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 ${\omega _{\boldsymbol{RF}}} + 2{\omega _{\boldsymbol{LO}}}$ 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 ${\omega _{\boldsymbol{RF}}} - 2{\omega _{\boldsymbol{LO}}}$ 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.
Highlights
Owing to the inherent characteristics such as broad bandwidth, low loss and immunity to electromagnetic interference (EMI), microwave photonic links have become more attractive and have been applied in radio over fiber (RoF) system, phased-array beamforming and high-speed signal processing, etc. [1]–[3].A frequency mixer is a very important component of transceiver to implement frequency conversion for the radio frequency (RF) signal with the frequency of ωRF by using a corresponding local oscillator (LO) signal with the frequency of ωL O [4]
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 dualpolarization dual-parallel Mach–Zehnder modulator (DP-dual-parallel MZM (DPMZM)), an electrical 90° hybrid coupler, and an optical bandpass filter
The upper sub-Mach-Zehnder modulators (MZM) of DPMZM2 is only modulated by the LO signal, which operates at the maximum transmission point to achieve DSB modulation of the 2nd-order LO sidebands where the VD C4 is tuned to 12.2 V
Summary
Jingnan Li ,1 Yunxin Wang ,1 Dayong Wang, Tao Zhou, Jiahao Xu, Xin Zhong, Feng Yang, Dengcai Yang, and Lu Rong.
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