| DWith the advent of 5G mobile communication,the rapid development of artificial intelligence,virtual VR,big data,satellite mobile communication,remote sensing,radar and other services,the sharp increase of traffic has brought great challenges to the high-speed transmission of information.At present,the resources in the middle and low frequency bands have become crowded and unable to meet people’s daily needs.In order to seek rich spectrum resources from higher frequency bands,academic researchers have turned their eyes to the high frequency millimeter wave stage to further meet the requirements of high-of contemporary communication transmission.With the frequency response of electronic equipment is limited,typical electrical means become difficult and expensive,in addition,millimeter wave signal in the atmospheric transmission process space path loss,within this wavelength range,atmospheric gas and water vapor will lead to additional attenuation,and photon auxiliary millimeter wave generation technology can effectively overcome the electronic bottleneck,can well adapt to optical fiber transmission,the loss is small,by photon means of millimeter wave transmission is considered to be an important solution to meet the current communication requirements.The reported millimeter wave purity based on polarization modulator cascade or parallel mode is not particularly ideal,and the structure is complex.The millimeter-wave doubling frequency factor produced based on the Mach-Zehnder Modulator（MZM）and the polarization modulator（Polarization Modulator,Pol M）is lower.In view of the above problems of millimeter wave generation based on（Radio over Fiber,RoF）system,this paper proposes a new scheme of millimeter wave signal generation of 16 F frequency and 32 F frequency,respectively.The main contributions of this article are provided as follows:（1）A new filter generation for 16 x frequency millimeter wave（Millimetre Wave,MMW）based on multiple MZM cascades is proposed.This scheme uses four cascade structures of MZM to obtain the±8 order target optical sibband by controlling the transmission point of MZM and the extinction ratio.Next,the photodetector is used to obtain an electrical signal of 160GHz.The experimental results demonstrate the feasibility of the solution,and the resulting RF stray and optical sideband suppression ratios are 51.26d B and 62.82d B,respectively,in addition,the scheme is verified again mathematically.（2）A new scheme for filter-free 32 x frequency MMW generation based on multiple parallel backcades of MZM is presented.This scheme uses optical attenuator and optical phase shift to suppress the central carrier.Two parallel MZM can produce±8 order and±12 order by adjusting the modulation index of MZM,cascade two parallel MZM and the phase difference of signal source to produce±16 order optical sidebands forπ/4 structure.Oscilating in the photodetector produces 32times the millimeter-wave frequency.In theory and experiment,the optical sideband suppression ratio（Side-Mode Suppression Ratio,OSSR）of±16 signal and the RF stray suppression ratio（Radio Frequency spurious suppression Ratio,RFSSR）of the SSB signal are 59.96 d B,53.94 d B and 60.02 d B,56.34d B,respectively.The experimental results are consistent with the theoretical analysis and verify the feasibility of the scheme.Furthermore,the effects of the extinction ratio,initial phase,RF driven signal amplitude,and DC bias drift on the signal-generating OSSR and RFSSR were investigated.The experimental results show that the proposed scheme has high doubling factor and high purity,which is suitable for contemporary and next generation communication systems.（3）To further improve the transmission performance of the communication system,Proposed a scheme based on vector millimeter-wave signal generation,Using wave multiplexing（Wavelength Division Multiplexing,The WDM）multiplexer realizes the superposition of vector signal and RF signal to generate a new vector signal,The experimental results prove that the bit error rate of generating30GHz16QAM vector millimeter wave signal transmission of 10km is less than the threshold of hard decision forward error correction3.8×10-3,besides,The new multiple frequency vector components are generated by stacking the vector signal over the RF signal,It is universal to generate a vector millimeter wave signal with any frequency. |
