Research On High Fidelity Microwave Photonic Link Modularization

Microwave photonics technology is a new subject that integrates microwave technology with photonics technology.It can process microwave signals in the optical domain,including signal generation,transmission,mixing and filtering.Compared with the traditional electronic technology,microwave photonics technology has the advantages of wide bandwidth,low loss,small in size and anti-electromagnetic interference,so it has great prospects in satellite communications,radar,electronic warfare,cable television,and other fields.This thesis mainly studies the modular design of the microwave photonics link?MPL?,researches and tests the basic performance parameters and communication data transmission rate of the link.Besides,an optimization scheme for gain equalization is proposed to improve the performance of the optical link.First,this thesis introduces the research background,application fields and development trends of the MPL,and compares the system's configuration between the directly modulating microwave photonics link?DML?and the externally modulated microwave photonics link?EML?.Then we analyze the advantages and disadvantages between the DML and the EML,and focus on the DML studying its high-frequency small-signal equivalent circuit model.Simultaneously,the DML's main performance parameters are also analyzed.Finally,an ultra-wideband microwave photonics link?UW-MPL?transceiver module with a working frequency of 1GHz⁶GHz has been designed and manufactured based on the TO-CAN direct-modulation DFB laser and the TO-CAN photodetector.Experiments about the UW-DML's performance and communication capabilities have been carried out.The experiment result shows that the optical module designed in this thesis has a gain flatness of±7.5dB over the entire working bandwidth.In the 2.4GHz band,the input 1dB co compression point is 6.4dBm,the compression dynamic range is 144dBc/Hz and the spurious-free dynamic range is 105dBc/Hz,meanwhile the noise figure is 39dB.In the5GHz band,the input 1dB co compression point is 17.4dBm,the compression dynamic range is 145dBc/Hz,the spurious-free dynamic range is 101dBc/Hz,and the noise figure is47dB.The communication capabilities test result of the module in the WIFI communication frequency band shows that the DML has 5.5MB/s data transmission rate in the 2.4GHz band and 10MB/s data transmission rate in the 5GHz band,which is better than wireless communication.Besides,the module's transmission bit error rate is less than10^-6,and the confidence level is higher than 99%.The last part of this thesis is the optimization of the optical module.First,the reason why the link's gain flatness is not normal has been discussed.So a gain equalization circuit has been designed based on the optical module's frequency response curve.Then,a simulation about the circuit's frequency response has been performed using ADS.The result indicates that the circuit has a gain equalization accuracy of less than±2dB for the target frequency.The circuit has been applied to the original optical transceiver module for optimizing its frequency response,and the ADS's simulation result shows that the gain flatness is within±1.8dB which is a great improvement compared to the original.In addition,in order to compensate for the overall gain reduction caused by the equalizer circuit,a gain equalization circuit for a radio frequency amplification chip named SBB5089 has also been designed and simulated.After applying the equalized amplifier circuit to the equalized circuit of the optical link,the link's average gain is-2.5dB,and the gain flatness is within±1.7dB.It can be concluded that if the designed optical link's gain equalization circuit and the amplifier's gain equalization circuit are applied to the original optical link,the gain flatness of the link can be effectively improved and the gain can be maintained unaffected.