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Stratosphere Troposphere Radar
Medical Electronics

ST Radar is clear air weather radar operating at 212.5 MHz, has been established at GauhatiUniversity Campus (26.140N, 91.730E, 50 mts above MSL) by SAMEER, Mumbai. It is the world’sfirst system with cutting edge indigenous technology in 200 MHz band with open configuration(Antennas, T/R Modules and Cables placed in the open field) wherein active phased arrayconcept has been used. It is a coherent pulsed Doppler radar operating in Doppler BeamSwinging (DBS) mode. It consists of 576 antenna elements arranged in a circle with squaregrid. Each antenna is connected with its own Transmit-Receive Module (T/R Module) togenerate high quality wind data (wind speed and its direction) with high spatial and temporalresolution on continuous basis.
This data when fed to weather numerical models or similarnumerical models would lead to forecasting and nowcasting of atmospheric phenomena innorth east region will be helpful to various sectors such as meteorology, agriculture & civilaviation, disaster management etc. The Radar will be utilised extensively byuniversities/research laboratories in North-East region of India and will train manpower in thearea of atmospheric science and RF technology.

System Description

The block diagram of ST radar shows the various sub-systems of the radar and how they areinterconnected. System works on 3 phase 415V AC 50 Hz electric supply. Then electric supplyis connected to four UPSs which in turn are connected to 12 numbers of high power AC-DCsupplies (48 V DC) placed in four Sub-Control Rooms. 48 V DC supply is routed from thesecontrol rooms to antenna array to power 576 T/R modules. Mains supply is also carried tofifth Sub-Control Room known as Master Control Room (MCR) where it connects to the fifthUPS. Its output gives supply to radar controller, radar display unit, digital receiver & excitersub-system and digital receiver interface (DRI) unit.

SYNC and CAN signals are distributed from MCR to four Sub-Control Rooms and then toAntenna Array to feed each of 576 T/R Module units. CAN provides connectivity betweenRadar Controller and 576 T/R Module Controllers (TRMC) sitting in each T/R Module. Theradar parameters are downloaded to each TRMC by Radar Controller over the CAN interface.Each TRMC has an FPGA which generates all the control signals for that T/R Module. The SYNCSignal is generated by FPGA in the Digital Receiver. Sync Signal is like an IPP with a width of1µs and variable PRF. TRMC signal generation starts after sync signal. SYNC signals aredifferential signals and routed to each T/R Module separately.

System clock is 10 MHz OCXO which is used as reference source. It locks 212.5 MHz PLL whichis amplified and fed to 576 T/R Modules through chain of power divider/combiner networkplaced in the Antenna Array field. During reception, signals are combined coming out of thereceive section of T/R Module through the same set of power dividers/combiners and fed todigital receiver through DRI unit for further processing. The digital receiver generates I andQ signals at base band level and the same is decoded, in case of coded transmission,coherently integrated and spectral estimation is done using FFT techniques in real time toestimate the three spectral parameters viz., received power, Doppler and spectral width.The data is displayed on a high end graphical work station. Graphical Display of wind data isshown in standard display formats. The Radar controller is the interface between operatorand the Radar. It generates the operating parameters of the wind profiler, selects the beampositions and sets the Radar for collecting the data in different operating parameters. 


ST Radar specifications:

Type of System 576 element Active Phased Array with T/R Modules
Frequency 212.5 MHz
Bandwidth 4 MHz
Antenna Element Four element Yagi-Uda Antenna
Antenna element gain 7.9 dBi
Height Coverage 500 m to 20 kms (Depending upon Cn2)
Range Gates 256 (programmable)
Modes of Operation DBS
Height Resolution ~ 75 m to 300m (Programmable)
Antenna Area 572 m2 (Aperture Diameter 27m)
Effective Apperture  522 m2
Array Beam width ~ 3.20 nominal
Antenna Array gain 34.5 dBi nominal
Off -zenith angle 00 to 200 in steps of 10 (Programmable)
Azimuth angle 00 to 3600 in steps of 10 (Programmable)
Pulse width 0.5 to 64 µs
Modulation Binary phase shift keying (BPSK) coded compression
Code Complimentary code / Barker Code
Baud 0.5 to 4 µs
Pulse repetition frequency (PRF) 250Hz to 5KHz
TRM peak power 400 W (Typical per element)
Total peak power 230.4 kW
Duty ratio Up to 10% (Max)
Peak power × Effective Aperture
product (PAP)
~ 1.2 × 108 Wm2
Receiver Noise Figure 3.0 dB
UVW Components of Wind
Colour coded Power spectra plots
Block Diagram
ST Radar Subsystems
  • Antenna Array and RF and Control Feeder Network
  • Transmit Recieve Modules and its Local Controller
  • Digital Reciever
  • Signal Processing
  • Radar Controller
  • Power Supply, CAN & SYNC Signal Distribution
Antenna Array
Transmitter Reciever (T/R) Module
Control Racks
Power Divider/ Combiner
Digital Reciever
Radar Controller

Color Coded power spectra

Actual Result image

Normal Power Spectra observed

Customised mechanical

Graphical User Interface

MW based bamboo straightening
Typical Applications
  • Meteorology
  • Input for Weather Prediction
  • Disaster Management
  • Civil Aviation
  • Ionospheric Studies, Atmospheric Research
  • Study of Precipitating Clouds