Photonic implementation of a switchable dual-channel single-sideband mixer without optical filters

A dual-channel single-sideband mixer with high spurious suppression, high channel isolation, and wide operational bandwidth is proposed. The scheme employs a dual-polarization dual-drive Mach-Zehnder modulator (DPol-DDMZM) to simultaneously modulate two independent radio frequency (RF) signals. Carrier suppression for both RF signals with different power ratios is achieved by adjusting the polarization angle of the local oscillator (LO). Switching between up- and down-conversion within each channel is controlled by the phase difference of the corresponding RF input, allowing independent channel operation. Output channel selection is realized by tuning the parameters of a polarizer. Simulation results show that the system achieves a spurious suppression ratio exceeding 29.63 dB and channel isolation above 30 dB, demonstrating high spurious rejection and isolation. When driven by a 250 MHz 16-quadrature amplitude modulation (16-QAM) signal, the mixer achieves an adjacent channel power ratio (ACPR) up to 45.6 dB and a minimum error vector magnitude (EVM) of 0.9%. Furthermore, by adjusting the polarization controller within a ±0.4^∘ range, carrier suppression better than 56 dB is maintained for two RF signals with a power ratio of up to 16 dB, demonstrating robust performance under imbalanced received signal conditions.