Vol. 1, Issue 4 (2017)
Performance of three different radiators of 8 X 8 Acoustic array antenna for Doppler Sodar
Author(s): KT Rao, V Naveen Kumar, Ganna Kiran, S Sreedevi, MP Rao
Abstract: The need for quality measurements of the wind profilers in the first 200m of the atmosphere for wind energy and other emerging areas applications demands new antenna for enhanced echo-signal intensity. This forces antenna designers to look for transducer systems with better conversion efficiencies and to seek for more versatile configurations. In the present experiment, an array antenna of size 8 x 8 with three different transducers is designed and fabricated for an operation frequency of 2 kHz. Basically, two types of transducers made with piezoelectric and neodymium materials are used. The models of Philips 1X9101 and Ahuja APT-165 belong to piezoelectric category and MA Audio MA588 to neodymium. The spacing between any two successive elements 0.5𝜆. The six elements at each corner of the planar array are removed as part of the optimization of the side lobe levels and the beam width of the main lobe. The antenna was systematically characterized, in an acoustic anechoic chamber, with respect to its axial and also studies transmit, receive conversion efficiencies and directional response. These measurements should be performed in free field conditions. The anechoic chamber at Naval Science and Technological Laboratories (DRDO), Visakhpatnam was used to conduct the measurements. A maximum intensity of 113 dB, 86.4 dB and 92.5 dB is observed at zenith angle at 2 kHz with a beam width of 160, 180 and 150 for Philips, Ahuja and M.A audio array antenna respectively. Among three antenna the MA588 antenna is suitable for profilers up to 500 meters of the boundary layer and capable of high power handling. Before installing the elements in the array, each element was individually characterized for its forward and reverse conversion efficiencies.