Broadband Low-pass Filter Circuit Design For Single-photon GHz Gated Detection

The single-photon detection technology based on the gated working method,as an ultra-high-sensitivity detection scheme,is widely used in many fields such as bioluminescence detection,micro-scale ranging,quantum communication and so on.In recent years,with the increase of the gating frequency,the pulse width of the gate signal has been continuously shortened,and the aliasing of the spike noise signal and the avalanche signal in the gateable detectable window is unavoidable,which brings great challenges to the detection.The detection circuit based on the filter scheme can effectively solve the above difficulties and separate the aliased signal from the frequency domain.In order to accurately detect the weak avalanche signal,the filter is required to have a wide bandwidth,high stopband attenuation,high linearity and Low noise performance.By constructing a GHz gated circuit simulation model,Simulation and analysis spectral characteristics of the avalanche signal and spike noise signal,and the transmission characteristics and circuit architecture of the filter are determined.based on this.Aiming at broadband,low noise,high linearity,etc.,a 10-order Gm-C low-pass filter is designed through the cascaded double quadratic structure,and the specific circuit structure is given.The difficulty of the high-order broadband low-pass filter is the compromise of power consumption performance and the guarantee of stability.Therefore,this paper focuses on the research of the transconductance amplifier,common mode negative feedback circuit,quadratic filter structure and band gap reference circuit.The transconductance amplifier uses a complementary fully differential structure to improve transconductance energy efficiency,and an auxiliary cross pair tube is added to eliminate non-linearity.The linear term improves the linearity of the transconductance;Aiming at the circuit stability problem under the wideband design,frequency compensation is added to the common mode negative feedback circuit to improve the stability of the circuit under the wideband;and the current mode bandgap with higher temperature and process accuracy is used to provide multiple reference voltages and The current bias ensures the stability of the multi-stage cascade of the secondary filter structure.On the basis of completing the filter design,it is integrated with the remaining circuits at the layout level into the single-photon detection system circuit to verify the correctness of its function.Based on the TSMC 0.18?m standard CMOS process,the filter circuit is simulated using the Candence Spectre tool,and the filter bandwidth is 500 MHz,the stop band attenuation at 1GHz is-58.8d B,the integrated noise is0.51 m V in the frequency range of 5MHz-1GHz,and IIP3 is 5.1d Bm,power consumption is 41 m W.In view of the limited narrow-gated test conditions in GHz,the single-photon detection system was tested using an external signal superimposed analog excitation method.The test results show that the system circuit has the GHz gate detection capability,which proves that the filter designed in this paper has the expected function and performance It meets the actual application requirements and indirectly verifies that the filter circuit meets or approaches the index requirements.