Journal: Micromachines

Article Title: Spectrum Fitting Approach for Passive Wireless SAW Sensor Interrogation Using Software-Defined Radio

doi: 10.3390/mi16060656

Figure Lengend Snippet: ( a ) A single-cycle 10.100 M Hz quadrature sinusoidal signal with exponential decay envelope employed in the simulation. ( b ) FFT spectrum of an 8192-point concatenated time-domain signal incorporating random amplitude noise and random frequency deviation: raw data, filtered output, and fitting results.

Article Snippet: Taking the logarithm of the spectral amplitude yields a downward-opening parabola: (6) ln p ( f ) = − 1 2 ln ( 2 π σ 2 ) − ( f − μ ) 2 2 σ 2 Therefore, performing a quadratic fit on the logarithmic spectrum, the parabola vertex corresponds to the mean μ , which in turn represents the estimated frequency f 0 ^ . visualizes the theoretical analysis above, where a is a single-period 256-point 10.100 M Hz quadrature sinusoidal signal with an exponentially decaying envelope generated in MATLAB R2022b that simulates the SAW echo signal in IF band, and b is the FFT spectrum of the 8192-point concatenated signal; each segment of the concatenated signal incorporates random amplitude noise and random frequency deviation.

Techniques: