Low-Cost Fast-Start Amplifier Architecture for AC-Coupled Measurement of Low-Frequency Signals

As sensors become more widely deployed around humans, radar sensors have seen considerable use as a method of measuring low-frequency body motions, such as heartbeat, respiration, and gesture commands. These sensors, however, can suffer from long startup times due to the need to preserve low-frequency information. This letter presents a fast-start amplifier architecture that leverages low-cost components in a simple architecture to improve the startup time of practical sensors without impacting low-frequency response. The theory of the fast-start circuit is presented and verified through simulation to demonstrate the startup time improvement offered by the architecture. The system is then evaluated experimentally using a custom test board, with results showing an improvement in startup time compared with traditional amplifier architectures, which makes it highly useful for low-cost, low-frequency motion sensors.