Photonic generation of binary differential phase-coded microwave signals

A scheme for photonic generation of binary differential phase-coded microwave signals is proposed and demonstrated. In the proposed system, two optical sidebands are generated and phase modulated by an electrical signal. Then, the two optical sidebands are separated by a Mach-Zehnder interferometer (MZI) and properly delayed between each other before combined at an optical coupler. By balanced photodetection after the optical coupler, a binary differential phase-coded microwave signal is generated. The carrier frequency of the generated signal is doubled compared with the signal source in the system, thus the requirement for high frequency electrical devices is relaxed. The proposed system is the first microwave photonic signal generator with differential phase coding, which can find applications in radar and communication systems.