An Introduction to the Airports Authority of India : Part-1

• Design, development, operation and maintenance of international and domestic airports and civil enclaves.

• Expansion and strengthening of operation area such as runways, aprons, taxiway, etc.

• Provision of communication and navigation aids such as ILS, VOR/ DME, Radar, etc.

• Construction, modification and management of passenger terminals.

Alphabet Coding used in Airport/Aviation for Communication:

Communication Navigation Surveillance (CNS):

• Communication: It can be defined as the exchange of data information and voice between the pilot and air traffic controllers or flight information centre.

• Navigation: Navigation element of CNS/ATM systems is meant to provide accurate, reliable, and seamless position determination capability to aircrafts.

• Surveillance: The surveillance systems can be divided into two main types:

a) Dependent surveillance: In dependent surveillance systems, aircraft position is determined on board and then transmitted to ATC. The current voice position reporting is a dependent surveillance system in which the position of the aircraft is determined from on-board navigation equipment and then conveyed by the pilot to ATC.

b) Independent surveillance: Independent surveillance is a system which measures aircraft position from the ground. Current surveillance is either based on voice position reporting or based on radar (primary surveillance radar; PSR) or (secondary surveillance radar, SSR) which measures range and azimuth of aircraft from the ground station.

Communication: It involves in the exchange of voice and data information between Aircraft and ATS.

• Communication is done through VHF (very high frequency).

• The range of VHF is 30 MHz – 300 MHz.

• It is a type of line of sight communication.

• Modulation technique used here is Amplitude Modulation and PCM.

• AAI uses the VHF frequency range of 108-137 MHz.

• Folded Dipole antenna is used to radiate signal in omni-direction.

• In VHF for each frequency two transmitter are used, one in working and other in standby.

• ALB-M: Analog Line Barrier block converts analog signal to digital signal.

• Baseband: It performs two functions in VHF transmitter and receiver i.e.,

a) Generation of carrier frequency.

b) Modulation index (0 & 1).

• Transmitter: In transmitter module, the in-phase and quadrature signals are converted from digital to analog signal. Then, the modulated signal is transmitted through Transmitter Antenna.