A balanced detector system with a high signal-to-noise ratio (SNR) is the key technology for 2 μm coherent wind lidar, which can enhance the ability for the digital receiver to detect extremely weak signals. The photodiode is the main detection component of a balanced detector system. The variance of junction capacitance of different photodiodes will cause the degradation of SNR. Based on the linear relationship between the junction capacitance of a photodiode and the reverse voltage in the double logarithmic coordinates, a balanced detector system is designed to have the ability to adjust the reverse voltage by using the external digital-to-analog converter. An optimization of the circuit performance can be achieved by adjusting the junction capacitance, which significantly affects the circuit noise and signal bandwidth in the design of the high bandwidth transimpedance amplifier, which is sensitive to parasitic capacitance and component error. A simplified optical system is built to test the performance of the designed balanced detector system. The results show that the SNR of the detector system is ∼10% higher than that of the commercial product, which can further increase the detection distance of the wind lidar by ∼1.5 km for the detection limit of 10 km.

中文翻译：

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2 μm相干测风激光雷达高信噪比平衡探测器系统

具有高信噪比（SNR）的平衡探测器系统是2 μm相干测风激光雷达的关键技术，它可以增强数字接收机对极微弱信号的探测能力。光电二极管是平衡探测器系统的主要探测元件。不同光电二极管结电容的差异会导致信噪比下降。基于光电二极管结电容与反向电压在双对数坐标中的线性关系，设计了一种平衡检测器系统，具有通过使用外部数模转换器调整反向电压的能力。通过调整结电容可以实现电路性能的优化，在对寄生电容和元件误差敏感的高带宽跨阻放大器的设计中，这会显着影响电路噪声和信号带宽。构建了一个简化的光学系统来测试设计的平衡探测器系统的性能。结果表明，探测器系统的信噪比比市售产品高~10%，对于10km的探测极限，测风激光雷达的探测距离可进一步提高~1.5km。