Radio Technical TACAN system
Radio Technical TACAN system

Radio Technical TACAN system

The system is different from the system TACAN VOR. Azimuth TACAN system is carried out by non-directional signal light and the rotating direction of the signal, which is proportional to the phase difference between the azimuth relative to the direction to the north. The carrier of the TACAN system lies in the frequency range of the order of 1000 Hz. Rotary directional signal from variable phase obtained by mechanical rotation of the antenna elements.

Furthermore, kardnoda variable phase rotates at 15 Hz signal is further modulated with a frequency 135 Hz, the phase of which is also compared with the reference phase signal.

The result of this comparison makes it possible to get a nine-fold increase measurement accuracy azimuth.

The system consists of a TACAN ground equipment AN / URN-3 and aircraft device AN / ARN-21, it allows you to continuously and automatically determine on board the aircraft of its polar coordinates (azimuth and range). Determination of the polar coordinate position of the aircraft on board carried out with great precision, which allows to use them for the introduction of specific computing devices and a variety of solutions of navigation tasks, such as the flight of the aircraft on any straight path, and so on orbits. D.

TACAN system belongs to a class of impulse radio navigation systems. One of its important features is the transmission of information on the aircraft azimuth and range on the same channel. The presence in the 126 such frequency channels giving it operational flexibility and allows the use of the channels for other tasks, such as instrument landing aircraft using the same aircraft equipment.

Range depends on the altitude of the aircraft and is in the line of geometric visibility.

"Dead" funnel azimuth is of the order 95-100 °.

Radio Technical TACAN system

The influence of local objects on the accuracy of the system is significantly reduced compared to the VOR beacon due to the use of the decimeter wavelength range, pulsed operation mode, as well as] a special nine-lobe antenna pattern in the horizontal plane. Determination of the distance of the aircraft from the ground installation TAKAN is normal way on a "request-response", based on the measurement of the propagation time of the pulse emitted by the airborne interrogator, and return it back to a receiving device on an aircraft ground equipment installation AN / URN-3.

Transfer to the plane bearing information is carried out thanks to the presence in the ground installation of special antennas, creating radiation pattern in the horizontal plane as a cardioid, rotating at a constant frequency 15 Hz. As a result of the rotation of the cardioid pulses emitted by land-based device exposed on the plane of the spatial frequency amplitude modulation 15 Hz, the phase of the modulation frequency, which is the envelope of the received signals is proportional to the azimuth of the aircraft.

By using an airborne measuring device 15 phase modulating frequency Hz with respect to the phase of the reference signal to obtain data on the azimuth plane. As reference signals used pulses emitted by the device surface at a time when maximum pattern (cardioid) it passes the antenna system via the north, in connection with which the reference signals are often referred to as "north" reference signals.

The above method of measuring the azimuth is used only in a so-called coarse azimuth channel. In order to achieve higher measurement accuracy azimuth about 1 ° kardpoidnaya characteristics of the antenna ground of the lighthouse with an additional frequency modulation 135 Hz is converted into devyatilepestkovuyu cardioid, which provides a second measurement channel precise azimuth.

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