Photonic microwave frequency down-converter with image rejection via carrier suppression single sideband modulation and photonic microwave phase shift

The combined use of carrier suppression single sideband (CS-SSB) modulation and photonic microwave phase shift is described and analyzed to realize microwave frequency down-conversion with image rejection. Based on the idea of phase cancellation, the image signals have identical amplitude and opposite phase to be suppressed, while the useful signals have identical amplitude and phase through an electrical 90 degree hybrid to be strengthened. The approach is investigated in theory and demonstrated using simulation. It is shown that the power of the useful IF signal is nearly 60 dB larger than that of the image IF signal. Besides, the zero-IF receiving capability of our approach has been also investigated when a modulated RF signal with different format input. The 2.5 Gbit/s RF modulated signals centred at 15 GHz with quadruple-, 8-, 16- phase shift keying (QPSK, 8PSK, 16PSK), and 16-quadrature amplitude modulation (16QAM) formats are successfully demodulated with good error vector magnitudes (EVMs) and constellation diagrams in wide power range of input RF carrier.