Reconfigurable high-resolution photonic fractional Fourier transformer for broadband frequency measurement and large-scale chirp rate characterization of microwave signals

Abstract A reconfigurable photonic fractional Fourier transformer is proposed to realize broadband frequency measurement and large-scale chirp rate characterization of microwave signals with a high resolution. This scheme is based on three parallel frequency-shifting loops (FSLs) with co-prime free spectral range (FSR). Tunable high-resolution fractional Fourier transform is achieved through simply changing the frequency shift in each FSL with a small FSR, and large unambiguous frequency and chirp rate measurement range are guaranteed by the proposed recovery algorithm. In the numerical verification, non-aliasing frequency measurement range up to 14.7404 GHz and unambiguous chirp rate characterization range from -4.35 × 105 to 4.35 × 105 GHz/ μ s are obtained by using three FSLs with FSRs of 17.13 MHz, 17.21 MHz and 17.39 MHz, where the frequency resolution and the chirp rate resolution are 139.12 kHz and 0.3356 GHz/ms, respectively. Through properly setting the FSR in each FSL, the frequency and chirp rate measurement range can be further improved, which can find application in electronic warfare to achieve microwave signal recognition