Research On Analog Front-end Circuit Testing Method For CCD Imaging

As a key device for the acquisition of image information,CCD image sensor is widely used in military optoelectronic detection and imaging for its advantages of high imaging quality,large charge capacity,low fixed pattern noise and very low dark current.Analog front-end circuit is used to convert the analog voltage signal output by CCD image sensor into digital signal after amplification.The AFE includes several modules,such as sampling-holding circuit,adjustable gain amplifier,high speed ADC,DAC for auxiliary calibration and high speed digital output.Its evaluation is different from the pure simulator test and the pure digital circuit test.Its testing process is integrated with high precision and low noise analog signal evaluation,which requires high skills and rich debugging experience,including signal conditioning,filtering and amplification.Its test also includes high-speed digital signal test,including data capture,timing matching,digital signal processing,and so on.In the test,both signals should be excited and measured simultaneously,and a relatively high degree of isolation between them should be required to avoid interference.Therefore,it is quite challenging to evaluate its test.This paper starts from the technical development background of the industry at home and abroad,under the premise that there is no clear test standard and test method guidance at home and abroad,starts from the internal structure and function division of the circuit,reverses the test parameters with the function characterization,finds out the scientific and accurate test parameters of the analog front-end circuit from both sides of the circuit principle and application scenario,and tests the theory from the data converter and amplifier In this paper,we look for a scheme that can realize the parameter engineering test,and verify it from two dimensions of laboratory accurate evaluation and automated mass production test.The test result is that the dual channel resolution is 14 bits,the sampling rate is 5 ~ 40 Msps,the noise floor is lower than-77 dB,the channel isolation is higher than 79 dB,and the BMD is less than 6mV.The research contents of this paper are as follows:1.Investigated the technical development of analog front end circuit,understood and introduced the technical level of analog front end circuit of mainstream companies in the industry,the status quo of parameter testing and existing problems;2.The basic working principle of the analog front end circuit is analyzed,and the parameter characterization of the analog front end circuit is illustrated from the internal structure and the working mode.3.The key dynamic parameter testing technology in S/H mode,bimodal unbalance testing technology in CDS mode,channel matching calibration technology,adjustable gain amplifier testing technology and linearity error parameter evaluation technology are respectively studied.4.Designed the test system platform from the aspects of instrument index,program-controlled filter,PCB signal integrity and power integrity design,etc.5.Performance evaluation and parameter test verification were conducted by building two sets of system based on building block instrument and ATE in the laboratory,and the test results reached the predetermined requirements.