Evaluation of different Laser Distance Measurement Methods and Implementation of an RF-chirped AMCW Prototype with an FPGA

Abstract

Laser ranging devices can be implemented using a lot of different architectures like Timeof-Flight (ToF), Triangulation, Amplitude Modulated Continuous Wave (AMCW) and Frequency Modulated Continuous Wave (FMCW). Depending on the desired accuracy, measurement range and overall cost of the ranging system, different architectures are more suitable than others. Advances in FPGA development have made it possible to implement high frequency hardware designs in the GHz frequency range. This is made possible by the use of modern FPGAs with ADCs and DACs in the GSPS range, which also opens up new possibilities for laser range finders, such as the generation of high frequency chirp signals. This thesis proposes a range-finding system that uses an RF-chirped AMCW architecture. In this architecture, a custom laser frontend takes an RF-chirped signal from an FPGA and modulates it onto the driving signal of a laser diode. The emitted laser light travels to a target and is reflected back to the frontend. The reflected laser light signal is received by a photodiode and processed by the FPGA. Based on this architecture, a Python simulation was first created to analyze the expected performance of the system. A prototype frontend was then implemented and tested. The performance and problems of the implementation are analyzed.

Date of Award	2025
Original language	English
Supervisor	Markus Pfaff (Supervisor)