SMART-L

SMART-L on board the Hessen (F 221)

The SMART-L (Signaal Multibeam Acquisition Radar for Tracking, L-Band ) is a rotating wide-range radar with phased array antenna from the former Dutch manufacturer Hollandse Signaalapparaten (Signaal), now Thales Naval Nederland . The radar, which is passive phase-controlled in the elevation angle, was developed specifically to locate stealth aircraft .

The SMART-L is based on the SMART family, more precisely formulated the SMART-S Mk2. However, only the dimensions for the rigid, radar signature-optimized antenna surface and the antenna mass of around 1000 kg were adopted. The SMART-L uses a lower frequency and a different arrangement of the antenna elements. The Koninklijke Marine awarded the development and production contract on July 24, 1991, and tests began in September 1995. The first operational platform has been the De Zeven Provinciën class since 2002 .

In the meantime, an improved version with higher transmission power is available with the S1850M , which was first used in 2008 in the Horizon class . Both models were also exported.

technology

General

F221 Hessen of the Navy with the SMART-L-Radar (the black rectangular antenna in the foreground)

The antenna with the dimensions of 8.2 × 4 m consists of 24 rows of receiving modules stacked on top of each other. With the SMART-L, the number of modules per row can be determined from poorly resolved images as 49. Of these, 16 rows can both send and receive, the rest can only receive. The radar uses the chirping D-band (1–2 GHz) solid-state transmitter (D-SSTX) of the LW-09 radar to transmit . The transmitter module, made up of 16 units connected in parallel, generates a peak power of 4 kW, which is then amplified in 32 power amplifier modules to 100 kW pulse power. These systems are located in the deck structure under the radar; the signal then travels through a waveguide to the antenna. There it is emitted via digital phase shifters . The phase control of the transmission energy achieves both vertical beam pivoting and antenna stabilization. The opening angle in normal operation is 2.2 ° in azimuth. In burn-through mode, the energy is focused more strongly; depending on the source position, the opening angle should then be 8 °. The SMART-L only transmits with medium pulse repetition rates.

The signals of all 24 input rows pass through the phase network, each row is mixed down with the help of a surface acoustic wave filter and pulse compressed, and then digitized by an analog-digital converter with 12 bit and 20 MHz. The data stream is then modulated onto an optical signal and sent to optical receivers via an optical rotary transmitter. Here the data is subjected to a fast Fourier transformation to enable digital beamforming . This creates a graduation of 14 different virtual signal lobes in the range from 0 to 70 °, which are processed in parallel in 24 receiving channels, one for each row. In addition, two further virtual signal cones are generated below the horizon. The signal cones have an opening angle of 6–6.5 ° to assign the target to one of 14 elevation angles. The results are interpolated between the signal lobes to enable an exact determination of the elevation angle of the targets. The elevation angle can thus be determined with an accuracy of 1 to 3 mrad (0.06 ° to 0.17 °). Since the antenna only rotates around its vertical axis at 12 rpm but is otherwise rigid, the rolling and pitching is electronically compensated.

Signal processing

The Daring class is equipped with the more modern S1850M.

The simultaneous observation of the entire elevation range, together with the average pulse repetition rates, ensures that the illumination time is sufficient to discover all targets with a sufficient radial speed component up to the maximum displayed range without creating gaps in the field of view. The electronically generated directional characteristic corresponds roughly to a Cosecans² diagram . When searching, the radar creates a clutter and jammer map in order to be able to detect and track targets with a radar reflecting area of ​​well under 0.1 m². Radar pulses ascending from the horizon are evaluated without moving target indication , and the first echo is used for the clutter card. In angles with little or no clutter, a Doppler filter bank is used to detect targets with a radial velocity of zero. A woe card is also being drawn up, details of which were not disclosed. It is conceivable that the interferers are identified and targeted and a distance estimate is carried out. The radar always selects the least disturbed frequency. The influence of EloGM can be reduced by the signal processing using adaptive zeroing to set zeros in the antenna diagram in order to suppress interferers.

In order to be able to detect low-flying aircraft better, multi-path reception is used by receiving signals below the horizon. If a target is hit by the radar beam, part of the radar energy is reflected towards the ground due to the shape of the target. If it hits the ground (earth or water surface) and then reaches the antenna through reflection or diffuse scattering, the signal processing can use this information to determine the target position. For this purpose, the two virtual signal cones below the horizon and two above are used to correlate the results of the four cones so that the fluctuation of the elevation angle due to the multipath reception can be calculated out.

The performance of the radar places high demands on the signal processing: Since the SMART-L is supposed to locate stealth targets, the antenna is so sensitive that practically every radar echo contains a Doppler shift. In addition, there is the problem that, in addition to the disturbance data , mainly birds are located at great distances. To avoid overloading the plot extractor with false targets, 1000 air targets, 100 surface targets and 32 jammers can be tracked simultaneously. The target correlation to tracks is carried out from scan to scan via the distance and radial speed of the contact using Multiple Hypothesis Tracking (MHT). Areas in which speed and distance cannot be measured (due to clutter, EloGM) are taken into account. The MHT filter calculates all plausible traces of flight on the basis of the contacts, the most likely hypotheses are passed on to the ship's combat system.

