Secondary Surveillance Radar System Research Articles

Frequency-Separating Devices for Secondary Surveillance Radar Systems

Frequency-Separating Devices for Secondary Surveillance Radar Systems

ИСПОЛЬЗОВАНИЕ МЕТОДА TDOA ДЛЯ ПОДТВЕРЖДЕНИЯ ДОСТОВЕРНОСТИ ИНФОРМАЦИИ РАДИОВЕЩАТЕЛЬНОГО АВТОМАТИЧЕСКОГО ЗАВИСИМОГО НАБЛЮДЕНИЯ

The paper considers the possibility of using the Time Difference of Arrival (TDOA) method, which can be applied to confirm the reliability of information coming from multiple sources. TDOA method can be applied to validate the information received from several ground automatic dependent surveillance stations of broadcast type (ADS-B). The paper is aimed at studying the TDOA method and its application to ADS-B stations. This method makes it possible to use the ADS-B as the only means of surveillance at the airfield. Currently, according to ICAO recommendations, ADS-B stations are not allowed to be used as a stand-alone surveillance aid due to the problems related to the possibility of distorting a signal or introducing some false information into messages, so the operation of this type of stations is possible only together with other means of surveillance, such as multi-position surveillance systems (MLAT) or secondary surveillance radar systems (SSR) thus increasing the cost of organizing surveillance on the airfield. Thus, the relevance of the work is related to the need to find an alternative method of confirming the validity of an ADS-B message.

Estimation of the relative throughput of aircraft transponders of secondary airspace surveillance radar systems

Secondary radar systems for monitoring airspace play a significant role in the information support of airspace control systems and air traffic control. These systems provide radar surveillance of airborne objects equipped with aircraft transponders and provide two-way communication via data request and response channels between ground radar stations and airborne objects.
 The paper assesses the relative throughput of aircraft transponders of secondary radar systems for monitoring airspace under the influence of correlated and uncorrelated interference in the request channel. The assessment of the throughput of the aircraft transponder shows that the aircraft transponder does not reach the maximum load included in the existing identification system under the influence of deliberate correlated interference. This indicates a sub-optimal determination of the aircraft transponder load factor of the existing secondary radar system. Incorrect determination of the maximum load of the aircraft transponder leads to a decrease in the noise immunity of both the aircraft transponder and the entire secondary radar system. At the same time, it should be noted that the interested party has the possibility of unauthorized use of an aircraft transponder to obtain information or paralyze the latter when applying interference of the required intensity.

Compensation of Positioning Errors Caused by Tropospheric Wave Propagation in Wide-Area Multilateration Systems

Introduction. Wide area multilateration (WAM) systems are the main competitors of secondary surveillance radar (SSR) systems used in air traffic control (ATC). The general principle of WAM operation is based on the assessment of pseudoranges between a signal source (an aircraft airborne transponder) and the ground receivers with precisely known geographical coordinates deployed over the ATC area. The aircraft position is estimated by measuring pseudoranges. A significant factor affecting the accuracy of aircraft positioning is tropospheric refraction, a phenomenon caused by the inhomogeneity of the earth's atmosphere and manifested in a deviation in the direction of the rays along which the signal of an aircraft transponder propagates. Refraction increases the lengths of ray paths, thus increasing the corresponding pseudoranges. As a result, the estimate of the aircraft position receives an additional bias. Altitude estimates produce unreasonably large errors.Aim. To develop a mathematical model for the signals received by a WAM system, which accounts for tropospheric wave propagation, as well as to derive an algorithm for aircraft positioning with compensated tropospheric errors.Materials and methods. Equations for the pseudorange estimation errors caused by wave propagation in a spherically stratified atmosphere were derived using the method of geometrical optics.Results. This paper proposed a mathematical model for pseudorange estimates in WAM systems, which accounts for the bias associated with the phenomenon of tropospheric refraction. An analysis of the proposed model showed that pseudorange errors depend linearly on the distance between the aircraft transponder and the receiver. This conclusion allowed an algorithm for aircraft positioning with compensated tropospheric errors to be developed. The proposed algorithm yields an unbiased estimate of the aircraft position. The standard deviation of altitude estimates increases by 60%, although remaining within the limits permissible for WAM systems.Conclusions. The developed mathematical model of WAM signals, which considers tropospheric propagation errors in pseudorange estimation, as well as the algorithm for aircraft positioning with compensated tropospheric errors, can be used in the development of spatially distributed navigation systems.

A digital model of airport surface traffic

The article proposes a digital model for determining permissible trajectories of objects moving within the air-port landside area. This model can be used for assessing the reliability of information provided by automatic dependent surveillance systems, as well as for filtering false targets. False targets can arise due to reflection of radio signals emitted by surveillance systems from large objects, as well as due to active interference or spoofing attacks. The developed model is of particular importance for assessing the reliability of information provided by automatic dependent surveillance-broadcast systems at aerodromes with an average level of traffic complexity, since it allows simpler solutions in terms of surveillance compared to multilateration systems or secondary surveillance radar systems operating in Mode S.

