ATMEGA ULTRASONIC RANGE FINDER FAKHRUL ADLEE BIN ...

356.1.1 Radiation PatternAll ultrasonic sensors have their specific radiation pattern associated with it.Thisacoustic radiation pattern is a function of spatial angle called beam angle. Beamangle, Ωis defined as the total angle between the points at which the sound powerreduces to half its peak value, commonly known as 3 dB points. The spot diameter ofthe beam can be formulated as :D = 2R tan (0.5 Ω)D = spot diameter in centimeters.R = target range in centimeters.Ω = beam angle in degrees.At minimum range, R = 50 cm and Ω = 30º.D = 2 * 50 * tan (15º) = 26.795 cm.At maximum range, R = 400 cm and Ω = 30º.D = 2 * 400 * tan (15º) = 214.359 cm.Radiation pattern consists of a main lobe and side lobes. Radiation power isdominant mainly in the front region of the sensor, so as to say that the main lobe isdirectly in front of the sensor, followed by side lobes sidewise with null region inbetween these lobes. Radiation pattern is mainly determined by factors such as thefrequency of operation and the size, shape and acoustic phase characteristics of thevibrating surface. The beam pattern of the transducer is independent of its nature as atransmitter or receiver.