Multiple-Frequency CW Radar and the Array Structure for Uncoupled Angle-Range Indication

The frequency diverse array (FDA) radar has drawn great attention due to its range-, angle-, and time-dependent beampattern. However, the FDA radar suffers ambiguities in determining target locations, i.e., angle and range of targets are coupled. In this letter, we find that the key to decoupling the target location lies in destroying the mutual dependence of angle and range. Hence, the multiple-frequency continuous wave (MFCW) radar is proposed. The range measurement is obtained by transmitting continuous waves with multiple frequencies and separating the multiple echoes by digital mixer in the receiving end. The range information exists in the phase difference among the multiple echoes, and this process can be seen as sampling in range by multiple frequencies. Then, if a receiving array is used for spatial sampling, an angle measurement is obtained and the target location is decoupled. Four modes of the MFCW radar are derived and the reason for the uncoupled angle-range indication in the beampattern is analyzed in detail. The effectiveness of the proposed scheme is verified by simulation results.