A Microwave Photonic Mixer Using a Frequency-Doubled Local Oscillator

Abstract

A microwave photonic mixer based on a frequency-doubled local oscillator (LO) is proposed. The carrier-suppressed single-sideband (CS-SSB) modulation of the -first-order radio frequency (RF) and ±second-order LO sidebands can be generated by using a dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM), an electrical 90° hybrid coupler, and an optical bandpass filter. The upconverted intermediate frequency (IF) signal with the frequency of ωRF + 2ωLO is output by frequency beat at a photodetector. Meanwhile, the -first-order RF sideband can be easily changed to +first-order RF sideband by adjusting one dc bias voltage of the DP-DPMZM. The downconverted IF signal with the frequency of ωRF 2ωLO is obtained correspondingly. The experimental results show that the spur suppression ratios of upconverted and downconverted IF signal are 19.0 dB and 25.5 dB, respectively. The spurious-free dynamic range of the proposed mixer is 96.5 dB·Hz2/3. The output electrical spectrums are pure owing to the optimal design of the CS-SSB modulation. The proposed mixer reduces the frequency requirement of LO signal since the second-order LO single sideband is used, and the upconversion and downconversion can be switched to each other by a simple electrical operation.

Keywords

• Fiber optics links and subsystems
• radio frequency photonics
• analog optical signal processing.