Once the target position and course have been determined, friend-foe recognition according to STANAG 4182 can be carried out. Since this also takes place in the L-band, no separate antenna is required. If the friend-foe identification is negative, the SMART-L can determine the type of air target through non-cooperative target identification . Details are not given, but L-band data for High Range Resolution (HRR) were also collected at NATO level . The use of Inverse Synthetic Aperture Radar (ISAR) fails because of the rotating antenna. The SMART-L was developed as a hands-off system with (in principle) only one operating mode, but in practice there are three selectable modes:

• Local Area: Anti-stealth mode, with low transmission power near the ground and maximum transmission power at higher elevation angles.
• Long Range: Mode for conventional targets, with high transmission power near the ground because of. Scattering losses with multi-path reception and low transmission power at higher elevation angles.
• Burn Through: ECCM mode, the maximum available radar energy is more strongly focused in order to achieve the greatest possible effective radiated power .

In the long term, a ballistic missile defense mode is to be integrated, the antenna diagram should then be directed upwards. The radar can also reduce its emissions in certain sectors to avoid detection.

Range

S1850M on the HMS Daring (D32)

At the European Radar Conference (EuRAD) 2004, Thales stated a burn-through range of 280 km against a fighter aircraft under noise interference , and 225 km against low- flying aircraft in the same position. The size of the radar cross-section and the amount of interference energy were not published. According to Signaal, the SMART-L can locate a target with a radar cross-section (RCS) of 0.001 m² over 65 km. The radar equation thus gives:

• 0.001 m² over 65 km
• 0.01 m² over 116 km
• 0.1 m² over 206 km
• 1 m² on 366 km

The S1850M has a 7% longer range, see below. With these values, which at first glance seem unspectacular, it must be taken into account that manufacturers and apologists of stealth technology only specify the smallest RCS of an aircraft, with the optimal angle and frequency. The front of the F-117 , for example, had an RCS of 0.025 m² in the X-band (8-12 GHz). At low frequencies (long wavelengths), radar-absorbing materials and shapes become increasingly ineffective. Through measurements on models, Deutsche Aerospace was able to determine a frontal radar cross-section of 6–10 dBsm (4–10 m²) in the VHF band and about 6 dBsm (4 m²) in the UHF band. In the L-band, about -6 dBsm (0.25 m²) were measured from the front.

variants

• SMART-L: Standard version as described above. The displayed range is 400 km and was increased to 480 km by the Extended Long Range (ELR) software update in order to be able to detect ballistic missiles earlier. In 2007 the armaments procurement authority of the Netherlands signed a contract with Thales, according to which the indicated range is to be increased to 1000 km and the radar for defense against ballistic missiles is optimized.
• S1850M: Version improved by BAE Systems and Thales, originally named Smartello . The L-band solid-state transmitter was taken over from the Marconi Martello, which is slightly more powerful with 132 kW. Using the radar equation, a 7% greater range can be calculated. The rest is identical to the SMART-L.

Users

country	image	class	Type	Commissioning of the first ship	number	displacement	length	Remarks
Netherlands		De Zeven Provinciën class	frigate	2002	4th	6,050 t	144 m	Based on the Trilateral Frigate Cooperation
Germany		F124	frigate	2004	3	5,690 t	143 m	Based on the Trilateral Frigate Cooperation
South Korea		Dokdo class	Amphibious assault ship	2007	2	18,800 t	199 m
France / Italy		Horizon class	destroyer	2007	4th	7,050 t	152.87 m	Use of the S1850M variant
United Kingdom		Daring class	destroyer	2009	6th	7,350 t	152.4 m	Use of the S1850M variant
Denmark		Iver Huitfeldt class	frigate	2012	3	5,850 t	139 m
United Kingdom		Queen Elizabeth class	Aircraft carrier	planned for 2020	2	70,000 t	284 m	Use of the S1850M variant

Individual evidence

1. ↑ ^{a b c d e f g h i j} Gerrit Dedden (Thales Nederland BV): SMART-L Multibeam Radar . In: EURAD. First European Radar Conference, 11-15. October 2004 . 2004, ISBN 1-58053-993-9 , pp. 17-20 .
2. ^ ^{A b c d e f g h i} Norman Friedman: The Naval Institute Guide to World Naval Weapons Systems . US Naval Inst Pr, 2006, ISBN 1-55750-262-5 , pp. 262-263 .
3. ^ Norman Friedman: The Naval Institute Guide to World Naval Weapons Systems, 1997-1998 . US Naval Inst Pr, 2007, ISBN 1-55750-268-4 , pp. 316 .
4. ^ Phased Arrays and Radars - Past, Present and Future. (PDF; 1.0 MB) In: Microwave Journal. January 2006, accessed October 19, 2013 .  
5. ↑ SMART-L radar. In: Radar Tutorial. 2013, accessed October 19, 2013 .  
6. ↑ ^{a b c} SMART-L 3D Long Range Surveillance Radar. (PDF; 3.1 MB) In: Thales. October 19, 2012, accessed October 19, 2013 .  
7. ↑ Nicholas J. Willis, Hugh Griffiths: Advances in Bistatic Radar . Institution Engineering & Tech, 2007, ISBN 1-891121-48-0 , pp. 94-95 .
8. ^ Thales on track in TBMD. (No longer available online.) In: Thales. December 8, 2006, archived from the original on September 20, 2012 ; accessed on October 19, 2013 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
9. ↑ SMART-L For Smart Defense? (No longer available online.) In: Aviation Week. June 27, 2012, archived from the original on October 20, 2013 ; accessed on October 19, 2013 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
10. ↑ Eric Wertheim: The Naval Institute Guide to Combat Fleets of the World: Their Ships, Aircraft, and Systems . US Naval Inst Pr, 2007, ISBN 978-1-59114-955-2 , pp. 845 .
11. ↑ Martello S-723. In: Radar Tutorial. 2013, accessed October 19, 2013 .