The Readout Circuit Design For The Weak Signal Sensors

The underwater sonar, recently, as for the acoustic analog front-end receiver, the deficiency of weak input signal and the wide linearity gain range have becoming to be the key problems to be breakthrough. Furthermore, with the development of CMOS integrate circuit; the large scale area array acoustic receiver has been integrated into a chip, which be helpful to scale the equipment and realize miniaturization and portable.Sonar sensors improve the development of the sonar readout circuit with the scale continuously becoming small. So the special sonar readout chip for the novel sonar sensor arrays is now facing challenges. Traditional sonar readout circuitry scale is not suitable for the development of technology. This48-channel analog front-end sonar sensor readout circuit chip is innovatively designed with integrating the adjustable gain control circuit and output multiplexers. Not only the circuit scale has been effectively reduced, the power consumption is also optimized which are consistent whit the current trend of technological development.The purpose of the sonar receiver is to amplify the weak signal effectively as while as depress the harmonic distortion and interference of adjacent channels. According to the design specifications of the acoustic receiver system, the suitable circuit topology is selected. The variable gain amplifiers with the exponential gain control, multi-channel output data strobe circuit, output buffer and the fourth-order Butterworth low pass filter. With the simulation verification and test, the system can offer0dB～50dB linearity gain dynamic range, the max gain is50dB, the equivalent input noise is5.7nV/V(?)@1.5MHz,-3dB bandwidth is [15MHz,39MHz], the gating time is2μ S with each channel. When the gain is less than55dB, the second-order harmonic distortion is less than-40dB. When the signal to noise ration (SNR) is14dB, the receiving sensitivity is50μV. The power consumption of each channel is6mW from a5V power supply. And then the output buffer and fourth-order Butterworth low-pass filter are designed in the test circuit to increase the whole gain of system to68dB.The readout circuit chip for large scale sonar sensor area array is suitable for IF weak signal sensor application.