Lower Wind Atmospheric Profiler

The lower atmospheric wind profiler also known as the Boundary layer radar is a coherent pulse Doppler phased array radar operating at 1357.5 MHz with a peak power of 1 kW. The phased array consists of 576 antenna elements arranged in a 24 x 24 matrix over an area of 3.8 m x 3.8 m. This system was installed by CRL, Japan, under the Indo- Japanese collaboration program, as part of the ground validation of the TRMM program.

The antenna elements are circular micro strip patch type with coaxial feed. The array is energized by a 1kW solid state power amplifier through a beam changer switch and hybrid circulator. The 1 kW peak power is delivered by a parallel array of four outputs from the solid-state power amplifier, each feeding 250 W to one quadrant of the array. The required reference IF and LO waveforms are generated using the crystal oscillators and PLO sections. The up conversion is carried out within the transmitter unit. The power distribution across the array is tapered to obtain better sidelobe suppression. The array generates a radiation pattern with a beam width of about 4.5o and a side lobe level of –25 dB. This radar uses a fixed sequence of three beam directions in a cyclic manner: 15o due North, 15o due East from Zenith and Zenith.

The echo received by the antenna array from the atmosphere is delivered to the receiver via the circulators. The receiver is a phase coherent heterodyne type having quadrature detector at the final output and delivers the video outputs to the signal processor. The signal processor and the data processing units together acquire the analog video signals, process the received data, and also facilitate the control of the radar subsystems by setting experimental parameters and generating the necessary timing control signals. Data acquisition and signal processing system features same as that of MST radar

LAWP supports observation from 450 m to 4 km during clear air condition with range resolution of 150 m. LAWP is a potential tool to carry out studies related to the atmospheric dynamics and waves in the lower atmosphere, boundary layer, precipitation etc.

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