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Assessment of Aircraft Radar Cross-Section for Detection Analysis
Swedish National Defence College, Department of Military Studies, Military-Technology Division. KTH Royal Institute of Technology.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hiding from and surprising an opponent are tactics that have been used in warfare throughout history. They were features that aircraft originally possessed when they were first used in military operations. However, development of military technology is an endless struggle between advances in technology and counter technology. During World War II this struggle led to the development of a new technology called radar, which was designed to detect sea vessels and aircraft at a distance and deny them the element of surprise. This laid the foundation for modern air defenses and simultaneously created a need for aircraft to penetrate such defenses. Central to the tactics and technological development that followed from the deployment of radar on the modern battlefield is the radar cross-section (RCS) of aircraft, which dictates the range at which aircraft can be detected by radar. In this thesis some aspects of the RCS of aircraft in radar detection are investigated. A combination of experimental measurement of aircraft and digital model development of the RCS of aircraft has been used.

From flight experiments, the uncertainty in aspect angle to a threat sensor, due to aircraft dynamics, is quantified for various aircraft. In addition, the RCS fluctuation behavior of a military jet trainer is investigated by dynamic in-flight measurement. The monostatic and bistatic RCS of an F-117 are modeled and findings show that spline interpolation provides superior accuracy when interpolating the RCS data. Smooth and conservative RCS models are suggested and a new RCS sampling scheme is presented. A model based on experimental data is suggested for determining the range of aspect angles that an aircraft is likely to orient towards a threat sensor, and experimental RCS data is compared to the classical Swerling radar target models.

Possible consequences for military operations and the design of military systems are discussed and considerations for modeling the interaction between air defenses and aircraft penetrating those defenses are given.  

This thesis should be of interest to military actors and the defense industry, since the analyses of the ability to detect aircraft using radar are important for military operations and their planning.

 

Abstract [sv]

Att kunna gömma sig för att sedan överaska sin motståndare är en taktik som har använts inom krigsföring genom historien, detta var också en möjlighet flygplan erbjöd när de började användas i militära samanhang. Utveckling av teknik för militära ändamål är emellertid en ständigt pågående kamp mellan framsteg inom det befintliga teknikfältet och utveckling för att kunna motverka sådan teknik. Under andra världskriget ledde denna kamp till utvecklingen av radar, en teknik som används för att upptäcka och följa fartyg och flygplan på stora avstånd, vilket kraftigt försvårade möjlighet att överaska motståndaren med hjälp av flygplan. Utvecklingen av radar är en hörnsten inom moderna luftvärnssystem, vilket också har skapat ett behov för luftstridskrafter att kunna motverka och penetrera sådana skydd. Centralt för den teknik och taktikutveckling som skede till följd av att radar introducerades på det moderna slagfältet är flygplans radarmålarea, som är avgörande för på vilket avstånd det är möjligt att upptäcka flygplanet. I den här avhandlingen undersöks aspekter kring hur flygplans radarmålarea påverkar detektionsmöjligheterna för en hotradar. Avhandlingen består av både mätningar på faktiska flygplan samt forskning kring digitala modeller av radarmålarea.

Flygförsöken gav kvantitativa exempel på hur stor osäkerhet i aspekt vinkel ett givet flygplan kan förväntas ha emot en hot sensor på grund av flygdynamik. Utöver detta så utfördes även en dynamisk mätning av radarmålarea på ett jetdrivet skolflygplan, för att undersöka fluktuationerna i radarmålarea. Både monostatisk och bistatisk radarmålarea har beräknats för en F-117 modell och resultaten tyder på att spline-interpolation ger den bästa noggrannheten vid interpolation. Vidare föreslås hur jämna och konservativa modeller av radarmålarea kan uppnås samt att en ny samplingsstrategi för radarmålarea presenteras. En modell som bygger på experimentell data föreslås för att uppskatta hur stor ändring av aspektvinkel ett givet flygplan kan förväntas ge emot en hotsensor, samt att mätdata av radarmålarea jämförs med de klassiska Swerling modellerna.

