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在中红外波段,大多数气体分子吸收光谱的线宽都很窄,因此红外光电探测器输出信号为窄脉冲信号。对此脉冲信号的处理要求前置放大器必须兼具精度与速度,而对放大器输出信号的采集也需要在保证带宽的情况下尽量提高数字化的精度。本文中设计了高速并行采样电路,利用两片双通道高速ADC实现了1GSPS的采样速度与12bit的垂直分辨率。信号链的最后一环是FPGA数据处理电路,我们应用CORDIC算法对采集系统的时间误差进行了校正。本文最后给出了光电信号高速采集电路的设计与测试结果,在输入参考信号频率为100MHz时,采集系统整体信噪比达到60d B,无杂散动态范围达到70d B。
In the mid-infrared band, most gas molecules have very narrow linewidths for absorption spectra, so the output of the infrared photodetector is a narrow pulse signal. The processing of this pulse signal requires that the preamplifier must have both precision and speed, and the acquisition of the output signal of the amplifier also needs to maximize the digitization accuracy under the condition of guaranteed bandwidth. This paper designed a high-speed parallel sampling circuit, the use of two dual-channel high-speed ADC to achieve a 1GSPS sampling rate and 12bit vertical resolution. The last part of the signal chain is the FPGA data processing circuit, we use CORDIC algorithm to correct the time error of the acquisition system. At the end of this paper, the design and test results of the optoelectronic signal high-speed acquisition circuit are given. When the input reference signal frequency is 100MHz, the overall signal-to-noise ratio of the acquisition system reaches 60d B and the spurious-free dynamic range reaches 70dB.