A monopulse secondary surveillance radar is configured to integrate replies to active interrogations and passive squitter reception into a single surveillance system, and includes: a three-channel antenna arrangement; a redundant ADS-B antenna arrangement including a first and second omnidirectional ADS-B antenna, each having a low noise amplifier, and each being integrated with a GPS antenna; and a pair of redundant four-channel interrogators. The three-channel antenna arrangement is configured to transmit interrogations, and to receive corresponding replies from an aircraft transponder. The first ADS-B antenna is coupled to a first of the pair of redundant four-channel interrogators, and the second ADS-B antenna is coupled to a second of said pair of redundant four-channel interrogators, for the monopulse secondary surveillance radar to provide real-time passive detection of ADS-B-equipped aircraft and active radar detection of aircraft to each of the pair of redundant four-channel interrogators.

An ADS-B spoofer being an false ADS-B squitter, an ADS-B squitter being an aircraft position information signal transmitted to secondary radars, the ADS-B squitters being detected over time at different bearings of the antenna in rotation of the radar, the method comprises, for each secondary radar, at least the following steps: a first step of detection of an ADS-B spoofer; a second step of location of the position in azimuth of the ADS-B spoofer generator, the second step comprising the following operations: measurement of the azimuth of the antenna of the secondary radar and of the received powers on the sum, difference and control patterns of the antenna upon the detection of an ADS-B squitter; generation and storage of at least one assumption of azimuth of the spoofer for each ADS-B squitter detected, the assumption being equal to the sum of the azimuth of the antenna and of the estimated bearing of the spoofer, the estimated bearing being characterized by the ratio of the received power on the sum pattern to the received power on the control pattern on the one hand and by the ratio of the received power on the difference pattern to the received power on the control pattern on the other hand.

The present invention provides a low-cost and low-volume mode A/C/S transponder positioning system to detect the position of a target aircraft, or intruder, outside the range of a secondary surveillance radar system. The system uses a signal of the intruder to pinpoint the location of the intruder. The system can be used on both the ground and on an aircraft in a full 360 degree range around the system.

The present invention relates generally to a method and system (10) for classifying vehicle behaviour, particularly abnormal behaviour of civil aircraft (12). The method may comprise receiving aircraft data from an aircraft (12) which is to be classified; and determining whether the received aircraft data comprises identification information for the aircraft (12). In response to a determination that the received aircraft data comprises identification information, the method may comprise using said identification information to classify the behaviour of the aircraft (12). In response to a determination that the received aircraft data does not comprises identification information, the method may comprise obtaining the position of the aircraft and comparing the obtained position to an expected route for the aircraft to classify the behaviour of the aircraft (12).

An adaptive interrogation method is provided, the method including determining application of an adaptive whisper shout interrogation sequence. The determination may be predictive and based on an anticipation of garbled replies or may be reactive and based on a plurality of replies to an initial ATCRBS interrogation, there being interference between the replies such that the replies are unable to be properly decoded. The adaptive whisper shout interrogation sequence includes adapting a subsequent ATCRBS interrogation. The adaptation may be a change in an amplitude difference between an interrogation pulse and a suppression pulse of the subsequent ATCRBS interrogation (i.e. a bin width), as compared to the initial ATCRBS interrogation; or the adaptation may be a change in a power of the subsequent ATCRBS interrogation as compared to the initial ATCRBS interrogation. The subsequent ATCRBS interrogation is then transmitted, and one or more replies are received.

Each pattern being associated with a reception channel, over a given time period, the unsolicited asynchronous replies, of long ADS-B squitters type, transmitted by targets present in the airborne environment of the radar, are detected, each of the squitters containing position information on the target which transmits it; for each detection, the long ADS-B squitter is decoded to check that the detected target is located in accordance with the position information contained in the squitter, the non-conforming detections being rejected; for each detection retained, the time of the detection, the value of the azimuth of the main beam of the antenna and the received power value on each of the reception channels is associated with the detection, the position information contained in the squitters giving the elevation segment wherein the detection is situated; the values obtained over the period being stored, the measured patterns being sampled, by elevation segment, from the stored values.

Various communication systems may benefit from enhanced reception methods. For example, various transponders and surveillance systems may benefit from reception methods that can distinguish between overlapping pulses from multiple sources. A method can include receiving, at an antenna, a first series of pulses from a first source. The method can also include receiving, at the antenna, a second series of pulses from a second source. The first series and the second series can at least partially overlap each other. The method can further include de-interleaving the first series from the second series using at least one non-time-domain technique.

The radar includes an antenna having a radiation pattern forming a sum channel, SUM, a radiation pattern forming a difference channel, DIFF, and a pattern forming a control channel, CONT, a first transmission and reception chain being associated with the SUM channel and a second transmission and reception chain being associated with the CONT channel, a reception channel being associated with the DIFF channel. Each of the transmission and reception chains is able to transmit and to receive simultaneously, the transmission chain comprising a filtering operation that filters signals transmitted at 1090 MHz and the reception chain comprising a filtering operation that filter signals transmitted at 1030 MHz, in such a way that the chains operate independently of one another.

A mode S Interrogation Side Lobe Suppression System (ISLS) for an electronically scanned interrogator is described. One aspect introduces the 90° phase offset between the main and control beams thereby enabling the full power capability of the TRU to be effectively utilized and the effective beamwidth in Mode S to be sharply defined. The system allows the transmission of the simultaneous ISLS pulse of a Mode S all-call interrogation to be transmitted using the same array as is used by the main beam.

Various communication systems may benefit from enhanced reception methods. For example, various transponders and surveillance systems may benefit from reception methods that can distinguish between overlapping pulses from multiple sources. A method can include receiving, at an antenna, a first series of pulses from a first source. The method can also include receiving, at the antenna, a second series of pulses from a second source. The first series and the second series can at least partially overlap each other. The method can further include de-interleaving the first series from the second series using at least one non-time-domain technique.