Optimal Policies Search for Sensor Management : Application to the AESA Radar

This report introduces a new approach to solve sensor management problems. Classically sensor management problems are formalized as Partially-Observed Markov Decision Process (POMPD). Our original approach consists in deriving the optimal parameterized policy based on stochastic gradient estimation. Two differents techniques nammed Infinitesimal Approximation (IPA) and Likelihood Ratio (LR) can be used to adress such a problem. This report discusses how these methods can be used for gradient estimation in the context of sensor management . The effectiveness of this general framework is illustrated by the managing of an Active Electronically Scanned Array Radar (AESA Radar)

Price vs. Performance: The Value of Next Generation Fighter Aircraft

The United States Department of Defense (DoD) is currently recapitalizing its aging fighter aircraft inventory with the F-22A and F-35. While the DoD may consider cost and performance issues, it does not use a quantitative model that effectively measures the tradeoffs between the two. This thesis constructs a hedonic model of the fighter aircraft market to measure the implicit price on fighter performance characteristics and specifically applies it to next-generation aircraft. Data from 50 aircraft from 1949-present were used to construct two models – one based on procurement costs and one based on research, design, test, and evaluation (RDT&E) costs. The models, based on a linear Box-Cox transformation, demonstrated that the unique F-22A trait, the ability to super-cruise, has the highest per-unit implicit price ($68.5M), followed by the stealth technology ($58.7M) and large-scale integrated circuitry ($55.3M). The high marginal value for the super-cruise trait implies that, depending on how super-cruise is used operationally, the F-35A may be a more effective purchase in terms of resource allocation than the F-22A

Investigations on Monolithic Radome Interactions with Active Electronically Scanned Array on Fighter Platform

The conventional fighter aircrafts are often equipped with fire control radar (FCR) using mechanically scanned antenna (MSA) with passive slots enclosed with monolithic conical radome. When the fighter platforms get upgraded with the modern active electronically steered array (AESA) FCR for better mission capabilities, even though radome change is desirable for optimum performance of AESA, it may not be feasible due to development time. This necessitate the evaluation of AESA radar with the existing monolithic radome. Hence active antenna aperture radiation pattern is required to be assessed with monolithic radome. To address this issue, simulation is preferred over physical testing, due to the reduced cost, time and complexity in measurements and ability to verify compatibility. In the present paper, the influence of monolithic radome on the active antenna radiation patterns are simulated and analysed. The characterisation studies helped for better optimisation of active aperture, optimum size for new radome development and additional space on fighter platforms that can be used for integration of new subsystems. Simulations are performed at two different locations of antenna inside radome. Experimental validations have been carried out to prove the efficacy of simulated results, which are in agreement

The correction method of transmission complex coefficients code matrix for AESA TRM

Приемопередающие модулей (ППМ) используемые в современных радарах на базе активных фазированных антенных решеток для дистанционного зондирования земли (ДЗЗ) имеют в своем составе дискретные фазовращатели и аттенюаторы. Описывается метод коррекции матрицы кодов измеренных комплексных коэффициентов передачи (ККП) ППМ для оптимального соответствия идеальным значениям. Приведены значения ошибок, которые являются результатом несовершенства состояния ККП для пары 6-битных фазовращателя и аттенюатора, до и после использования метода.A large majority of modern Transmit-Receive modules (TRM) for AESA radar uses phase discrete shifters and attenuators. The method of matrix code correction of measured TRM's complex transmission coefficient (CTC) for optimal correspondence to ideal one is described. Errors which are the result of imperfection complex state of a pair 6-bit phase shifter and attenuator are presented before and after using the method

Digital elevation modelling by radargrammetry in real-beam ground mapping mode

In this thesis the problem of estimating terrain elevation using two-dimensional radar data from the multirole ghter aircraft JAS 39 Gripen is considered. Radar data contains information about range from the aircraft to the reflecting terrain, as well as horizontal angle. In general, radar data has high resolution in range and low resolution in angle, giving rise to interesting problems. A new radar with higher resolution is in development for the next-generation Gripen. This thesis aims at answering whether estimation of terrain height can be done using available radar data, in order to evaluate the plausibility of doing this with data from the new radar. The approach is to find matching terrain features in subsequent images of the ground, and use this information to calculate terrain elevation. Two approaches are implemented and studied, both on simulated radar data and on real datasets. One approach uses Harris corner detection and the other uses Speeded-Up Robust Features (SURF). Conclusions drawn are that the algorithms do not work for the available radar data, but that they possibly could work when higher resolution data from the new radar is available

