Small radars enable detection in coastal zones

Story

January 29, 2015

 

MIL-EMBEDDED: How are small radars being leveraged for military applications?

RADFORD: In recent years, a number of smaller ‘compact surveillance radars’ (CSR) were launched for military force protection and gap filling applications. Such CSR have reduced the antenna size below 0.5 meters, but due to the inevitable inaccuracy in the angular measurement, can only offer useful performance out to limited ranges of around 1 kilometer. An angular error of ±2 degrees at 500 meters is just ±17 meters, but at 5 kilometers is a whopping ±175 meters.

MIL-EMBEDDED: How much smaller will these radar systems go in the future?

RADFORD: The limiting factor for radar system size is primarily the size of the antenna required to achieve useful accuracy in the angular measurement of detected targets. Laws of physics dictate that a radar antenna that is, say, 0.5 meters across, will detect targets to an accuracy of approximately 1 to 2 degrees – perhaps 0.5 to 1 degree through the use of additional tracking software.

MIL-EMBEDDED: What are the biggest technical challenges involved in designing small radar systems?

RADFORD: The key challenge is being able to amass all of the design disciplines necessary to design a compact radar system. Such systems require a synergy of radar system design, RF and microwave, waveform generation, digital signal processing, radar data processing, power supply, and mechanical design skills such as thermal analysis. Unless every part of the radar system is designed with a deep understanding of the other system components, compromises will inevitably occur. The smaller the radar system, the greater the concentration of compromises.

MIL-EMBEDDED: What types of form factors and processing are involved? Custom design or not?

RADFORD: When designing Blighter radar, the hardware engineers took a modular approach that allowed both off-the-shelf and custom-designed modules to be used. For instance, the processor, synthesizer, and FPGA processing modules are all designed in-house and have a fully customized form factor. Modules such as the compass and GPS are ‘bought-in,’ off-the-shelf.

MIL-EMBEDDED: Do the Blighter radar products use many off-the-shelf solutions?

RADFORD: Our radar doesn’t use many embedded, off-the-shelf systems because there is insufficient control of all of the parameters that affect performance within the system. For example, all clocks used within the design need to be phase-locked to one another to avoid spurious internal emissions that could reduce radar sensitivity or create false targets.

MIL-EMBEDDED: How do you handle the cooling of electronics in the radar design?

RADFORD: Blighter radars neither use nor require any active cooling and don’t need to be placed or operated from inside any sort of protective radome enclosure. Instead, the complete radar unit – including the antennas, signal processing, and plot extractor – is typically just mounted at the top of tall, fixed surveillance towers or on extendable pump-up vehicle masts. As such, much of the outer case of the radar is exposed to heavy solar loading during daylight hours, so it was important to keep the radar’s power consumption and dissipation to a minimum (see Figure 1).

 

Figure 1: Pictured is the Blighter B400 radar.

(Click graphic to zoom by 1.9x)

 

From the outset, our radars were designed with the goal of consuming and dissipating only very small amounts of power, compared to both traditional mechanically scanned radars and active electronically scanned array (AESA) radars.

Power consumption is kept low by using the much more efficient frequency modulated continuous wave radar processing technology instead of the traditional ‘pulse’ radar technology used since the invention of radar. Whereas pulse radars generally emit many kilowatts of radar energy, Blighter emits 4 Watts in its highest power version and just 1 Watt in its standard power version. So while a pulse radar can consume – and dissipate – between 500 Watts to 2 kWm, ours consume 40 to 100 Watts, which is roughly equivalent to the power consumption of a standard household incandescent light bulb.

Our radars also use low-power passive electronically scanned array (PESA) technology on its transmit and receive channels to electronically steer the radar beam in azimuth. Adoption of such digital beam forming allows the radars to detect both small and slow-moving targets that mechanically scanned radars would be unable to detect. PESA technology is also more power efficient than competing AESA technology. Implementing an AESA-based e-scan radar would necessitate the use of many tens of active transmit and receive radar modules/elements, which would each be power-hungry and costly to manufacture.

MIL-EMBEDDED: How do these radars enable detection of objects or people within coastlines and coastal zones?

RADFORD: Our Blighter B400 e-scan radar’s algorithms – including a sea wave clutter filter and non-moving target detector – and its frequency modulated continuous wave transmission technology, combined with sensitive Doppler signal processing target detection, enables it to detect the small and uncooperative targets that traditional coastal surveillance radars such as vessel traffic systems and maritime radars are simply not designed to detect.

These features enable protection for complex coastlines from intruders such as smugglers, pirates, illegals, and terrorists at ranges of as far away as 16 kilometers. It can detect and locate small targets day and night, in almost all weather conditions, including rough seas, heavy rain, or dense fog.

In terms of size, it’s about the equivalent of a large briefcase and transmits 4 Watts of power, while consuming 100 Watts. This allows operation via solar panels and easy installation in difficult to reach areas such as rocky or inaccessible coastal regions. The radar’s low data bandwidth requirement also allows remote operation over narrowband wireless links or satellite communication systems.

Mark Radford has worked in the radar industry since 1985, initially as a designer of high-performance signal processing solutions for naval radar systems, and then later as a system designer and development manager. Since joining Blighter Surveillance Systems in 2000, he has been involved in various radar development projects, including the specification, design, and development of the electronic-scanning frequency modulated continuous wave (FMCW) Doppler surveillance radar.

Blighter Surveillance Systems +44-1799-533200 www.blighter.com