Design and Implementation of AGC in Gas Ultrasonic Flowmeter

The paper proposes a new circuit of all-digital automatic gain control (AGC) in the gas ultrasonic flowmeter at first. The design is implemented on the EP1S40F1020 FPGA chip. A scheme, design of main function modules and test are given in the paper. This design can achieve 40dB dynamic range control, with advantages of high precision, high rangeability, little environment influence, good stability and excellent reliability. In order to achieve a larger dynamic range control, the circuits which are composed of all-digital AGC and analog AGC using AD8367 are proposed and tested. The result is when the input signal dynamic range is from -60dBm to OdBm, the output fluctuation is under 3dB and the designed AGC system is more suitable for the demand of the gas ultrasonic flowmeter's real-time and high precision.