Monopulse Secondary Radar: Practical Realization and Achievement Mode S: The Radar of Tomorrow,

There can be no doubt that Mode S will be part of tomorrows ATC radar. Its assets in terms of air traffic surveillance and data link are recalled. Fundamental characteristics are its compatibility with existing SSRs, selective interrogation and monopulse reception. The monopulse SSR is a landmark in the transition towards Mode S it contributes several major improvements, without requiring onboard transponders to be changed. Choices made in implementation of the system are discussed, in particular as regards the antenna, transmitter, reception and processing techniques. Through these options, full Mode S compatibility is maintained. Practical results have turned out to be conclusive, and so the system was taken into production and already many stations are operational round the world. The Mode S extension which has to be added the monopulse radar is also described, and it is being operated at Orly as part of an experimental development programme.