Linear sweep controller design and FPGA implementation for FMCW radar applications

Frequency Modulated ContinuousWave (FMCW) radar systems rely on linear frequency sweep and Voltage Controlled Oscillators (VCO) are being in use for the sweep generation. However, developing VCO with linear transfer functions at microwave frequencies is a challenging study and availability of such components is limited. Especially for the long-distance FMCW radar applications, the non-linear frequency sweep due to the VCO insuf ? ciency, results in range resolution degradation. In order to develop a solution for this problem; a case study is completed for an FMCW Radar Altimeter at 4.3 GHz center frequency with 62.5 Hz triangle wave modulated 152.6 MHz frequency sweep. Open-loop control solution like voltage pre-distortion method are not adequate for the application like FMCW Radar Altimeter because of the noisy and non-stationary structure of the system due to environmental condition. In these situations closed-loop control systems like Phase Lock Loop (PLL) provide more adequate results. In this research; a PLL structure is implemented on an Field Programmable Gate Array (FPGA) by a Direct Digital Synthesizer (DDS) as the Reference Signal Generator, an improved Phase-Frequency Detector as the Phase Detector and a Kalman Filter as the Loop Filter. For design veri ? cation and analysis FPGA-In-the-Loop (FIL) simulations are generated by the use of Mathworks Simulink and Xilinx System Generator.