Graceful Degradation An Airborne Surveillance Radar Perspective

Active electronically scanned antenna (AESA)-based radars imbibe the desirable feature of ‘graceful degradation’. Such radars use miniaturised transmit-receive (TR) modules and a failure of few modules does not lead to failure of the mission. For example, in AESA-based ground MTI radar, failure of a few modules does not affect the array performance. In such a case, the static ground clutter is centred on zero frequency does not have a motion dependent Doppler spread. However, in airborne AESA radars, the ground clutter has an angle dependent Doppler frequency due to the platform motion and clutter leaking in through antenna side-lobes. Hence, the antenna side lobe levels dictate the side lobe clutter against which target detection is to be performed. The detection performance is governed by the signal to interference plus noise ratio (SINR). For Airborne surveillance radar the effect of random and systematic failures of TR modules and their effect on SINR is characterised. It is shown that single channel processing does not effectively provide the graceful degradation feature as the SINR loss due to failures is significant. However, the effect of systematic failure on SINR loss is less as compared to random failures. An effective scheme for feeding the array is also proposed

Refinement of a Novel Compact Waveguide

abstract: Presented is a design approach and test of a novel compact waveguide that demonstrated the outer dimensions of a rectangular waveguide through the introduction of parallel raised strips, or flanges, which run the length of the rectangular waveguide along the direction of wave propagation. A 10GHz waveguide was created with outer dimensions of a=9.0mm and b=3.6mm compared to a WR-90 rectangular waveguide with outer dimensions of a=22.86mm and b=10.16mm which the area is over 7 times the area. The first operating bandwidth for a hollow waveguide of dimensions a=9.0mm and b=3.6mm starts at 16.6GHz a 40% reduction in cutoff frequency. The prototyped and tested compact waveguide demonstrated an operating close to the predicted 2GHz with predicted vs measured injection loss generally within 0.25dB and an overall measured injection loss of approximately 4.67dB/m within the operating bandwidth.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Rethinking SEAD: Employment of contemporary Fighter Aircraft Capabilities against an A2/AD-System of Systems of a peer Adversary in Europe

The Russian full scale invasion of Ukraine has demonstrated, how relevant the discussion about a potential NATO article 5 intervention in Europe is. A frequently used term in this context is Anti Access/ Area Denial. While this term is not existent in Russian strategy, the Integrated Air Defense System it encompasses poses a major challenge to NATO’s freedom of movement in case of a conflict. The air power role Suppression of Enemy Air Defenses can provide means to tackle the threat the Russian IADS poses to NATO. This thesis elaborates on NATO’s capabilities to counter the Russian IADS with SEAD capabilities. The topics SEAD and A2/AD are analyses in an extensive literature review. A qualitative small-N study based on subject matter expert interviews is conducted in order to identify, how the way SEAD operations are executed must be adjusted based in the present SEAD capabilities in NAT

Dwell Time Optimization of Alert-Confirm Detection for Active Phased Array Radars

Alert–confirm detection is a highly efficient method to improve phased array radar search performance. It comprises sequential detection in two steps: alert detection, in which a target is detected at a low detection threshold, and confirm detection, which is triggered by alert detection with a longer dwell time to minimize false alarms. This paper provides a design method for applying the alert–confirm detection to multifunctional radars. We find optimum dwell times and false alarm probabilities for each alert detection and confirm detection under the dual constraints of total false alarm probability and maximum allowable dwell time per position. These optimum values are expressed as a function of the mean new target appearance rate. The proposed alert–confirm detection increases the maximum detection range even with a shorter frame time than that of uniform scanning

Assessment of Air Power in India and China (Report No: NIAS/CSS/ISSSP/U/RR/067/2019)

The assessment of air power is very significant in the present scenario as India is facing a lot of security threats from China and Pakistan. Even though numerous studies were done in the field of air power, there has been no assessment of India’s and China’s air power capability till now. This paper makes a thorough analysis on the fighter aircraft of Indian Air Force (IAF) and People’s Liberation Army Air Force (PLAAF) mainly focussing on the avionics. The paper concludes by claiming that India should have more number of fighter aircraft squadrons to maintain the balance of air power and should have an advanced self-reliant avionics to prevent supply chain risks and to protect her from any kind of threat from her adversary