SMART-L
The SMART -L ( Signaal Multibeam Acquisition Radar for Tracking, L band ) is a rotating wide-range radar with the former Dutch manufacturer Hollandse Signaalapparaten ( Signaal ) phased array antenna, now Thales Naval Nederland. The elevation angle in the passive phased array radar was explicitly designed to locate stealth aircraft.
The SMART -L is based on the SMART family, more precisely formulated SMART -S Mk2. However, only the dimensions of the rigid, radar signature optimized antenna surface were taken and the antenna mass of about 1000 kg. SMART L uses a lower frequency and a different arrangement of the antenna elements. The Koninklijke Marine awarded on 24 July 1991, development and production contract, September 1995 began testing. The first betting industry since 2002, the De - Zeven - Provinciën class.
Meanwhile, with the S1850M an improved version with higher transmission power available, which was first used in 2008 on the Horizon class. Both models were also exported.
Technology
Generally
The antenna having the dimensions of 8.2 x 4 m composed of 24 stacked rows of receiving modules. The number of modules per row can be determined from low-resolution images to 49 at the SMART -L. Of these 16 rows can both transmit and receive, receive the remaining only. The radar used to send the chirping D- band (1-2 GHz) solid-state transmitter ( D- SSTX ) of the LW -09 radar. The transmitter module of 16 parallel connected units generates a peak power of 4 kW, which is then amplified in 32 power amplifier modules for 100 kW peak power. These systems are located in the superstructure under the radar; The signal then passes through a waveguide to the antenna. There is emitted via digital phase shifter. By the phase control of the transmitting power of both the vertical beam steering as well as an antenna stabilization is achieved. The opening angle is in normal operation, in azimuth 2.2 °. In the burn- through mode, the energy is more focused on the source location, the opening angle is then ( nonsensical ) be 8 °. The SMART -L sends exclusively with medium pulse repetition rates.
The signals of all 24 input lines through the phase network, each row is thereby down-mixed by means of a surface acoustic wave filter and the pulse is compressed, and then digitized by an analog -to-digital converter of 12 bits and 20 MHz. The data stream is then modulated onto an optical signal, and passed through an optical rotary joint in optical receivers. Here, the data of a fast Fourier transform to be subjected to digital to allow beamforming. This produces a graduation of 14 different virtual signal lobes in the range of 0 to 70 °, to be processed in parallel receiving channels 24, one for each row. Furthermore, two more virtual signal lobes produced below the horizon. The signal lobes have an opening angle of 6-6.5 ° to assign a target of 14 elevation angles. To allow an accurate determination of the elevation angle of the targets, the results are interpolated between the signal beams. The elevation angle can be determined to 1 to 3 mrad ( 0.06 ° to 0.17 ° ) exactly. Since the antenna only with 12/min about its vertical axis rotates but otherwise is rigid, the rolling and pitching is compensated electronically.
Signal processing
The simultaneous observation of the entire elevation range, together with the average pulse repetition rates that the lighting is sufficient time to discover all the targets with sufficient radial velocity component up to the maximum indicated range without gaps in the field of view arise. The directional characteristic of electronically generated corresponds approximately to a cosecant square diagram. The radar created when looking for a Clutter and Jammer card to detect and track targets with a radar cross section of well below 0.1 m can. In this case, radar pulses from the horizon to be evaluated without ascending moving target indication, and the first echo for Clutterkarte used. In angles without or with little clutter Doppler filter bank is used to detect targets with a radial velocity of zero. Furthermore, a Jammer map is created, details, were not disclosed. It is conceivable that the interferers are identified and targeted as well as a distance estimation is performed. The radar is always chosen the least perturbed frequency. The influence of EloGM can be reduced by placing the signal processing by Adaptive nulling zeros into the antenna pattern to hide interferers.
