Clive M. Alabaster

Medium PRF radar PRF selection using evolutionary algorithms

Evolutionary algorithms are applied to the optimization of pulse repetition frequency (PRF), for both eight-and nine PRFs, in medium PRF radar while considering the detailed effects of sidelobe clutter and many other technical factors. The algorithm presented also ensures that all the solutions produced are fully decodable and have no blind velocities. The evolutionary algorithm was able to identify near-optimum PRF sets for a realistic radar system with only a modest computational effort.

Performance comparison of PRF schedules for medium PRF radar

Previous work has shown how evolutionary algorithms (EAs) are an effective tool in optimising the selection of pulse repetition frequency (PRF) values of medium PRF schedules in an airborne fire control radar (FCR) application requiring target data in three PRFs. The optimisation is driven by the requirement to minimise range/Doppler blindness whilst maintaining full decodability. In this paper we detail work in which the optimisation process is applied to design novel short medium PRF schedules requiring target data in just two PRFs. The paper reports on the testing of a variety of near-optimum schedules to compare their blindness, decoding, and ghosting performances. The results show that in many situations, the 2 of N schedules are a practical alternative to conventional 3 of N processing.

The metrication of low probability of intercept waveforms

In recent years, military radar operators have been concerned that the transmitted radar signals will beacon the presence of the radar to an enemy. If intercepted, the radar signals alert a target to an attack which could prompt evasive measures or countermeasures to be taken by the target including the possibility of a reprisal attack using an antiradiation missile. Furthermore, intercepted signals can divulge operating parameters of the radar to the enemy. In response to this low probability of intercept (LPI) requirement, waveforms have been designed to minimize the probability of intercept by an enemy receiver. These are largely based on the use of low peak powers and spread spectrum waveforms offering large processing gains. The interception of signals is a function of both the transmitted radar waveform and the intercept receiver. The aim of this work is to deduce a metric which may be used to quantify and hence compare how “discrete” many of the commonly used LPI radar waveforms actually are. This study considers the following LPI waveforms [1]: Linear Frequency Modulation (LFM), Sinusoidal Frequency Modulation (Sin FM), PolyPhase Shift Keying (PPSK) techniques including Frank, P1, P2, P3, and P4 codes Costas code Frequency Shift Keying (FSK), and Costas-Barker Hybrid (FSK/PSK). This work represents the first attempt to be published in the open literature to quantify the LPI properties of transmitted radar waveforms. Secure waveform coding strategies to minimize the risk of divulging radar capabilities is known as low probability of exploitation (LPE) and is not considered here.

Is it a bird or is it a plane

This paper describes the application of low-cost radar technology for the detection and analysis of the Doppler signatures of wild life, in particular birds and bats. We demonstrate the ability to extract the wing beat frequency in real-time. Such processing affords a method of readily discriminating between animals and other flying objects such as micro-unmanned aerial vehicles. The timing waveforms used for sampling and integration can have a significant impact on the fidelity of the data that can be captured and on the response time of the system to detect and analyse animals in motion. This work paves the way for future research in support of target classification and conservation ecology.

Medium PRF radar PRF optimisation using evolutionary algorithms

In this paper we employ evolutionary algorithms for the selection of optimal pulse repetition frequency (PRF) sets to minimise range-Doppler blindness in a model of a medium PRF radar. Both eight and nine PRF schedules are considered and the algorithm ensures that all the solutions produced are fully decodable and have no blind velocities. We consider the detailed effects of side-lobe clutter and the many technical factors affecting the choice of radar PRF in a medium PRF mode of operation of a practical airborne fire control radar.

Radar based automatic target system

This paper describes the novel application of both dual tone CW and ISAR techniques to measure the position of a small high velocity projectile as it passes through a defined sensory virtual plane, so forming the basis of an automatic targeting system for live fire training. Simulation and initial experimental results are presented, as well as a general description of the system.

Novel PRF schedules for medium PRF radar

Previous work has demonstrated that evolutionary algorithms (EAs) are an effective tool for the selection of optimal pulse repetition frequency (PRF) sets to minimise range-Doppler blindness of a medium PRF radar. This paper reconsiders the concepts of decodability in medium PRF radar, and how new and novel schedules can be generated using an EA. Traditionally, target data is required in a minimum of 3 PRFs (e.g. a 3 of 8 scheme). In this paper, we describe the generation of schedules requiring data in only 2 PRFs. Results are presented for a comparison between schemes requiring target data in two and three PRFs. The results indicate that blindness is minimised in schedules with greater numbers of PRFs and requiring target data in fewer PRFs. The concept of dynamic selection of PRI schedules that are fully decodable and have no blind velocities is outlined and is concluded to be feasible.

Holographic reconstruction of multistatic breast microwave radar images: Initial results on synthetic phantoms

During the last decade, Microwave Radar has been proposed as a complementary technology for breast cancer detection. This imaging modality has several features that make it beneficial from a clinical viewpoint such as the use of non-ionizing radiation. Nevertheless, the reconstruction of this data is non-trivial due to the phase wrapping introduced by the scan geometry and the near field distances between the antenna and the targets. This paper presents preliminary results obtained using a novel algorithm to reconstruct images from experimental multistatic breast microwave radar data. This image formation approach performs a series of operations in the frequency domain to compensate the effects of the scan geometry. Compared with its monostatic counterpart, the proposed reconstruction algorithm generated images with a higher signal to noise ratio and contrast.

A holographic reconstruction method for circular multistatic subsurface radar

In recent years, the use of Subsurface Radar (SR) has been proposed for some emerging applications such as breast imaging and wood inspection. A circular scan geometry is usually used in these applications to better suit the morphology of the scan region. Nevertheless, the reconstruction of these kind of datasets is a non-trivial task due to the nature of the phase wrappings introduced by the scan geometry and the near field distances between the antenna and the targets. In this paper, a novel reconstruction algorithm for multistatic SR datasets recorded along cylindrical scan geometries is proposed. This image formation approach performs a series of operations in the frequency domain to compensate the effects of the scan geometry. The performance of the proposed method was evaluated using a series of simulated datasets. Compared with its monostatic counterpart, the proposed reconstruction algorithm generated images with a higher signal to noise ratio, spatial accuracy and focal quality.

Microwave radar imaging of inhomogeneous breast phantoms using circular holography

Circular holography is a novel reconstruction technique for Breast Microwave Radar (BMR) imaging. Compared to current state of the art BMR image formation methods, this reconstruction approach yields spatially accurate images with higher signal to noise ratios and no artifacts. Nevertheless, a preclinical study is required to assess the feasibility of this technique in realistic breast imaging scenarios. In this paper, a series of preliminary results showing the performance of circular holography on preclinical datasets are presented. These datasets were recorded from inhomogeneous breast phantoms that mimic the dielectric properties and the anatomy of the different breast tissues. These phantoms were fabricated using Magnetic Resonance (MR) images a base model to emulate the shape and volumes of dense tissue regions. The reconstructed BMR images show that tumor and fibroglandular tissue responses can be effectively distinguished, suggesting that circular holography can be used as BMR reconstruction approach in clinical scenarios.