Direction Measurement in Air Using Sensitivity Compensated Signal and Pulse Compression
Dai Chimura, Ryo Toh, Seiichi Motooka · 2013
Ultrasonic pulse-echo method is widely employed for acoustical measurement in ocean or remote sensing in air such as automobiles and robots.Time-of-flight (TOF) is usually employed for target ranging.In order to acquire TOF with higher accuracy, pulse compression method is usually employed.For high-resolution measurement, frequency-modulated (FM) signal is used as transmitting signal.However, owing to sensitivities of the ultrasonic transducers, the spectrum of the received pulse echo signal will be uneven and narrow-banded.In order to acquire the received pulse echo signal with broader and flatter spectrum, we have proposed sensitivity compensated (SC) transmitting signal.The SC transmitting signal is calculated from the inversed spectrum of a measured signal, which is mainly influenced by sensitivities of the ultrasonic transducers.Using the SC signal as transmitting signal, it is expected that the signal with broader and flatter spectrum will be received.In this paper, the efficiency of pulse compression method using the SC signal for 2-D direction measurement is studied experimentally.A transmitter and two receivers are arranged for direction measurement.The direction of the target is calculated by measured TOF from two receivers.Comparison of the traditional linear FM transmitting signal (Chirp wave) and SC transmitting signal is discussed.The results of efficiency of pulse compression show that the pulse width of compressed signal derived by using SC transmitting signal is shortened to be about 1/5 of that by using the Chirp wave.The accuracies of direction measurement using SC signal are improved slightly than that of using the Chirp wave.