Den påverkan resultaten förväntas ha på militära operationer och system diskuteras och några överväganden som bör beaktas vid modellering av interaktionen mellan flygplan och radar ges.

Denna avhandling torde vara av intresse för såväl militära aktörer som försvarsindustri, eftersom analysen och möjligheten att upptäcka flygplan med radar är en viktig del av luftstrid och tillhörande planering.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 21 p.
National Category
Aerospace Engineering
Research subject
Militärteknik
Identifiers
URN: urn:nbn:se:fhs:diva-6083Libris ID: 19417969ISBN: 978-91-7595-936-8 (print)OAI: oai:DiVA.org:fhs-6083DiVA: diva2:919338
Public defence
2016-05-13, Sverigesalen, Drottning Kristinas Väg 37, Stockholm, 15:28 (English)
Opponent
Supervisors
Funder
VINNOVA, 2010-01259
Available from: 2016-04-22 Created: 2016-04-13 Last updated: 2016-04-22Bibliographically approved
List of papers
1. On Modeling RCS of Aircraft for Flight Simulation
Open this publication in new window or tab >>On Modeling RCS of Aircraft for Flight Simulation
2014 (English)In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 56, no 4, 34-43 p.Article in journal (Refereed) Published
Abstract [en]

This paper investigates the implementation of the radar cross section (RCS) of aircraft in modeling and simulation (M&S). More specifically, it addresses the tradeoff between accuracy and computational cost introduced by spatial RCS fluctuations. High-resolution RCS matrices, generated using Physical Optics (PO), were used in an investigation of RCS matrix resolution, and an evaluation of different bilinear interpolation methods is presented. The spatial Fourier transform was used for resolution analysis. It was found that the smallest RCS interpolation error was obtained using splines. Furthermore, results showed that the distribution of the relative interpolation error in detection range was well approximated by a log-normal distribution.

Place, publisher, year, edition, pages
IEEE Antennas and Propagation Society, 2014
Keyword
Electromagnetic modeling, aerospace simulation, computer simulation, interpolation modeling and simulation, radar cross sections, radar detection
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Militärteknik
Identifiers
urn:nbn:se:fhs:diva-5005 (URN)10.1109/MAP.2014.6931656 (DOI)
Projects
Värdering av flygplans överlevnad, NFFP5
Funder
VINNOVA, 2010-01259
Available from: 2014-11-11 Created: 2014-11-11 Last updated: 2017-07-06Bibliographically approved
2. Conservative RCS Models for Tactical Simulation
Open this publication in new window or tab >>Conservative RCS Models for Tactical Simulation
2015 (English)In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 57, no 1, 217-223 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a procedure for generating conservative radar cross section (RCS) models able to meet the computational requirements imposed by simulation and related applications. The key concept is to downsample calculated or measured RCS data retaining local extreme values; thus, a conservative RCS matrix is obtained. Spline approximations are used in order to obtain continuity in the RCS models. RCS models with varying resolution have been generated and analyzed, and it is shown how spatial Fourier transforms can be used when determining feasibility for certain decision making applications. Furthermore, it is found that the interpolation errors obtained from the conservative RCS models are well described by generalized extreme value theory.

Keyword
Electromagnetic modeling, Fourier transforms, military equipment, modeling and simulation, physical optics, radar cross section (RCS), statistical distributions
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Militärteknik
Identifiers
urn:nbn:se:fhs:diva-5595 (URN)10.1109/MAP.2015.2397151 (DOI)000352237400020 ()
Available from: 2015-10-30 Created: 2015-10-30 Last updated: 2016-11-07Bibliographically approved
3. Empirical Study of Flight-Dynamic Influences on Radar Cross-Section Models
Open this publication in new window or tab >>Empirical Study of Flight-Dynamic Influences on Radar Cross-Section Models
2016 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 53, no 2, 463-474 p.Article in journal (Refereed) Published
Abstract [en]

