Performance analysis for the ultrasonic spread spectrum ranging system excited with pulse codes

There are two major problems in a multi-channel ultrasonic ranging system, one is the crosstalk phenomenon, and the other is the contradiction between effective ranging distance and ranging resolution. To solve these two problems, spread-spectrum technology and coding method are applied to the ultrasonic ranging field. In this paper, six kinds of pseudo-random binary codes, combined with three types of binary modulation technique, are used to construct eighteen kinds of pulse-coded digital-modulation excitation sequences. In order to evaluate the performances of each kind of excitation sequence, four indexes, which are correlation degree of echo sequences, main-lobe width of auto-correlation function, energy and energy efficiency of excitation and echo sequences, are analyzed via experiments. Results show that the six applied pseudo-random codes, especially the chaotic, Gold and m sequences, achieve outstanding comprehensive performances both in correlation and energy characteristics when modulated by binary frequency shift keying (BFSK).