Design Of Conditioning Circuit For Laser Guidance

Laser guidance technology is widely used in national defense modernization,automatic navigation and other fields,it has important military and civilian significance.As an important part of the laser guidance system,the laser guidance conditioning circuit amplifies and processes the current signal which is on the photodiode into a voltage signal for realizing the laser-guided function for the post-stage operation,its accuracy,response speed and other performance directly determines the system function and performance of the laser guidance system.On the other hand,the circuit of laser guidance conditioning is usually achieved by the form of connecting the discrete chips through the circuit board,the volume is very large,energy consumption and production costs are high.With the development of integrated circuit manufacturing technology and the development direction of laser guide miniaturization is proposed,the monolithic opto-electronic integrated circuits with low cost,high integration,low power become development trend of laser-guided conditioning circuit in the future.Therefore,the research and design of the laser-guided conditioning circuit and monolithic integration is of great significance.In this paper,the circuit of laser guide conditioning is designed,variable gain amplifier(VGA),trans-impedance Amplifier(TIA),comparator,proportional,summing amplifier and output buffer module are included.The following components of laser guide conditioning circuit is designed focally.Firstly,the realization method of the gain dB linear vga is analyzed,the gain control stage is improved based on the traditional circuit,a two cascade gain control stage variable gain amplifier is proposed.The effect of the gain error result caused by the gm stage shutdown incompletely and gain range caused by the limited of the control voltage are both reduced,the gain error is reduced and the gain range is increased.Secondly,in order to improve the linearity of the tia,the structure with a op-amp is used and its noise characteristic is analyzed.Thirdly,the two stage open loop comparator is used to increase bandwidth and reduce the transmission delay of the comparator,a cascade of push-pull inverter structure is increased to increasing the drive capability.Finally,the non-unity gain stable op-amp is used in the proportional amplifier,which is conducive to increasing the bandwidth to improve its speed of closed-loop response.The circuit and layout of laser guide conditioning circuit are designed with HHGrace 0.35μm CMOS process,the area of circuit is 840.5μm×638.0μm.The simulation results show gain range of VGA is 50 dB,gain error is ±0.7dB and IMD3 is-75.19 dBc.The 3dB bandwidth of the output signal is 23.8MHz,the 0.1% build time is 35.2ns,the synchronization signal generation time is 36.8ns.The laser guidance conditioning circuit designed in this paper has a good accuracy and response speed and achieve the desired design indicators,it can be used in the laser guidance system.