To increase signal-to-noise ratio(SNR)of medical ultrasound image

a frequency-modulated(FM)ultrasound transmitted imaging method is developed

where a weighted linear FM ultrasound is transmitted to enhance the emission energy without increasing the emission ultrasound pressure

and the image signal is formed by the demodulated ultrasound. Employing the impulse response model of ultrasound transducer and the modulating-demodulating principle of FM signal

the simulation for ultrasound imaging is carried out. The simulation results show that the SNR of the image formed with FM signal transmitting gets 10 dB higher than that formed with traditional pulse transmitting. By the aid of the self-designed FM signal transmitting ultrasound imaging experiment system

the B-mode ultrasound images of phantom are gained. The results reveal that the SNR is enhanced by 5-8 dB with the proposed method

which performs better with the increasing imaging depth.