Distortion Estimation of SAW Time Inversion System Based on Delta Function Approximation

Time inversion can be obtained using surface acoustic wave (SAW) devices with no more than two chirp filter elements. This time inversion method is based on the fact that the Fourier transform of a linear frequency modulated (FM) signal, whose envelope is modulated by a given time function, has (approximately) the time-inverted function as its amplitude. The different distortions inherent in the method are discussed. Procedures are suggested to eliminate some of these distortions, while others, inherent due to the approximation used, are estimated. It is shown that the average of the output distortion is upper-bounded by w2/16μ, where w is the signal bandwidth and μ is the chirp filter's dispersive slope. Simulation results supplement the analysis.