Quality of the turbine engine directly affects aircraft performance. In order to improve engine efficiency and ensure its safe work, it is important to monitor the clearance between the blade tip and the engine casing. This paper introduces a continuous wave sensing system, which can achieve precise ranging by calculates the phase difference between transmitting RF signals and receiving RF signals. To speed up the signal processing of the measurement system, FPGA is used to process the acquired signal to obtain the phase. Besides, the Xilinx Vivado HLS compiler is used for algorithm development so that further reduces the cost of development and optimization.