Q-par Angus Ltd has designed, built and operated ground, sea- and airborne-based radar systems for a variety of national and international government organisations including UK MoD, DTI, DSTL, US DoD, NASA, DSTO as well as academia and industry. Experience of radar systems that operate from HF through to W-band and above, is extensive. Recent radar systems that have been developed include a millimetre wave airfield runway debris avoidance radar.

Environmental radar

A lightweight, ultra-wide band (UWB), polarimetric millimetre wave 94 GHz radar with high resolution, that uses random binary phase coding to provide an all-weather remote measurement capability, is under development by Q-par Angus Ltd for environmental and other short range applications. UWB and random signal W-band radar technologies are combined with polarimetric and super-resolution processing techniques to provide a compact remote sensing capability that is man-portable. An all-weather capability is provided for accurate and high resolution measurement of the physical size, relative distance, bearing, altitude, direction, velocity and classification of stationary and moving objects at ranges of less than 10 km. Attributed information relating to the sensed environment such as local surface features, water depth, terrain topology and object classification is derived from remote millimetre wave radar measurements including polarisation. This will be demonstrated later in 2006 in a proof-of-concept surface mapping mode, with ultra-high resolution at millimetric wavelengths, in a representative environment.

A major threat to global stability is the inevitable change to the Earth’s climate. Average annual temperatures continue to increase and the UK Department of Environment Food and Rural Affairs (DEFRA) reports that the UK may experience wetter winters and drier summers. Extreme sea levels associated with the combined effects of high tides, sea level rise and storms will occur more frequently. These have profound consequences upon the threat to life and economies with wide impact upon assets, changes to natural habitats, political stability, socio-economic and physical boundaries. Uncertainty of the impact of climate change is incorporated into long-term regional, national and international decision-making, and reflected in environmental standards and targets. Our understanding of the complex interaction between the Earth’s surface and the atmosphere is required to be greatly enhanced beyond the current state of the art. An accurate description of local surface features (or topography) and timely monitoring by readily available and affordable means are of fundamental importance for all organisations and authorities that are concerned about the impact of climate change.

An all-weather remote sensing capability is being developed by Q-par Angus Ltd with UK DTI support. UWB and random signal radar (RSR) technology are exploited together with polarisation diversity and super-resolution techniques. This powerful combination results in a lightweight millimetre wave radar that is capable of providing accurate measurements of objects down to less than a few millimetres in size. The radar will remotely sense and consequently resolve very small features. This capability is not found in the usual radars that work at centimetre wavelengths, and uses a new type of millimetre wave source to produce the radio frequency power and highly accurate antennas to form very narrow beams. Importantly, since the wavelength is short the radar is smaller and more compact than conventional radars. It is therefore lightweight and readily man-portable. This distinct advantage eases the logistics of physically positioning large and bulky radar systems to overcome obscuration, shadowing, distortion and interference. Furthermore, this approach directly addresses the dichotomy of how to achieve coverage including foliage penetration (FOPEN), with all-weather remote measurements of fine angular resolution.

The resolution of all electromagnetic sensors is largely constrained by the influence of physical aperture and illumination wavelength. The use of HF radar operating between 3 MHz and 30 MHz is well known for its capability for remote wave monitoring of wide areas of sea from ground-based sites. However, the resolution of measured HF radar data is limited by the physical size of antennas. This can be impractical for portable or transportable systems.

The use of microwave technology in conjunction with advanced processing techniques such as Synthetic Aperture Radar (SAR) can improve the basic resolution for airborne and satellite based radar systems. Satellite-based radar (such as TOPEX POSEIDON, Jason, ERS, RA-2 and Envisat), usually at C-band, Ku- and Ka band, has a very wide coverage from in-orbit positions above the Earth and other heavenly bodies. Resolution of better than 5 m azimuth and 10m to 70 m range resolution with an elevation accuracy of about 50cm. However, the time delay between successive data acquisitions as represented by the measurement repeat cycle determined by the satellite orbit can be many weeks. Typically, the entire globe may be covered once every week. This latency is excessively long for local applications such as flood management that typically require high resolution data at specific sites within minutes.

The excess absorption of the atmosphere at operating frequencies above Ka-band precludes the application of SAR techniques in millimetre wave radar upon satellite based platforms. However, these disadvantages can be overcome with ground-based short range millimetre wave radar. This system can be located beneath tree canopies to overcome foliage and vegetation shielding. This lightweight radar may also be readily installed upon air platforms with severe size, weight and power (SWAP) requirements such as UAVs and High Altitude Platforms (HAPS).

Applications

The primary application of this radar is the observation of surface and near-surface movements of water, thereby providing an aid in flood defence planning, possibly warning of flood escalation and deployment of limited and valuable flood defences. Ripples on water surfaces can be resolved by this radar to indicate flow rates, rate of change, flow direction and below-surface features. This capability will aid the management of water resources, drainage, irrigation planning and pollution detection. Pollution in the form of particulate debris, or oils causing changes in surface features, may be detected and monitored. High resolution surface mapping is part of a requirement for environmental monitoring. This has particular application to bathymetry where knowledge of the depth and currents flowing in water is needed in order to predict future trends and to prevent flooding. Other detailed high resolution measurements of ground surface features can provide valuable environmental data. At present such studies may be undertaken using LIDAR, a laser scanning system fitted into an aeroplane. This has a number of disadvantages that include unavailability in all-weather conditions and obscuration, particularly from glint during exposure during strong sunlight. LIDAR is relatively expensive to use and only one system is readily available in the UK. One of the effects of global warming is to cause glaciers to become unstable. Monitoring using lasers can be compromised by fog and snow, whereas this radar system can remotely sense through fog and snow to provide continuous 24-hour monitoring. Further applications include all-weather air surveillance. The UK has very crowded airspace and small GA (General Aviation) airfields cannot generally afford to procure, operate and maintain a radar-based air surveillance capability. The radar system outlined would fill this need and thereby increase safety within the circuit of an airfield. Clearly, requirements in homeland defence for border and restricted area monitoring, and for surveillance in harbours and waterways are further applications of this millimetre wave radar system. The radar system that is described has sufficient high resolution for this work and is portable whilst being relatively affordable.