Fig. 1. (a) Experimental configuration of photonic analog-to-digital conversion for X-band wideband signal detection. (b) Schematic of the relation between the wideband input signal and the aliased frequency in each channel. AMLL, actively mode locked laser; TWI-MUX, time-wavelength interleaving multiplexer; MZM, Mach–Zehnder modulator; DEMUX, demultiplexer; AWG, arbitrary waveform generator; PD, photo-detector; ADC, analog-to-digital converter.

Fig. 2. Simulated results of the X-band linear frequency modulation signal. (a) Temporal waveform. (b) Normalized short-time Fourier transform of the waveform in (a).

Fig. 3. (a) Normalized input and output microwave response of the PADC system. (b) Normalized FFT spectrum of the digitized data compared with the theoretical simulation and the effective microwave response.

Fig. 4. Working principle of the channel mismatch compensation algorithm for the wideband signal. TWI, time-wavelength interleaving; STFT, short-time Fourier transform.

Fig. 5. Experimental results. Normalized STFT spectra of the digitized LFM signal (a) before and (b) after mismatch compensation.

Fig. 6. Comparison between the instantaneous STFT spectra before and after channel mismatch compensation at the instantaneous frequencies of (a) 9 GHz and (b) 11 GHz.

Fig. 7. Characterized signal-to-distortion ratio (SDR) for different channel mismatches. (a) Channel mismatches after hardware adjustments and algorithmic compensation. (b) SDR measured from STFT spectra (dashed curve) and from the instantaneous spectrum at one specific frequency (dotted curve with symbols) after each step adjustment.