This sub-theme has two separate topics, the first being the utility of using Low Probability of Intercept (LPI) waveforms in the future battlefield, and the second the value of HF radar techniques.

In the LPI study, the aim is to retain a robust sensing capability whilst achieving LPI capability in a practical military environment. The impact of LPI waveforms on radar design, performance and operation will be considered as will the use of ESM and ECMs to counter LPI waveforms.

HF radar technology offers unique advantages for over the horizon sensing. This study concentrates on two areas: technology to support a deployable HF radar system, and techniques for the detection of low observable targets.


Expected benefits of effective LPI techniques are reduced vulnerability of sensor platforms with minimal adverse impact on performance.
HF radar can provide a long range, over the horizon surveillance capability which, because of its low operating frequency, is well-suited to the detection of low observable targets. It can offer a cost-effective alternative to higher frequency radars which are often limited by line-of-sight problems.


To catalogue and assess LPI/LPE techniques which will be employable over the next ten years to make radars harder to detect
To determine in which situations real tactical advantages will be obtainable by employing LPI techniques
To determine the robustness of such advantages and to compare LPI radar with other methods of obtaining the same information
Development of techniques for the detection of small targets using HF radar
Development of techniques to support rapidly deployable HF radar systems


LPI/LPE Techniques-The first task will be to consider scenarios where LPI is likely to be significant, to guide the rest of the study. LPI radar techniques (including omnidirectional transmission, random search patterns, bistatic operation, very wide band operation and waveform agility) which may enhance performance will then be examined and assessed.

The other side of LPI is the abilities of the ESM system and the operating environment. Likely future enhancements to ESM capabilities (e.g. matched detectors or reconfigurable digital receivers) and the effects of practical propagation paths on ESM sensitivity and accuracy in particular environments will be considered.

Methods of exploiting emitters once they have been detected will be considered. These include deducing position and intention, noise and deception jamming, the possibility of attack by ARM and exploiting the radar as a transmitter of opportunity for a bistatic radar.

The major part of the project will be a comprehensive report containing assessments, backed by quantitative calculations, of the contributions these factors will play in the maintenance or undermining of an LPE capability. In order to ensure a realistic appraisal of the utility of LPE, the studies above will be balanced by an effort to understand the current military view of the utility of LPI/LPE. This will also consider the ways the military intend to exploit detection of systems using LPI/LPE and how that view is expected to change in the future.

Additionally, a short programme of experiments is planned for the second year. This work is planned to use the ‘Dual Linear Array’ (DLA) at THALES, a one-dimensional active phased array using FMCW modulation, suitably modified to allow the use of less predictable waveforms and scan patterns. It is anticipated that the array will probably only be required to operate in transmit mode as it will be the ability to intercept and characterise the transmissions which will be measured.

HF Radar- HF Surface Wave Radar offers a unique over the horizon capability for the detection of air and sea targets. A coastal HF Surface Wave Radar can provide economic and rapid large area search of coastal areas as well as the detection of low observable targets at shorter ranges, using fixed or re-deployable systems.

The research will investigate and develop novel radar modes and signal processing techniques that will allow the reliable detection of small fast RIB type craft at ranges of tens of kilometres, together with the detection of conventional targets.

HF radar systems tend to be physically large and work to date has only considered fixed installations. A deployable sensor would offer a much more flexible military capability. The proposed research will develop a viable system concept for a rapidly deployable sensor, with the aim being that it can be remotely sited, unmanned and autonomous in operation.

Key enabling technologies for the architectures developed within the study will be investigated as appropriate. In particular it is anticipated that there will be a requirement to develop novel low profile antenna technology and high power PIN diode-based duplexer techniques that will provide the basis for mobile deployable antennas.


The LPI/LPE research work is aimed at incremental development of existing work and will draw heavily on the expertise of the researchers and the DTC Consortium, particularly involvement with the ABSR programme. The planned research work is considered novel.

The HF research will be carried out by BAE SYSTEMS Advanced Technology Centre which has a strong track record in HF radar. The planned research builds on and extends this previous work.

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