具有背景抑制功能的长波红外读出电路

Long wavelength infrared readout circuit with background suppression function

为了提高红外焦平面检测目标的灵敏度,目标辐射产生的载流子应尽可能长时间保持,同时应尽可能减少热激发和背景辐射激发的比例。高背景条件下长波红外读出电路的积分电容较快饱和,且长波红外探测器暗电流的非均匀性会影响焦平面的固定图形噪声。基于共模背景抑制结构以及长波碲镉汞探测器暗电流分析的基础上,设计了具有非均匀性矫正的背景抑制电路。传统的背景抑制电路采用单一共模背景抑制或差模背景抑制。差模背景抑制模块的高精度背景记忆一般在小范围区间内。本文背景抑制结构采用共模背景抑制与差模背景抑制相结合,可以在较大的背景噪声范围内有效地降低固定图形噪声以及增大动态范围。该背景抑制结构中共模背景抑制采用电压-电流转换法,差模背景抑制采用电流存储型背景抑制结构。差模背景抑制通过背景记忆时信号放大,背景抑制时信号缩小来提高背景抑制精度。电路采用标准CMOS工艺流片。测试结果表明:读出电路的FPN值为2.08 mV。未开启背景抑制时,焦平面FPN值为48.25 mV。开启背景抑制后,焦平面FPN值降至5.8 mV。基于探测器的暗电流非均匀分布,计算其理论FPN值为40.9 mV。长波红外焦平面输出信号的RMS噪声在0.6 mV左右。

In order to improve the sensitivity of target detection by IRFPA,the carrier generated by target radiation should be maintained as long as possible.And the proportion of thermal excitation and background radiation excitation should be reduced as much as possible.The integral capacitance of the long-wave infrared(LWIR)readout circuit(ROIC)is easily saturated under high background conditions.And the non-uniformity of the LWIR detector dark current will affect the fixed pattern noise(FPN)of the focal plane array(FPA).Based on the common mode background suppression(BDS)structure and the analysis of dark current for long-wave HgCdTe detector,the BDS circuit with non-uniformity correction was designed.Traditional background suppression circuits only used common mode background suppression or differential mode background suppression.The high-precision background memory of the differential mode background suppression module was generally within a small range.Common mode BDS and differential mode BDS were used for BDS module in this paper,which can effectively reduce the fixed graphics noise and increase the dynamic range in a larger background noise range.For this background suppression circuit,the common mode background suppression used a voltage-current conversion method,and the differential mode background suppression used a current storage type background suppression structure.The background signal was amplified during background memory and signal was reduced during BDS for differential mode BDS.It could improve BDS accuracy.The circuit adopted standard CMOS process tape out.The test result shows that the FPN of ROIC is 2.08 mV.The FPN of the FPA without background suppression is 48.25 mV.When background suppression is turned on,its FPN noise is 5.8 mV.Based on the detector’s non-uniform distribution of dark current,the theoretical FPN value is calculated to be 40.9 mV.The RMS noise of the output signal of the long-wave infrared focal plane is about 0.6 mV.