Sea Power: CEAFAR - now a fourth-generation radar | ADM Apr 08

1 April 2008

By Tom Muir

Digital beamforming of their phased array radars is set to boost the defensive capabilities of the ANZAC Class frigates.

Late last year CEA Technologies demonstrated to a coterie of DMO and DSTO stakeholders, the capabilities of the phased array radar system planned for incorporation in the Anzac Class frigates as part of their anti-ship missile defence upgrade.

A 'smallface' engineering development model (EDM) that hosts the capabilities of the CEAFAR phased array radar on a quarter sized face, during the test successfully achieved the required through-air radar performance.

That outcome was never in doubt but what was more to the point was CEA's ability to demonstrate important aspects of its digital beamforming technologies.

These, it seems, had been implemented on the EDM, well in advance of their scheduling for this stage of the program.

In completing this test CEA had taken an important step towards completing the evolution of what the company calls its fourth generation digital active array radar.

Thanks to digitisation, CEAFAR stands today at the forefront of phased array technology.

Phased array systems have an obvious advantage over conventional radars in that their beams are electronically steered from fixed panels, readily detecting and locking onto moving targets.

Because the radars require no physical movement the beam can scan fast enough to track many individual targets, and still run a wide-ranging search periodically.

Conventional ships' surveillance radars rely on rotating antennas to scan the horizon.

When a target is detected it can only be 'seen' once in every 360-degree scan.

While the scan rate can be increased target definition falls away commensurately.

One of the most important aspects of CEA's ongoing development of its CEAFAR phased array radar and illuminator has been the implementation of digital beamforming.

Digital beam forming is the most advanced approach to phased array antenna pattern control.

When implemented at the sub-array or element level, it leads to significant improvements in the beamforming of simultaneous multiple independent beams, as well as other advantages compared to traditional analogue array control techniques.

Increased coverage
The radiating beam transmitted from the antenna elements in the tiles is steered and shaped by electronically modifying (or phase shifting) the output of the antennas.

Thus the beam can be spread for searching, narrowed for tracking, or even split into two or more virtual radars.

Digital beamforming is achieved in CEAFAR and CEAMOUNT by digitising what the company calls the 'backend' that is the controllers responsible for the phase shifting (steering) of the transmit/receive (T/R) modules within each of the tiles in the radar faces.

Digitising enables the radar to preserve all incoming information and this data can then be used to form as many radar beams as necessary to track as many objects as appear.

Digital beamforming of its transmit only array has also greatly increased the capabilities of the CEA MOUNT missile illuminator, which has been designed to meet the guidance needs of the semi-active homing ESSM and SM-2 family of missiles.

Multiple beam operation of CEAMOUNT can increase the number of missiles in terminal illumination, limited primarily only by the firing rate restrictions of vertical launch systems.

Ian Croser says digital beamforming has led to extraordinary increases in raw signal processing power and provides additional capacity that is always welcome.

"These gains in overall radar performance will ensure the ANZAC Class will be fitted with the latest digital radar capabilities available to modern warships," Croser says.

With this added power and capacity, virtually all of which is managed at the back of the arrays, has come the need to cool the faces and their 'backend' controllers.

The PAR face design for the ASMD requirement comprises the 4x4 tile antenna configuration under a flat protective exterior radome.

The cold plate has cooling passages through its body and the front end tiles and backend modules have intricately machined cooling structures to collect and transfer heat to the faces of the cold plate.

These structures are machined at the company's own machining plant in Melbourne.

We understand that the sandwich construction of each the radar's six faces, including the cooling water, is well within design weight goals set in 2005.

The cooling water does not require chilling and is circulated through a simple pump and sea water exchange system.

An interesting point is that the water, circulated in the frame, weighs less than aluminium.

Problem fixed
Ship weight and stability, particularly topweight, and electronic compatibility and interference between various sensors, have been factors addressed in the extensive mast design and antenna location studies.

The configuration now proposed sees the existing Sea Giraffe target indication radar and its lattice mast structure removed to make way for an enclosed mast accommodating a six-face CEA-FAR system immediately above the four-face CEAMOUNT illuminator.

The long range SPS-49 air search radar is mounted at the top.

Two months ago CEA received a $21 million contract amendment to continue production related activities including for the first two pre-production shipsets, the first for qualification and validation requirements and the other for installation on the first ship.

The first installation shipset is due for delivery in December 2009, with ship combat system level integration and testing commencing this year.

Of course CEA is not alone in the development of digital phased array radar and subsequent to the company's achievement in demonstrating its digital beamforming technology.

Almost a month later Lockheed Martin also successfully demonstrated digital beamforming capability to locate and track live targets with its Scalable Solid-State S-band Radar (S4R) engineering development model.

"Our S4R demonstration successes are quickly moving next generation radar technology - such as digital beamforming - from the laboratory to the fleet," said Carl Bannar, vice president and general manager of Lockheed Martin's Radar Systems.

"S4R will bring a huge radar technology leap to next generation multi-mission radars, ranging from littoral operations to ballistic missile defence."

Like its Australian counterpart, the S4R engineering development model is an active, electronically-steered digital array radar designed to be scalable to support multiple missions, including air surveillance, cruise missile defence, ballistic missile defence, counter target acquisition and littoral operations.

Inspiration
The digital array radar design is derived from the S-band antenna developed for the US Navy's next-generation destroyer.

The digital beamforming signal processor was derived from the Aegis Ballistic Missile Defense signal processor.

However, from the outset, CEA's phased array radar offered advantages in terms of scalability, and thus size and weight through their unique, modular, micro-wave tile design.

This tile is normally available as an 8x8 array of elements, providing full 3D capability suitable for shipboard or fixed applications.

32x2 array configuration is available for high resolution 2D requirements such as man-portable GSR or coastal surveillance systems and array face sizes can be constructed from the tiles to meet specific operational performance needs.

And costwise, CEA's active phased-array 3D radar is competitive with modern 2D radars.

But CEA is also developing other phased array radars including an L-Band long range surface search digital radar and of course AUSPAR.

AUSPAR is a highpowered version of the CEAFAR architecture.

The purpose of the AUSPAR program (Phase 5B of SEA 4000) is to undertake further development of CEA's advanced scalable radar technology so that it can be used in medium to long range air warfare, and potentially demonstrate its capability for meeting theatre ballistic missile defence requirements.

A Project Arrangement for the Australia/US Phased Array Radar (AUSPAR) Project between the US and Australia was signed on 21 April.

According to questions we originally put to Defence the AUSPAR program aims to develop innovative radar technologies with the potential to contribute to future advanced radar programs in Australia and the US.

We understand that USN program funding will match that of Australia and is for an initial three years.