航空电子设备-二次雷达及应答机.ppt

Secondary Radar and Transponder Mode A/C XPDR Mode S Interrogations Civil Aviation Flight University of China Secondary Radar and Transponder Mode S System During the 1990s, a new addressable secondary radar transponder system was installed throughout the world to replace the venerable ATCRBS system. This new system is called mode S —the S means select. The mode S transponder can be made to reply only when that specific transponder is interrogated. This reduces the amount of synchronous garble in the air traffic radar system and allows for more aircraft to be under surveillance. Civil Aviation Flight University of China Secondary Radar and Transponder Mode S System An important characteristic of the mode S system is that each aircraft has a unique identity. The mode S secondary radar system can have more than 16 million different identities, enough for each airplane in the world to have a unique identity. In addition, there is the ability to transmit data, bi-directionally, between the ground facility and the mode S transponder to aid in air traffic control. Civil Aviation Flight University of China The mode S transponder has some similarities to the ATCRBS transponder. First, the mode S transponder operates on the same frequencies as the older ATCRBS system, that is, the transponder receives interrogations on 1,030 MHz and replies in 1,090 MHz. The transmitter power output is similar to the ATCRBS transponder as is the receiver sensitivity which insures that mode S transponders will have similar service ranges as ATCRBS transmissions. Secondary Radar and Transponder Mode S System Civil Aviation Flight University of China Secondary Radar and Transponder All-Call Interrogations Figure 6.7 There are two categories of mode S interrogations: all-calls and selective. All-call interrogations are just what their name suggests-all transponders of the Th