Of new radar technologies and their future applications
Air Cmde Trilok Chand (Retd)
The last two decades saw the greatest strides in the development of Information and Communication Technologies (ICT), especially for commercial use. Radar and related technological development pace, on the other hand, remained slow mainly due to their highly specialised applications and higher cost involved in hardware and infrastructure associated with these systems. Of late, the situation has changed dramatically, as many ICT applications have found their way into radar systems.
Advancements in nanotechnology and semiconductors have also contributed to miniaturisation and diversified utilities of the radar. Most radar applications are of dual-use in nature. Any radar designed for surveillance, weather, navigation and landing use can also be used for early warning, battlespace weather forecast, mission planning and recovery of military aircraft. Exclusive military applications such as tracking, fire control, identification of Friend and Foe (IFF) are also revolutionised equally by the newer radar technologies.
Basic radar range equation in its new avatars continues to inspire new design and innovations of both commercial and military radars. Important new radar technologies such as Multiple Inputs, Multiple Output (MIMO) systems, Digital Beam Forming (DBF) techniques, Active Electronically Steered Array (AESA) radar, millimetre wave radar, Passive Coherent Location Radar (PCLR) Systems, semiconductor Power Amplifiers (PA), Intelligent signal coding and radar Digital Signal Processing (DSP) have inspired many modern radar designs in recent times.
Multiple Inputs, Multiple Output Radar
MIMO radar technology has evolved from communication systems where it has been used for improving the coverage area and signal quality. MIMO radars simultaneously radiate uncorrelated signals, with orthogonal polarisation. This improves the coverage and the received signal quality. The decorrelation of each transmit signal is important for picking up small targets at long distances. A decorrelation of about 70 decibels can be possibly achieved through proper modulation. The newer generation of Synthetic Aperture Radar (SAR) system makes use of multiple elevations and azimuth receiver channels combined with digital beam forming (DBF) capability. This allows for the synthesis of multiple digital receiver beams for improved signal discernment and reduced noise figure.
Digital Beam Forming Technique
The Digital Beam Forming (DBF) is achieved by transmitting and receiving multiple independent weighted beams formed by an array of antenna elements. The received signals of each antenna element are down converted from analogue to digital form and stored in a memory. From the memory, an arbitrary number of beams can be digitally processed simultaneously. The major advantage is that the large beam coverage can be simultaneously processed to form multiple beams. Thus, DBF could be used for achieving higher angular resolution and wide coverage without mechanical moving parts in modern radars.
Active Electronically Steered Array Radar
AESA radar technology employs new generation of Trans-Receive (TR) modules which are highly capable Software Defined Radios (SDR) that can also be used for radio communication with very high data rates. AESA radar is exceedingly being used for the upgrade and replacement of erstwhile radar technology. The AESA design uses modular concept and thus enhances reliability. A failure in the critical TR module will not make the whole radar unserviceable and the system could be restored by replacing the module in very little time.
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