In order to improve the transmission efficiency of ultrasonic guided waves in the rail

a method of optimizing the efficiency of piezoelectric ultrasonic transducer based on frequency tracking at the receiving end is proposed. Combining with the idea of variable step-size sweeping strategy

using the mechanism of pitch-catch

the amplitude and power spectral density of the received signal after frequency sweeping are analyzed by software in time domain and frequency domain. So that the optimal excitation frequency of piezoelectric ultrasonic transducer can be corrected in real time and the conversion efficiency of the transducer can be improved. Field tests are carried out at different distances of 50

100 and 200 m. The experimental results show that the optimal excitation frequency obtained after frequency sweeping is much higher than the series resonance frequency of 34 k Hz transducer

and the FFT amplitude and power spectral density（ PSD） of the received signals after frequency sweeping are all obviously increased. In particular

when the test distance is 50 m

the FFT amplitude and PSD of the central frequency is increased by 86. 17 % and 51. 04 %.