The Researh On Integrated Multi-channel Millimeter-wave Signal Generation Based On Silicon Photonic Chips

Driven by the mobile internet and the Internet of Things(IoT),the global mobile data traffic will grow by more than 1,000 times in the next decade,which is difficult to be satisfied by current 4G network.In fifth-generation(5G)mobile networks,large-scale antenna array systems operating at millimeter-wave(MMW)frequencies have been intensively studied to support the large-capacity data traffic.The MMW frequency band can provide massive amount of underutilized spectrum resources to overcome the bandwidth bottleneck induced by low-frequency wireless carriers.In addition,the short wavelengths of MMW frequencies enable a small physical size to pact large number of antennas,which are desired for the multi-input multi-output(MIMO)systems.However,due to the large number of antenna elements,realizing large-scale MMW antenna arrays in practical systems faces some challenges in terms of size,weight,hardware cost and power consumption.Photonic integrated circuit(PIC)technology,as an alternative approach to implement high performance MMW systems,has attracted significant interests.One motivation is that the MMW generation based on photonic techniques can provide high-quality signals with low phase noise and wide frequency tuning range.PIC technology also opens up attractive possibilities in phased arrays for optical beam steering.Several PIC structures for microwave or MMW signal generation have been demonstrated based on either silicon photonics or III-V photonics to date.For the large-scale antenna array systems in 5G multi-user MIMO scenarios,however,a multi-channel MMW generation PIC scheme is highly desirable to distribute multiple user data at same wireless carrier frequencies based on space multiplexing.Due to the unique advantages of low fabrication costs,compact size,and compatibility with complementary metal oxide semiconductor(CMOS),silicon photonics has the great potential to offer an integrated solution for this problem.In this paper,we propose an on-chip silicon-based multi-channel MMW signal generation scheme for large-scale antenna arrays.The proposed 7-channel integrated silicon chip has a compact footprint of 1.1×2.1 mm~2,with each channel implementing two fundamental functions.The first is multi-channel MMW signal generation by beating a local oscillator(LO)light with multi channels of optical baseband data carried by an identical optical carrier;the second is automated silicon polarization control(SPC),consisting of on-chip polarization control units and off-chip sub-control systems,to align the polarization directions of the optical baseband signals with the optical LO light.In the proof-of-concept experiment,we have demonstrated the automated silicon polarization tuning with~7-ms tuning time and>27dB extinction ratio.After this process,7 channels of 28-GHz MMW carrying4-Gb/s QPSK signals are successfully generated and demodulated with~17.5 dB SNR of each channel.