Estimation of receiving waveform of ultrasonic aerial back sonar calculated by finite difference time domain method

In order to develop a high-performance aerial back sonar for a car, we predicted the waveforms of the received pulse using the finite difference time domain (FDTD) method. The echo pulses reflected from the target were calculated as a function of the target's height in air at an inhomogeneous temperature. The maximum amplitudes of the pulse train changed with the target's height. The amplitude and propagation time of the reflected pulse markedly differed with shape of targets at a constant temperature. The result shows that an aerial sensor should be able to detect a square target at an inhomogeneous temperature such as that in summer. However, it is very difficult to detect a slanted target.