Study And Design On Chirp Source Used In Automotive Collision Avoidance Radar

In this treatise, a chirp source use for 24GHz automotive radar system was designed. In bases of small size, low cost, high signal quality, and high universal of the chirp source which are required by automotive radar applications, we introduce and use a chirp signal generation solution based on phase locked loop. The main work of this treatise includes:1. In theoretical knowledge, we did a brief description on working principle of linear frequency modulation continuous wave radar system, and introduced the working principle of the phase-locked loop briefly because the chirp signal generation scheme used in this treatise is based on phase-locked loop.2. In theoretical analysis, ADS was used for modeling and simulation of the system, by observing and summarizing the simulation results and data processing, we discussed the impact of the divider changing interval and the bandwidth of the loop filter on the linearity of the chirp signal, and give a solution to the contradiction between phase noise and linearity of the signal when choosing the loop bandwidth. When the loop bandwidth was set to 100 kHz and divider changing interval set to 1μs, the linearity of the chirp signal is better than 0.3% after the solution dealt with.3. In the actual circuits, based on the chirp signal generator solution which has been introduced, we provide a chip source circuit set up solution using fractional N PLL chip ADF4158 which is produce by the ADI and the VCO chip provide by our partners.