Monopulse secondary surveillance radar system

A monopulse secondary surveillance radar configured to integrate replies to active interrogations and passive squitter reception into a single surveillance system, said monopulse secondary surveillance radar comprising:

• a three-channel antenna arrangement comprising a sum channel, a difference channel, and an omega channel, said three-channel antenna arrangement configured to transmit interrogations, and to receive corresponding replies;
• a pair of redundant four-channel interrogators, each coupled to said three-channel antenna arrangement, and each comprising a transmitter and a receiver;
• a redundant secondary antenna arrangement, each comprising:
• a first omnidirectional (Automatic Dependent Surveillance-Broadcast) ADS-B antenna;
• a second omnidirectional ADS-B antenna;
• wherein said first omnidirectional ADS-B antenna is coupled to a first of said pair of redundant four-channel interrogators;
• and wherein said second omnidirectional ADS-B antenna is coupled to a second of said pair of redundant four-channel interrogators;
• and wherein said monopulse secondary surveillance radar is thereby configured to provide real-time passive detection of ADS-B-equipped aircraft in addition to active radar detection of aircraft to each of said pair of redundant four-channel interrogators, to lower active Mode S all-call interrogations needed by said three-channel antenna arrangement.