Improving Data Rate Using Cyclic Shifts in an FMCW Radar System Combining Ranging and Communication

In this paper, frequency-modulated continuous wave (FMCW) radar for enabling a more comfortable traffic environment is discussed and a scheme that integrates ranging and communication is proposed. A method to increase the data rate while maintaining ranging accuracy is proposed. Data are modulated onto the sweep function of the FMCW radar. Both up-chirp and down-chirp signals are utilized for data modulation. Furthermore, multiple sweep functions are generated by applying cyclic time shifts to the sweep function. By selecting different sweep functions in accordance with the data to be modulated, a transmitted transmitting additional data bits is generated. At the receiver, the beat frequency is calculated from the reflected signal and reference signals, enabling distance measurement as in the conventional beat frequency ranging scheme. The root mean square error (RMSE) and bit error rate (BER) of the proposed scheme are evaluated through simulations and compared with those of conventional FMCW radar. The performance of the proposed scheme is better than that of the conventional scheme that modulates 1-bit data using up- and down-chirps at the same data rate. Under higher signal-to-noise ratio (SNR) conditions, the proposed scheme achieves convergence to the same RMSE as does the conventional FMCW radar without data modulation. Therefore, the proposed scheme is effective in increasing the data rate.