Generation of frequency tripled and quintupled PSK millimeter wave signal without phase multiplication employing parallel phase modulators

摘要

The scheme of frequency tripled and quintupled phase shift keying (PSK) signal without phase multiplication based on two parallel phase modulators (PM) is proposed. To eliminate the impact of the reduction of the vector signals' Euclidean distance induced by the phase-precoding, a novel phase precoding method is proposed and applied to the original PSK signal. A phase-precoded PSK signal with the same amplitude, same carrier frequency but opposite phase compared with the original PSK signal is generated and modulates the optical carrier via one PM. The original PSK signal modulate the same optical carrier via the other PM. A pair of proper harmonics from the output of the PMs is selected by the wavelength selective switch (WSS). Then the optical millimeter wave (MMW) signal is injected into the fiber. After certain distance of the fiber link transmission, the desired MMW PSK signal is generated after the Photodiode (PD) detection. To verify the feasibility of the proposed scheme, a radio over fiber (RoF) system with 1 Gbit/s rate data has been implemented and the tripled and quintupled frequency of QPSK signal has been generated by numerical simulation. The error vector magnitude (EVM) of the 60-GHz and 100-GHz QPSK signal has been measured versus the transmission distance of the fiber link and the launched power into PD with the optical signal noise ratio (OSNR) of 15 dB and 18 dB respectively. And the result shows that the proposed MMW PSK signal generation scheme could realize tripled and quintupled frequency upconversion of the QPSK signal and reliable transmission at least 80 km when the launched power into PD is higher than -5 dBm.