PEGASUS—Performance Experiments in Germany on ADS-B Using Mode S Extended Squitter

Future surveillance systems have to be capable of operating worldwide and to co-exist with other systems in the same frequency band. Extended Squitter is an ADS-B system which uses the same frequencies as current SSR (Secondary Surveillance Radar) systems (also called ATCRBS = Air Traffic Control Radar Beacon System). The German CAA, Deutsche Flugsicherung GmbH (DFS), and the U.S. Department of Transportation/Federal Aviation Administration (FAA) agreed to collaborate on a measurement activity in 2000 using Extended Squitter as the ADS-B medium. The Extended Squitter frequency 1090 MHz is actively being used for replies to secondary surveillance radars and for TCAS air-to-air surveillance. Frankfurt was chosen to perform the measurements under high interference conditions.The primary objective of the tests was the Extended Squitter performance measurement in the dense interference environment of Frankfurt. Both air-to-air and air-to-ground receptions were to be tested. For a good understanding of the results and to allow estimates for future environments, measuring the interference environment, the aircraft density and distribution was another objective. Results of these background measurements as well as of Extended Squitter performance in this specific environment are presented below.

受動型SSRによる空域監視網の提案

Even in these days, almost small airports and heliports have no equipment for aircraft surveillance. Many air traffic operation and airport operation service providers then request to develop the equipment for monitoring airspace to improve their service performance. We then think it is important to make the most effective use of conventional Secondary Surveillance Radar (SSR) system currently widely used, and we propose a Passive SSR (PSSR) to meet the request. The PSSR is the slave system for a conventional SSR of the mode-A/C system. The PSSR is a very compact and potable system consisting an omnidirectional antenna to receive the SSR replies from aircraft, an antenna to receive the SSR interrogations from a master SSR system, and a digital signal processor such as a personal computer for identifying aircraft and calculating the position of the aircraft. The PSSR installed within the coverage of the conventional SSR can provide SSR mode-A/C information without any radio transmission as interrogation. An Airspace Surveillance Network will be able to be established economically by utilizing PSSRs and InterNet.

空港面監視システムの検討

Today, the congestion of aircraft in the important airports is a serious problem, and equipment for decreasing the task load of tower controllers is required. Then, we develop a method for using the conventional SSR (Secondary Surveillance Radar) system as a sensor for identifying aircraft on the surface of the airport and for measuring their positions. In this paper the results of the simulation for estimating the performance of the method are described. From the results more than 95% of aircraft were identified under the condition that three replies were garbled, and the positions of identified aircraft were calculated within the error of several tens of meters (〜50m) for about 90% of cases. The possibility of realizing a new airport surface surveillance system based on SSR is shown.

Mode S system design and architecture

Mode Select (Mode S) is a secondary surveillance radar system that is designed as an evolutionary improvement to the current Air Traffic Control Radar Beacon System (ATCRBS). Mode S provides improved aircraft surveillance through the use of selective interrogation and monopulse processing and provides a ground-air-ground digital data link. The authors provide an overview of the Mode S aircraft surveillance and data link communications characteristics. This includes a description of monopulse azimuth determination, elimination of synchronous garble, time sharing between ATCRBS and Mode S activities, and the monopulse aircraft surveillance characteristics that provide improved ATCRBS performance. The Mode S sensor architecture and design are described, including the techniques used to provide a high level of sensor reliability, error protection, and a fault tolerance capability that supports data link operations. The authors also present an overview of the Mode S data link communications characteristics and a description of the planned data link applications. >

Status of the TCAS Program

An airborne collision avoidance system, using the existing transponder equipment of the Secondary Surveillance Radar system as its basic cooperative element, has been under development since the mid 1970's. In June 1981, the FAA Administrator announced the FAA's commitment to implementing the Traffic Alert and Collision Avoidance System (TACS), with a low cost system for general aviation and a more sophisticated system for air carriers. This paper summarizes the status of the FAA's TCAS program.

Multipath and interference effects in secondary surveillance radar systems

Secondary surveillance radar (SSR) offers many advantages for air traffic control (ATC) compared to normal (or primary) radar including substantially lower cost and improved performance. Because of the increasing reliance being placed on SSR by ATC a number of the system problems associated with SSR are becoming less easily tolerated. The paper discusses these problems, which mainly arise from multipath and mutual interference effects, and proposes solutions.

Differential Lobing in Sidelobe Suppression Systems

The sidelobe suppression function in the secondary surveillance radar system is analyzed when separate main and control antenna are used. Their vertical lobing structures are not matched with each other, so a differential lobing pattern comes out whose maxima and minima are enveloped by smooth curves depending on vertical displacement of phase centers and horizon cutoff rates. The developed analysis provides a method for the evaluation of the system performance for any antenna configuration and for the determination of design guidelines.

Address Selective Surveillance Radar

An improved Secondary Surveillance Radar system which will overcome many of the present defects in today's SSR has been developed by Cossor Electronics Limited working in conjunction with the Royal Signals and Radar Establishment (RSRE) and the Civil Aviation Authority.

Some problems of secondary surveillance radar systems

This paper considers the system engineering of a secondary surveillance radar, comprising a ground interrogator and airborne transponders, for use in an air traffic control system. It deals in general terms with the choice of frequencies, considers how closely it should be associated with the primary radars now used for the control of air traffic and deals with other system problems as follows: the elimination of interrogations by the sidelobe of the ground radar radiation, the design of ground and airborne aerials, transponder saturation and methods of countdown, the difficulty of airborne units being “captured” by one ground station to the exclusion of others, second-time-round signals, unlocked responses due to remote ground stations, and the form of coding which may be used, with particular emphasis on the air-to-ground channel. The discussion is kept intentionally at the systems level so that the general considerations can be appreciated unhampered, so far as possible, by technical detail. It has nevertheless been thought necessary at some places to point the argument with sufficient detail to give some further insight into the problems involved.