PSI - Issue 84

Donato Fiore et al. / Procedia Structural Integrity 84 (2026) 417–424

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Fig. 2. Range bin.

The radar emits continuous electromagnetic waves and processes their reflected phase to detect displacements between each measurement. The system operates on the Stepped Frequency - Continuous Wave (SF-CW) principle, generating high-resolution one-dimensional images through frequency variation (Fig. 3).

Fig. 3. Stepped continuous frequency diagram.

Measurement accuracy depends on the signal-to-noise ratio, with achievable precision around 0.001 mm in perfect condition, although theoretical limits are not always reached and it is advisable to consider a precision around 0.01 mm depending on distance and SNR which represent reflectivity level of the structure (Fig. 4).

Fig. 4. Measurement accuracy plot as a function of signal-to-noise ratio (SNR) in dB. In general, each corner of discontinuity of the infrastructure can be a reflection point but if necessary, additional target (corner reflector) can be added to increase reflectivity or to detect displacement at a particular point. The obtained results demonstrate the method's capability to identify, through the measurement of resonance frequencies at multiple points (range-bins) along the viaduct, the following deformation parameters: real time displacement, vibration