DME
DME (Distance Measuring Equipment) is a radio aid for short and medium distance navigation. It can allows 100 aircrafts simultaneously to measure their distance from a ground reference (DME transponder). The distance is determined by measuring the propagation delay of a gaussian pulse, which is emitted by the aircraft transmitter and returned by the ground station after reception.DME operates in the frequency range of(960 to 1215 MHz).
Aircraft's airborne interrogator transmit encoded interrogating pulse pairs on the ground station. The DME station in turn, transmits encoded reply pulse pairs on the air-borne equipment, The real distance information is the time interval between interrogation emission and reply reception. Aircraft's equipped with DME transmit encoded interrogating RF pulse pairs about the beacon's obtaining channel. The beacon, consequently, emits encoded reply pulse pairs about the receiving channel with the air-borne tools, that is 63 MHz apart from the transmitter frequency former.
Time interval among interrogation emission and reply reception provides the aircraft with all the real
distance data through the ground station; this info could be go through from the pilot or even the navigator straight around the airborne indicator. The ground transponder is capable to reply approximately about 200 interrogators at a time (i.e. 4800 pulse pairs/s). Generates random pulse pairs ("squitter") to take care of a minimum PRF of 800 to 2700 pulse pairs per
2nd (programmable) whenever the amount of decoded interrogations is decrease than that.
This reply is obtained and decoded by the airborne receiver, where unique timing circuits automatically measure the lapse between interrogation and reply and convert this measurement into electrical output indicators. The beacon introduces a fixed delay, known as reply delay, among the reception of each encoded interrogating pulse pair and also the transmission of the corresponding reply.
distance data through the ground station; this info could be go through from the pilot or even the navigator straight around the airborne indicator. The ground transponder is capable to reply approximately about 200 interrogators at a time (i.e. 4800 pulse pairs/s). Generates random pulse pairs ("squitter") to take care of a minimum PRF of 800 to 2700 pulse pairs per
2nd (programmable) whenever the amount of decoded interrogations is decrease than that.
This reply is obtained and decoded by the airborne receiver, where unique timing circuits automatically measure the lapse between interrogation and reply and convert this measurement into electrical output indicators. The beacon introduces a fixed delay, known as reply delay, among the reception of each encoded interrogating pulse pair and also the transmission of the corresponding reply.
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