V-beam
A V-beam is an arrangement of two antennas on a radar device, with which it is also possible for a 2D radar to measure an additional height determination, i.e. a third coordinate. A technical prerequisite is a construction of a pair of radar antennas in which one antenna is rotated by around 15 ° to 30 ° relative to the horizontal plane. Both antennas form a fan or cosecans² diagram and are fed by transceiver systems of different frequencies. The different frequency is a prerequisite for the radar data from both antennas to be able to be separated cleanly.
Both aircraft are recorded at the same time by the diagram emitted by the horizontal antenna, which determines the bank angle and lean distance. The high-flying aircraft is perceived a little later than the low-flying aircraft due to the second antenna diagram, here pivoted by 30 °. Both echoes are displayed with different intensities (brightness) on a PPI viewing device. Each target is thus represented by two target characters on the PPI viewer. The lighter target sign from the lower antenna is the position of the aircraft and the lateral angle distance of the darker target sign (echo from the upper antenna) next to it is the measure of its elevation angle.
In this way, an additional height determination is also possible on a PPI viewing device . This technology was already used in the Russian radar device P-20 "Periscope" (NATO designator: "TOKEN"), which was introduced into the armament of the former Soviet army in 1949.
With the introduction of plot extractors , which enable digital target processing and representation, this method received a renaissance. The Russian air traffic control radar 1L117M received this typical V-shaped antenna construction again.