A Smart Analog Filtering Approach For Laser Range Finder Systems

A tunable analog bandpass filter operating in the frequency range of $\mathbf{4 5 ~ k H z}-\mathbf{4. 2 ~ M H z}$ is presented for Laser Range Finder (LRF) modules which is application of smart systems in the field of electro-optical sensors. To filter the noised signal seen in the Avalanche Photo Diode (APD) sensor in LRF modules and to make more accurate measurements, the 4th-order bandpass filter is used which is designed with multiple feedback implementation. The pass band of the filter is tuned according to the frequency of the input signal by a secondary controller. Thus, the peak frequency of the signal to be filtered is defined and then the required capacitance value is transmitted to the filter circuit by creating a related capacitance value in the Capacitance multiplier circuit. The APD sensor data were generated at a $300-\mathrm{mV}$ amplitude level within the frequency range determined based on real measurement data from the literature. The model training process was conducted by accounting for all environmental and hardware noise, as well as deviations observed in previous studies. The data were subsequently optimized for testing within the 45 kHz to 4.2 MHz frequency range. As a result, the filter becomes a tunable filter in the specified frequency range. Simulation results of the Capacitance multiplier circuit and filter circuit exhibit significant theoretical and simulated responses.