A Plan Position Indicator (PPI) There is a type of radar display that represents the radar antenna at the center of the display, with distance from it and height above the ground drawn as concentric circles. As the radar antenna rotates ,Displays a map of the target region as shown in the figure. It is an intensity modulation type display that simultaneously induces both range and azimuth angle in the target's polar coordinate.
The radar antenna sends pulses rotating 360 degrees around the radar site at a fixed elevation angle. It can then change the angle or repeat at the same angle as required. Returns from targets are received by the echo antenna and processed by the receiver and the most direct performance of those data is PPI.
In this system, intensity modulation of the CRT is performed, in which the signal from the receiver is applied to the grid of the CRT after demodulation, keeping the CRT's bias slightly different from the cut-off, allowing only the corresponding beam beam of the target to pass through. Which causes the screen to glow. Scanning waveforms on a pair of coils located behind and located in the tube's neck. This means that the magnetic deflection is given by the saw-tooth current. The coils in the yoke are rotated at the same angular velocity as the antenna is rotated. Therefore, the beam not only rapidly deflects outside the center and returns but it also rotates around the tube.
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R - Range
θ -Azimuth Angle of Target
Radar (Radio Detection And Ranging)The brightness of a point on the screen is indicative of the presence of the target. The position of which represents physical position and its range is measured from the center. High-resolution phosphors are used on the screen to reduce the face flicker of the PPI screen. The scanning speed here is lower than the scanning speed used in television (60 fields per second) so that many parts of the screen are of lower intensity between successive scans.
The resolution of the screen depends on the following factors
- Antenna band width
- Pulse length
- Transmitted frequency
- CRT beam diameter
PPI displays are more used for search radars, especially when particle scanning is used. If PPI is used on aircraft, deformation occurs under real conditions. This results in distortion of measurements even when the signal is not placed directly below the antenna. If the PPL is used in an aircraft and the antenna is not directly oriented downwards, an error may occur in the correct map position. The PPI screen is usually circular in diameter from 30 to 40 cm.
Uses
PPIs are used in many domains, demonstrating range and positioning, especially in radar, including air traffic control, ship navigation, meteorology, board ships and aircraft, etc. PPI displays are also used to display sonar data, especially in underwater warfare. However, because the speed of sound in water is much slower than in air microwaves, a sonar PPI has an expansion cycle that starts with each transmitted "ping" of sound. In meteorology, a competitive display system is CAPPI (Constant Altitude Plan Position Indicator) when a multi-angle scan is available.
Using computers to process data, installation of modern sonar and LIDAR can also display radar PPIs.
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