In this work, measurements and a method for analyzing flight-dynamic effects on radar cross-section models for aircraft are presented. Flight-dynamic effects need to be considered when designing combat aircraft and creating target models for radar simulators. The work is based on flight data from three different types of aircraft: Piper PA-28 Archer II, Boeing 737, and Saab JAS 39 Gripen. Using inertial navigation and global-positioning systems, the motions of the three aircraft are recorded in flight. From the data, aspect angles toward a radar station located in the extension of the intended flight path are generated using a simulator. It is found that the major contribution to perturbations in aspect angles is due to the rotational degrees of freedom and that bivariate normal distributions are a good candidate for approximating the uncertainty in aspect angles for all three aircraft types. It is also found that each rotational degree of freedom is close to a normal distribution but that the parameter values of the distribution vary with altitude and aircraft type.

National Category
Aerospace Engineering
Research subject
Militärteknik
Identifiers
urn:nbn:se:fhs:diva-6082 (URN)10.2514/1.C033566 (DOI)000373945100016 ()
Available from: 2016-04-13 Created: 2016-04-13 Last updated: 2016-10-19Bibliographically approved
4. Reduction of RCS Samples Using the Cubed Sphere Sampling Scheme
Open this publication in new window or tab >>Reduction of RCS Samples Using the Cubed Sphere Sampling Scheme
2016 (English)In: Progress In Electromagnetics Research M, ISSN 1937-8726, Vol. 48, 103-112 p.Article in journal (Refereed) Published
Abstract [en]

An alternative to the traditional method of sampling radar cross section data from measurements or electromagnetic code is presented and evaluated. The Cubed Sphere sampling scheme solves the problem of oversampling at high and low elevation angles and at equal equatorial resolution the scheme can reduce the number of samples required by approximately 25%. The analysis is made of an aircraft model with a monostatic radar cross section at C-band and a bistatic radar cross section at VHF-band, using Physical Optics and the Multilevel Fast Multipole Method, respectively. It was found that for the monostatic radar cross section, the Cubed Sphere sampling scheme required approximately 12% fewer samples compared to that required for traditional sampling while maintaining the same interpolation accuracy ever the entire domain. For the bistatic data, it was possible to reduce the number of samples by approximately 45% for high sampling resolutions. Using spline interpolation the number of samples required could be reduced even further. 

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering; Militärteknik
Identifiers
urn:nbn:se:fhs:diva-6099 (URN)10.2528/PIERM16022503 (DOI)
Funder
VINNOVA, 2010-01259
Available from: 2016-04-13 Created: 2016-04-20 Last updated: 2017-06-15Bibliographically approved
5. Radar Target Modeling Using In-Flight RCS Measurements
Open this publication in new window or tab >>Radar Target Modeling Using In-Flight RCS Measurements
2017 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 54, no 1, 284-291 p.Article in journal (Refereed) Published
Abstract [en]

A flight experiment with the Saab 105 aircraft and the radar cross-section measurement system Arken has been performed at C and Ku bands. Two types of trajectories were flown and the flight state was recorded using inertial and satellite navigation equipment.  The data was used to recreate the flight in a simulator where aspect angles and range to the measurement system could be calculated. The measured radar cross-section as a function of time is presented and compared to various statistical fluctuation models, including the distributions used in Swerling cases. Findings show that the Generalized Pareto distribution fits the measured data best and that Swerling Case 2 is also a good candidate for describing the dynamics of the radar cross-section at Ku-band when the aircraft approaches the radar head on. The measured radar cross-section data was analyzed using the Fast Fourier Transform from which fluctuation rates for different carrier frequencies and trajectories could be estimated.

National Category
Aerospace Engineering
Research subject
Militärteknik
Identifiers
urn:nbn:se:fhs:diva-6100 (URN)10.2514/1.C033932 (DOI)
Available from: 2016-04-13 Created: 2016-04-20 Last updated: 2017-05-02Bibliographically approved

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