. Airborne radar. Airplanes; Guided missiles. 628 DISPLAY SYSTEM DESIGN PROBLEMS. Film Strip Direction Fig. 12-11 Intensity-Modulated Ground-Mapping Display. Example 2. As a second example, the AI radar discussed in Chapters 2 and 3 might be considered. This system employed a beamwidth of about °, a pulse length of 1 microsec, an azimuth coverage of 120°, and a total surveillance range of about 25 miles. Thus, a B-scope search display (see Fig. 12-6) must be capable of handling 33 angular elements and 300 range elements. If the display height is 5 inches, then there are 60 range elements pe
. Airborne radar. Airplanes; Guided missiles. 628 DISPLAY SYSTEM DESIGN PROBLEMS. Film Strip Direction Fig. 12-11 Intensity-Modulated Ground-Mapping Display. Example 2. As a second example, the AI radar discussed in Chapters 2 and 3 might be considered. This system employed a beamwidth of about °, a pulse length of 1 microsec, an azimuth coverage of 120°, and a total surveillance range of about 25 miles. Thus, a B-scope search display (see Fig. 12-6) must be capable of handling 33 angular elements and 300 range elements. If the display height is 5 inches, then there are 60 range elements per inch — a resolution capability that may be preserved by an indicator with 120 resolvable elements per inch. In this case, however, it is important to note that radar resolution is not a vital factor for mission accomplishment -— the radar antenna size and pulse length were governed by other consider- ations such as detection range, and the radar resolution capability need only be great enough to resolve targets separated by several miles. Thus, in contrast to the first example, the system performance is relatively insensitive to indicator resolution, and this property of the indicator may be traded for other properties more important to the AI radar detection problem. Relative to requirements of this type, it is of interest to consider the typical resolution characteristics of cathode ray tubes. These devices provide the highest resolution of all the various types of display devices. The spot size of the CRT is obviously a determining factor in the resolution of the display. The smallest spot size obtainable at this time with careful control of the electron-optics system and at a low beam current is approxi- mately mil at the center of the screen. Tubes having such small spot size utilize magnetic focus. However, to reduce misalignment problems and weight, electrostatic focus is used in most airborne cathode ray tubes. At low beam currents and high anode potentials
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