| Analog Radio over Fiber(ARoF)technology has become a highly attractive implementation method for high-density deployment of base stations with the low-cost advantage of centralized control of base station functions and simplified remote base station structure.However,research on performance improvement in ARoF links,such as electrical domain signal gain,the output power of terminal photoelectric conversion modules,and DC conversion efficiency,is still incomplete.In response,this thesis has studied key issues such as improving the electrical domain signal gain in the link,establishing a large signal equivalent circuit model for photoelectric conversion devices,and improving the output power and DC conversion efficiency of the terminal.The main research and innovation are as follows:1.Two large signal equivalent circuit models of PIN photodiodes(PIN-PD)and Unitraveling carrier photodiodes(UTC-PD)was established,providing a device model for circuit design and simulation.Based on the model,it is found that reducing the junction capacitance can effectively improve the output power and gain flatness of photodiodes;Based on the PIN-PD model,a set of parallel RC networks is introduced to characterize the effects of the carrier collection layer in UTC-PD.At the same time,a packaging parameter model is introduced to establish a model of the UTC-PD module.The model’s accuracy is verified by comparing it with the measured data of the device.2.An impedance matching network at the UTC-PD output is designed to improve RF output power and efficiency performance effectively.A simplified design method for bias networks is proposed,and harmonic control technology is used in the design of matching networks for PD operating at 3.2-3.8 GHz;The test results show that the saturated output power is improved by 1-2.35 d B and the efficiency is improved by 6.5%-18.7%;To verify the feasibility at high frequencies,a matching network for PD operation at 10-10.5 GHz was designed.It is analyzed that the connection method between the module PD and the matching network biased the performance towards the high-frequency band.This phenomenon was verified through simulation.Finally,the matching network improved the output power by 0.89-3.95 d B and efficiency by 1.4%-6.6% in the 10.2-11 GHz band;To avoid the impact of module packaging parameters,a matching network for chip PD operating at 9.8-10.7 GHz was designed by presetting the power supply network of the chip PD.The saturated output power was improved by 1.72 to 3.85 d B,and the efficiency was improved by 6.7% to 14.1%.3.Active load modulation technology is used to effectively improve the efficiency of the link in a 6 d B backoff state.By controlling the bias point of the laser to achieve Class B of the carrier path and Class C of the peak path,a matching network being capable of achieving load modulation was designed for ARoF links operating at 3.4-3.6 GHz,obtaining saturation output power greater than 23 d Bm,saturation efficiency of 23.3%-26%,and efficiency of 6 d B backoff point of 19.1%-22.6%;The influence of the real part of the output impedance of UTC-PD in the off state on the performance of the download wave path in the back off state is analyzed. |
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