In order to better detect low-flying aircraft, a multipath is used by the receiving signals below the horizon. A destination is made by the radar beam, a part of the radar energy is reflected by the shape of the target air towards the floor. If it hits the ground ( earth or water surface) and then passes through reflection or diffuse scattering in the antenna, the signal processing can use this information to determine the target position. For this, the two virtual signal lobes can be used below the horizon, as well as two on to correlate the results of the four lobes, so that the fluctuation of the elevation angle may be calculated out by the multipath.
The performance of the radar makes high demands on the signal processing: Since the SMART -L stealth objectives is to locate the antenna is so sensitive that virtually every radar echo contains a Doppler shift. Then there is the problem that in addition to the clutter also mainly birds be located at a great distance. To avoid overloading the Plotextraktors by false targets, air targets in 1000, 100 surface targets and 32 jammer can be pursued simultaneously. The target correlation to tracks from scan to scan is done on the distance and radial velocity of the contact by Multiple Hypothesis Tracking ( MHT). Areas where speed and distance can not be measured (due to clutter, EloGM ) are considered. The MHT filter calculates all plausible flight paths based on the contacts, the most likely hypotheses are passed on to the combat system of the ship.
Are target position and course determines a friend or foe according to STANAG 4182 can be carried out. As this takes place also in the L-band, no separate antenna is needed. If the friend - foe identification is negative, the SMART -L can be determined by non-cooperative target identification the type of aerial target. Details can not be given, however, L -band data for High Range Resolution ( HRR ) were collected at NATO level. Use of Inverse Synthetic Aperture Radar ( ISAR ) fails due to the rotating antenna. SMART -L has been developed as a hands -off system (in principle) only one mode of operation, in practice, there are three selectable modes:
- Local Area: Anti- Stealth Mode, with low transmission power close to the ground, and maximum transmission power at higher elevation angles.
- Long Range: Mode for conventional targets, with high transmission power close to the ground wgn. Scattering losses in multipath, and low transmission power at higher elevation angles.
- Burn Through: ECCM mode, the radar energy maximum available is more focused to achieve maximum effective radiated power.
In the long term nor a Ballistic Missile Defense mode are integrated, the antenna pattern should then be directed upwards. The radar can reduce its emissions in certain sectors, in order to avoid discovery.
Range
Thales announced at the European Radar Conference ( Eurad ) 2004 Burn -through range of 280 km against a fighter aircraft under noise disturbances, and 225 km against low-flying aircraft in the same situation. The size of the radar cross-section, and the amount of interference energy have not been published. According Signaal a target, the SMART -L with a radar cross section ( RCS) of 0.001 m² to 65 km locations. Due to the radar equation is thus:
- 0,001 m² to 65 km
- 0.01 m to 116 km
- 0.1 m to 206 km
- 1 m to 366 km
The S1850M is higher by 7% range, see below. In this unspectacular at first glance, however, the manufacturer values and apologists of stealth technology must be taken into account, only specify the smallest RCS of an aircraft, at an optimal angle and frequency. The F-117 was, for example, a frontal RCS of 0.025 m in the X band (8-12 GHz). At low frequencies ( long wavelength) radar absorbent materials and design are increasingly ineffective. Measurements of models German Aerospace for the F -117 was a frontal radar cross section of 6-10 dBsm (4-10 m ) in the VHF band, and about 6 determine dBsm (4 m²) in the UHF band. L-band about -6 dBsm (0.25 m ) were measured again.
Variants
- SMART L: standard version as described above. The displayed range is 400 miles and was supported by the Extended Long Range ( ELR) software update increased to 480 km, in order to detect ballistic missiles earlier can. Signed in 2007, the Defence Procurement Agency of the Netherlands with Thales a contract, according to which the displayed range should be increased to 1000 km, and the radar is optimized for ballistic missile defense.
- S1850M: From BAE Systems and Thales improved version with the original name Smartello. The L- band solid-state transmitter was acquired by Marconi Martello, which is slightly more powerful 132 kW. Due to the radar equation can thus greater by 7% range are calculated. The rest is the same as the SMART -L.