Dual-Output Microwave Photonic Frequency Up- and Down-Converter Using a 90° Optical Hybrid Without Filtering

Abstract

A dual-output microwave photonic frequency up- and down-converter using a 90° optical hybrid without filtering is proposed. By using a dual-parallel Mach-Zehnder modulator and a Mach-Zehnder modulator in parallel to realize carrier suppressed single sideband and carrier suppressed double sideband modulation, respectively, with a 90° optical hybrid and 90° electrical hybrid coupler, this scheme can implement two functions: simultaneous up- and down-conversion signal generation, or high image rejection in down-conversion. Simulation results show that the proposed structure can achieve an up-conversion with a tunable range of 17–23 GHz or a down-conversion with a tunable range of 1–7 GHz, respectively, based on a fixed 8 GHz LO signal. The unwanted signal suppression ratio of desired signal is about 27.2 dB for up-conversion and 30.0 dB for down-conversion. In addition, we have tested and analyzed the conversion gain, noise figure and spurs free dynamic range of the system. For image rejection in down-conversion, we can achieve an image rejection ratio (IRR) about 65.2 dB. Moreover, the impact of the phase drift, RF frequency, amplitude and phase variation on IRR is discussed. Finally, the influence of half-voltage imbalance of the DPMZM sub-modulators on IRR is analyzed, and a compensation method is given.