Michael Inggs

Bill Millin was a Scottish soldier serving as the personal piper to Simon Fraser, 15th Lord Lovat, the commander of the British 1st Special Service Brigade going ashore in Normandy, in the D-Day landings on 6 June 1944. Lovatt ordered Millin to play his pipes on the beach to encourage the soldiers advancing under heavy German fire. Remarkably, Millin was untouched, despite marching up and down the beach, playing regimental tunes, strongly motivating the soldiers charging up the beach.

This document is a necessarily selective overview of achievements in Synthetic Aperture Radar (SAR) Technology during the 50 years of the Aerospace and Electronic Systems Society's (AESS') existence. Advances in radar technology, fuelled by the digital revolution, have led to a concomitant flowering of SAR applications in land, sea, air and space. The development of coherent radar during World War II led to the concept of forming a large, synthetic aperture, enabling microwave images with high lateral resolution that are largely impervious to time of day and weather. We follow the history of this technology, from airborne platforms, onwards onto satellites. We examine some of the achievements of SAR in a wide range of applications. SAR technology has now truly moved into the commercial exploitation phase, with almost an exponential growth in systems available to customers.

This article presents the results of a series of measurements of multistatic radar signatures of small UAVs at L‐ and X‐bands. The system employed was the multistatic multiband radar system, NeXtRAD, consisting of one monostatic transmitter‐receiver and two bistatic receivers. NeXtRAD is capable of recording simultaneous bistatic and monostatic data with baselines and two‐way bistatic range of the order of a few kilometres. The paper presents an empirical analysis with range‐time plots and micro‐Doppler signatures of UAVs and birds of opportunity recorded at several hundred metres of distance. A quantitative analysis of the overall signal‐to‐noise ratio is presented along with a comparison between the power of the signal scattered from the drone body and blades. A simple study with empirically obtained features and four supervised‐learning classifiers for binary drone versus non‐drone separation is also presented. The results are encouraging with classification accuracy consistently above 90% using very simple features and classification algorithms.

Accurate and stable time and frequency transfer (TFT) is typically required in distributed sensing. Whilst this has historically been a limiting factor in the design of netted radars, the rise of modern TFT techniques has paved the way to nanosecond level time accuracy, absolute phase synchronisation, and sub-Hertz frequency accuracy. In particular, netted systems comprised of mobile nodes have benefited immensely from TFT based on Global Navigation Satellite Systems (GNSS). However, GNSS systems are liable to denial of service interruption. This article demonstrates the use of a fibre-optic White Rabbit (WR) network in an operational multistatic radar — NeXtRAD, and directly compares the results to one-way multi-channel GPS Disciplined Oscillators acting under common-view TFT.

Fractional-N phase-locked loops (PLLs) offer a low-cost solution to the precision frequency ramp requirements of frequency-modulated continuous-wave (FMCW) radar. Regrettably, however, these PLLs are known to produce undesirable spurii in their synthesized output. A subset of these spurii has recently been shown to manifest as frequency chirps, also known as spur chirps, in the deramped beat signal. These so-called spur chirps give rise to Fresnel ripples in the range domain after standard Fourier processing. Spur chirps are of particular concern for heterodyne receiver systems because the Fresnel ripples may appear at levels that far exceed the noise floor. In this article, the authors present guidelines for the avoidance of spur chirps and identify existing interference suppression techniques that are transferable to this problem. Furthermore, the authors put forward a novel technique termed range-Doppler spur masking (RDSM) that was designed specifically for the suppression of spur chirps. The developed technique was applied to both the simulated and measured synthetic aperture radar (SAR) data. Simulations reveal that RDSM significantly outperforms time-domain zeroing in terms of peak sidelobe ratio (PSLR) and other metrics. When applied to the measured data, RDSM is shown to eliminate the effects of the spur chirps in SAR imagery when masking only 0.15% of the available Doppler bins.

Fractional‐N phase locked loops (PLLs) offer a low‐cost solution to the precision frequency ramp requirements of frequency‐modulated continuous‐wave (FMCW) radar. In this application, however, the infamous spurious signals generated by these PLLs have not received adequate analysis. In this Letter, the authors investigate the impact of integer boundary spurs on FMCW radar performance. They show that the offset of these spurs is swept during the course of waveform generation, and that undesirable spur chirps manifest in the beat signal as a result. These spur chirps span the radar's intermediate frequency bandwidth and produce Fresnel ripples in the range profile which reduce spurious‐free dynamic range. They present simulations and measurements that demonstrate how reduction of PLL bandwidth can be used to suppress these spurii.

The development of software-defined radio (SDR) systems using field-programmable gate arrays (FPGAs) compels designers to reuse pre-existing Intellectual Property (IP) cores in order to meet time-to-market and design efficiency requirements. However, the low-level development difficulties associated with FPGAs hinder productivity, even when the designer is experienced with hardware design. These low-level difficulties include non-standard interfacing methods, component communication and synchronization challenges, complicated timing constraints and processing blocks that need to be customized through time-consuming design tweaks. In this paper, we present a methodology for automated and behavioral integration of dedicated IP cores for rapid prototyping of SDR applications. To maintain high performance of the SDR designs, our methodology integrates IP cores using characteristics of the dataflow model of computation (MoC), namely the static dataflow with access patterns (SDF-AP). We show how the dataflow is mapped onto the low-level model of hardware by efficiently applying low-level based optimizations and using a formal analysis technique that guarantees the correctness of the generated solutions. Furthermore, we demonstrate the capability of our automated hardware design approach by developing eight SDR applications in VHDL. The results show that well-optimized designs are generated and that this can improve productivity while also conserving the hardware resources used.

In this paper we examine an FM based PCL radar system and attempt to quantify its performance in the presence of various different jamming waveforms namely broadband noise and a single tone on the carrier. It is shown that effective jamming can be achieved with relatively low jamming power. The importance of an effective direct signal canceller is also shown as a means of suppressing the jamming signal. The effect of these jamming scenarios is shown through simulation and then compared to a representative measured result from a real FM based PCL radar system.