital converters (A/D);
(3) faster and more powerful digital processing; and (4) better awareness of the limita-
tions, and therefore requisite solutions, of adapting MTI systems to the environment. These
four advances have made it practical to use sophisticated techniques that were considered,
and sometimes tried, many years ago but were impractical to implement. Examples of
early concepts that were well ahead of the available technology were the velocity indicat-
ing coherent integrator (VICI)
1
and the coherent memory filter (CMF).
2,54
Although these improvements have enabled much improved MTI capabilities,
there are still no perfect solutions to all MTI radar problems, and the design of an MTI
system is still as much of an art as it is a science. Examples of current problems include
the fact that when receivers are built with increased dynamic range, system instability
limitations will cause increased clutter residue (relative to system noise) that can cause
false detections. Clutter maps, which are used to prevent false detections from clutter
residue, work quite well on fixed radar systems, but are difficult to implement on, for
example, shipboard radars, because as the ship moves, the aspect and range to each
clutter patch changes, creating increased residues after the clutter map. A decrease in
the resolution of the clutter map to counter the rapidly changing clutter residue will
preclude much of the interclutter visibility (see later in this chapter), which is one of
the least appreciated secrets of successful MTI operation.
MTI radar must work in the environment that contains strong fixed clutter, birds, bats
and insects, weather, automobiles, and ducting. The ducting, also referred to as anoma-
lous propagation, causes radar returns from clutter on the surface of the Earth to appear
Chapter 2
ch02.indd 1 12/20/07 1:42:40 PM
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2008 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.
Source: RADAR HANDBOOK
