Photonic generation of background-free frequency-doubled phase-coded microwave pulses with immunity to periodic power fading.

A novel (to the best of our knowledge) photonic approach for the generation of background-free frequency-doubled phase-coded microwave pulses with immunity to periodic power fading is proposed. By switching between the carrier suppressed double sideband (CS-DSB) modulation with reverse quadrature phase difference and carrier suppressed single sideband (CS-SSB) modulation, background-free phase-coded microwave pulses with frequency doubling of the local oscillator signal can be obtained. Thanks to the CS-DSB/CS-SSB modulation, the generated microwave pulses can be directly transmitted via single-mode fiber (SMF) without the influence of the periodic power fading. Since no filter is utilized, the proposed scheme owns a wide frequency tunable range. An experiment is conducted to verify the proposed approach. Two 1 Gbit/s phase-coded microwave pulses with center frequencies of 6 and 12 GHz are generated and successfully transmitted through a 25 km SMF. The pulse compression ratio and main-to-sidelobe ratio after the transmissions are measured as 13 and 8.84 dB, respectively.