Fig. 1. Diagram of system structure

Fig. 2. Diagram of FPGA and its peripheral circuit

Fig. 3. (a) Waveform of original signal; (b) waveform of down conversion signal

Fig. 4. Principle of IQ demodulation

Fig. 5. Diagram of IQ demodulation module of FPGA

Fig. 6. Verification of IQ demodulation of FPGA

Fig. 7. Software flow chart of DSP

Fig. 8. Location curve

Fig. 9. (a) Original image; (b) intercept image

Fig. 10. Image enhancement. (a) Original image; (b) mean filtering; (c) Laplacian sharpening; (d) image after enhancement

Fig. 11. Images of binaryzation, expansion and corrosion of (a)-(c) PZT vibration images, (d)-(f) vibration images when car is passing through and (g)-(i) artificial disturbance images

Fig. 12. FDR of each feature

Fig. 13. Model of BP neural network