RDM (Radar Doppler Multimode) can operate in several air-to-air, air-to-ground, and air-to-sea modes, and is standard fit in export Mirage 2000s. The Fr350 million (£33 million) development has been company funded. The first 50 French Air Force air-defence Mirage 2000s will have RDM, but the remaining 150 will have the RDI interception radar. Although RDI design is frozen, this radar will not enter service until 1986. RDI is French Government funded, and 30 per cent of the work is performed by Electronique Serge Dassault (ESD).
In addition to the 200 air-defence Mirage 2000s, the French Air Force expects to buy about 50 deep-penetration 2000Ns. These will carry Aerospatiale ASMP medium-range nuclear-attack missiles, and will have ESD Antelope V terrain-following radars.
RDM performance has been proven by five proto¬types and three pre-production radars—the first flew in January 1980. In air-to-air configuration the pilot selects Doppler or non-Doppler modes according to clutter level. Search patterns are conical "super-search", vertical search, and boresight aiming. The first two use a ±60° search pattern in elevation, and elevation is controlled manually for bore-sight aiming.
Assuming a four-bar search pattern over 120° in azimuth, 90 per cent of 5m2 fighter-aircraft targets will be detected out to 50 n.m. in clear air, according to Thomson-CSF. If a single-bar search pattern is used and azimuthal scan is reduced to 30°, clear-air range extends to 60 n.m. In pulse-Doppler mode, used for looking down into ground clutter, the RDM's range is 20 n.m. with a 120° search pattern.
Thomson-CSF points out that RDM gives an instantaneous range readout as soon as a target is detected. A pre-acquisition track-while-scan phase follows target detection, until the target is 35 n.m. away. Lock-on must be achieved 10 n.m. from the target, but track-while-scan is not available at short range or in pulse-Doppler mode.
For air-to-ground operation, RDM provides a ground map 30° to either side of its centreline. The optional Doppler Beam Sharpening (DBS) unit operates on a sector about 25° wide. As well as being used for inertial-navigation update and for ground-target ranging, RDM has a terrain-avoidance mode in which two clearance planes are shown on the head-down display. Thomson-CSF says that RDM will detect a patrol boat at 60 n.m. with a 120° search pattern when used in anti-ship mode.
RDM's coherent travelling-wave-tube transmitter operates in the X-band. The roll-stabilised inverted-cassegrain antenna has a 655mm diameter and a 3-6° beam-width. The receiver uses digital pulse-compression at long range and constant false-alarm rate digital processing at medium and short ranges. The 245kg weight is distributed among ten line-replaceable units (LRUs), including optional DBS and continuous-wave illuminator units- the latter is for use with the Matra Super 530 air-to-air missile.
Each LRU has its own built-in test equipment, and can be replaced without wire connections or adjustments to the rest of the radar. Thomson quotes 13,000 direct man-hours to produce RDM, leaving out management time.
RDI and RDM installations are interchangeable but they have little in common electronically. RDI uses a higher pulse-repetition frequency for its dedicated interception role. Maximum clear-air range against a head-on fighter target is about 66 n.m., but the RDI's major performance improvement compared with RDM is when looking down. Here, range is between 18 n.m. and 50 n.m., depending on closing speed and degree of clutter.
RDI has taken three years longer to develop than RDM, mainly because of the small space available in the Mirage 2000. This has necessitated the introduction of more hybrid circuits in RDI, but the new, smaller RDI has beer flying since last autumn Thomson now has to validate the tests and get RDI into production.
AA Lookup modes
1 Master oscillator
2 Power supply
3 Data processor
4 Doppler beam-sharpening unit (option)
5 X-band transmitter
6 72MHz shift unit
7 Continuous-wave illuminator (option)
8 Air-to-air receiver/processor
9 Air-to-ground receiver/processor
10 Antenna servo mechanism
11 Inverted-cassegrain antenna
Serval (Systeme d'Ecoute Radar et de Visualisation de l'ALerte) RWR is used on the Mirage 2000. It uses crystal video receivers, covering the E-J bands, and a hybrid analogue-digital processor. Two receiver blocks are in the wingtips, a block is mounted in the tip of the vertical tail, with an omnidirectional low band receiver below the aircraft.
Serval shows target type and direction on a CRT display. It gives a rough range indication from recieved signal strength.
Thales have developed an improved version (Serval NG-D) that uses new software algorithms (involving micro-variations in received parameters )to give accurate range measurement.