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A pencil-beam radar A moving or sweeping pencil-beam radar. In optics, a pencil or pencil of rays, also known as a pencil beam or narrow beam, is a geometric construct (pencil of half-lines) used to describe a beam or portion of a beam of electromagnetic radiation or charged particles, typically in the form of a cone or cylinder.
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. [1] This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference.
Consider the following example : if the radar antenna is located at around 15 m above sea level, then the distance to the horizon is pretty close, (perhaps 15 km). Ground targets further than this range cannot be detected, so the PRF can be quite high; a radar with a PRF of 7.5 kHz will return ambiguous echoes from targets at about 20 km, or ...
And for the same examples : the radar horizon for the radar at a 1-mile (1.6 km) altitude will be 102-mile (164 km) and the one at 75 feet (23 m) will be 12-mile (19 km). Furthermore, layers with an inverse trend of temperature or humidity cause atmospheric ducting , which bends the beam downward or even traps radio waves so that they do not ...
Monopulse radar is a radar system that uses additional encoding of the radio signal to provide accurate directional information. The name refers to its ability to extract range and direction from a single signal pulse. Monopulse radar avoids problems seen in conical scanning radar systems, which can be confused by rapid changes in signal strength.
Given an example antenna that generates a beam of 2 degrees width – fairly typical – a conical scanning radar might move the beam 1.5 degrees to one side of the centerline by offsetting the feed slightly. The resulting pattern, at any one instant in time, covers the midline of the antenna for about 0.5 degrees, and 1.5 degrees to the side.
The radar mile is the time it takes for a radar pulse to travel one nautical mile, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration.
A popular example is displaced phase center antenna (DPCA), which is a form of data-independent STAP in the beamspace, pre-Doppler. [7] The goal is to perform beamforming such that the beam appears stationary as the airborne radar is in motion over discrete time periods so the clutter appears without Doppler. [2]