An RF Amplifier Circuit for Enhancement of Echo Signal Detection in Bathymetric LiDAR

The echo signal from the water bottom in bathymetric light detection and ranging (LiDAR) onboard unmanned boat is very weak. As a result, the signal's amplitude cannot be resampled using an analog-to-digital (AD) sampling module after being detected by the photomultiplier tube (PMT). In addition, the traditional methods, which adopt the trans-impedance circuit, cannot provide sufficient gain and bandwidth, resulting in incorrect detection of echo signals. For the reasons above, this article presents an radio frequency (RF) amplifier circuit for signal amplification, in which a dc paranoid network associated with a matching circuit is used to ensure the stable operation of the circuit; the ac-coupled and low-noise voltage stabilizers are adopted to ensure a low-noise signal output; the shielding is adopted to suppress the interference of electromagnetic fields and static electricity. The validations are conducted in indoor and outdoor laboratories, including a simulated amplitude and bandwidth using a signal generator in the indoor laboratory, the water tank, the test well, the pond, and the pool. The experimental results show that the proposed RF amplifier circuit can amply the gain of 25.31 dB when using a signal generator in the bandwidth range of 500 MHz, 650 MHz, and 800 MHz; 1 GHz; and 34.63, 31.62, and 25.78 dB under the experiments in the water tank, in the test well, and in the pond when the PMT control voltages are 0.4, 0.5, and 0.7 V, respectively, and amplify the echo signals to 451-568 mV under the bandwidth of 500 MHz.