Intermediate frequency variation in long‐range FMCW radar for harmonics cancellation

This study presents a technique for removing the inevitable harmonic distortions and intermodulation products that primary frequency‐modulated continuous wave (FMCW) radars inherently generate in the baseband. The required mixers and baseband amplifiers are non‐linear devices that introduce signal distortions, depending on the positions of targets in the field of view. Target distances are directly coupled to their corresponding baseband frequencies. The mitigation strategy presented in this study involves changing the resulting baseband frequencies of targets by varying the mixer deramping frequency input. After applying a processing algorithm that involves spectral rotation and combination, harmonic contributions can be suppressed to a high degree, while target‐related signals remain the same. After only four iterations, a gain of 30 dB in spurious free dynamic range can be achieved that can even be improved with more time on target. This behaviour is not only observed in simulations, but is also proven with measurements using an FMCW radar, working at a 3 GHz carrier frequency. The algorithm is applicable to radar systems that work in any frequency band.