Fig. 1. Schematic diagram of I/Q mixer and diagram of zero-IF mixing. (a) Schematic diagram of I/Q mixer; (b) diagram of zero-IF mixing

Fig. 2. Simulation results of zero-IF quadrature modulation. (a) Amplitude and phase imbalances of I/Q signal; (b) frequency spectra of 20 RF signals after orthogonal demodulation

Fig. 3. Schematic diagram of microwave photonic orthogonal demodulation based on TODL

Fig. 4. Conversion loss of microwave photonic link. (a) Conversion loss versus amplitude of LO signal when intensity of RF signal is 5.5 dBm; (b) conversion loss versus amplitude of RF signal when intensity of LO signal is 8.8 dBm

Fig. 5. Test results of amplitude and phase consistency of devices in I/Q links. (a) (b) Low-pass filter; (c) (d) PD; (e) (f) ADC

Fig. 6. Experimental results of microwave photonic zero-IF receiver without IF amplitude/phase calibration. (a) Amplitude imbalance and (b) phase imbalance of I/Q link without calibration; (c) results of 20 different RF signals acquired by zero-IF acquisition; (d) image rejection of zero-IF receiver without IF amplitude and phase calibration

Fig. 7. Experimental results of microwave photonic zero-IF receiver after IF amplitude and phase calibration. (a) Amplitude imbalance and (b) phase imbalance of I/Q link after calibration; (c) results of 20 different RF signals acquired by zero-IF acquisition; (d) image rejection of zero-IF receiver